npl report eng 57 final report to the cct on key ...npl report eng 57 final report to the cct on key...
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NPL REPORT ENG 57 Final report to the CCT on key comparison CCT-K6 – Comparison of local realisations of dew-point temperature scales in the range -50 °C to +20 °C S Bell, M Stevens, H Abe, R Benyon, R Bosma, V Fernicola M Heinonen, P Huang, H Kitano, Z Li, J Nielsen, N Ochi, O A Podmurnaya, G Scace, D Smorgon, T Vicente, A F Vinge, L Wang, H Yi April 2015
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Final report to the CCT on key comparison CCT-K6 – Comparison of local realisations of dew-point temperature scales in the
range -50 °C to +20 °C
S Bell1, M Stevens2, H Abe3, R Benyon4, R Bosma5, V Fernicola6, M Heinonen7, P Huang8, H Kitano3, Z Li9, J Nielsen10, N Ochi3, O A Podmurnaya11, G Scace8, D Smorgon6, T Vicente4, A F Vinge11, L Wang12, H Yi9 1 Engineering Measurement Division, National Physical Laboratory (NPL), Teddington, UK 2 United Kingdom Accreditation Service (UKAS), Feltham, UK 3 National Metrology Institute of Japan (NMIJ), Tsukuba, Japan 4 Instituto Nacional de Técnica Aeroespacial (INTA), Madrid, Spain 5 Van Swinden Laboratorium (VSL), Delft, The Netherlands 6 Istituto Nazionale di Ricerca Metrologica (INRIM), Turin, Italy 7 Centre for Metrology and Accreditation (MIKES), Espoo, Finland 8 National Institute for Standards and Technology ( NIST), Gaithersburg, USA 9 National Institute of Metrology (NIM), Beijing, China 10 Danish Technological Institute (DTI), Århus, Denmark 11 National Scientific and Russian Research Institute for Physical, Technical and Radiotechnical Measurements – East Siberia Branch (VNIIFTRI-ESB), Irkutsk, Russia 12 National Metrology Centre, Agency for Science, Technology and Research (NMC), Singapore
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Queen’s Printer and Controller of HMSO, 2015
ISSN 1754-2987
National Physical Laboratory Hampton Road, Teddington, Middlesex, TW11 0LW
Extracts from this report may be reproduced provided the source is acknowledged and the extract is not taken out of context.
Approved on behalf of NPLML by Teresa Goodman,
Optical Measurement Group
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CONTENTS
1 INTRODUCTION ........................................................................................................................ 6
2 ORGANISATION OF THE COMPARISON ........................................................................... 7
2.1 PARTICIPANTS, AND STANDARDS USED IN THE COMPARISON ............................... 8
2.1.1 INRIM ................................................................................................................................ 8
2.1.2 INTA .................................................................................................................................. 9
2.1.3 MIKES ............................................................................................................................... 9
2.1.4 NIM ................................................................................................................................. 10
2.1.5 NIST................................................................................................................................. 10
2.1.6 NMC ................................................................................................................................ 11
2.1.7 NMIJ ................................................................................................................................ 11
2.1.8 NPL ................................................................................................................................. 11
2.1.9 VNIIFTRI......................................................................................................................... 12
2.1.10 VSL .............................................................................................................................. 12
2.2 COMPARISON SCHEME ...................................................................................................... 13
2.3 COMPARISON SCHEDULE ................................................................................................. 13
3. COMPARISON METHOD ....................................................................................................... 15
3.1 TRANSFER STANDARDS .................................................................................................... 15
3.2 REPORTING ........................................................................................................................... 15
3.3 IMPARTIALITY ..................................................................................................................... 16
3.4 COMPLIANCE WITH OTHER REQUIREMENTS .............................................................. 17
4 PERFORMANCE OF THE TRANSFER STANDARDS....................................................... 17
4.1 PROBLEMS WITH THE TRANSFER STANDARDS .......................................................... 18
4.2 CHECKS OF SAFE TRANSPORTATION ............................................................................ 21
4.3 CONSISTENCY OF PERFORMANCE OF INSTRUMENTS THROUGHOUT THE
COMPARISON ................................................................................................................................ 22
4.4 STABILITY OF EACH HYGROMETER .............................................................................. 23
4.4.1 Pilot measurements ......................................................................................................... 23
4.4.2 INTA measurements of Hyg2........................................................................................... 24
4.4.3 Drift estimates and discussion......................................................................................... 26
5 PARTICIPANT RESULTS ....................................................................................................... 31
6 BILATERAL EQUIVALENCE ................................................................................................ 34
7 KEY COMPARISON REFERENCE VALUES (KCRV) ...................................................... 44
7.1 CALCULATION OF KCRV ................................................................................................... 44
7.2 CHI-SQUARED TEST ............................................................................................................ 45
7.3 COMPARISON RESULTS PRESENTED IN TERMS OF KCRV ........................................ 46
8 DISCUSSION ............................................................................................................................. 49
9. CONCLUSION ........................................................................................................................... 50
10. ACKNOWLEDGEMENTS ....................................................................................................... 50
REFERENCES .................................................................................................................................... 50
APPENDIX 1: TECHNICAL PROTOCOL ..................................................................................... 53
APPENDIX 2: RESULTS REPORTED BY THE PARTICIPANTS ............................................ 71
APPENDIX 3: UNCERTAINTY ANALYSES OF PARTICIPANTS ......................................... 104
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1 INTRODUCTION
At the 19th
(1996) meeting of the International Bureau of Weights and Measures (BIPM)
Consultative Committee for Thermometry (CCT), the Working Group on Humidity
Measurements (CCT/WG6) was formed. The Working Group was charged with organising
an international comparison in the field of humidity standards. Preparations for a key
comparison began with an initial protocol drafted by NIST and reviewed by CCT WG7 (key
comparisons).
At its 2001 meeting, the CCT appointed NPL as pilot, and NMIJ as assistant pilot. It was seen
that the time-consuming nature of comparison measurements in this field would require that
the number of participants be limited in order to keep the duration of the comparison within
reasonable limits. The CCT agreed a limit of 10 participants. The balance of representation
between Regional Metrology Organisations (RMOs) was proposed by the CCT based on the
level of humidity standard activity within the RMOs.
During 2002, RMOs nominated institutes to participate, and the comparison protocol was
revised and agreed with participants. At this time, the role of pilot for EUROMET.T-K6 was
transferred from NPL to MIKES (Finland), and the CCT-K6 and EUROMET.T-K6 protocols
and reporting templates were developed in close alignment.
The CCT-K6 protocol was reviewed by WG6 when they met in September 2002, approved
by K6 participants in March 2003, with agreed minor changes arising from comments from
CCT WG7 who approved the protocol in July 2003.
At the start of preparations, measurement comparison methods in the field of humidity were
not well established, so in-depth trials of (initially) three travelling standards were carried
out. In consultation with participants, two preferred instruments were identified for use.
In late 2002 NPL performed the initial pilot set of comparison measurements using the
travelling standards, marking the effective start of the comparison. Measurements by
participants proceeded until 2009, interspersed by a large number of delays, repairs,
additional checks and participant changes, which all contributed to extending the duration of
the comparison. The details of the incidents and checks are given in Section 3. Despite the
extended timescale and several minor repairs to the instruments, the checks of consistency
and drift of the instruments provide satisfactory evidence that the results are reliable enough
for the purpose of the comparison, as discussed in Section 4.
By the time of conclusion of CCT-K6, the corresponding RMO comparisons APMP.T-K6 [1]
and EUROMET.T-K6 [2] had already been completed, and results were in use to support
claims of calibration and measurement capability (CMCs) of NMIs involved. These
comparisons are therefore available for linkage via common participants, limited only by the
continuity of the realisations at those institutes.
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2 ORGANISATION OF THE COMPARISON
The purpose of the comparison was to establish the degree of equivalence between
realisations of local scales of dew/frost-point temperature of humid gas, in the range -50 °C
to +20 °C, among the participating national measurement institutes.
The key comparison is a comparison of the measurand “realisation of local scale of dew-point
temperature” at the participating national institutes. The dew-point scale comprises dew
points and (below the freezing point of water) frost points.
The comparison was designed to provide
Estimates of bilateral equivalence between every pair of participants at each measured
dew point
A key comparison reference value (KCRV) for each nominal value of dew/frost point
in the comparison.
Estimates of equivalence of each participant to the KCRV
The technical protocol for the comparison is shown in Appendix 1. The comparison was
made by circulation of a pair of travelling transfer standards. Each transfer standard was used
to independently measure dew/frost-point temperature of a sample of moist gas (air or
nitrogen) produced by a participant's standard generator using the same measuring process.
Measurements were made at dew point nominal values of -50 °C, -30 °C, -10 °C, +1 °C and
+20 °C. The points were chosen to test the main range of interest, covering frost and dew
regions. The nominal value of +1 °C represents the range near 0 °C while being far enough
above it to avoid ambiguities that can arise around the freezing point of water.
The comparison took the form of a closed circulation in two consecutive loops. There was
one pair of hygrometers, which were at all times measured nominally simultaneously.
Simultaneous measurements using a pair of standards gives information about the within-
laboratory consistency of the measurements, the reproducibility of the instrument
performance, and continuous feedback about the successful transport of the instruments
without any major shift in performance.
The values of dew-point temperature reported for the travelling standards are “arbitrary”
values calculated from the measured resistance output. The travelling standards are used
simply as comparators.
Further below, values of Key Comparison Reference value (KCRV) are calculated, but it is
important to note that any KCRV in this comparison has no absolute significance – it does
not represent a reference value in the SI, only a comparison parameter.
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2.1 PARTICIPANTS, AND STANDARDS USED IN THE COMPARISON
A list of the participants is given in Table 1, including concise indication of their standard
generator types, and references to publications.
Table 2.1 List of participants. (Institute current names and abbreviations are given – at the start of the
comparison several of them were known by other names). The type of standard is also given, as two-
pressure (2-P), or single-pressure (1-P).
Participant Acronym Standard
type
Centre for Metrology and Accreditation (Finland) [3] MIKES 1-P
Instituto Nacional de Technica Aeroespacial (Spain) [4,5,6,7] INTA 2-P
Istituto Nazionale di Ricerca Metrologica (Italy) 1 [8,9] INRIM 1-P
National Institute of Metrology (China) 1 [10,11] NIM 2-P
National Institute for Standards and Technology (USA) [12,13] NIST 2-P
National Metrology Centre, Agency for Science, Technology and
Research (Singapore) 1 [14, 15]
NMC 2-P
National Measurement Institute of Japan (Japan) [16,17] NMIJ 2-P
National Physical Laboratory (UK) [18,19]] NPL 1-P
National Research Institute for Physicotechnical and Radio
Engineering Measurements (Russia) – East Siberia Branch 2 [20]
VNIIFTRI
ESB
2-P
Van Swinden Laboratorium (Netherlands) 1 [21, 22] VSL 1-P
Details of participant facilities used for the comparison are given in the following
subsections.
Participants have confirmed that no significant changes have been made to their dew point
standards between the time of measurement and the time of reporting. This ensures that the
results of any participant can form a valid link to the KCRV through other comparisons up to
the date of this publication at least. The only exceptions to this are NIST and VSL. The NIST
Low Frost Point Generator used for the -50 °C and -30 °C points in this comparison was
significantly modified after the comparison measurements (as discussed in Section 7.1). The
VSL generator used here for CCT-K6 was used also for EUROMET.T-K6 [2], but since then
has been replaced with a newly constructed standard [23, 24].
2.1.1 INRIM
The INRIM primary standards used in the comparison were INRIM-designed single-pressure
generators [8, 9]. For the comparison values -50 °C, -30 °C and -10 °C, the IMGC02 (now
INRIM 02) standard frost-point generator was used, and and at +1 °C and +20°C the
IMGC01 (now INRIM 01) standard dew point generator was used.
1 At the start of planning the comparison, several participant institutes were known by previous names: INRIM
was IMGC, NIM was NRC-CRM, NMC was SPRING, and VSL was NMi. Throughout this report, current
names of institutes are used.
2 Initially, VNIIM was the planned participant for Russia, but later VNIIFTRI was nominated.
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In the INRIM 02 generator, a stream of N2 gas flows through a heat exchanger and, then, over
a surface of ice inside an isothermal saturator held in a temperature bath. The gas is re-
circulated many times over the isothermal surface, achieving an equilibrium saturation whose
temperature is monitored with two PRTs installed at the outlet of the saturator in the ice layer
and in the air flow. The system was constructed with vacuum-grade fittings and
electropolished tubing. A centrifugal pump is used to re-circulate the carrier gas (N2) at any
flow value between 3 L min-1
and 10 L min-1
. A hygrometer in calibration is connected in a
branch of the main loop with gas flow rate to be set between 0.5 Lmin-1
and 1.5 L min-1
.
The INRIM 01 generator is a recirculating-type generator to cover the dew/frost point range
from -15 °C to +90 °C. The carrier gas can be N2 or air. It is designed to accommodate the
hygrometer in calibration either into an isothermal chamber (closed-circuit mode) or in a
secondary branch with a draw-off flow up to 1.5 L min-1
(open-circuit mode). The saturating
unit consists of a box where the air is forced to flow over a surface of water or ice for a length
of 1.2 m. The temperature is monitored at three different sections of the saturator by means of
three pairs of platinum resistance thermometers (PRTs): one thermometer is located
immediately underneath the water surface (the water depth never exceeds 10 mm) and the
other is placed in the gas, immediately above the first one. One pair of PRTs is at the outlet
where the saturator temperature is defined.
The traceability of the realisation is in terms of temperature through the calibration of the
saturator platinum resistance thermometers with traceability to the SI (ITS-90) via INRIM
temperature standards. Supporting electrical and pressure measurements are traceable through
calibrations at INRIM.
2.1.2 INTA
In the range from -50 °C to -10 °C, the INTA Low-range standard humidity generator is a
modified Thunder Scientific model 4500 two-pressure generator with saturation performed
with respect to ice. In the range from 1 °C to 20 °C the INTA High-range standard humidity
generator is a modified Thunder Scientific model 9000 two-pressure generator used with
saturation with respect to water. The generators were operated in two-pressure mode at
nominal flow rates of 2.7 and 50 L/min, respectively and with a saturator pressure below
300 kPa. The realised frost/dew-point temperatures in both cases were determined from
independent temperature and pressure measurements using standard platinum resistance
thermometers calibrated at the ITS-90 fixed points, precision resistance bridges (1 mA / 75
Hz) and low AC/DC difference standard resistors and precision digital absolute pressure
gauges. Temperature and pressure measurements are traceable to CEM and DC resistance,
AC/DC difference and voltage ratio are traceable to CEM, NPL and PTB, respectively. Both
generators were run on CO2-free air obtained from oil-free compressors fitted with heat
regenerated molecular sieve adsorption driers, and using high-purity deionized water of
nominal resistivity 18 M-cm [4,5,6,7].
2.1.3 MIKES
MIKES used the MIKES Dew/Frost-point Generator (MDFG) as the dew-point temperature
standard in this comparison [3]. The generator comprises three saturators: LRS2 (-80 °C to
+15 °C), LRS1 (-60 °C to +15 °C) and HRS (0 °C to +90 °C). In this comparison, LRS1 was
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used at measurement points -50 °C, -30 °C and -10 °C. HRS was used for measuring the
points +1 °C and +20 °C. All three saturators operate on the same principle. Air flowing at a
rate of typically less than 2 l/min is saturated with water vapour by a single pass through a
precision saturator located in a temperature-controlled liquid bath. A pre-saturator ensures
that the dew-point temperature of air entering a main saturator is slightly higher than the main
saturator temperature. Thus, condensation takes place in the inlet heat exchanger tube of the
main saturator. Saturation with respect to plane water or ice layer is completed by forcing air
flow on water or ice surface in a saturation chamber connected to the outlet of the heat
exchanger tube. Saturated air flows through an internally electropolished tubing to the
hygrometer under calibration. The tubing is heated when needed to prevent any water
condensation in it. The generated dew-point temperature is determined from the measured
saturator temperature, the saturator pressure and the air pressure in the hygrometer under
calibration. Being the primary realisation for dew-point temperature, MDFG provides
traceability to the SI through traceable temperature and pressure measurements. The
traceability of these measurements is established through calibrations at MIKES within its
CMCs published at the BIPM website.
2.1.4 NIM
A two-pressure generator constructed by NIM [10,11] was used for this comparison at the
comparison values -50 °C, -30 °C, -10 °C, +1 °C and +20°C. The two pressure generator
involves saturating a continuous stream of carrier gas with water vapour at a known
temperature and pressure. The uncertainty of the device is determined by the uncertainty of
the temperature and pressure measurements. The two-pressure generator consists of the heat
exchanger, the saturator and the test chamber. All pipe lines were constructed by the use of
internally polished tubing. The carrier gas flow rate range is 0.1 L/min to 2 L/min. The dew-
point/frost-point range is -75 °C to +25 °C. The temperature and pressure measurements are
traceable to NIM’s temperature and pressure standards.
2.1.5 NIST
The NIST primary standards used in the K6 comparison were NIST-designed thermodynamic
generators For the comparison values -10 °C, +1 °C, and +20°C the NIST Hybrid Humidity
Generator (HHG) [12] was used, and at -50 °C and -30 °C the NIST Low Frost-point
Generator (LFPG) [13] was used. The HHG was operated using the two-pressure principle.
When the HHG is operated this way, air flowing at a rate of typically 30 l/min is saturated
with water vapour by a single pass through a temperature-controlled saturator. Saturation
takes place with respect to the surface of water by vapour diffusion and mixing at a measured
controlled pressure that is often elevated. The generated amount fraction (mole fraction) is
determined using the temperature and pressure at the location immediately before the outlet
of the saturator. The generated dew/frost point is calculated using the generated amount
fraction and the pressure at the location of interest. The LFPG operates in a similar manner
as the HHG, except that 1) the operating gas is nitrogen, 2) the flow rate through the saturator
is 2 l/min, 3) the saturator contains ice, 4) the pressure difference Δp between the saturator
and the location of interest is very small, and 5) the frost-point temperature at the location of
interest is determined as the measured saturator temperature with a small correction for Δp.
Also, the LFPG uses internally electropolished tubing in its construction to minimize
adsorption/desorption on the surface of the tubing. The SI traceability of the realisation is in
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terms of temperature and pressure. The traceability of the temperature measurement is
through the calibration of the saturator’s standard platinum resistance thermometer using
ITS-90 fixed points maintained at NIST. The SPRT resistance measurements make use of
standard resistors calibrated at NIST. The calibrations of the two pressure gauges are
traceable to NIST pressure standards.
2.1.6 NMC
Two humidity generators were used as references to compare with the traveling standards
[14,15]. Both are Thunder Scientific products. The Model 4500 frost generator is based on
two-pressure and two-temperature principle and uses nitrogen as working gas. It was used for
the comparison at -50, -30 and -10 °C frost points. Nitrogen flow of 1.5 litres per minute was
used for all measurement points. The Model 2500 humidity generator is based on two-
pressure principle and uses air as working gas. It was used for comparison at -10, +1 and
+20 °C frost/dew points. Air flow of 10 to 20 litres per minute was used instead. The two
transfer standards were connected to each generator in parallel with a leaking valve in
between the generator and the transfer standards. Each standard had a flow approximately 0.5
litres per minute as given by the flow indicator of the standard and the leaking valve released
the extra gas from the generator. The system accuracy affecting parameters of the two
generators, such as pressure transducers and thermometers are regularly calibrated against
reference standards maintained at NMC/A*STAR, Singapore.
2.1.7 NMIJ
Two generators, frost-point generator (FPG) [16] and two-pressure generator (2PG) [17],
both of which were designed by NMIJ, were used for the NMIJ primary humidity standards
in the comparison. The FPG and 2PG were used for the comparison ranges of -50 °C
to -10 °C and +1 °C to +20 °C, respectively. The principle of the two generators is on the
basis of the generation of saturated water vapour using ice or water maintained at constant
temperature. Nitrogen and air were used as matrix gases for the FPG and 2PG, respectively.
The flow rates of the gases passing through the FPG and 2PG were 3 L/min and 20 L/min,
respectively. SUS316L stainless-steel tubes with an outer diameter of 6.35 mm (1/4”) whose
inner surfaces were electropolished were used to connect transfer standards to the FPG. The
pressure and temperature of the saturated gases were measured using pressure gauges and
platinum resistance thermometers, which are traceable to the International System of Units
(SI) using calibrations services at NMIJ or at calibration laboratories accredited by IA Japan.
2.1.8 NPL
The NPL primary standards used in the comparison were NPL-designed single-pressure
generators [18,19]. For the comparison values -50 °C, -30 °C and -10 °C the “NPL Low
Frost-point Generator” (LFG) was used, and at +1 °C and 20 °C the “Standard Humidity
Generator” (SHG2) was used. Both generators operate on the same principle: air flowing at a
rate of typically 0.5 l/min to 1 l/min is saturated with water vapour by a single pass through a
precision saturator located in a temperature-controlled liquid bath. Saturation takes place
with respect to surfaces of water or (below 0 °C) ice, by vapour diffusion and mixing, at
measured controlled pressure close to atmospheric pressure. The LFG is specialised for low-
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range operation by the use of internally electropolished tubing in its construction. The SHG2
is specialised for high-range operation by the use of an initial pre-saturation stage, and trace
heating for condensation protection. The “generated dew-point” is defined by the measured
temperature of the saturated flowing gas at the final stage within the saturator. The
traceability of the realisation is in terms of temperature through the calibration of the
saturator platinum resistance thermometer with traceability to the SI (ITS-90) via NPL
temperature standards. Supporting electrical and pressure measurements are traceable through
calibrations at NPL or at UKAS accredited laboratories in the UK.
2.1.9 VNIIFTRI
The Russian national humidity standard comprises two humidity generators with working
range from 5 °C to 90 °C and from -60 °C to +15 °C respectively. The humidity quantities of
relative humidity, dew/frost-point temperature, mole fraction are disseminated. Ordinary
hygrometers are traceable to the national primary standard in accordance with the state
hierarchical chain for measuring means of gas humidity. The common working range (dew
points from 5 °C to 15 °C) allows comparison of the generators. The generators use the phase
equilibrium method to generate humid gas defined in terms of dew/frost-point temperature
from -79 °C to +90 °C. The expanded uncertainty in dew/frost-point temperature is no more
than 0.12 °C.
2.1.10 VSL
The VSL humidity generator used for the comparison was a dew-point generator of the
circulating single-temperature, single-pressure type [22]. A pump recirculates air or nitrogen
gas over two saturators immersed in temperature-controlled liquid baths in which the
temperature is measured using platinum resistance thermometers, and this determines the
realised value of dew point for the saturated gas. One or other saturator can be selected,
depending on the temperature range within an overall envelope of −60 °C to +70 °C.
Circulation is controlled by means of a centrifugal impeller and switching valves to select the
flow path. Traceability of dew point is provided by calibration of the thermometers by
comparison against standards calibrated to ITS-90.
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2.2 COMPARISON SCHEME
The comparison scheme is illustrated in Figure 2.1. It is shown in two geographical loops
(Europe and rest-of-world) separated by pilot measurements. However the loops ware made
in series, not concurrently, and therefore for purpose of analysis the comparison was
functionally a single loop. Additional intermediate checks were also made (discussed further
below in Section 4).
Figure 2.1 Scheme of the comparison in two geographical loops (Europe and rest-of world) made in series,
separated by pilot measurements. Loops were sequential, not concurrent.
The comparison can be linked to EUROMET.T-K6 through INRIM, INTA, MIKES, NPL
and VSL. A link to APMP.T-K6 is available through NMIJ, NIM and NMC. NIST provides a
link to SIM, and VNIIFTRI provides a link to COOMET. CCT bilateral comparisons will
link to CCT-K6 via key comparison participants.
2.3 COMPARISON SCHEDULE
The approximate measurement dates for the comparison are shown in Table 2.2. Each
laboratory initially proposed an estimated duration of measurements and shipping (typically 8
weeks). Although many participants complied with these estimates, there were many and
frequent disruptions to the schedule, mainly due to instrument breakdowns and repairs, and
consequent need for extra measurement checks by the pilot and others. The outcome of these
repairs is not believed to affect the instrument readings. More detailed discussion of this is in
NPL
NMIJ
Pilot
Assistant Pilot
Participants
INRIM
MIKES
NIST VSL
NIM
NMC
VNIIFTRI
INTA
Loop 1 Loop 2
NPL
14
Section 4. However the simple fact of extending the comparison due to multiple delays
requires a particularly careful consideration of the impact of any possible long-term drift in
the instruments.
NIST obtained agreement to make two sets of measurements, against two different humidity
generators, but afterwards agreed to submit results for just one of these to the comparison.
The 2006 measurements by NMIJ were intended to provide an extra mid-comparison check
of instrument stability. However these were not reported or used, due to a number of extra
checks made by NPL and INTA.
Table 2.2 Approximate measurement dates of the comparison.
Measurement
start
Measurement
finish
NPL Jul-02 Jul-03
NMIJ Sep-03 Oct-03
VSL Oct-03 Dec-03
MIKES Jan-04 Mar-04
INTA Mar-05 Apr-05
INRIM May-05 Jul-05
NPL Sep-05 Feb-06
NMIJ Mar-06 Jul-06
NIST1 Nov-06 Dec-06
NIST2 Jan-07 Feb-07
NMC Mar-07 Apr-07
NIM Oct-07 Dec-07
NPL Feb -08 Mar 08
VNIIFTRI Dec-08 Mar 09
NPL Apr-09 May 09
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3. COMPARISON METHOD
3.1 TRANSFER STANDARDS
After some discussion and trials of several hygrometers, the participants agreed on the use of
two transfer-standard condensation-principle dew-point hygrometers – one Michell
Series 4000 serial number 92-0319, owned by NPL (identified as Hyg1) and one MBW
model DP 3DSH III K-1806, serial number 114155 / 91527, owned by INTA (identified as
Hyg2). Further details of the instruments are given in the protocol in Appendix 1.
These individual instruments were selected because they had the resolution required for the
comparison, and in both cases had an established history of reliability, minimal drift, and
established operating conditions in terms of supplementary cooling, flow rate, short-term
stability, etc. The hygrometers contained integral refrigeration units to provide reproducible
supplementary cooling.
No additional changes in the instruments were made for the comparison. No specific separate
calibrations were made of key components (such as the mirror PRT). (Although this can in
modern instruments provide extra confidence and scope for checking, it was considered
sufficient to treat the instrument “as a whole”).
Towards the end of the comparison, transit data loggers were transported with the
hygrometers to monitor both temperature and mechanical shock during transportation. No
significant events were recorded.
For the purpose of establishing instrument history, past calibration data for Hyg2 were
supplied to the pilot by INTA in confidence, not revealed to other participants, and did not
compromise the “blindness” of comparison measurements by INTA or other participants.
3.2 REPORTING
Each laboratory realised and reported:
5 dew/frost points
each dew/frost point separately reproduced 4 times
each realisation measured using two travelling standards simultaneously, resulting in
40 individual transfer standard results (20 per transfer standard).
Participants were instructed to re-form the condensate layer for every separate measurement.
Participants realised and measured values within 0.5 °C of the comparison nominal values.
Participants reported:
applied dew/frost point from the participant standard generator
measured values (both travelling standards simultaneously)
difference (applied dew point minus – measured dew point) for both travelling
standards
uncertainties associated with these (including short-term standard deviation of
travelling standards)
Difference values are the results compared and analysed for the comparison.
16
Supporting information was reported, including pressure and flow rates of sample gas
supplied to the hygrometers, coolant temperatures, and other relevant background
information. All measurements were made at nominally (just above) atmospheric pressure
and at flow rates of approximately 0.5 l/min through each instrument.
The indicated value of dew point for the instrument was derived from the measured resistance
of the mirror PRT after stabilisation of the instrument at each condition measured. This
resistance value was converted to a nominal temperature indication by using the nominal
PRT resistance-temperature characteristic in IEC 60751 (1995-07) (corresponding to
EN 60751:2008), defined as follows:
For temperature above 0 °C:
Rt = R0(1 + At + Bt2) (1)
and for temperature below 0 °C:
Rt = R0[1 + At + Bt2 + C(t-100)t
3] (2)
where
t = temperature (ITS-90), °C,
Rt = resistance at temperature t,
R0 = nominal resistance of 100 Ω at 0 °C
A = 3.9083 × 10-3
°C-1
,
B = -5.775 ×10-7
°C-2
,
and
C = -4.183 × 10-12
°C-4
.
Note that this is a deliberately arbitrary nominal temperature value for the purpose of
comparison, with no absolute significance.
Reporting templates are shown in the appendices to this report
3.3 IMPARTIALITY
The impartiality (“blindness”) of the comparison was ensured by the pilot conserving the
confidentiality of the data throughout, and no communication of results between partners was
allowed during the comparison. This was true during instrument evaluation, during
participant measurements, and during interim decisions about the comparison where needed.
Any limited data shared during the comparison for the purpose of discussing concerns about
the instruments (See Section 4 below) was strictly in coded terms, not absolute values.
The use of a general function (IEC 60751) for conversion of resistance to temperature,
together with the tendency of these instruments to have (stable) calibration offsets, both also
contributed to the blindness of the measurements.
For a period overlapping this comparison, some participants also took part in the
corresponding RMO comparison EUROMET.T-K6. This involved INRIM, INTA, MIKES,
NPL, and VSL. However there is no reason to suggest this affected the blindness of CCT-K6.
17
Since NPL, as the pilot, measured at more than one time during the comparison, the first full
set of NPL results is used as the reported comparison data, while other NPL results are used
for instrument drift assessment.
3.4 COMPLIANCE WITH OTHER REQUIREMENTS
Other requirements of the CIPM Mutual Recognition Arrangement [25] are met in respect of
the following points.
The comparison participants have formally approved this report.
Consistency has been ensured between this CCT key comparison and the several
corresponding RMO and bilateral comparisons to date. Protocols or reports of corresponding
comparisons to date have been reviewed by CCT/WG7 for consistency with this one, even
though several of these comparisons, notably APMP.T-K6 and EUROMET.T-K6, were
initiated or completed before CCT-K6 itself. Certain of the comparisons have covered more
measurement points than CCT-K6. For these cases, it has been noted that linkages to CCT-
K6 are possible at values measured in common between comparisons, but not at other values.
4 PERFORMANCE OF THE TRANSFER STANDARDS
Stability of the transfer standards is critical to the uncertainty and validity of the comparison.
This was particularly a concern for two reasons: the long duration of the comparison, and the
several interventions made to diagnose and repair problems with the instruments.
The performance of the transfer standards during the comparison was monitored in three
ways:
On receipt of the instruments, every participant was required to execute comparison
measurements at a dew point of 20 °C as a first step, and to report the results immediately
to the pilot. From this, the pilot assessed the consistency of agreement between the two
transfer standards as an indication of safe transit, and confirmed to the participant to
proceed with full measurements.
Secondly, the between-instrument agreement at all measured values throughout the
comparison gives an indication of consistent performance of the instruments.
Thirdly, drift of the instruments over the whole period of the comparison was assessed
from pilot measurements at the beginning and end of the comparison, and at certain times
in between, especially at times of repair or other concern raised about the hygrometers. In
addition, extra measurements by INTA of Hyg2 before, during and after the comparison
gave further evidence of stability of this instrument.
The three types of checks are detailed further below in sub-sections 4.2 to 4.4.
18
4.1 PROBLEMS WITH THE TRANSFER STANDARDS
The transfer standards represented the state of the art when the comparison started, and were
selected for their history of stable and reliable operation. However, due to the age of the
instruments, they suffered a large number of minor failures. There was also a suspected
electrical measurement anomaly that was not an instrument failure. The repairs and other
interruptions considerably delayed the comparison at many stages. However, no significant
effect on the long-term characteristic of either instrument was observed (as detailed in Sub-
sections 4.2 to 4.4 below). At every intervention, the pilot briefed participants and secured
participant agreement to appropriate actions. The incidents are summarised in Table 4.1 to
put into context the results of checks of instrument stable performance throughout the
comparison.
Overall there were more than 12 distinct breakdowns or problems with the instruments. Only
a small number of these (queries over NMI and MIKES measurements, and head-heater
problem at NPL) have any potential implications for the comparison outcome. The checks
throughout the comparison assume extra significance because of the need to be able to
demonstrate that none of the incidents affected comparison results. Where relevant, the
events are marked as A to Q on the graphs in Section 4.
It was not obvious how any of these instrument problems could have been avoided at the
time. However the recent new generation of similar hygrometers is more reliable, and
subsequent comparisons have benefited from that.
19
Table 4.1 List of problems with the transfer standards, and interventions made
Date Event Problem Action Impact on comparison
results
Oct to
Dec
2003
A After measurements
completed, VSL
expressed some concern
about reproducibility of
Hyg1 in low range.
No action, but scrutiny of
subsequent results at all
participant labs
Direct concern only for
VSL data. Not observed
to affect other results
Jan to
May
2004
B MIKES results
(completed Jan-Mar and
analysed up to May)
appeared to show
discrepancy between AC
and DC resistance
measurements of
hygrometer PRT, of up
to 0.07 °C.
Extensive investigation on
identical model at NPL could
not replicate the effect. Lesser
effects (due to stray
capacitance, inductance, self-
heating) were measurable or
calculable – none significant at
this level.
MIKES accepted that
the anomaly could not
be reproduced, and
chose which results to
report. Participants were
involved in discussion,
but “blindness” of
results was preserved
throughout.
April
2004
C Hyg2 light source (part
of optical detection of
condensate formation
and feedback) failed
while at INRIM.
Hygrometer component
(measuring head) sent to INTA
for replacement of light source,
then returned to INRIM where
gain of photodiode circuit was
adjusted in situ. This element
of the instrument is part of the
control electronics, but does
not determine the instrument
reading.
Delay, but no impact on
instrument
characteristic.
May
2004
D Hyg2 refrigerator failed
at INRIM –
Complete replacement of
refrigeration system needed.
Repaired by manufacturer
(necessarily travelling via
INTA, as owner). Instrument
then checked at INTA (against
past calibration history, but
retaining “blindness” of
comparison). Instrument was
then re-checked at NPL.
Delay, but checks did
not show any departure
from previous
characteristic.
Late
2004
E Hyg2 failure of a
compressor valve within
refrigeration system
Returned to manufacturer for
further repair,
Delay, but no impact on
instrument
characteristic.
Late
2004
F Hyg1 film thickness control
reinstated on front panel of
instrument (from internal
position) for improved
usability. Instrument was then
re-checked by pilot, alongside
Hyg2.
No impact on instrument
characteristic
Sep
2005
G Mid-comparison measurements
as planned, by pilot (NPL)
No adverse findings
20
Date Event Problem Action Impact on comparison
results
May
2006
H Hyg2 photodiode failed
while at NMIJ.
Measuring head sent to
manufacturer agent in Japan for
repair. NMIJ made extra
measurements to confirm
satisfactory operation after
repair. The photodiode is part
of the control electronics but
does not determine the
instrument reading.
Delay, but no impact on
instrument
characteristic.
August-
Sep
2006
I Additional check at NPL to
confirm no change due to
photodiode replacement
Delay, but no adverse
findings
March
2007
J Hyg2 failed to operate at
NMC
Identified as failure of a power
supply smoothing capacitor. On
manufacturer’s advice,
remedied by removal of
capacitor.
Delay, but no impact on
instrument
characteristic.
March
2007
K Hyg2 “mirror check”
indicator flashing
False indication, solved by
switching to “standby” and
switching off, as needed
No impact on instrument
characteristic.
March-
April
2007
L Hyg1 power supply cut
out several times
Cause unsure. No action. No impact on instrument
characteristic.
May to
August
2007
M Instruments re-checked at NPL.
Delay, but no impact on
instrument
characteristic.
May to
August
2007
N Query over sensitivity of
instrument readings to
coolant temperature
Additional checks made by
NPL.
Delay, but no adverse
findings
Oct-Dec
2007
P Hyg1 display panel
meter failed at NIM
(display not used or
reported in comparison)
NIM completed measurements
by data-logging electronically
as planned. On return to NPL,
the loose connection to one pin
of the display was repaired by
the manufacturer.
No impact on instrument
characteristic.
Jan 08 Q While at NPL, Hyg2
head heater control
failed, leading to
excessive heating of
head.
Head heater control was
repaired in situ by the
manufacturer. This was the first
and only problem with risk of
affecting key comparison
results. Full set of repeat NPL
measurements carried out after
repair, to be sure no effect on
results.
Delay, but no adverse
findings.
21
4.2 CHECKS OF SAFE TRANSPORTATION
Results of initial between-instrument consistency checks at a nominal dew point of 20 °C are
shown in Figure 4.1. These served to inform the pilot as in indication of safe arrival at each
participant lab (in some cases after remedying instrument problems). The results at 20 °C
were sent to the pilot immediately for review. In every case results were judged sufficiently
consistent by inspection.
From Figure 4.1, retrospective analysis shows that:
Although scatter at 20 °C varies from participant to participant, no lab or labs have
significantly worse scatter or deviation than the typical.
Instrument events (A to Q) are shown relative to the progress of the comparison. By
inspection, no clear effects of breakdown or repair are visible at a dew point of 20 °C.
Further discussion is included in Section 8.
Figure 4.1 Between-instrument initial consistency checks at a nominal dew point of +20 °C, on
arrival at each participant laboratory. Standard uncertainty of individual measurements ranged
between 0.02 °C and 0.05 °C approximately. Data shown are differences (Hyg1 minus Hyg2). Event
markers A, B, C etc. refer to Table 4.1.
22
4.3 CONSISTENCY OF PERFORMANCE OF INSTRUMENTS THROUGHOUT THE
COMPARISON
The consistency of between-instrument differences at all measured values throughout the
comparison gives a measure of consistent performance of the instruments throughout the
comparison. Figure 4.2 shows the between-instrument differences summarised for all
participant sets of measurements at all five nominal dew-point values measured.
The difference data for NMIJ, VSL and NIM showed some untypical features. However, the
consistent pattern of results among a majority of participants at beginning, middle and end of
the comparison gives one form of assurance of the stability and consistency of the instrument
pair. No clear progressive drift or trend is evident. If the difference were changing suddenly
or progressively with time, this would imply a change in at least one instrument. This was not
observed.
Although the pilot reviewed difference values for the 20 °C point immediately, as a check of
safe arrival, difference values at lower ranges showed some greater disparities (not analysed
until later).
Figure 4.2 Graph showing consistency of the difference between the transfer standards as reported by
the participants, four measurements (usually), at all five nominal values. Each data point is the
difference between results of two hygrometers measuring simultaneously. NPL additional data (NPL
2, 3, 4, 5 and 6) were limited checks, rather than full sets of four measurements. Standard uncertainty
of individual measurements ranged between 0.02 °C and 0.08 °C approximately.
I
23
By inspection, data from NMIJ, VSL and NIM appear to have more scatter than others. NMIJ
and NIM data appear to show an unusual pattern between results in different parts of the
range. Other isolated cases of scatter in individual measurements can be seen.
4.4 STABILITY OF EACH HYGROMETER
4.4.1 Pilot measurements
Measurements were made by the pilot NPL to monitor the stability of both travelling
standards relative to the NPL standards. These checks were made as full sets of
measurements at planned stages at beginning, middle and end of the comparison, plus some
more limited checks at other stages. Figure 4.3 shows a graph of data for Hyg1 and figure 4.4
for Hyg2. The data are plotted as difference (pilot applied values minus instrument dew/frost-
point temperatures calculated from the resistance measurement results). Only the mean values
are shown. For measurements in 2003, 2005, 2008 and 2009 these were means of full sets of
reproduced measurements – in most cases sets of four. At other dates, measurements were
fewer (single results at each dew point). Event markers A to Q are also shown.
Figure 4.3 Graph showing overview of pilot stability checks on Hyg1 hygrometer (lines joining the
data to guide the eye).
24
Figure 4.4 Graph showing overview of pilot stability checks on Hyg2 transfer standard, (lines joining
the data to guide the eye).
4.4.2 INTA measurements of Hyg2
As owner of Hyg2, INTA performed measurements before and after the comparison, as well
as their own comparison measurements, plus another measurement set after one of the
instrument repairs. The results are shown in the graphs in Figure 4.5 and 4.6. Each data point
in these figures represents the result of a single calibration; hence the uncertainties as shown
by the error bars are somewhat larger than uncertainties elsewhere in this report which are for
aggregated multiple results.
25
Figure 4.5 INTA data for overall calibration characteristic for Hyg2, years 2000 to 2010.
Uncertainties shown are at coverage factor k=2.
Figure 4.6 Graph showing INTA measurements for Hyg2 relative to INTA standard generator(s),
with straight-line weighted fits to the data to indicate trend. Uncertainties shown are at coverage
factor k=2.
In general, the INTA data show much less scatter than the NPL data, but with larger
uncertainties. This is considered in the analysis of drift that follows.
26
4.4.3 Drift estimates and discussion
The data for each instrument were analysed to establish whether any significant secular drift
should be taken into account in the comparison results and uncertainties. There are two
possible cases: drift estimated to be not detectably significant, counted as “zero drift” with
some assigned uncertainty – or a significant rate of drift detected and estimated with some
uncertainty, and a correction for drift applied to results where relevant.
The pilot data for travelling standards, at several occasions spread through the whole
comparison, were analysed for drift by evaluating a best-fit curve for data at each dew-point
temperature. The fitting used an NPL-developed validated function in MSExcel,
XLGENLINE V1.1 [26], to provide a weighted best-fit straight line, together with
uncertainty in gradient taking into account both residuals and number of data. In each case a
check was made to confirm that a higher order fit did not appear better (smaller residuals).
The results are shown in Table 4.2, which gives the drift as gradient in degrees Celsius per
year, and as a total drift for the whole comparison, and the uncertainty in both of these taking
into account the measurement uncertainty together with the residuals from fitting. In addition,
the outcomes of INTA drift checks on Hyg2 are also shown. The uncertainties for INTA
values are larger than those or NPL, partly because of the larger uncertainty of the INTA
references used, and partly due to fewer INTA data.
Table 4.2 Estimates of hygrometer drift, per year, and for the total duration of the comparison, Hyg1
data from NPL, Hyg2 data from NPL with additional results from INTA.
Instrument Dew-point
temperature
(°C)
Gradient (°C
/yr)
Standard
uncertainty in
gradient (°C
/yr)
Total
estimated
drift (gradient
x time
interval) °C
Standard
uncertainty
in total drift
(°C)
Hyg1 -50 +0.001 0.002 +0.003 0.013
Hyg1 -30 -0.002 0.002 -0.009 0.013
Hyg1 -10 -0.005 0.002 -0.027 0.013
Hyg1 +1 -0.006 0.002 -0.034 0.012
Hyg1 +20 +0.006 0.002 +0.036 0.012
Hyg2 (NPL) -50 +0.000 0.002 +0.000 0.013
Hyg2 (NPL) -30 -0.003 0.002 -0.016 0.013
Hyg2 (NPL) -10 -0.002 0.002 -0.010 0.013
Hyg2 (NPL) +1 -0.008 0.002 -0.045 0.012
Hyg2 (NPL) +20 -0.002 0.002 -0.012 0.012
Hyg2 (INTA) -50 +0.001 0.007 +0.008 0.041
Hyg2 (INTA) -30 +0.002 0.006 +0.011 0.037
Hyg2 (INTA) -10 +0.001 0.003 +0.007 0.018
Hyg2 (INTA) +1 +0.001 0.004 +0.004 0.022
Hyg2 (INTA) +20 +0.000 0.004 -0.001 0.022
Drift can be approximated as zero where the best-fit gradient is not significantly different
from zero when considered along with its k=2 uncertainty. According to this criterion, drift
was found to be negligibly different from zero in the range below 0 °C. However, for Hyg1 at
1 °C and 20 °C, and for Hyg2 at 1 °C, the criterion was not met. In these cases it is necessary
27
to decide whether to treat this as a sign of significant drift, and whether to make an allowance
for this as a correction or additional uncertainty.
An overview of the drift data is shown in the graphs in figures 4.7, 4.8, and 4.9. These show
for Hyg1, Hyg2, and for the two together, estimated drift, and uncertainty in this, at all five
comparison values.
Figure 4.7 Estimated total drift of Hyg1 hygrometer during comparison based on pilot NPL
measurements. Error bars show standard uncertainty of drift estimates.
Figure 4.8 Estimated total drift of Hyg2 hygrometer during comparison based on pilot NPL
measurements (squares) and INTA measurements (triangles). Error bars show standard uncertainty of
drift estimates.
28
Figure 4.9 Summary graph of estimates of total drift of both hygrometers during comparison based
on pilot NPL measurements (Hyg1 diamonds, Hyg2 squares) and INTA measurements (Hyg2
triangles). Error bars show standard uncertainty of drift estimates.
Overall, the estimates of drift from the INTA measurements had larger uncertainties then
those from the NPL measurements. However, INTA generally obtained particularly
reproducible results (as can be seen from the low scatter in figures 4.5 and 4.6). In addition
the relatively smooth trend found by INTA across the range (Figure 4.8) is more believable
than the variations that would be suggested by the NPL results.
The drift estimates and their uncertainties are summarised in Table 4.3. Drift can be
considered negligible if the estimated amount of drift, relative to its uncertainty, is not
significantly different from zero. This is the case for Hyg1 at -50 °C and -30 °C, and for
Hyg2 at all values except +1 °C. In addition, all but one of these individual drift values are
small − approximately 0.01 °C or less (one is less than 0.02 °C).
The drift estimates needing special consideration are those for Hyg1 at and above -10 °C and
for Hyg2 at +1 °C. Each of these taken in isolation suggests possible drift of more than
0.02 °C – which, if true, could be considered significant relative to the participant
uncertainties. Impact on the KCRV, and on the agreement of individual results with this,
could be up to half the magnitude of total drift (up to of order 0.01 °C).
For Hyg2 at +1 °C, the two drift estimates are discrepant – INTA results suggesting a
minimal drift upwards of order +0.004 °C ±0.022 °C (standard uncertainty) over the whole
comparison, while the NPL estimated downwards drift is -0.045 °C ±0.012 °C (standard
uncertainty). Their k=2 uncertainties would overlap, however. In spite of having larger
uncertainty, the INTA estimate of drift is credible, because of the small scatter, and because
across the range any physically feasible drift is unlikely to take the overall form implied by
the NPL +1 °C result.
29
For Hyg1, at 1 °C the NPL estimate of total drift is -0.034 °C and at 20 °C the estimate is
+0.036 °C. These both differ from zero by more than 2 standard uncertainties, and would
both be considered significant levels of drift. However drift of this type seems implausible,
because it does not fit known, physically feasible explanations – it would be surprising to
have little drift below 0 °C tending towards downward drift at 1 °C and upward drift at 20 °C.
In addition, the doubt about the NPL estimate of drift for Hyg2 at 1 °C may also cast doubt
on the estimate for Hyg1 at the same value.
In considering drift, the main component capable of drifting is the instrument PRT. For this,
there are a small number of physically feasible mechanisms of drift. One would be drift in R0
(resistance at 0 °C) which would result in drift in one direction, for all measured values.
Another would be change in PRT sensitivity, which would be reflected in a trend (slope) of
data points in Figures 4.7 to 4.9. A third possibility would be loss of thermal contact of the
PRT with the measurement head, which would result in a change likely to be more significant
at the lowest values measured. The discrepant drift data do not clearly fit any of these
patterns. Checks were also made to be sure the anomaly was not an inversion of results
(“error” versus “correction”).
One further consideration is whether the pilot reference (NPL generator) could have
performed anomalously in the range, from -10 °C upwards. However the overall comparison
results in Section 5 do not suggest this: NPL results generally show good agreement with the
KCRV.
Overall, what evidence there is for significant drift from -10 °C upwards is too conflicting to
allow a clear conclusion – one that would support the application of a correction for drift, and
allow a value of such a correction to be confidently proposed. The potentially anomalous drift
estimates cannot be rejected, because no cause is identified. Nor can any of the anomalies be
treated as a single “rogue” value: each is the combination of multiple results. Therefore,
instead, an additional uncertainty to allow for the doubt about drift has been added to the
instrument-related uncertainty.
It should be noted that the impact of any drift (and its uncertainty) in either instrument is
partly mitigated by the derivation of the reported comparison results from the average of both
instrument readings. According to this, the combined effect of the estimated drift is shown in
Table 4.3 below.
30
Table 4.3 Table comparing outcomes of using estimates of drift, and uncertainty in this, based on
either NPL data for Hyg2 or INTA data for that instrument. Estimated drift and its standard
uncertainty, shown for Hyg1 and Hyg2 individually, and combined effect. Uncertainty values marked
(*) are used in the subsequent analysis.
In summary, for the range of the comparison below -10 °C there is little evidence for
significant drift. At and above -10 °C the evidence of drift is inconclusive. For the values
where there is more doubt, a larger estimated uncertainty is assigned to allow for this,
conservatively, by directly adding a component to the uncertainty – so that when a coverage
factor of 2 is applied, the entire bounds of the apparent discrepancies will be included in the
interval. In the rest of the analysis that follows, the values from Table 4.3 marked with
asterisks (*) are used as standard uncertainties due to instrument drift. Those for -50 °C
and -30 °C are based on the pilot (NPL) data, which appear reliable; at other values the larger
uncertainty estimate of the two (NPL or INTA) is used.
Instrument drift does not contribute uncertainty to the individual laboratory results, but needs
to be taken into account in the assignment of KCRV and in the calculations of equivalence.
Dew
point
Total proposed
standard uncertainty
in (zero) correction
°Cdue to drift, enlarged
for discrepancy
Estimated
driftu
Estimated
driftu
Estimated
mean driftu
°C °C °C °C °C °C °C °C
-50 0.003 0.013 0.000 0.013 0.0014 0.0093 0 0.010*
-30 -0.009 0.013 -0.016 0.013 -0.0126 0.0093 0 0.016*
-10 -0.027 0.013 -0.010 0.013 -0.0182 0.0093 0 0.019*
1 -0.034 0.012 -0.045 0.012 -0.0395 0.0088 0 0.028*
20 0.036 0.012 -0.012 0.012 0.0116 0.0088 0 0.015
-50 0.008 0.041 0.0058 0.0213 0 0.024
-30 0.011 0.037 0.0009 0.0197 0 0.020
-10 0.007 0.018 -0.0098 0.0113 0 0.016
1 0.004 0.022 -0.0152 0.0128 0 0.020
20 -0.001 0.022 0.0172 0.0128 0 0.022*
NPL
NPL
Lab
(NPL estimates and
standard uncertainty)
Combined estimates (drift
of mean of Hyg1 and
Hyg2, and combined
standard uncertainty of
mean)
Proposed
correction
for drift
Lab
NPL
Hyg2
(NPL and INTA estimates,
and standard uncertainty)
As above As above INTA
Hyg1
31
5 PARTICIPANT RESULTS
Participant data are reported for measurements using the instrument pair simultaneously, for
four measurements separately reproduced at each of the five dew-point values. The full data
sets are reported in the Appendices of this report.
NPL and INTA both made extra measurements, due to providing several checks and drift
estimates for the hygrometers. However just one set of measurements was considered for the
comparison: for NPL the first complete set of measurements was used, and for INTA the
main scheduled comparison measurements at March to April 2005 were used.
For each participant, at each nominal dew point, the data were aggregated by taking a mean
of pooled results for both instruments to provide a single result for comparison and
calculation of KCRV. (The calculated mean of simultaneous readings of two instruments is
the mid-point between the two instrument mean readings, and the combined uncertainty is the
uncertainty in the value of that mid-point.) Following the same notation as used for
EUROMET.T-K6 [2] already reported, the result Rlab i at each dew point can be given as
4
1
Hyg2Hyg1
4
1
Hyg21Hyg )(8
1)(
2
1
4
1
ii
ilab RRRRR , (3)
where (RHyg1 and RHyg2) are the results of the two transfer standards, and where
dInddrefn ttR Hyg , (4)
with tdref the laboratory reference value for the applied dew/frost-point temperature and tdInd
the dew/frost-point temperature indicated (calculated) from the PRT resistance .
The uncertainty of the results are those reported by the participants taking into account both
Type B estimates as routinely reported, plus type A estimates of components such as short-
term variation (standard deviation) in repeated readings during the comparison
measurements.
All participants have independent dew-point scale realisations, including independent
traceability of supporting temperature measurements to national realisations of the
International Temperature Scale (ITS-90). The uncertainties can therefore be expected to be
uncorrelated between participants. Where within-laboratory correlations are known,
participants have taken these into account in the values reported.
Below, results for each participant at all dew points are plotted for Hyg1 in Figure 5.1, and
for Hyg2 in Figure 5.2. Mean results Rlab for the two instruments are shown for all
participants at all measured values in Figure 5.3.
Each set of results was initially reviewed by the pilot on receipt, to check for anomalies in
case of misreporting or other causes. In only one case, results as received appeared unusual,
and that participant was notified of a possible anomaly at certain measured values (but not the
magnitude or sign of the apparent discrepancy – as specified in Guideline CIPM MRA – D-
05) [27]. After making additional checks, the participant did not propose any change to
reported results.
32
In some cases participants observed supercooled water on hygrometer mirrors at the
nominal -10 °C point, and applied conversions to obtain equivalent frost point, using
formulae for saturation vapour pressure curve of water. This is not expected to affect the
validity of those results.
Figure 5.1 Mean reported values of applied condition minus measured value for Hyg1, shown in
participant time sequence. Connecting lines between data are shown to guide the eye.
Figure 5.2 Mean reported values of applied condition minus measured value for Hyg2, shown in
participant time sequence. Connecting lines between data are shown to guide the eye.
33
Figure 5.3 Results of entire comparison shown as reported values for mean (mid-point) of Hyg1 and
Hyg2 results combined (Rlab), grouped by dew-point value (data points staggered in x-direction for
visibility). Error bars show participant reported standard uncertainties (k=1). As shown here,
uncertainty allowance for instrument drift is not included.
34
6 BILATERAL EQUIVALENCE
Bilateral equivalences at each dew point were calculated from differences Dij between
participants i and j, where
Dij = jlabilab RR , (5)
The bilateral degree of equivalence (DoE) is determined as
(Dij, Uij) = (Dij, ku(Dij)) , (6)
where the coverage factor k=2 provides a coverage probability of 95 % for sufficiently large
effective number of degrees of freedom of u(Dij). [28].
In this case, u(Dij) is given by
u2(Dij) = u
2(Rlab i) + u
2(Rlab j) + u
2drift, (7)
where u2
drift is the uncertainty in the comparison due to drift of both hygrometers at a given
dew point value, with drift having been assigned an expectation value of value of zero as in
Section 4. For simplicity here, u2
drift, is assigned a single generalised value at each dew point,
irrespective of whether participants measured in immediate succession or separated in time.
The DoE was calculated for each pair of participants at each nominal measurement point. The
results are summarised in tables 6.1 to 6.5. In a small number of cases, where participants
assigned a coverage factor k greater than 2, due to a low effective number of degrees of
freedom of an uncertainty estimate, the larger coverage factor is used to obtain the 95 %
coverage interval for equivalences.
35
Table 6.1 Degree of equivalence between the participants of CCT-K6 at the frost-point temperature -50 °C. DoE is expressed as (Dij, Uij) in degrees Celsius. Instrument drift
uncertainty is included in the uncertainty shown.
Table 6.2 Degree of equivalence between the participants of CCT-K6 at the frost-point temperature -30 °C. DoE is expressed as (Dij, Uij) in degrees Celsius. Instrument drift
uncertainty is included in the uncertainty shown.
-50 °C NPL NMIJ VSL MIKES INTA INRIM NIST NMC NIM VNIIFTRI
NPL 0.037 0.123 0.167 0.136 -0.023 0.048 0.026 0.039 0.014 0.042 0.142 0.036 0.059 0.070 0.074 0.121 0.025 0.038
NMIJ -0.037 0.123 0.131 0.180 -0.060 0.128 -0.011 0.125 -0.022 0.126 0.105 0.124 0.023 0.138 0.038 0.169 -0.012 0.124
VSL -0.167 0.136 -0.131 0.180 -0.191 0.140 -0.142 0.137 -0.153 0.138 -0.025 0.136 -0.108 0.149 -0.093 0.178 -0.142 0.137
MIKES 0.023 0.048 0.060 0.128 0.191 0.140 0.049 0.051 0.038 0.053 0.165 0.049 0.083 0.077 0.098 0.125 0.048 0.050
INTA -0.026 0.039 0.011 0.125 0.142 0.137 -0.049 0.051 -0.011 0.046 0.117 0.040 0.034 0.072 0.049 0.122 -0.001 0.042
INRIM -0.014 0.042 0.022 0.126 0.153 0.138 -0.038 0.053 0.011 0.046 0.128 0.043 0.045 0.074 0.060 0.123 0.011 0.045
NIST -0.142 0.036 -0.105 0.124 0.025 0.136 -0.165 0.049 -0.117 0.040 -0.128 0.043 -0.083 0.071 -0.068 0.121 -0.117 0.039
NMC -0.059 0.070 -0.023 0.138 0.108 0.149 -0.083 0.077 -0.034 0.072 -0.045 0.074 0.083 0.071 0.015 0.135 -0.035 0.072
NIM -0.074 0.121 -0.038 0.169 0.093 0.178 -0.098 0.125 -0.049 0.122 -0.060 0.123 0.068 0.121 -0.015 0.135 -0.049 0.122
VNIIFTRI -0.025 0.038 0.012 0.124 0.142 0.137 -0.048 0.050 0.001 0.042 -0.011 0.045 0.117 0.039 0.035 0.072 0.049 0.122
-30 °C NPL 0 NMIJ VSL MIKES INTA INRIM NIST NMC NIM VNIIFTRI
NPL 0.083 0.080 0.019 0.119 0.018 0.072 0.037 0.069 0.007 0.069 0.106 0.067 0.062 0.083 0.089 0.109 0.047 0.068
NMIJ -0.083 0.080 -0.064 0.115 -0.065 0.066 -0.046 0.062 -0.076 0.062 0.023 0.060 -0.022 0.078 0.006 0.105 -0.037 0.061
VSL -0.019 0.119 0.064 0.115 -0.001 0.110 0.018 0.108 -0.012 0.108 0.087 0.107 0.043 0.118 0.070 0.137 0.028 0.107
MIKES -0.018 0.072 0.065 0.066 0.001 0.110 0.019 0.052 -0.011 0.052 0.088 0.050 0.044 0.070 0.071 0.099 0.029 0.050
INTA -0.037 0.069 0.046 0.062 -0.018 0.108 -0.019 0.052 -0.030 0.048 0.069 0.045 0.025 0.067 0.052 0.097 0.010 0.046
INRIM -0.007 0.069 0.076 0.062 0.012 0.108 0.011 0.052 0.030 0.048 0.099 0.045 0.055 0.066 0.082 0.097 0.040 0.045
NIST -0.106 0.067 -0.023 0.060 -0.087 0.107 -0.088 0.050 -0.069 0.045 -0.099 0.045 -0.044 0.065 -0.017 0.096 -0.059 0.043
NMC -0.062 0.083 0.022 0.078 -0.043 0.118 -0.044 0.070 -0.025 0.067 -0.055 0.066 0.044 0.065 0.027 0.108 -0.015 0.065
NIM -0.089 0.109 -0.006 0.105 -0.070 0.137 -0.071 0.099 -0.052 0.097 -0.082 0.097 0.017 0.096 -0.027 0.108 -0.042 0.096
VNIIFTRI -0.047 0.068 0.037 0.061 -0.028 0.107 -0.029 0.050 -0.010 0.046 -0.040 0.045 0.059 0.043 0.015 0.065 0.042 0.096
36
Table 6.3 Degree of equivalence between the participants of CCT-K6 at the frost-point temperature -10 °C. DoE is expressed as (Dij, Uij) in degrees Celsius. Instrument drift
uncertainty is included in the uncertainty shown.
Table 6.4 Degree of equivalence between the participants of CCT-K6 at the dew-point temperature +1 °C. DoE is expressed as (Dij, Uij) in degrees Celsius. Instrument drift
uncertainty is included in the uncertainty shown.
-10 °C NPL NMIJ VSL MIKES INTA INRIM NIST NMC NIM VNIIFTRI
NPL 0.023 0.070 -0.061 0.057 -0.024 0.056 -0.006 0.054 -0.031 0.055 0.046 0.054 0.036 0.066 0.099 0.104 0.039 0.052
NMIJ -0.023 0.070 -0.084 0.068 -0.046 0.067 -0.028 0.066 -0.054 0.066 0.024 0.065 0.013 0.076 0.076 0.111 0.016 0.064
VSL 0.061 0.057 0.084 0.068 0.038 0.054 0.056 0.052 0.030 0.053 0.107 0.052 0.097 0.064 0.160 0.103 0.100 0.050
MIKES 0.024 0.056 0.046 0.067 -0.038 0.054 0.018 0.051 -0.008 0.052 0.070 0.050 0.059 0.063 0.122 0.103 0.062 0.049
INTA 0.006 0.054 0.028 0.066 -0.056 0.052 -0.018 0.051 -0.026 0.050 0.052 0.048 0.041 0.062 0.104 0.102 0.045 0.047
INRIM 0.031 0.055 0.054 0.066 -0.030 0.053 0.008 0.052 0.026 0.050 0.077 0.049 0.067 0.062 0.130 0.102 0.070 0.048
NIST -0.046 0.054 -0.024 0.065 -0.107 0.052 -0.070 0.050 -0.052 0.048 -0.077 0.049 -0.011 0.061 0.053 0.102 -0.007 0.046
NMC -0.036 0.066 -0.013 0.076 -0.097 0.064 -0.059 0.063 -0.041 0.062 -0.067 0.062 0.011 0.061 0.063 0.109 0.003 0.060
NIM -0.099 0.104 -0.076 0.111 -0.160 0.103 -0.122 0.103 -0.104 0.102 -0.130 0.102 -0.053 0.102 -0.063 0.109 -0.060 0.101
VNIIFTRI -0.039 0.052 -0.016 0.064 -0.100 0.050 -0.062 0.049 -0.045 0.047 -0.070 0.048 0.007 0.046 -0.003 0.060 0.060 0.101
+1 °C NPL NMIJ VSL MIKES INTA INRIM NIST NMC NIM VNIIFTRI
NPL 0.043 0.082 0.101 0.132 0.028 0.076 0.023 0.074 0.034 0.073 0.056 0.074 0.074 0.094 0.116 0.097 0.071 0.073
NMIJ -0.043 0.082 0.058 0.131 -0.015 0.074 -0.020 0.072 -0.009 0.071 0.013 0.072 0.031 0.092 0.073 0.095 0.028 0.071
VSL -0.101 0.132 -0.058 0.131 -0.073 0.127 -0.078 0.126 -0.067 0.126 -0.045 0.126 -0.027 0.139 0.015 0.141 -0.030 0.126
MIKES -0.028 0.076 0.015 0.074 0.073 0.127 -0.005 0.064 0.006 0.063 0.028 0.065 0.046 0.086 0.088 0.090 0.043 0.063
INTA -0.023 0.074 0.020 0.072 0.078 0.126 0.005 0.064 0.012 0.061 0.033 0.062 0.051 0.085 0.093 0.088 0.048 0.061
INRIM -0.034 0.073 0.009 0.071 0.067 0.126 -0.006 0.063 -0.012 0.061 0.022 0.061 0.039 0.084 0.082 0.087 0.037 0.060
NIST -0.056 0.074 -0.013 0.072 0.045 0.126 -0.028 0.065 -0.033 0.062 -0.022 0.061 0.018 0.085 0.060 0.088 0.015 0.062
NMC -0.074 0.094 -0.031 0.092 0.027 0.139 -0.046 0.086 -0.051 0.085 -0.039 0.084 -0.018 0.085 0.042 0.105 -0.003 0.084
NIM -0.116 0.097 -0.073 0.095 -0.015 0.141 -0.088 0.090 -0.093 0.088 -0.082 0.087 -0.060 0.088 -0.042 0.105 -0.045 0.088
VNIIFTRI -0.071 0.073 -0.028 0.071 0.030 0.126 -0.043 0.063 -0.048 0.061 -0.037 0.060 -0.015 0.062 0.003 0.084 0.045 0.088
37
Table 6.5 Degree of equivalence between the participants of CCT-K6 at the dew-point temperature +20 °C. DoE is expressed as (Dij, Uij) in degrees Celsius. Instrument drift
uncertainty is included in the uncertainty shown.
+20 °C NPL NMIJ VSL MIKES INTA INRIM NIST NMC NIM VNIIFTRI
NPL -0.014 0.065 -0.009 0.061 -0.008 0.056 -0.029 0.052 -0.028 0.052 -0.008 0.055 0.014 0.084 0.083 0.077 -0.010 0.051
NMIJ 0.014 0.065 0.005 0.071 0.006 0.067 -0.015 0.064 -0.014 0.064 0.006 0.066 0.028 0.092 0.097 0.085 0.004 0.063
VSL 0.009 0.061 -0.005 0.071 0.002 0.062 -0.020 0.059 -0.019 0.059 0.001 0.061 0.023 0.089 0.092 0.082 -0.001 0.058
MIKES 0.008 0.056 -0.006 0.067 -0.002 0.062 -0.022 0.054 -0.021 0.054 0.000 0.057 0.021 0.086 0.090 0.078 -0.003 0.053
INTA 0.029 0.052 0.015 0.064 0.020 0.059 0.022 0.054 0.001 0.050 0.021 0.053 0.043 0.083 0.112 0.076 0.019 0.049
INRIM 0.028 0.052 0.014 0.064 0.019 0.059 0.021 0.054 -0.001 0.050 0.020 0.053 0.042 0.083 0.111 0.075 0.018 0.049
NIST 0.008 0.055 -0.006 0.066 -0.001 0.061 0.000 0.057 -0.021 0.053 -0.020 0.053 0.022 0.085 0.091 0.077 -0.002 0.052
NMC -0.014 0.084 -0.028 0.092 -0.023 0.089 -0.021 0.086 -0.043 0.083 -0.042 0.083 -0.022 0.085 0.069 0.100 -0.024 0.083
NIM -0.083 0.077 -0.097 0.085 -0.092 0.082 -0.090 0.078 -0.112 0.076 -0.111 0.075 -0.091 0.077 -0.069 0.100 -0.093 0.075
VNIIFTRI 0.010 0.051 -0.004 0.063 0.001 0.058 0.003 0.053 -0.019 0.049 -0.018 0.049 0.002 0.052 0.024 0.083 0.093 0.075
44
7 KEY COMPARISON REFERENCE VALUES (KCRV)
7.1 CALCULATION OF KCRV
In comparisons of dew/frost-point temperature scales, comparison reference values have no
absolute significance outside the comparison. However the availability of a comparison
reference value is essential to the use of comparison results for review of CMC claims.
In this comparison and other corresponding RMO comparisons, a reference value is
calculated for each nominal value of dew point, treating them as separate data populations
for this purpose.
For each nominal dew point value, a key comparison reference value (KCRV) [28] was
calculated as the weighted mean, y, of results xi
𝑦 =𝑥1 𝑢2(𝑥1)⁄ + … +𝑥𝑁 𝑢2(𝑥𝑁)⁄
1 𝑢2(𝑥1)⁄ + … +1 𝑢2(𝑥𝑁)⁄, (8)
this method of calculation having been agreed by CCT Working Group 6. For comparison,
values of arithmetic mean and median were also calculated. The uncertainty in weighted
mean due to dispersion was calculated from [28]
1
𝑢2(𝑦)=
1
𝑢2(𝑥1)+ … +
1
𝑢2(𝑥𝑁). (9)
After collection of participant results, but before circulation of Draft A, results of NIST
at -50 °C and -30 °C were identified as outliers. NIST confirmed that they recognised an
inconsistency with expected results at these values (relative to additional data for another
NIST generator). A multimeter used for comparison measurements was identified as a
possible cause of the inconsistency. However it was not possible to make further
measurement checks, because of a lengthy breakdown of the NIST generator refrigeration
system, and eventual updating of the LFPG facility.
Calculations of weighted mean were made both with and without the outlying results.
Values of arithmetic mean and median were also calculated. These are summarised in
Table 7.1. At +20 °C and -50 °C the median is somewhat lower than the general trend,
which suggests consideration of whether a skew or outlier is present in the data. As well as
the uncertainty in weighted mean due to dispersion, an additional uncertainty in KCRV was
included for the drift of the hygrometers (expectation value zero, with standard uncertainty
as given in Section 4.4). The uncertainties are summarised in Table 7.2.
45
Table 7.1 Values of weighted mean, arithmetic mean and median at each nominal dew point,
estimated from all results, and also after exclusion of outlying results at -50 °C and -30 °C (in italics)
Dew-point
value
°C
Weighted
mean
°C
Arithmetic
mean
°C
Median
°C
-50 +0.028 +0.017 -0.003
-50 +0.055 +0.027 -0.003
-30 +0.072 +0.077 +0.071
-30 +0.090 +0.084 +0.080
-10 +0.096 +0.092 +0.085
1 +0.111 +0.102 +0.098
20 +0.147 +0.134 +0.106
Table 7.2 Standard uncertainties due to variance of weighted mean, combined effect of
hygrometer drift, and their quadrature sum, for each dew point, estimated from all
results, and also after exclusion of outlying results at -50 °C and -30 °C (in italics)
Dew-
point
value
°C
Standard
uncertainty of
weighted mean
°C
Standard uncertainty
due to combined
hygrometer drift
°C
Quadrature
sum
°C
-50 0.005 0.010 0.011
-50 0.006 0.010 0.012
-30 0.005 0.016 0.017
-30 0.006 0.016 0.017
-10 0.004 0.019 0.019
+1 0.004 0.028 0.028
+20 0.004 0.022 0.022
7.2 CHI-SQUARED TEST
A chi-squared test [28] was carried out on the results with and without the identified NIST
outliers, as a measure of the consistency of the data and uncertainties. Based on the
participant reported uncertainties alone, the test fails. Repeating the test with correct
inclusion of uncertainty allowance for instrument drift, the test succeeds for results above -
10 °C, but initially fails for the full set of participant results at -10 °C, -30 °C and -50 °C.
Discrepant results can be identified using the criterion [28]:
)()(2 22
KCRVilabKCRVilab RuRuRR (10)
Inspection of the data and the test for discrepancy show that several participant results
deviate from the KCRV by between 2 and 3 standard uncertainties, u(Rlab i). Only 1
participant (NIST) had any result with greater deviation relative to uncertainty – by more
46
than 4 standard uncertainties at -50 °C. Removal of the NIST results from the KCRV and
chi-squared test at -50 °C and -30 °C allows the remaining results to pass the test at those
points. At -10 °C the chi-squared test fails, but is passed if the VSL result is removed.
The results that cause the chi-squared test to fail at -30 °C and -10 °C are not dramatic
outliers. The decision whether to exclude marginally-outlying data is also a matter of
considering the impact on the KCRV. Inclusion of the NIST outliers at -50 °C and -30 °C
influences the KCRV significantly at those points – reducing it by 0.027 °C and 0.018 °C
respectively. In contrast, exclusion of the VSL -10 °C result would affect the KCRV at that
value by only 0.004 °C, which can be considered not a significant influence. Accordingly,
the NIST results -50 °C and -30 °C have been excluded from the calculation of KCRV, but
the VSL result at -10 °C has been included.
Overall, the chi-squared test is only narrowly passed, suggesting that the uncertainties are
probably not generally overestimated.
7.3 COMPARISON RESULTS PRESENTED IN TERMS OF KCRV
The results of all laboratories relative to the KCRV are shown in Table 7.3 below, and in
figures 7.1 to 7.5, with uncertainties as shown in Table 7.4. The error bars in the graphs
show a combination of the participant reported error with the uncertainty allowance due to
hygrometer drift, at coverage probability of 95 %, using a coverage factor k=2 in most cases
except where participants assigned a higher coverage factor.
Table 7.3 Participant result, Rlab, minus KCRV (weighted mean), in degrees Celsius.
-50 °C -30 °C -10 °C +1 °C +20 °C
NPL +0.014 +0.034 +0.007 +0.045 -0.014
NMIJ -0.023 -0.050 -0.015 +0.002 +0.000
VSL -0.153 +0.015 +0.069 -0.056 -0.005
MIKES +0.037 +0.016 +0.031 +0.017 -0.006
INTA -0.012 -0.003 +0.013 +0.022 +0.016
INRIM 0.000 +0.027 +0.039 +0.010 +0.015
NIST -0.128 -0.072 -0.039 -0.011 -0.006
NMC -0.046 -0.028 -0.028 -0.029 -0.028
NIM -0.060 -0.055 -0.091 -0.071 -0.097
VNIIFTRI -0.011 -0.013 -0.031 -0.026 -0.003
47
Table 7.4 Uncertainty in difference between participant result and KCRV, at 95 % coverage
probability, in degrees Celsius.
-50 °C -30 °C -10 °C +1 °C +20 °C
NPL 0.028 0.064 0.050 0.071 0.049
NMIJ 0.100 0.057 0.062 0.070 0.062
VSL 0.134 0.105 0.047 0.125 0.057
MIKES 0.043 0.046 0.046 0.061 0.051
INTA 0.034 0.041 0.044 0.059 0.048
INRIM 0.037 0.040 0.045 0.058 0.047
NIST 0.030 0.038 0.043 0.060 0.050
NMC 0.067 0.062 0.058 0.083 0.082
NIM 0.119 0.094 0.099 0.086 0.073
VNIIFTRI 0.032 0.038 0.041 0.058 0.046
Figure 7.1 Difference between participant results and KCRV, at the nominal frost-point temperature -50 °C.
Error bars show the expanded uncertainties at coverage probability of 95 %. Estimated uncertainty due to
instrument drift is included. “NPL Final” values are shown but not included in evaluation of KCRV.
Figure 7.2 Difference between participant results and KCRV, at the nominal frost-point temperature -30 °C.
Error bars show the expanded uncertainties at coverage probability of 95 %. Estimated uncertainty due to
instrument drift is included. “NPL Final” values are shown but not included in evaluation of KCRV.
48
Figure 7.3 Difference between participant results and KCRV, at the nominal frost-point temperature -10 °C.
Error bars show the expanded uncertainties at coverage probability of 95 %. Estimated uncertainty due to
instrument drift is included. “NPL Final” values are shown but not included in evaluation of KCRV.
Figure 7.4 Difference between participant results and KCRV, at the nominal dew-point temperature +1 °C.
Error bars show the expanded uncertainties at coverage probability of 95 %. Estimated uncertainty due to
instrument drift is included. “NPL Final” values are shown but not included in evaluation of KCRV.
Figure 7.5 Difference between participant results and KCRV, at the nominal dew-point temperature +20 °C.
Error bars show the expanded uncertainties at coverage probability of 95 %. Estimated uncertainty due to
instrument drift is included. “NPL Final” values are shown but not included in evaluation of KCRV.
49
8 DISCUSSION
The comparison results mainly demonstrate consistency with the key comparison reference
value, within the estimated uncertainties. A small proportion (8 %) of results are not within
two standard uncertainties of the KCRV. Only one participant (NIST) had any result
deviating by more than three standard uncertainties.
It was understood, from the outset of the comparison, that the reproducibility of the
available state-of-the-art travelling standard hygrometers would be barely sufficient to
provide a stringent test of equivalence of standards at the level of uncertainty claimed by the
participants. However, the travelling standards were at least expected to be reliable, given
their history, and so the failures of components were unexpected. Fortunately, there is no
evidence that the instrument values were affected by any of the breakdowns or repairs.
Future dew-point key comparisons can benefit (or already have done) from a new
generation of transfer standard hygrometers that have been improved in several respects.
The long duration of more than six years for participant measurements was far from ideal.
It raises two concerns: potential drift of the travelling standards; and the question of linkage
to regional comparisons that are separated in time by several years.
The drift of the travelling standard hygrometers has been considered in detail in Section 4.
They appear to have been sufficiently stable, but some of the evidence in the drift
assessment is conflicting. Because of that ambiguity, the uncertainty allowed for instrument
drift is slightly conservative in this analysis. Less conservative treatment of drift was also
considered, but would not significantly change the broad outcome of which participant
results were consistent with the KCRV within the uncertainties. In general, the results of
participants with the smaller uncertainties were the most affected by the inclusion and the
extent of drift-related uncertainty.
In evaluating the magnitude and significance of travelling standard drift, and the impact on
KCRV and bilateral equivalences, various other measures have been considered, not
detailed fully here. These included: the character of the within-laboratory deviations; the
pilot initial and final values as a simple measure of drift; the impact of potential drift on
agreement of those measuring early and late in the comparison; and others. None of these
considerations contradicted the chosen approaches to the analysis of the comparison.
Between-instrument consistency (as discussed in Section 4.3) was also reviewed in case it
might provide further insight about drift. While the degree of consistency appears worse for
some of the participants whose agreement with the KCRV is weaker, there was no obvious
further conclusion to be drawn from this.
Two participants, MIKES and NIST, reported doubts about the electrical measurements they
had made during the comparison, using multimeters. For VSL, some results had
unexpectedly high scatter which also could possibly have arisen from electrical
measurement problems – although the cause was not identified.
Linkages between key comparisons are generally of interest and the KCRV is relevant to
these. However, in this field of measurement, the value of the KCRV is only a comparison
parameter, with no absolute significance in the SI (unlike, for example, a fixed-point
temperature in thermometry). To enable valid linkage it is important that RMO and CC
50
comparisons have consistent protocols. For dew-point key comparisons, this consistency is
generally being ensured through review by the CCT Working Group on Key Comparisons.
The consideration of linkages between this key comparison and those of regional metrology
organisations is a matter for further discussion, with the primary responsibility being with
the coordinators of other comparisons requiring links to this one.
9. CONCLUSION
This comparison was lengthy and challenging, because of the numerous difficulties
encountered with the travelling standard hygrometers. However, careful study of the results
does not reveal any shift in hygrometer performance attributable to instrument failures or
repairs. It is therefore believed that the instrument problems did not compromise the results
of the comparison.
Instrument stability over the long period of the comparison was assessed, and drift was
concluded to be low, although with some inconsistency in the evidence at and above -10 °C.
The assessment of drift at these values was not conclusive enough to merit correction for
drift, but an additional uncertainty allowance was made, because of the associated doubt.
With the provisos above, a key comparison reference value was evaluated, together with
bilateral equivalences between pairs of participants, and between participants and the
KCRV. Mainly good agreement was demonstrated between participants.
The comparison was effective despite instrument difficulties. However, comparison
uncertainties would potentially have been reduced if more reliable travelling instruments
had been available at that time, if comparison measurements had been more quickly
completed, and if evidence about drift had been unambiguous.
10. ACKNOWLEDGEMENTS
In addition to the listed authors, Leena Uusipaikka is acknowledged for contributions to the
measurements at MIKES.
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the temperature range -75 °C to 0 °C ”, Proceedings of TEMPMEKO 1999, pp185-190.
[10] Hong Yi, Zhan-yuan Li and Chang-qing Ren, “Evaluation of uncertainty on standard device
of two pressure humidity generator”, Metrology & Meas. Tech. 26 (z1) 90-92 (2006)
[11] Hong Yi et al, “A Hybrid Low Frost Point Generator”, ACTA Metrologica Sinica, 29(5A)
360-363 (2008)
[12] Scace Gregory E, Meyer Christopher W, Miller William W and Hodges Joseph T,” An
overview of the NIST Hybrid Humidity Generator”, 5th
International Symposium on
Humidity and Moisture – ISHM 2006 Brazil, May 02 – 05, 2006 – Rio de Janeiro, Brazil
[13] Scace G E and Hodges J T. "Uncertainty of the NIST low frost-point humidity
generator." Proceedings of TEMPMEKO. 2001.
[14] Wang Li and Victor Tan, "Facilities for Humidity Calibration and Their
Characterisations"; Proc. Tempmeko'96, 6th International Symposium on Temperature
and Thermal Measurement in Industry and Science, Torino, September 10-12, 1996,
pp 589-594
[15] Wang Li and Victor Tan, “Characterization of PSB Frost Point Generator by Using a
High Precision Dew Point Meter”; Proc. Tempmeko’2001, 8th International
Symposium on Temperature and Thermal Measurement in Industry and Science,
Berlin, June 19-21, 2001, pp 339-344
[16] Ochi N, Takahashi C and Kitano H, “Uncertainty of a new NMIJ frost-point
generator”, Papers from the 4th International Symposium on Humidity and Moisture 2
(2002) 61-67.
[17] Takahashi C, Kitano H, Ochi N and Yokota T, “Uncertainty in dew-point hygrometer
calibration by a two-pressure two-temperature humidity generator”, Papers from the
4th International Symposium on Humidity and Moisture (2002) 54-60.
[18] Stevens M and Bell S A, “The NPL Standard Humidity Generator - An analysis of
uncertainty by validation of individual component performance” Measurement Science
and Technology 3 (1992) pp 943-952
[19] Stevens Mark, “The new NPL low frost-point Generator” in Proceedings of
TEMPMEKO '99, 7th International Symposium on Temperature and Thermal
Measurements in Industry and Science, (Delft, 1999), pp191-196 [20] The Russian national standard of gases humidity and traceability system of humidity
measurements. Book of Abstracts. Vol A, Joint International Symposium on Temperature,
Humidity, Moisture in Industry and Science 31 May- 4 June 2010.Portoroz. Slovenia, p 182
52
[21] de Groot M J, Papers and Abstracts from the Third International Symposium on
Humidity and Moisture, National Physical Laboratory, UK, 1998, pp 53-61
[22] Nielsen J and de Groot M J, “Revision and uncertainty evaluation of a primary dew
point generator”, Metrologia 41, n.3 pp 167-172 (2004)
[23] Bosma R and Peruzzi A, “Development of a dew-point generator for gases other than
air and nitrogen and pressures up to 6 MPa”, Int.J.Thermophys. September 2012 33
Issue 8-9, pp 1511-1519
[24] Bosma R, Mutter D and Peruzzi A, “Validation of a dew-point generator for pressures
up to 6 MPa using nitrogen and air”, Metrologia 49 (2012), 597-606
[25] CIPM, MRA. "Mutual recognition of national measurement standards and of calibration and
measurement certificates issued by national metrology institutes." Comité International des
Poids et Measures (1999).
[26] Smith, Ian, Software for determining polynomial calibration functions
by generalised least squares: user manual NPL REPORT MS 11, December 2010
(Teddington, UK: National Physical Laboratory)
[27] Measurement comparisons in the CIPM MRA, CIPM MRA-D-05, Version 1.4 June
2013, www.bipm.org/utils/common/CIPM_MRA/CIPM_MRA-D-05.pdf (accessed
4 October 2013)
[28] Cox M, “The evaluation of key comparison data”, Metrologia 39 (2002) 589-595
53
APPENDIX 1: TECHNICAL PROTOCOL
The following pages show the technical protocol for CCT-K6, together with its Appendix 5
listing conditions to be reported as background information. The names of participating
institutes and the measurement sequence shown are those at the time the comparison started.
In addition (not shown here) the protocol included appendices giving: participant contact
details; reporting template to document safe receipt of instruments and checklist of
associated items; IEC 60751 (EN 60751) formula for nominal resistance-temperature
relationship (see Section 3.2); and MS Excel reporting templates for comparison results and
uncertainty.
54
International Committee for Weights and Measures (CIPM)
Consultative Committee for Thermometry (CCT)
CCT-K6 Key Comparison of Humidity Standards
Dew/Frost-Point Temperature –50 °C to +20 °C
Technical protocol
55
1. INTRODUCTION
1.1 Under the Mutual Recognition Arrangement (MRA)3 the metrological equivalence
of national measurement standards will be determined by a set of key comparisons
chosen and organized by the Consultative Committees of the CIPM working closely
with the Regional Metrology Organizations (RMOs).
1.2 At its 20th meeting in April 2000, the Consultative Committee for Thermometry,
CCT, considered a Key Comparison on humidity as imperative for the related
laboratories. It was decided that the Working Group on Humidity Measurements
(WG 6) be called upon to draft a key comparison protocol.
1.3 To date, the Working Group consists of 13 members, the National Institute of
Standards and Technology, USA (NIST, Chair), the National Physical Laboratory,
UK (NPL), the National Metrology Institute of Japan (NMIJ-AIST), the Korea
Research Institute of Standards and Science, Republic of Korea (KRISS), the
Standards, Productivity and Innovation Board, Singapore (SPRING Singapore), the
National Research Centre for Certified Reference Materials, China (NRCCRM) the
Consiglio Nazionale delle Ricerche - Istituto di Metrologia "G. Colonnetti", Italy
(IMGC), the Bureau National de Métrologie - Cetiat, France (BNM-Cetiat), the D.I.
Mendeleyev Institute of Metrology, Russia (VNIIM), Nederlands Meetinstituut –
Van Swinden Laboratorium, the Netherlands (NMi-VSL), the Physikalisch-
Technische Bundesanstalt, Germany (PTB), the Measurement Standards Laboratory,
New Zealand (MSL) and the Ulusal Metroloji Enstitüsü, Turkey (UME).
1.4 This technical protocol has been drawn up by the working group described above,
and in consultation with the nominated participants listed in Section 2.
1.5 The procedures outlined in this document cover the technical procedure to be
followed during measurement of the transfer standards. The procedure, which
follows the guidelines established by the BIPM4, is based on current best practice in
the use of dew/frost-point hygrometers and takes account of the experience gained
from the regional comparisons and that of the working group over the years.
1.6 This comparison is aimed at establishing the degree of equivalence between
realisations of local scales of dew/frost-point temperature of humid gas, in the
range -50 °C to +20 °C, among the participating national measurement institutes.
3 MRA, Mutual Recognition Arrangement, BIPM, 1999.
4 T.J. Quinn, "Guidelines for key comparisons carried out by Consultative Committees," Appendix F to the
MRA, BIPM, Paris.
56
2. ORGANIZATION
2.1 Participants
2.1.1 A list of participants representing RMOs of SIM, APMP, EUROMET and
COOMET has been approved by the CCT. Details of mailing and electronic
addresses are given in Appendix 1. The nominated institutes5* are:
Centre for Metrology and Accreditation (MIKES) Finland
DI Mendeleyev Institute of Metrology (VNIIM) Russia
Instituto Nacional de Técnica Aeroespacial (CEM/INTA) Spain
Istituto di Metrologia “G. Colonnetti” (IMGC) Italy
National Institute for Standards and Technology (NIST) USA
National Metrology Centre (SPRING) Singapore
National Metrology Institute of Japan (NMIJ) Japan
National Physical Laboratory (NPL) UK
National Research Centre For Certified Reference Materials (NRCCRM) China
Nederlands Meetinsituut (NMi)
Netherlands
2.1.2 NPL is the Pilot of the key comparison, taking main responsibility for running the
key comparison.
2.1.3 NMIJ is assigned as Assistant Pilot in verifying the data analysis for the draft A.
The assistant will also perform additional measurements as required.
2.1.4 By their declared intention to participate in this key comparison, the laboratories
accept the general instructions and the technical protocol written down in this
document and commit themselves to follow strictly the procedures of this protocol as
well as the version of the "Guidelines for Key Comparisons" in effect at the time of
the initiation of the Key Comparison.
2.1.5 Once the protocol and list of participants have been approved, no change to the
protocol or list of participants may be made without prior agreement of all
participants.
2.1.6 All participants must be able to submit an uncertainty budget of their humidity
standard generators.
2.2 Method of comparison
2.2.1 The key comparison is a comparison of the realisations of the scale of dew-point
temperature at the participating national institutes.
2.2.2 The comparison will be made by calibration of a pair of travelling transfer standards.
Each transfer standard will independently measure dew/frost-point temperature of a
* At the time of planning the comparison, several participant institutes were known by previous names: INRIM
was IMGC, NIM was NRC-CRM, NMC was SPRING, and VSL was NMi.
57
sample of moist gas (air or nitrogen) produced by a participant's standard generator
using the same measuring process.
2.2.3 Simultaneous measurements using a pair of standards gives information about the
within-laboratory consistency of the measurements, the reproducibility of the
instrument performance, and continuous feedback about the successful transport of
the instruments without any major shift in performance.
2.2.4 The comparison will take the form of a closed circulation in two consecutive loops.
There is one pair of hygrometers, which are at all times measured simultaneously.
Measurements will start in the pilot laboratory. The assistant will perform the
measurements next. The other participants in Loop 1 will then make comparison
measurements at the dew/frost-point temperatures required. After loop 1, the
travelling standards will return to the Pilot for checks mid-way through the
comparison, and optionally to the Assistant Pilot to repeat these checks. The
comparison will then proceed through loop 2, and the last participant will then return
the transfer standards to the pilot to carry out final measurements to monitor drift.
The assistant will also carry out repeat measurements following those of the pilot.
The sequence would therefore be*: NPL NMIJ MIKES NMi IMGC
INTA NPL ( NMIJ optional) NIST SPRING NRCCRM VNIIM
NPL NMIJ. Allowing between 6 and 8 weeks per set of measurements (and
additional time for shipping), this set of measurements will take up to 32 months.
2.2.5 The proposed circulation scheme for travelling standards for CCT dew-point key
comparison is illustrated below*.
* At the time of planning the comparison, several participant institutes were known by previous names: INRIM
was IMGC, NIM was NRC-CRM, NMC was SPRING, and VSL was NMi
58
2.2.6 All results are to be communicated directly to the pilot within six weeks of the
completion of the measurements by a laboratory.
2.2.7 Each laboratory has estimated a time for measurement and transportation. If for
some reason, the measurement facility is not ready or customs clearance takes too
much time in a country, the participating laboratory must contact the pilot laboratory
immediately. Exclusion of a participant's results from the report may occur if the
results are not available in time to prepare the draft report.
2.2.8 In case of serious difficulty with customs, or other delays which might over-run the
time period of the ATA Carnet or temporary import licence, the pilot may request
the instruments be returned to NPL, or the sequence of participation be changed to
the most practical arrangement.
2.3 Handling of artefacts
2.3.1 The artefacts should be examined immediately upon receipt at the laboratory. All
participants are expected to follow all instructions in the operator's manual provided
by the instrument manufacturers for proper unpacking, subsequent packing and
shipping to the next participant. During packing and unpacking, all participants
should check the contents with the packing list including the operator's manual.
2.3.2 The transfer standards should only be handled by authorized persons and stored in
such a way as to prevent damage.
NPL
NMIJ
Pilot
Assistant Pilot
Participants
IMGC
MIKES NIST
NMi
NRCCRM
SPRING
VNIIM INTA
Loop 1 Loop 2
59
2.3.3 During operation of the transfer standards, if there is any unusual occurrence, e.g.,
loss of heating or cooling control, the pilot laboratory should be notified
immediately before proceeding.
2.4 Transport of artefacts
2.4.1 The transportation process begins when the artefact leaves the sending laboratory
and does not end until it reaches the destination laboratory. All participants should
follow the following general guidelines:
(1) Plan the shipment well in advance. The recipient should be aware of any
customs issues in their country that would delay the testing schedule. The shipping
laboratory must be aware of any national regulations covering the travelling standard
to be exported;
(2) Mark the shipping container "FRAGILE SCIENTIFIC INSTRUMENTS" “TO
BE OPENED ONLY BY LABORATORY STAFF” and with arrows showing
"THIS WAY UP"; attach tip and shock indicators if such devices are available;
(3) Determine the best way to ship the travelling standard to the next participant;
(4) Obtain the recipient's exact shipping address. If possible, have it shipped
directly to the laboratory;
(5) Coordinate the shipping schedule with the recipient. The sending laboratory
should provide the recipient with the carrier, the exact travel mode, and the
estimated time of arrival;
(6) Instruct the recipient to confirm receipt and condition upon arrival to the sender
and the pilot. A form for reporting on the receipt of the travelling standards is shown
in Appendix 2.
2.4.2 Each transfer standard is supplied with its shipping container, which is sufficiently
robust to ensure safe transportation.
2.4.3 The artefacts will be accompanied by a suitable customs ATA Carnet or temporary
import bond (TIB) (as deemed most appropriate by the pilot laboratory) and
documentation uniquely identifying the item. Care should be taken with the timing
of the ATA Carnet, which only lasts for one year.
2.5. Shipping Costs
2.5.1 Each laboratory is responsible for the cost of shipping to the next participant
including any customs charges and insurance. The insurance should be sufficient to
cover the costs of the travelling standards and any damages that could occur.
60
2.6. Timetable
Activity Start Month Provisional date
Submission of a revised technical protocol to
Participants for unanimous approval
Re-submitted Feb
2003
Submission of revised protocol to CCT/WG7 for
approval
Mar 2003
Travelling standards characterized by the pilot 2002-early 2003
Pilot’s fist set of key comparison measurements
according to the protocol
Month 1-2 May-Jun 2003
Travelling standards sent to assistant pilot and
successive participants for measurements
Month 3-12 July 2003
Travelling standards re-measured by pilot(s) at
mid-point
Month 13-14 May-Jun 2004
Completion of measurements Month 28 approx Mid 2005
Draft A ready Month 32 approx Late 2005
Deadline for comments on draft A Month 35 approx Early 2006
Draft B ready and submitted to CCT Month 40 approx Mid 2006
3. DESCRIPTION OF THE TRANSFER STANDARDS
3.1. Artefacts
3.1.1 Two travelling standards selected for the key comparison are state-of-the-art,
commercially available chilled-mirror type of dew-point hygrometers. They have
proven to be robust with known performance characteristics such as repeatability
and transportability.
3.1.2 Details of travelling standards:
Travelling Standard #1 Travelling Standard #2
(Figure 1) (Figure 2)
Model: Michell S4000 MBW DP 3DSH III K-1806
Serial Number: 114155 / 91527 92-0319
Size
(in Packing case): 60 cm x 65 cm x 105 cm 60 cm x 55 cm x 60 cm
Weight (in Packing case): 55 kg 55 kg
Manufacturer: Michell Instruments, UK MBW Elektronik AG,
Switzerland
Owner: NPL, UK CEM-INTA, Spain
Electrical supply: 240 V 50 Hz 240 V 50 Hz
Electrical connection:2 × UK 3-pin plugs 1 × European 2-pin plug
Power: 1500 W total 500 W
(100 W plus 1400W approx)
Approximate value £25 000 £15 000
for insurance and
customs declaration
61
Figure 1. Travelling standard 1, Michell S4000
Figure 2. Travelling standard 2, MBW
62
4. MEASUREMENT INSTRUCTIONS
4.1 Measurement process
4.1.1 All participants should refer to the operating manuals for instructions and
precautions for using the travelling standards. Participants may perform any initial
checks of the operation of the hygrometers that would be performed for a normal
calibration. In the case of an unexpected instrument failure at a participant institute,
the pilot institute should be informed in order to revise the time schedule, if
necessary, as early as possible.
4.1.2 Sample gas generated by a participant's standard generator, is introduced into the
inlet of a travelling standard hygrometer through a stainless steel tube terminating
with a 6 mm Swagelok fitting for the Michell and ¼ inch Swagelok fitting for the
MBW. The instruments should be connected in parallel. For dew points near ambient
temperature (e.g. +20 °C) normal precautions (heating of pipework) should be used
to protect against condensation in sample lines.
4.1.3 A total of five dew-point temperatures humidity levels are used for the comparison
at nominal values of +20 °C and +1 °C and frost-point temperatures at nominal
values of –10 °C, -30 °C and –50 °C. The value of +1 °C nominally represents 0 °C,
while avoiding any complication due to phase change between water and ice.
4.1.4 At –10 °C, the applied condition should be generated with respect to ice in the
saturator of a single-pressure generator. Where a two-pressure generator is used, the
phase in the saturator at elevated pressure will be according to local procedure, to
result in a water vapour pressure corresponding to saturation over ice at –10 °C at
the pressure of the travelling standards. Participants should report the applied
condition in terms of frost-point temperature. The phase of condensate apparent on
the mirrors of the travelling standards should also be reported. At -30 °C and –50 °C,
all data will be assumed to be with respect to ice unless otherwise reported.
4.1.5 Measurements should be made in rising order of dew/frost point.
4.1.6 The condensate should be cleared and re-formed for each value or repetition of
dew/frost point.
4.1.7 The values of dew/frost point applied to the travelling standards should be within
±0.5 °C of the five agreed nominal values for the comparison, and ideally closer than
this. Deviations greater than this may increase the uncertainty in the comparison, for
a particular result.
4.1.8 The conditions for operation of the travelling standard Michell S4000:
(1) Set the Michell S4000 to “Standby” and “Manual”.
(2) Clean the mirror surface using cotton tips with distilled or de-ionised water. This
may be preceded by initial cleaning with alcohol if necessary
(3) Set the coolant temperature to 30 °C above the generated frost point, for
63
measuring frost-point temperatures of –50 °C and –30 °C. The cooling must be
switched off for all other points.
(4) Set the indicated flow rate of sample gas at approximately 0.5 litres per minute.
(5) Monitor the cooling as detailed in 4.2.3 below
(6) After the cooling has stabilised for 20 minutes press the “Initiate” button to
initiate an optical balance cycle. Set the “Optical Balance Control” to the centre
position. When the balance cycle is complete switch from “Standby” to “Operate”.
(7) A cable is connected between the 100 °C cut-out socket of the measurement head
and the temperature measurement socket of the monitor. This is to allow monitoring
of the operating temperature of the back of the Peltier element. When connected in
this way, the hygrometer display and the analogue output both indicate the Peltier
temperature (not the dew/frost-point). The analogue output is nominally 10 mV per
degree Celsius, with 0 volts equal to 0 °C.
(8) The dew/frost-point indication of the hygrometer is measured directly from the
hygrometer PRT resistance, using the supplied cable (See below, 4.2 Data
collection).
4.1.9 The conditions for operation of the travelling standard MBW K1806:
IMPORTANT:
Due to the nature of the mechanical configuration of the head and endoscope, the
head should only be opened once the following instructions have been read and fully
understood. Failure to observe these may result in severe damage to the transfer
standard. The unit is provided with a blank outer cover for transport.
(1) Ensure the service jack is inserted and set the MBW to Standby, with the
automatic mirror check set to “Off”.
(2) Set the mode switch to “Cooler Temp” and set the temperature to 30°C. Wait for
the mirror temperature indication to reach at least 25 °C.
(3) In order to gain access to the mirror for cleaning, carefully follow the instructions
below:
-Starting from the closed position “at 6 o’clock”, turn the bayonet socket release of
the endoscope 90 ° anti-clockwise until the notch on the endoscope guide tube and
the rotatable arm are aligned.
- Gently withdraw the endoscope. (Special care must be observed to ensure no
bending moment is applied to the endoscope at any time).
- Turn the outer blue alloy head cover anti-clockwise using the knurled surface (not
the endoscope guide tube).
- Remove the grey head cover along the guide pin.
- The mirror is now ready for cleaning.
(4) Clean the mirror surface using cotton buds with distilled or de-ionised water.
This may be preceded by initial cleaning with alcohol if necessary.
(5) In order to replace the measurement head cover, carefully follow the instructions
below:
- Replace the grey head cover, aligning the hole with the guide pin.
- Replace the outer blue alloy head cover by turning it clockwise until the endoscope
guide tube is at the “12 o’clock” position. This should only be finger-tight. Correct
alignment can be checked by observing the light emitted from the head, ensuring that
the full circular cross-section of the tube (reduced by the internal o-ring) is visible.
- Slowly insert the endoscope until a slight resistance is felt as the tip touches the o-
ring.
64
If the endoscope cannot be inserted smoothly, remove and slightly adjust the
position of the outer head cover. Once the endoscope passes the o-ring, align the
notch on the endoscope with that of the guide tube, at the 6 o’clock position. Once
the endoscope has been fully inserted, starting from the open position “at 3 o’clock”
with the two notches aligned, turn the bayonet socket release of the endoscope 90 °
clockwise.
IMPORTANT:
Never turn the head with the endoscope inserted. Special care must be observed to
ensure no bending moment is applied to the endoscope at any time.
(6) Do not adjust the light intensity potentiometer. If the mirror check fails consult
the pilot before proceeding.
(7) Control the flow rate of sample gas at approximately 30 litres per hour.
(8) Ensure the cooler mode switch is set to “Cooler Temp” and set the temperature to
30 °C higher than a nominal frost-point temperature to be measured. This is a setting
(nominal value) and the actual value achieved will not be exactly the set value.
(Note: For the measurement points below 0 °C, ensure that the hygrometer has been
adequately purged by the sample gas to a dew-point temperature below the nominal
cooler temperature setting, before setting the cooler temperature.)
(9) Monitor the cooling as detailed in 4.2.3 below.
(10) After the cooling has stabilised for 20 minutes, ensure the service jack is
inserted and activate the “Mirror Check”. When this is complete, take the MBW off
“Standby”.
(11) During the mirror check, when the mirror is heated, the pointer should lie just to
the left of the boundary between the red and green backgrounds.
(12) Once the mirror check has finalised (the illumination of the meter is
extinguished), the service jack is replaced by the measurement cable provided and
the potentiometer attached to the cable adjusted until the indication of the
hygrometer display is nominally “+60 °C”. This cable provides direct electrical
access to the PRT in the mirror.
IMPORTANT:
Once the measurement cable is connected to the hygrometer, the Manual “Mirror
Check” function must not be activated and the automatic function must remain in the
“Off” position.
(13) Hygrometer head heater is to remain off during all measurements.
4.1.10 Each measurement should be conducted with the instruments measuring in parallel
and nominally simultaneously. Each dew/frost-point temperature should be
separately repeated (reproduced) four times, to reduce the effect of any
irreproducibility of the travelling standards.
4.1.11 Participants should avoid lengthy additional measurements, except those necessary
to give confidence in the results of this comparison.
4.1.12 The transfer standards used in this comparison must not be modified, adjusted, or
used for any purpose other than described in this document, nor given to any party
other than the participants in the comparison.
4.1.13 The Pilot will make an assessment of any drift in the travelling standards during the
comparison, based on measurements at the Pilot laboratory at the beginning, middle
and end of the comparison period, and in case of doubt using optional extra
65
measurements at the Assistant pilot laboratory. If significant drift is found, then this
will be taken into account in the final overall analysis of the comparison.
4.1.14 If unacceptable performance or failure of a travelling standard is detected, the Pilot
will propose a course of action, subject to agreement of the participants.
4.2. Data collection
4.2.1 In the travelling standards, a 100-ohm platinum resistance thermometer (PRT) is
embedded beneath the surface of the chilled-mirror to measure the dew/frost-point
temperature. The current input to the PRT should be nominally 1 mA. The resistance
of the PRT should be measured using a calibrated multi-meter or a resistance bridge,
and then converted to a corresponding nominal dew/frost-point temperature using
the reference function of IEC 60751 as shown in Appendix 3. This reference
function should be used to convert resistance to (arbitrary nominal) temperature.
4.2.2 At each measured value, the mean and standard deviation of multiple readings of the
resistance of the PRT should be monitored. Participants may apply their own criteria
of stability for acceptance of measurements. When hygrometer is in equilibrium with
the gas sample, the standard deviation of a set of 10 resistance readings, taken over a
period of 10 to 20 minutes, is likely to be no more than 0.010 ohms or 0.025 °C
approximately.
4.2.3 As a supporting measurement, the coolant/Peltier temperature in the travelling
standards should be monitored. The mean and standard deviation a set of 10
readings, taken over the same period as the frost point measurements should be
reported. For the Michell, an analogue voltage signal from the USER I/O is
monitored while the 100 °C cut-out socket of the measurement head is connected to
the temperature measurement socket of the monitor. The output is nominally 10 mV
per °C, with 0 V corresponding to 0 °C. This temperature will not be the same as the
set temperature but is an indication of the temperature of the heat exchanger behind
the Peltier cooler. For the MBW the analogue voltage output from the Cooler Temp
plug is monitored (cables supplied). In this case also, the output is 10 mV per °C,
with 0 V=0 °C.
4.2.4 Values reported for dew/frost-point temperatures produced by a participant's
standard generator should be the value applied to the instruments, after any
allowances for pressure and temperature differences between the point of realisation
(laboratory standard generator) and the point of use (travelling standards).
4.2.5 The data reported for the pair of instruments should be for simultaneous or near-
simultaneous measurement of the same applied condition.
5. REPORTING OF MEASUREMENT RESULTS
5.1 Participants must report their measurement results of four repeated experiments,
within six weeks of completing their measurements.
66
5.2 The pilot should accumulate data continually and should analyse the results for
possible anomalies in the travelling standard. If problems arise, the pilot should
consult with the participant that submitted the data as soon as possible, and certainly
before the distribution of Draft A of the Report of the comparison.
5.3 The parameter to be compared between laboratories in CCT-K6 is the mean
difference found between the laboratory standard generator and the travelling
standards. Note that the values of dew-point temperature reported for the travelling
standards are “arbitrary” values calculated from the measured resistance output. The
travelling standards are used simply as comparators.
5.4 Participants should report results to the pilot in terms of dew/frost-point temperature.
The main measurement results comprise:
values of dew/frost-point applied to the travelling standards, and associated
standard uncertainty
values measured using both travelling standards simultaneously (and their
associated standard uncertainties derived from standard deviation of the set
of readings)
values of difference between applied dew/frost point and measured dew/frost
point.
A provisional template for reporting results is shown in Appendix 4, and can be
made available to participants in electronic form as an Excel spreadsheet. Use of this
format, including calculations of means and differences, allows participants to see
clearly the values and uncertainties of the parameters they are submitting for
comparison.
5.5 From the data measured by each participant, results will be analysed in terms of
differences between applied and measured dew points. In each case, the difference
will be taken between the applied (realised) value and the mean (mid-point) between
the two hygrometer values.
5.6 In addition, the difference between the two hygrometer readings on all occasions
will be analysed and will serve as a check of consistency.
5.7 The participants should report the conditions of realisation and measurement, as
background information to support the main results. These conditions should
include, where relevant, pressure and temperature in saturator, pressure difference
between saturator and travelling standards, measurement traceability, frequency of
AC (or DC) resistance measurement, travelling standard coolant measurements, and
other items. A provisional checklist for reporting conditions of measurement is
shown in Appendix 5.
5.8 Participants should provide a general description of the operation of their dew/frost-
point apparatus.
5.9 Participants should also provide an example plot of equilibrium condition (resistance
versus time) at a nominal frost-point temperature of -30 °C, over a suggested period
of at least one hour.
67
5.10 Any information obtained relating to the use of any results obtained by a participant
during the course of the comparison shall be sent only to the pilot laboratory and as
quickly as possible. The pilot laboratory will be responsible for coordinating how the
information should be disseminated to other participants. No communication
whatsoever regarding any details of the comparison other than the general conditions
described in this protocol shall occur between any of the participants or any party
external to the comparison without the written consent of the pilot laboratory. The
pilot laboratory will in turn seek permission of all the participants. This is to ensure
that no bias from whatever accidental means can occur. These constraints on
communication apply until the circulation of Draft A of the report of the
comparisons.
5.11 If a participant significantly delays reporting of results to the Pilot, then a deadline
will be agreed among the participants. If that deadline is not met, then inclusion of
those results in the comparison report will not be guaranteed.
6. UNCERTAINTY OF MEASUREMENT
6.1 The uncertainty of the key comparison results will be derived from some or all of:
o the quoted uncertainty of the dew/frost-point realisation (applied dew/frost point)
including any uncertainties due to pressure drop or other influences acting
between the point of realisation and the point of use (travelling standards).
o the estimated uncertainty relating to the short-term stability of the travelling
standards at the time of measurement
o the estimated uncertainty due to any drift of a travelling standard over the period
of the comparison (estimated by the pilot)
o the estimated uncertainty in mean values due to dispersion of repeated results
(reflecting the combined reproducibility of generator and travelling standards)
o the estimated uncertainty due to the resolution of the travelling standards (if
found to be significant)
o the estimated uncertainty due to non-linearity of the travelling standard in any
case where measurements are significantly away from the agreed nominal value
o the estimated covariance between applied (generator) and measured (travelling
standard) values of dew/frost-point (if found to be significant)
and
o any other components of uncertainty that are thought to be significant
6.2 Participants are required to submit detailed analyses of uncertainty for their dew-
point standards. Uncertainty analyses should be according to the approach given in
the ISO Guide to the Expression of Uncertainty of Measurement. A list of the all
significant components of the uncertainty budget should be evaluated, and should
support the quoted uncertainties. Evaluations should be given at a level of one
standard uncertainty. Type B estimates of uncertainty may be regarded as having
infinite degrees of freedom, or an alternative estimate of the number of degrees of
freedom may be made following the methods in the ISO Guide. A provisional
template for documentation of uncertainties is shown in Appendix 6, and can be
made available to participants in electronic form as an Excel spreadsheet. Individual
institutes may add to the template any additional uncertainties they consider relevant.
68
6.3 The pilot laboratory will collect draft uncertainty budgets as background information
to the uncertainties quoted by participants for the comparison measurements. The
pilot will review the uncertainty budgets for consistency among participants.
6.4 The uncertainty budget stated by the participating laboratory should be referenced to
an internal report and/or a published article.
7. DETERMINATION OF THE KEY COMPARISON REFERENCE VALUE
7.1 The outputs of the key comparison are expected to be:
Results of individual participants for comparison of the hygrometers against their
dew point reference in terms of mean values for each hygrometer at each measured
value, estimated standard uncertainty of each mean result and of comparison process
if necessary.
Estimates of bilateral equivalence between every pair of participants at each
measured dew point
A key comparison reference value (KCRV) for each nominal value of dew/frost
point in the comparison. The KCRV might be calculated as the arithmetic mean of
all valid results, or a weighted mean.
Estimates of equivalence of each participant to the KCRV. This might be expressed
in terms of the Degree of Equivalence (DOE) given as a difference and its
uncertainty (∆ ±U), in °C.
7.2 Values of the above will be reached by an appropriate method proposed by the Pilot,
subject to confirmation by the Assistant Pilot and agreement of all participants and
confirmation by CCT Working Groups 6 (Humidity) and 7 (Key Comparisons).
7.3 In the field of dew-point standards, the KCRV does not have any absolute
significance with respect to an SI unit. It is calculated only for purposes such as the
presentation and inter-relation of key comparison data for the MRA.
7.4 The Pilot will make an assessment of any drift in the travelling standards during the
comparison. The assessment will be based on initial measurements by the Pilot and
Assistant Pilot, together with measurements when the instruments return to the pilot
mid-way through the comparison (repeated by the Assistant Pilot if necessary), and
final measurement by both Pilot and Assistant Pilot. If significant drift of one or both
travelling standards is observed, then this will be taken into account in the final
overall analysis of the comparison. This may be by assigning a time-dependent value
to the KCRV, or by other suitable method so that estimates of equivalence can be
meaningfully calculated between results taken at different times.
7.5 If a travelling standard fails or performs poorly during the comparison, the Pilot and
Assistant Pilot will propose a course of action, subject to agreement of the
participants. If the results of one of the travelling standards (from some or all
participants) are deemed un-usable, and if measurements cannot be re-attempted, the
69
KCRV and estimates of equivalence may be based on the results of satisfactory
measurements using only one travelling standard.
70
APPENDIX 5. PROVISIONAL CHECKLIST FOR REPORTING OF
CONDITIONS OF MEASUREMENT
The following is guidance for reporting of the background information to the key
comparison measurements. This information is likely to be of secondary importance, but
will become relevant if there should be any need to resolve anomalies which might appear
in the results. Reporting of the main results is outlined in Appendix 4.
The report should include the following information:
A full description of the humidity generator used in the comparison and the
traceability of the realisation to the SI, including
o The gas used (air or nitrogen)
o The connection between the hygrometer and the standard - tubing material
and dimensions
o Description of cleaning the mirror
o Value of flow rate set for each hygrometer
o Frequency of AC (or DC) resistance measurement of hygrometer PRTs, and
current used.
o Description of any problems with the hygrometers, or with the participant’s
generator system.
For each separate repetition of each measurement point:
o Applied reference value(s) (generated dew-point temperature determined by
the generator, after any correction for pressure drop to the point of use)
o Standard deviation of the applied value(s)
o Standard uncertainty of the applied value(s)
o Values indicated by the travelling standard hygrometers
o Standard deviation of the hygrometer indicated values
o Difference between the applied (generator) value and the measured
(hygrometer) values
o Combined standard uncertainty of the difference
o Date when the measurements were carried out
o Hygrometer coolant temperature settings
o Measured temperatures of MBW coolant and Michell Peltier
o Temperature and pressure in saturator of generator
o Pressure difference between the hygrometer and the generator, and value of
correction(s) applied to compensate for this, if any.
o Environmental conditions (temperature, humidity, pressure)
o Number of recorded values
o Stabilisation time
o Time interval taken to record the values
o “Raw data” in units of resistance for the PRT measurements, and in units of
voltage for the analogue outputs
71
APPENDIX 2: RESULTS REPORTED BY THE PARTICIPANTS
The participant reported results are shown on the following pages in the form of extracts
pasted from the MS Excel reporting template for the comparisons. In general, each result is a
standard uncertainty reported at sufficiently high number of effective degrees of freedom that
a coverage factor k=2 can be used to give a coverage probability of 95 %. In cases where a
lower number of effective degrees of freedom necessitated a larger coverage factor, to give a
95 % coverage probability, participants were asked to calculate and report that, and where
relevant details are given in Appendix 3.
72
NPL
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -50 °C Lab name NPL
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -50.16478 80.26079 -50.11455 -0.05023 -50.16478 80.1708 -50.341085 0.176305
Meas 2 -50.160017 80.26184 -50.11191 -0.048107 -50.160017 80.17319 -50.335115 0.175098
Meas 3 -50.16478 80.25266 -50.13502 -0.02976 -50.16478 80.16229 -50.3625 0.19772
Meas 4 -50.37259 80.1762 -50.32754 -0.04505 -50.37259 80.08754 -50.55071 0.17812
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.015 0.015 0.015 0.015 0.015 0.015 0.015 0.015
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.009 0.009 0.018 0.018 0.023 0.011 0.011 0.011
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.017 0.017 0.023 0.023 0.027 0.019 0.019 0.019
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.04329 0.181811
Type A standard uncertainty due to reproducibility of difference results 0.009 0.011
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.014 0.015
I column
Difference between 2 means (each the mean of 4 results) -0.2251 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** # 0.069262 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** # 0.010 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -30 °C Lab name NPL
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -29.854992 88.2796 -29.853102 -0.00189 -29.854992 88.19335 -30.071659 0.216667
Meas 2 -29.67928 88.32125 -29.747505 0.068225 -29.67928 88.23359 -29.969635 0.290355
Meas 3 -29.91683 88.25534 -29.914606 -0.002224 -29.91683 88.17278 -30.123804 0.206974
Meas 4 -29.845501 88.2749502 -29.86489 0.019389 -29.845501 88.20569 -30.040387 0.194886
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.015 0.015 0.015 0.015 0.015 0.015 0.015 0.015
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.0127 0.0137 0.0084 0.0132 0.0074 0.0122 0.0199 0.00964
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.020 0.020 0.017 0.020 0.017 0.019 0.025 0.018
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.020875 0.227221
Type A standard uncertainty due to reproducibility of difference results 0.033 0.043
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.035 0.044
I column
Difference between 2 means (each the mean of 4 results) -0.20635 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** # 0.124048 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** # 0.028 (uncertainty in the parameter being compared)
73
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -10 °C Lab name NPL
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -9.7817855 96.15944 -9.812339 0.0305535 -9.7817855 95.59664 -10.0178 0.2360145
Meas 2 -9.7452112 96.18957 -9.73547 -0.0097412 -9.7452112 95.62716 -9.947 0.2017888
Meas 3 -9.6436027 95.76809 -9.62459 -0.0190127 -9.6436027 95.67374 -9.84021 0.1966073
Meas 4 -9.8018231 95.69577 -9.79003 -0.0117931 -9.8018231 95.60114 -10.0074 0.2055769
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.015 0.015 0.015 0.015 0.015 0.015 0.015 0.015
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.017 0.0148 0.005 0.003 0.011 0.0028 0.004 0.0015
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.023 0.021 0.016 0.015 0.019 0.015 0.016 0.015
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.0025 0.209996875
Type A standard uncertainty due to reproducibility of difference results 0.022 0.018
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.024 0.019
I column
Difference between 2 means (each the mean of 4 results) -0.2125 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** # 0.103749 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** # 0.016 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 1 °C Lab name NPL
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 0.860989 100.33017 0.844899 0.01608968 0.860989 100.24616 0.630002 0.23098633
Meas 2 0.863954 100.32975 0.844899 0.01905536 0.863954 100.23194 0.5946978 0.26925653
Meas 3 0.827529 100.30271 0.77462 0.05290925 0.827529 100.20634 0.527727 0.29940736
Meas 4 1.26788017 100.47733 1.221544 0.04494065 1.26788017 100.37381 0.956587 0.31546763
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.015 0.015 0.015 0.015 0.015 0.015 0.015 0.015
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.006 0.0062 0.0089 0.0063 0.004 0.0062 0.0053 0.0017
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.016 0.016 0.017 0.016 0.016 0.016 0.016 0.015
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.033249 0.278779
Type A standard uncertainty due to reproducibility of difference results 0.018 0.037
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.020 0.038
I column
Difference between 2 means (each the mean of 4 results) -0.24553 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** # 0.156014 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** # 0.022 (uncertainty in the parameter being compared)
74
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 20 °C Lab name NPL
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 19.644452 10765218 19.63628 0.008172 19.644452 107.54303 19.355476 0.288976
Meas 2 20.157491 107.85785 20.165633 -0.008142 20.157491 107.75373 19.897725 0.259766
Meas 3 19.698272 107.68064 19.709525 -0.011253 19.698272 107.57563 19.439278 0.258994
Meas 4 19.788426 107.71226 19.790905 -0.002479 19.788426 107.60687 19.519764 0.268662
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.015 0.015 0.015 0.015 0.015 0.015 0.015 0.015
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.012 0.023 0.0228 0.0096 0.0023 0.0124 0.0083 0.0033
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.019 0.027 0.027 0.018 0.015 0.019 0.017 0.015
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.00343 0.2691
Type A standard uncertainty due to reproducibility of difference results 0.009 0.014
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.014 0.016
I column
Difference between 2 means (each the mean of 4 results) -0.27252 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** # 0.132837 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** # 0.011 (uncertainty in the parameter being compared)
75
NMIJ
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -50 °C Lab name NMIJ
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW) Number of data
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C Hyg 1 Hyg 2
Meas 1 -49.964 80.400 -49.765 -0.199 -49.953 80.225 -50.205 0.252 73 73
Meas 2 -49.961 80.401 -49.761 -0.200 -49.950 80.220 -50.218 0.268 42 42
Meas 3 -49.969 80.400 -49.763 -0.206 -49.958 80.210 -50.242 0.285 52 52
Meas 4 -49.960 80.399 -49.768 -0.192 -49.949 80.223 -50.209 0.260 21 21
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.051 0.051 0.051 0.051 0.051 0.051 0.051 0.051
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.003 0.004 0.003 0.004 0.002 0.003 0.001 0.002
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.051 0.051 0.051 0.051 0.051 0.051 0.051 0.051
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.200 0.266 (average weighted proportional to number of data)
Type A standard uncertainty due to reproducibility of difference results 0.002 0.008
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.051 0.052
Effective degree of freedom of uncertainty of mean dew point difference 6.641 6.972
I column
Difference between 2 means (each the mean of 4 results) -0.466 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.033 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.049 (uncertainty in the parameter being compared)
Effective degree of freedom of uncertainty in average ** 5.974
Uncertainty in difference between 2 means 0.030
Effective degree of freedom of uncertainty in difference between 2 means 7.059
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -30 °C Lab name NMIJ
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW) Number of data
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C Hyg 1 Hyg 2
Meas 1 -30.010 88.284 -29.841 -0.169 -30.009 88.121 -30.255 0.246 20 20
Meas 2 -30.007 88.284 -29.843 -0.165 -30.006 88.122 -30.252 0.246 14 14
Meas 3 -30.004 88.283 -29.844 -0.160 -30.002 88.124 -30.246 0.244 22 24
Meas 4 -30.005 88.284 -29.842 -0.163 -30.004 88.124 -30.248 0.245 46 46
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.024 0.024 0.024 0.024 0.024 0.024 0.024 0.024
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.005 0.004 0.004 0.002 0.002 0.002 0.001 0.002
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.024 0.024 0.024 0.024 0.024 0.024 0.024 0.024
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.164 0.245 (average weighted proportional to number of data)
Type A standard uncertainty due to reproducibility of difference results 0.001 0.000
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.024 0.024
Effective degree of freedom of uncertainty of mean dew point difference 57.684 57.203
I column
Difference between 2 means (each the mean of 4 results) -0.409 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.041 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.024 (uncertainty in the parameter being compared)
76
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -10 °C Lab name NMIJ
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW) Number of data
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C Hyg 1 Hyg 2
Meas 1 -10.001 96.133 -9.880 -0.121 -10.000 95.981 -10.268 0.267 38 38
Meas 2 -9.998 96.126 -9.898 -0.100 -9.998 95.981 -10.267 0.270 12 12
Meas 3 -9.997 96.125 -9.901 -0.095 -9.996 95.983 -10.263 0.266 25 25
Meas 4 -9.996 96.126 -9.899 -0.098 -9.996 95.983 -10.263 0.267 40 40
-0.103 0.268
0.012 0.001
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.024 0.024 0.024 0.024 0.024 0.024 0.024 0.024
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.005 0.003 0.006 0.002 0.001 0.001 0.001 0.001
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.025 0.024 0.025 0.024 0.024 0.024 0.024 0.024
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.105 0.267 (average weighted proportional to number of data)
Type A standard uncertainty due to reproducibility of difference results 0.007 0.000
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.025 0.024
Effective degree of freedom of uncertainty of mean dew point difference 56.287 52.813
I column
Difference between 2 means (each the mean of 4 results) -0.372 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.081 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.024 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 1 °C Lab name NMIJ
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 0.993 100.412 1.054 -0.061 0.993 100.278 0.710 0.283
Meas 2 1.000 100.414 1.059 -0.059 1.000 100.283 0.725 0.274
Meas 3 1.013 100.417 1.068 -0.055 1.013 100.286 0.731 0.282
Meas 4 1.010 100.412 1.056 -0.045 1.010 100.283 0.723 0.287
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.016 0.016 0.016 0.016 0.016 0.016 0.016 0.016
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.002 0.002 0.004 0.005 0.002 0.002 0.002 0.002
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Uncertainty of resistance measurement 0.018 0.018 0.018 0.018 0.018 0.018 0.018 0.018
Combined standard uncertainty (8 values) 0.024 0.024 0.024 0.024 0.024 0.024 0.024 0.024
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.055 0.281
Type A standard uncertainty due to reproducibility of difference results 0.007 0.005
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.025 0.024
I column
Difference between 2 means (each the mean of 4 results) -0.337 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.113 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** # 0.021 (uncertainty in the parameter being compared)
77
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 20 °C Lab name NMIJ
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 19.987 107.795 20.004 -0.017 19.987 107.670 19.682 0.304
Meas 2 20.002 107.800 20.016 -0.014 20.002 107.675 19.695 0.307
Meas 3 20.002 107.799 20.013 -0.012 20.002 107.676 19.698 0.304
Meas 4 20.007 107.800 20.016 -0.009 20.007 107.676 19.697 0.310
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.017 0.017 0.017 0.017 0.017 0.017 0.017 0.017
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.003 0.003 0.003 0.003 0.002 0.002 0.002 0.002
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Uncertainty of resistance measurement 0.018 0.018 0.018 0.018 0.018 0.018 0.018 0.018
Combined standard uncertainty (8 values) 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.013 0.306
Type A standard uncertainty due to reproducibility of difference results 0.003 0.003
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.025 0.025
I column
Difference between 2 means (each the mean of 4 results) -0.319 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** # 0.147 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** # 0.021 (uncertainty in the parameter being compared)
78
VSL
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -50 °C Lab name NMi-VSL
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -50.00 80.3768 -49.82 -0.18 -50.00 80.3295 -49.94 -0.06
Meas 2 -50.01 80.3530 -49.88 -0.13 -50.01 80.3312 -49.94 -0.08
Meas 3 -50.02 80.3464 -49.90 -0.12 -50.02 80.3333 -49.93 -0.08
Meas 4 -50.02 80.3887 -49.79 -0.22 -50.02 80.3573 -49.87 -0.14
Uncertainties (in °C) Hygrometer 1(Michell) Hygrometer 2 (MBW)
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.026 0.026 0.026 0.026 0.026 0.026 0.026 0.026
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.003 0.007 0.007 0.006 0.007 0.008 0.006 0.004
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.027 0.027 0.027 0.027 0.027 0.027 0.027 0.027
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.143 -0.054
Type A standard uncertainty due to reproducibility of difference results 0.062 0.077
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 95% 0.136 0.163
I column
Difference between 2 means (each the mean of 4 results) -0.089 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** -0.098 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 95% 0.133 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -30 °C Lab name NMi-VSL
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -30.03 88.1814 -30.10 0.07 -30.03 88.1375 -30.21 0.18
Meas 3 -30.02 88.1727 -30.12 0.10 -30.02 88.1227 -30.25 0.23
Meas 4 -30.03 88.2331 -29.97 -0.06 -30.03 88.1404 -30.21 0.18
Meas 5 -30.03 88.2326 -29.97 -0.06 -30.03 88.1363 -30.22 0.19
Uncertainties (in °C) Hygrometer 1(Michell) Hygrometer 2 (MBW)
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.026 0.026 0.026 0.026 0.026 0.026 0.026 0.026
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.003 0.005 0.014 0.008 0.004 0.004 0.011 0.009
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.026 0.027 0.030 0.027 0.027 0.027 0.028 0.028
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.02 0.19
Type A standard uncertainty due to reproducibility of difference results 0.08 0.02
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 95% 0.177 0.072
I column
Difference between 2 means (each the mean of 4 results) -0.179 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.105 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 95% 0.100 (uncertainty in the parameter being compared)
79
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -10 °C Lab name NMi-VSL
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -10.00 96.0748 -10.03 0.02 -10.00 95.9667 -10.30 0.30
Meas 2 -10.01 96.0546 -10.08 0.07 -10.01 95.9687 -10.30 0.29
Meas 3 -10.00 96.0731 -10.03 0.03 -10.00 95.9749 -10.28 0.28
Meas 4 -10.00 96.0664 -10.05 0.05 -10.00 95.9748 -10.28 0.28
Uncertainties (in °C) Hygrometer 1(Michell) Hygrometer 2 (MBW)
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.027 0.027 0.027 0.027 0.027 0.027 0.027 0.027
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.009 0.002 0.007 0.027 0.012 0.003 0.010 0.017
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.029 0.027 0.028 0.038 0.030 0.028 0.029 0.032
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.043 0.287
Type A standard uncertainty due to reproducibility of difference results 0.019 0.009
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 95% 0.073 0.062
I column
Difference between 2 means (each the mean of 4 results) -0.245 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.165 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 95% 0.028 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 1 °C Lab name NMi-VSL
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 0.994 100.395 1.011 -0.016 0.994 100.317 0.810 0.184
Meas 2 1.002 100.377 0.965 0.037 1.002 100.296 0.758 0.244
Meas 3 1.000 100.391 1.001 -0.001 1.000 100.370 0.946 0.054
Meas 4 0.999 100.391 1.001 -0.002 0.999 100.381 0.974 0.025
Meas 5 1.001 100.391 1.000 0.001 1.001 100.381 0.975 0.026
Uncertainties (in °C) Hygrometer 1(Michell) Hygrometer 2 (MBW)
Meas 1 Meas 2 Meas 3 Meas 4 Meas 5 Meas 1 Meas 2 Meas 3 Meas 4 Meas 5
Standard uncertainty of applied condition 0.028 0.028 0.028 0.028 0.028 0.028 0.028 0.028 0.028 0.028
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.009 0.003 0.003 0.002 0.002 0.006 0.003 0.003 0.003 0.003
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.030 0.028 0.028 0.028 0.028 0.029 0.028 0.028 0.028 0.028
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.004 0.107
Type A standard uncertainty due to reproducibility of difference results 0.020 0.101
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 95% 0.069 0.209
I column
Difference between 2 means (each the mean of 4 results) -0.103 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.055 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 95% 0.111 (uncertainty in the parameter being compared)
80
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 20 °C Lab name NMi-VSL
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 19.88 107.7385 19.86 0.02 19.88 107.6449 19.62 0.26
Meas 2 19.95 107.7606 19.92 0.03 19.95 107.6719 19.69 0.26
Meas 3 19.94 107.7571 19.91 0.03 19.94 107.6741 19.69 0.25
Meas 4 19.96 107.7722 19.95 0.02 19.96 107.6774 19.70 0.26
Uncertainties (in °C) Hygrometer 1(Michell) Hygrometer 2 (MBW)
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.042 0.042 0.042 0.042 0.042 0.042 0.042 0.042
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.026 0.019 0.013 0.024 0.002 0.007 0.035 0.044
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.050 0.046 0.044 0.048 0.042 0.043 0.055 0.061
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.026 0.258
Type A standard uncertainty due to reproducibility of difference results 0.007 0.008
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 95% 0.095 0.107
I column
Difference between 2 means (each the mean of 4 results) -0.232 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.142 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 95% 0.036 (uncertainty in the parameter being compared)
81
MIKES
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -50 °C Lab name MIKES
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -49.58 80.495 -49.54 -0.04 -49.58 80.413 -49.75 0.17
Meas 2 -50.13 80.252 -50.16 0.02 -50.13 80.183 -50.33 0.20
Meas 3 -50.10 80.268 -50.12 0.02 -50.10 80.192 -50.31 0.21
Meas 4 -50.08 80.294 -50.05 -0.03 -50.08 80.210 -50.26 0.19
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.022 0.022 0.022 0.022 0.022 0.022 0.022 0.022
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.005 0.004 0.004 0.006 0.006 0.005 0.005 0.004
Std uncert due to long-term drift of travelling standard [if needed]
(Std uncert due to resolution of travelling standard [if needed]) Uncertainty of resistance measurement 0.052 0.052 0.052 0.052 0.023 0.023 0.023 0.023
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed] 9.70E-07 5.70E-07 -6.30E-07 1.10E-06 4.70E-07 2.70E-07 4.80E-07 -7.30E-07
Combined standard uncertainty (8 values) 0.057 0.057 0.057 0.057 0.032 0.032 0.032 0.032
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.01 0.19
Type A standard uncertainty due to reproducibility of difference results 0.03 0.02
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.033 0.019
I column
Difference between 2 means (each the mean of 4 results) -0.20 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.09 (aggregated result - parameter to be compared between institutes)
Standard uncertainty in average ** 0.019 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -30 °C Lab name MIKES
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -30.10 88.170 -30.13 0.03 -30.10 88.093 -30.33 0.23
Meas 2 -29.92 88.267 -29.89 -0.02 -29.91 88.176 -30.12 0.21
Meas 3 -29.97 88.240 -29.96 -0.01 -29.97 88.156 -30.17 0.20
Meas 4 -29.92 88.251 -29.93 0.01 -29.92 88.175 -30.12 0.20
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.030 0.022 0.022 0.022 0.026 0.022 0.022 0.022
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.005 0.005 0.006 0.003 0.002 0.002 0.003 0.003
Std uncert due to long-term drift of travelling standard [if needed]
(Std uncert due to resolution of travelling standard [if needed]) Uncertainty of resistance measurement 0.040 0.040 0.040 0.040 0.014 0.014 0.014 0.014
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed] -1.86E-07 4.40E-07 -3.90E-07 1.40E-07 -3.03E-06 1.40E-07 1.50E-07 2.50E-07
Combined standard uncertainty (8 values) 0.050 0.046 0.046 0.046 0.030 0.026 0.026 0.026
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.00 0.21
Type A standard uncertainty due to reproducibility of difference results 0.02 0.01
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.028 0.016
I column
Difference between 2 means (each the mean of 4 results) -0.21 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.11 (aggregated result - parameter to be compared between institutes)
Standard uncertainty in average ** 0.016 (uncertainty in the parameter being compared)
82
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -10 °C Lab name MIKES
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -10.10 96.053 -10.08 -0.02 -10.10 95.950 -10.34 0.25
Meas 2 -9.84 96.155 -9.82 -0.01 -9.84 96.050 -10.09 0.26
Meas 3 -10.02 96.082 -10.01 -0.01 -10.02 95.978 -10.28 0.26
Meas 4 -10.04 96.055 -10.08 0.04 -10.04 95.970 -10.30 0.26
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.028 0.022 0.022 0.022 0.022 0.022 0.022 0.022
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.004 0.007 0.003 0.004 0.002 0.005 0.004 0.008
Std uncert due to long-term drift of travelling standard [if needed]
(Std uncert due to resolution of travelling standard [if needed]) Uncertainty of resistance measurement 0.020 0.020 0.020 0.020 0.014 0.014 0.014 0.014
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed] 1.87E-06 1.50E-05 6.90E-07 2.40E-08 -3.00E-08 1.80E-05 -1.20E-06 9.10E-06
Combined standard uncertainty (8 values) 0.035 0.030 0.030 0.030 0.026 0.026 0.026 0.027
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.00 0.25
Type A standard uncertainty due to reproducibility of difference results 0.03 0.00
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.022 0.013
I column
Difference between 2 means (each the mean of 4 results) -0.25 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.13 (aggregated result - parameter to be compared between institutes)
Standard uncertainty in average ** 0.013 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 1 °C Lab name MIKES
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 1.01 100.383 0.98 0.03 0.99 100.284 0.73 0.26
Meas 2 1.01 100.395 1.01 0.00 1.00 100.290 0.74 0.26
Meas 3 0.99 100.390 1.00 -0.01 0.99 100.291 0.75 0.25
Meas 4 0.96 100.375 0.96 0.00 0.96 100.282 0.72 0.24
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.028 0.032 0.031 0.031 0.021 0.022 0.022 0.022
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.002 0.001 0.001 0.001 0.002 0.001 0.002 0.002
Std uncert due to long-term drift of travelling standard [if needed]
(Std uncert due to resolution of travelling standard [if needed]) Uncertainty of resistance measurement 0.017 0.017 0.017 0.017 0.012 0.012 0.012 0.012
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed] 1.92E-06 -4.43E-07 4.80E-07 -6.30E-09 -3.15E-06 -8.40E-07 5.17E-07 -9.62E-07
Combined standard uncertainty (8 values) 0.033 0.036 0.035 0.035 0.024 0.025 0.025 0.025
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.00 0.25
Type A standard uncertainty due to reproducibility of difference results 0.02 0.01
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.021 0.014
I column
Difference between 2 means (each the mean of 4 results) -0.25 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.13 (aggregated result - parameter to be compared between institutes)
Standard uncertainty in average ** 0.013 (uncertainty in the parameter being compared)
83
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 20 °C Lab name MIKES
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 19.99 107.779 19.96 0.03 20.00 107.691 19.74 0.26
Meas 2 19.99 107.786 19.98 0.01 20.00 107.695 19.75 0.25
Meas 3 19.93 107.767 19.93 0.00 19.94 107.669 19.68 0.26
Meas 4 19.76 107.692 19.74 0.02 19.78 107.593 19.48 0.29
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.035 0.035 0.035 0.023 0.023 0.023 0.022 0.022
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.011 0.002 0.001 0.005 0.001 0.000 0.001 0.001
Std uncert due to long-term drift of travelling standard [if needed]
(Std uncert due to resolution of travelling standard [if needed]) Uncertainty of resistance measurement 0.006 0.006 0.006 0.006 0.009 0.009 0.009 0.009
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed] -1.30E-06 -1.40E-06 2.00E-07 -9.70E-07 -3.00E-08 5.20E-07 1.70E-08 5.20E-07
Combined standard uncertainty (8 values) 0.037 0.036 0.036 0.024 0.025 0.025 0.024 0.024
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.02 0.27
Type A standard uncertainty due to reproducibility of difference results 0.01 0.02
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.019 0.018
I column
Difference between 2 means (each the mean of 4 results) -0.25 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.14 (aggregated result - parameter to be compared between institutes)
Standard uncertainty in average ** 0.013 (uncertainty in the parameter being compared)
84
INTA
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON CCT/K6 Nominal value: -50 °C Lab name INTA
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -50.009 80.3303 -49.939 -0.069 -50.009 80.2421 -50.162 0.153
Meas 2 -50.009 80.3264 -49.949 -0.060 -50.009 80.2423 -50.161 0.152
Meas 3 -50.009 80.3287 -49.943 -0.066 -50.009 80.2419 -50.162 0.153
Meas 4 -50.009 80.3278 -49.946 -0.063 -50.009 80.2420 -50.162 0.153
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.032 0.032 0.032 0.032 0.032 0.032 0.032 0.032
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.027 0.019 0.026 0.026 0.008 0.009 0.010 0.007
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point temperature [if needed]
Combination of these standard uncertainties in quadrature (8 values) 0.042 0.037 0.041 0.041 0.033 0.033 0.033 0.033
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.065 0.152
Type A standard uncertainty due to reproducibility of difference results 0.0065 0.0006
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.021 0.017
I column
Difference between 2 means (each the mean of 4 results) -0.217 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.044 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.013 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON CCT/K6 Nominal value: -30 °C Lab name INTA
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -30.005 88.2263 -29.9883 -0.017 -30.005 88.1422 -30.201 0.196
Meas 2 -30.005 88.2330 -29.9712 -0.033 -30.005 88.1408 -30.205 0.200
Meas 3 -30.005 88.2291 -29.9810 -0.024 -30.005 88.1403 -30.206 0.201
Meas 4 -30.004 88.2291 -29.9811 -0.023 -30.004 88.1418 -30.202 0.198
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.023 0.024 0.022 0.032 0.009 0.007 0.006 0.009
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point temperature [if needed]
Combination of these standard uncertainties in quadrature (8 values) 0.034 0.035 0.033 0.041 0.027 0.026 0.026 0.027
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.025 0.198
Type A standard uncertainty due to reproducibility of difference results 0.0117 0.0030
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.021 0.014
I column
Difference between 2 means (each the mean of 4 results) -0.224 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.087 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.013 (uncertainty in the parameter being compared)
85
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON CCT/K6 Nominal value: -10 °C Lab name INTA
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -9.991 96.1009 -9.962 -0.030 -9.991 95.9926 -10.238 0.247
Meas 2 -9.990 96.1007 -9.962 -0.028 -9.990 95.9926 -10.238 0.248
Meas 3 -9.988 96.0986 -9.967 -0.021 -9.988 95.9930 -10.237 0.249
Meas 4 -9.991 96.0952 -9.976 -0.014 -9.991 95.9914 -10.241 0.251
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.029 0.026 0.019 0.017 0.005 0.004 0.005 0.004
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point temperature [if needed]
Combination of these standard uncertainties in quadrature (8 values) 0.038 0.036 0.031 0.030 0.025 0.025 0.025 0.025
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.029 0.247
Type A standard uncertainty due to reproducibility of difference results 0.0015 0.0012
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.017 0.013
I column
Difference between 2 means (each the mean of 4 results) -0.276 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.109 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.011 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON CCT/K6 Nominal value: 1 °C Lab name INTA
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 0.988 100.3851 0.985 0.002 0.988 100.2807 0.718 0.269
Meas 2 0.984 100.3859 0.988 -0.004 0.984 100.2809 0.719 0.265
Meas 3 0.982 100.3839 0.982 0.000 0.982 100.2791 0.714 0.268
Meas 4 0.982 100.3849 0.985 -0.003 0.982 100.2795 0.715 0.267
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.003 0.008 0.006 0.004 0.002 0.004 0.004 0.004
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point temperature [if needed]
Combination of these standard uncertainties in quadrature (8 values) 0.025 0.026 0.026 0.025 0.025 0.025 0.025 0.025
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.001 0.267
Type A standard uncertainty due to reproducibility of difference results 0.0042 0.0030
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.013 0.013
I column
Difference between 2 means (each the mean of 4 results) -0.268 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.133 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.009 (uncertainty in the parameter being compared)
86
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON CCT/K6 Nominal value: 20 °C Lab name INTA
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 20.003 107.7856 19.980 0.024 20.003 107.6776 19.702 0.302
Meas 2 20.004 107.7860 19.981 0.023 20.004 107.6782 19.703 0.300
Meas 3 20.001 107.7859 19.980 0.021 20.001 107.6780 19.703 0.299
Meas 4 20.002 107.7860 19.981 0.022 20.002 107.6785 19.704 0.298
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.008 0.008 0.007 0.007 0.007 0.008 0.007 0.008
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point temperature [if needed]
Combination of these standard uncertainties in quadrature (8 values) 0.026 0.026 0.026 0.026 0.026 0.026 0.026 0.026
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.023 0.301
Type A standard uncertainty due to reproducibility of difference results 0.0006 0.0008
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.013 0.013
I column
Difference between 2 means (each the mean of 4 results) -0.278 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.1621 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.009 (uncertainty in the parameter being compared)
87
INRIM
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -50 °C Lab name INRiM
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference (applied
dp - meas dp) in °C
Meas 1 -50.149 80.2743 -50.081 -0.07 -50.149 80.1760 -50.328 0.18
Meas 2 -50.149 80.2811 -50.063 -0.09 -50.149 80.1796 -50.319 0.17
Meas 3 -50.142 80.2798 -50.067 -0.08 -50.142 80.1759 -50.328 0.19
Meas 4 -50.141 80.2734 -50.083 -0.06 -50.141 80.1732 -50.335 0.19
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.028 0.031 0.025 0.026 0.032 0.036 0.032 0.032
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed] 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.037 0.040 0.035 0.036 0.040 0.044 0.041 0.041
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.07 0.18
Type A standard uncertainty due to reproducibility of difference results 0.01 0.01
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.022 0.023
I column
Difference between 2 means (each the mean of 4 results) -0.25 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.06 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.016 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -30 °C Lab name INRiM
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference (applied
dp - meas dp) in °C
Meas 1 -30.353 88.0880 -30.339 -0.01 -30.353 87.9931 -30.579 0.23
Meas 2 -30.345 88.0877 -30.340 -0.01 -30.345 87.9938 -30.578 0.23
Meas 3 -30.354 88.0800 -30.359 0.01 -30.354 87.9834 -30.604 0.25
Meas 4 -30.179 88.1527 -30.175 0.00 -30.179 88.0550 -30.423 0.24
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.021 0.021 0.021 0.021 0.021 0.021 0.021 0.021
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.015 0.012 0.015 0.023 0.018 0.023 0.025 0.023
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed] 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.026 0.024 0.025 0.031 0.028 0.031 0.032 0.031
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.00 0.24
Type A standard uncertainty due to reproducibility of difference results 0.01 0.01
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.016 0.019
I column
Difference between 2 means (each the mean of 4 results) -0.24 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.12 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.012 (uncertainty in the parameter being compared)
88
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -10 °C Lab name INRiM
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference (applied
dp - meas dp) in °C
Meas 1 -9.908 96.1306 -9.886 -0.02 -9.908 96.0171 -10.176 0.27
Meas 2 -10.161 96.0202 -10.168 0.01 -10.161 95.9090 -10.451 0.29
Meas 3 -10.101 96.0503 -10.091 -0.01 -10.101 95.9416 -10.368 0.27
Meas 4 -10.016 96.0800 -10.015 0.00 -10.016 95.9697 -10.296 0.28
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.021 0.021 0.021 0.021 0.021 0.021 0.021 0.021
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.005 0.005 0.005 0.005 0.008 0.018 0.015 0.018
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed] 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.021 0.021 0.021 0.021 0.022 0.027 0.026 0.027
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.01 0.28
Type A standard uncertainty due to reproducibility of difference results 0.01 0.01
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.016 0.017
I column
Difference between 2 means (each the mean of 4 results) -0.28 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.14 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.012 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 1 °C Lab name INRiM
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference (applied
dp - meas dp) in °C
Meas 1 1.015 100.4050 1.036 -0.02 1.015 100.2932 0.750 0.26
Meas 2 1.014 100.4021 1.029 -0.02 1.014 100.2930 0.750 0.26
Meas 3 1.014 100.4060 1.039 -0.03 1.014 100.2931 0.750 0.26
Meas 4 1.012 100.4046 1.035 -0.02 1.012 100.2905 0.743 0.27
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.019 0.019 0.019 0.019 0.019 0.019 0.019 0.019
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.003 0.003 0.003 0.004 0.004 0.005 0.004 0.004
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed] 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.019 0.019 0.019 0.019 0.019 0.020 0.020 0.020
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.021 0.265
Type A standard uncertainty due to reproducibility of difference results 0.004 0.002
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.011 0.010
I column
Difference between 2 means (each the mean of 4 results) -0.29 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.12 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.007 (uncertainty in the parameter being compared)
89
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 20 °C Lab name INRiM
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference (applied
dp - meas dp) in °C
Meas 1 19.963 107.7754 19.953 0.01 19.963 107.6563 19.647 0.32
Meas 2 19.963 107.7745 19.951 0.01 19.963 107.6555 19.645 0.32
Meas 3 19.967 107.7805 19.967 0.00 19.967 107.6585 19.653 0.31
Meas 4 19.968 107.7804 19.966 0.00 19.968 107.6582 19.652 0.32
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.021 0.021 0.021 0.021 0.021 0.021 0.021 0.021
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.003 0.002 0.003 0.002 0.004 0.004 0.005 0.003
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed] 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.021 0.021 0.021 0.021 0.021 0.021 0.021 0.021
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.006 0.316
Type A standard uncertainty due to reproducibility of difference results 0.006 0.002
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.012 0.011
I column
Difference between 2 means (each the mean of 4 results) -0.31 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.16 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.008 (uncertainty in the parameter being compared)
90
NIST
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -50.000 °C Lab name NIST
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -50.005 80.374 -49.830 -0.174 -50.005 80.271 -50.089 0.084
Meas 2 -50.005 80.398 -49.769 -0.236 -50.005 80.280 -50.067 0.062
Meas 3 -50.002 80.396 -49.775 -0.228 -50.002 80.277 -50.073 0.071
Meas 4 -50.002 80.399 -49.767 -0.235 -50.002 80.276 -50.076 0.074
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition Type B uncertainty documented in paper 0.007 0.007 0.007 0.007 0.007 0.007 0.007 0.007
Standard deviation of the calculated dew / frost-point temperature (Deg. C) 0.032 0.051 0.045 0.041 0.007 0.005 0.009 0.006
Number of observations. 57 197 323 71 56 68 180 197
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.004 0.004 0.003 0.005 0.001 0.001 0.001 0.000
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values)
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.218 0.073
Type A standard uncertainty due to reproducibility of difference results 0.015 0.005
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.016 0.008
The value reported here is the standard uncertainty obtained by combining the type A value in the boxes
immediately above with the uncertainty of the humidity generator.
I column
Difference between 2 means (each the mean of 4 results) -0.291 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** -0.073 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.011 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -30.000 °C Lab name NIST
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -30.005 88.250 -29.927 -0.078 -30.005 88.160 -30.157 0.152
Meas 2 -30.007 88.264 -29.892 -0.115 -30.007 88.160 -30.157 0.150
Meas 3 -30.002 88.272 -29.873 -0.129 -30.002 88.164 -30.147 0.144
Meas 4 -30.004 88.270 -29.879 -0.125 -30.004 88.164 -30.147 0.144
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition Type B uncertainty documented in paper 0.007 0.007 0.007 0.007 0.007 0.007 0.007 0.007
Standard deviation of the calculated dew / frost-point temperature (Deg. C) 0.039 0.069 0.052 0.039 0.005 0.004 0.009 0.005
Number of observations. 82 540 428 255 77 117 534 255
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.004 0.003 0.002 0.002 0.001 0.000 0.000 0.000
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values)
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.112 0.148
Type A standard uncertainty due to reproducibility of difference results 0.012 0.002
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.013 0.007
The value reported here is the standard uncertainty obtained by combining the type A value in the boxes
immediately above with the uncertainty of the humidity generator.
I column
Difference between 2 means (each the mean of 4 results) -0.259 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.018 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.010 (uncertainty in the parameter being compared)
91
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -10.000 °C Lab name NIST
Results
Notes: The condensate for all of the -10C points is dew. The applied dew point of -11.2 Deg. C corresponds to a frost point temperature of nominally -10.0 Deg. C.
A correction of +.005C is applied to the temperatures reported as Output in Deg. C.
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -11.219 95.641 -11.130 -0.089 -11.219 95.529 -11.416 0.198
Meas 2 -11.206 95.646 -11.117 -0.089 -11.206 95.533 -11.406 0.200
Meas 3 -11.241 95.627 -11.165 -0.076 -11.241 95.519 -11.440 0.199
Meas 4 -11.199 95.646 -11.116 -0.082 -11.199 95.535 -11.399 0.200
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.008
Standard deviation of the calculated dew / frost-point temperature (Deg. C) 0.005 0.006 0.010 0.005 0.007 0.006 0.004 0.012
Number of observations. 42 57 116 207 42 57 89 207
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.001 0.001 0.001 0.000 0.001 0.001 0.000 0.001
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values)
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.084 0.199
Type A standard uncertainty due to reproducibility of difference results 0.003 0.001
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.009 0.008
The value reported here is the standard uncertainty obtained by combining the type A value in the boxes
immediately above with the uncertainty of the humidity generator.
I column
Difference between 2 means (each the mean of 4 results) -0.283 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.058 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.010 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 1.000 °C Lab name NIST
Results
Note: A correction of +.005C is applied to the temperatures reported as Output in Deg. C.
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 0.981 100.400 1.029 -0.048 0.981 100.285 0.734 0.246
Meas 2 0.981 100.398 1.025 -0.044 0.981 100.289 0.743 0.238
Meas 3 0.983 100.401 1.031 -0.047 0.983 100.287 0.739 0.244
Meas 4 0.984 100.397 1.020 -0.036 0.984 100.285 0.735 0.249
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.008
Standard deviation of the calculated dew / frost-point temperature (Deg. C) 0.002 0.001 0.001 0.003 0.001 0.001 0.001 0.001
Number of observations. 85 26 28 59 85 26 35 86
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values)
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.044 0.244
Type A standard uncertainty due to reproducibility of difference results 0.003 0.002
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.009 0.008
The value reported here is the standard uncertainty obtained by combining the type A value in the boxes
immediately above with the uncertainty of the humidity generator.
I column
Difference between 2 means (each the mean of 4 results) -0.288 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.100 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.010 (uncertainty in the parameter being compared)
92
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 20.000 °C Lab name NIST
Results
Note: A correction of +.005C is applied to the temperatures reported as Output in Deg. C.
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 20.058 107.814 20.059 -0.001 20.058 107.704 19.775 0.283
Meas 2 20.069 107.815 20.060 0.008 20.069 107.712 19.795 0.273
Meas 3 20.068 107.816 20.064 0.004 20.068 107.716 19.804 0.264
Meas 4 20.069 107.815 20.060 0.009 20.069 107.708 19.784 0.285
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 etc.
Standard uncertainty of applied condition 0.010 0.010 0.010 0.010 0.010 0.010 0.010 0.010
Standard deviation of the calculated dew / frost-point temperature (Deg. C) 0.001 0.001 0.001 0.001 0.001 0.001 0.003 0.003
Number of observations. 88 32 146 86 88 32 146 86
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values)
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.005 0.276
Type A standard uncertainty due to reproducibility of difference results 0.002 0.005
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.010 0.011
The value reported here is the standard uncertainty obtained by combining the type A value in the boxes
immediately above with the uncertainty of the humidity generator.
I column
Difference between 2 means (each the mean of 4 results) -0.271 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.141 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.012 (uncertainty in the parameter being compared)
93
NMC
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON
Nominal
value: -50 °C Lab nameNMC/SPRING
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied
frost point
(°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied fp -
meas fp)
in °C
Applied
frost point
(°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied fp -
meas fp) in
°C
Meas 2 -49.980 80.353 -49.881 -0.099 -49.987 80.278 -50.071 0.084
Meas 3 -49.986 80.328 -49.945 -0.040 -49.986 80.328 -50.055 0.069
Meas 4 -49.986 80.327 -49.947 -0.039 -49.986 80.277 -50.074 0.088
Meas 5 -49.980 80.348 -49.896 -0.084 -49.981 80.274 -50.081 0.100
Note: Meas 1 was not a full simultaneous dataset
Uncertainties (in °C)
Meas 2 Meas 3 Meas 4 Meas 5 Meas 2 Meas 3 Meas 4 Meas 5
Standard uncertainty of applied condition except type A 0.035 0.035 0.034 0.034 0.035 0.035 0.034 0.034
0.0018 0.0016 0.0017 0.0014 0.0018 0.0016 0.0017 0.0014
0.0241 0.0201 0.0311 0.0359 0.0159 0.0148 0.0127 0.0119
0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005
Std uncert due to resolution of traveling standard (resolution is 1 mK) 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003
Std uncert due to long-term drift of traveling standard [Not observed]
Std uncert due to non-linearity of traveling standard [not involved]
Covariance between applied and measured values of dew/frost-point [not applicable]
Difference between ABC/MMC (insignificant)
Drift due to longer waiting time (insignificant)
Combined standard uncertainty (8 values) 0.0425 0.0404 0.0461 0.0494 0.0385 0.0380 0.0364 0.0360
Average of combined standard uncertainty Auc 0.0446 0.0372
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences for Michell/MBW -0.066 0.085
Type A standard uncertainty due to reproducibility of difference results 0.030 0.013
two values (each derived from standard deviation of 4 values on same instrument)
0.054 0.039
Difference between 2 means (each the mean of 4 results) Hyg2-hyg1 0.151 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.010 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.033 (uncertainty in the parameter being compared)
Standard uncertainty of applied condition type A (when there are more than one records, max
value is taken)
Std uncert due to short-term stability (from standard deviation) of measurements of traveling
standard (type A) (when there are more than one records, the average of the standard deviations of
records is taken)
Std uncert due to the resistance measurement uncertainty of traveling standard (the uncertainty of
the two bridges is 1 mK 95% k=2)
Uncertainty of mean dew point difference for each instrument (2 values) (Auc combined with the
reproducibility
Hygrometer1 Hygrometer 2
94
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON
Nominal
value: -30 °C Lab name NMC/SPRING
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied
frost
point (°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied fp
- meas fp)
in °C
Applied
frost point
(°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied fp
- meas fp)
in °C
Meas 1 -29.974 88.245 -29.940 -0.034 -29.974 88.162 -30.151 0.177
Meas 2 -29.984 88.250 -29.929 -0.054 -29.984 88.170 -30.131 0.148
Meas 3 -29.978 88.247 -29.935 -0.042 -29.978 88.163 -30.150 0.172
Meas 4 -29.977 88.248 -29.934 -0.043 -29.977 88.162 -30.151 0.174
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition except type A 0.027 0.026 0.025 0.025 0.027 0.026 0.025 0.025
0.0016 0.0011 0.0010 0.0010 0.0016 0.0011 0.0010 0.0010
0.0275 0.0265 0.0223 0.0593 0.0090 0.0082 0.0108 0.0063
0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005
Std uncert due to resolution of traveling standard (resolution is 1 mK) 0.0003 0.0003 0.0003 0.0003 0.003 0.0003 0.0003 0.0003
Std uncert due to long-term drift of traveling standard [Not observed]
Std uncert due to non-linearity of traveling standard [not involved]
Covariance between applied and measured values of dew/frost-point [not applicable]
Difference between ABC/MMC (insignificant)
Drift due to longer waiting time (insignificant)
Combined standard uncertainty (8 values) 0.0386 0.0371 0.0335 0.0644 0.0287 0.0273 0.0273 0.0258
Average of combined standard uncertainty Auc 0.0434 0.0273
Aggregation of results
Hyg 1 Hyg 2
Mean of 5 dew-point differences -0.043 0.168
Type A standard uncertainty due to reproducibility of difference results 0.008 0.013
two values (each derived from standard deviation of 4 values on same instrument)
0.044 0.030
Difference between 2 means (each the mean of 4 results) Hyg2-hyg1 0.211 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.062 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.027 (uncertainty in the parameter being compared)
Standard uncertainty of applied condition type A (when there are more than one
records, max value is taken)
Std uncert due to short-term stability (from standard deviation) of measurements of
traveling standard (type A) (when there are more than one records, the average of the
standard deviations of records is taken)
Std uncert due to the resistance measurement uncertainty of traveling standard (the
uncertainty of the two bridges is 1 mK 95% k=2)
Uncertainty of mean dew point difference for each instrument (2 values) (Auc combined
with the reproducibility
95
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON
Nominal
value: -10 °C Lab name NMC/SPRING
Results Generator Model 4500
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied
frost
point (°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied fp
- meas fp)
in °C
Applied
frost point
(°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied fp
- meas fp)
in °C
Meas 1 -11.197 95.646 -11.122 -0.075 -11.211 95.547 -11.374 0.163
Meas 2 -11.197 95.644 -11.127 -0.070 -11.197 95.541 -11.389 0.193
Meas 3 -11.205 95.635 -11.150 -0.054 -11.205 95.534 -11.407 0.202
Meas 4 -11.196 95.636 -11.148 -0.048 -11.196 95.542 -11.388 0.192
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition except type A 0.020 0.020 0.020 0.020 0.020 0.020 0.020 0.020
0.0020 0.0020 0.0010 0.0016 0.0020 0.0020 0.0010 0.0016
0.0032 0.0029 0.0034 0.0027 0.0109 0.0013 0.0009 0.0014
0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005
Std uncert due to resolution of traveling standard (resolution is 1 mK) 0.0003 0.0003 0.0003 0.0003 0.003 0.0003 0.0003 0.0003
Std uncert due to long-term drift of traveling standard [Not observed]
Std uncert due to non-linearity of traveling standard [not involved]
Covariance between applied and measured values of dew/frost-point [not applicable]
Difference between ABC/MMC (insignificant)
Drift due to longer waiting time (insignificant)
Combined standard uncertainty (8 values) 0.0204 0.0203 0.0203 0.0203 0.0231 0.0201 0.0201 0.0201
Average of combined standard uncertainty Auc 0.0203 0.0208
Aggregation of results
Hyg 1 Hyg 2
Mean of 5 dew-point differences -0.062 0.188
Type A standard uncertainty due to reproducibility of difference results 0.013 0.017
two values (each derived from standard deviation of 4 values on same instrument)
0.024 0.027
Results Generator Model 2500
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied
dew
point (°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied
dp - meas
dp) in °C
Applied
dew point
(°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied
dp - meas
dp) in °C
Meas 1 -11.235 95.622 -11.184 -0.050 -11.235 95.522 -11.439 0.204
Meas 2 -11.228 95.628 -11.169 -0.059 -11.228 95.531 -11.415 0.187
Meas 3 -11.238 95.618 -11.193 -0.045 -11.238 95.523 -11.435 0.198
Meas 4 -11.242 95.617 -11.196 -0.045 -11.242 95.521 -11.440 0.199
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition except type A 0.035 0.035 0.035 0.035 0.035 0.035 0.035 0.035
0.0052 0.0065 0.0040 0.0058 0.0052 0.0065 0.0040 0.0058
0.0073 0.0099 0.0100 0.0080 0.0072 0.0038 0.0045 0.0042
0.0003 0.0003 0.0003 0.0003
Std uncert due to resolution of travelling standard (resolution is 1 mK) 0.0003 0.0003 0.0003 0.0003 0.003 0.0003 0.0003 0.0003
Std uncert due to long-term drift of travelling standard [Not observed]
Std uncert due to non-linearity of travelling standard [not involved]
Covariance between applied and measured values of dew/frost-point [not applicable]
Difference between ABC/MMC (insignificant)
Drift due to longer waiting time (insignificant)
Combined standard uncertainty (8 values) 0.0361 0.0369 0.0366 0.0364 0.0362 0.0358 0.0355 0.0357
Average of combined standard uncertainty Auc 0.0365 0.0358
Aggregation of results
Hyg 1 Hyg 2
Mean of 5 dew-point differences -0.050 0.197
Type A standard uncertainty due to reproducibility of difference results 0.006 0.007
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.037 0.037
Aggregation of results
Hyg 1 Hyg 2
Average of 2 generators -0.056 0.192
0.031 0.032
Difference between 2 means (each the mean of 4 results) Hyg2-hyg1 0.248 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.068 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.022 (uncertainty in the parameter being compared)
Uncertainty of mean dew point difference for each instrument (2 values) (average of the
uncertainties of the two generators)
Std uncert due to short-term stability (from standard deviation) of measurements of
traveling standard (type A) (when there are more than one records, the average of the
standard deviations of records is taken)
Std uncert due to the resistance measurement uncertainty of travelling standard (the
uncertainty of the two bridges is 1 mK 95% k=2)
Standard uncertainty of applied condition type A (when there are more than one
records, max value is taken)
Standard uncertainty of applied condition type A (when there are more than one
records, max value is taken)
Std uncert due to short-term stability (from standard deviation) of measurements of
traveling standard (type A) (when there are more than one records, the average of the
standard deviations of records is taken)
Std uncert due to the resistance measurement uncertainty of traveling standard (the
uncertainty of the two bridges is 1 mK 95% k=2)
Uncertainty of mean dew point difference for each instrument (2 values) (Auc combined
with the reproducibility
96
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON
Nominal
value: 1 °C Lab nameNMC/SPRING
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied
dew
point (°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied
dp - meas
dp) in °C
Applied
dew point
(°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied
dp - meas
dp) in °C
Meas 1 0.987 100.406 1.040 -0.053 0.987 100.304 0.778 0.208
Meas 2 1.008 100.410 1.048 -0.040 1.008 100.309 0.790 0.219
Meas 3 0.996 100.407 1.041 -0.045 0.996 100.307 0.786 0.210
Meas 4 0.991 100.405 1.038 -0.046 0.991 100.307 0.786 0.205
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition except type A 0.045 0.037 0.039 0.039 0.045 0.037 0.039 0.039
0.0044 0.0041 0.0038 0.0056 0.0044 0.0041 0.0038 0.0056
0.0096 0.0178 0.0084 0.0085 0.0043 0.0180 0.0034 0.0053
0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005
Std uncert due to resolution of traveling standard (resolution is 1 mK) 0.0003 0.0003 0.0003 0.0003 0.003 0.0003 0.0003 0.0003
Std uncert due to long-term drift of traveling standard [Not observed]
Std uncert due to non-linearity of traveling standard [not involved]
Covariance between applied and measured values of dew/frost-point [not applicable]
Difference between ABC/MMC (insignificant)
Drift due to longer waiting time (insignificant)
Combined standard uncertainty (8 values) 0.0462 0.0413 0.0401 0.0403 0.0455 0.0414 0.0393 0.0398
Average of combined standard uncertainty Auc 0.0420 0.0415
Aggregation of results
Hyg 1 Hyg 2
Mean of 5 dew-point differences -0.046 0.211
Type A standard uncertainty due to reproducibility of difference results 0.006 0.006
two values (each derived from standard deviation of 4 values on same instrument)
0.042 0.042
Difference between 2 means (each the mean of 4 results) Hyg2-hyg1 0.257 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.082 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.030 (uncertainty in the parameter being compared)
Standard uncertainty of applied condition type A (when there are more than one
records, max value is taken)
Std uncert due to short-term stability (from standard deviation) of measurements of
traveling standard (type A) (when there are more than one records, the average of the
standard deviations of records is taken)
Std uncert due to the resistance measurement uncertainty of traveling standard (the
uncertainty of the two bridges is 1 mK 95% k=2)
Uncertainty of mean dew point difference for each instrument (2 values) (Auc combined
with the reproducibility
97
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON
Nominal
value: 20 °C Lab nameNMC/SPRING
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied
dew
point (°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied
dp - meas
dp) in °C
Applied
dew point
(°C)
Resistance
output
(ohms)
Output
in °C
Difference
(applied
dp - meas
dp) in °C
Meas 1 19.983 107.791 19.995 -0.011 19.983 107.689 19.731 0.252
Meas 2 19.989 107.792 19.996 -0.007 19.989 107.691 19.735 0.253
Meas 3 19.988 107.794 20.001 -0.013 19.988 107.689 19.731 0.257
Meas 4 19.987 107.798 20.010 -0.023 19.987 107.695 19.746 0.242
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition except type A 0.048 0.04 0.048 0.048 0.048 0.04 0.048 0.048
0.0038 0.0042 0.0043 0.0049 0.0038 0.0042 0.0043 0.0049
0.0060 0.0081 0.0052 0.0054 0.0199 0.0219 0.0244 0.0204
0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005
Std uncert due to resolution of traveling standard (resolution is 1 mK) 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003
Std uncert due to long-term drift of traveling standard [Not observed]
Std uncert due to non-linearity of traveling standard [not involved]
Covariance between applied and measured values of dew/frost-point [not applicable]
Difference between ABC/MMC (insignificant)
Drift due to longer waiting time (insignificant)
Combined standard uncertainty (8 values) 0.0485 0.0410 0.0485 0.0485 0.0521 0.0458 0.0540 0.0524
Average of combined standard uncertainty Auc 0.0466 0.0511
Aggregation of results
Hyg 1 Hyg 2
Mean of 5 dew-point differences -0.014 0.251
Type A standard uncertainty due to reproducibility of difference results 0.007 0.007
two values (each derived from standard deviation of 4 values on same instrument)
0.047 0.051
Difference between 2 means (each the mean of 4 results) Hyg2-hyg1 0.265 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.119 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.035 (uncertainty in the parameter being compared)
Standard uncertainty of applied condition type A (when there are more than one
records, max value is taken)
Std uncert due to short-term stability (from standard deviation) of measurements of
traveling standard (type A) (when there are more than one records, the average of the
standard deviations of records is taken)
Std uncert due to the resistance measurement uncertainty of traveling standard (the
uncertainty of the two bridges is 1 mK 95% k=2)
Uncertainty of mean dew point difference for each instrument (2 values) (Auc combined
with the reproducibility
98
NIM
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -50 °C Lab name NIM China
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C) Output (mV)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -49.76 80.492 -49.53 -0.23 -49.76 -499.70 -49.97 0.21
Meas 2 -50.51 80.187 -50.30 -0.21 -50.51 -507.02 -50.70 0.19
Meas 3 -50.51 80.190 -50.29 -0.22 -50.51 -507.40 -50.74 0.23
Meas 4 -50.57 80.184 -50.31 -0.26 -50.57 -508.34 -50.83 0.26
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.008 0.005 0.006 0.005 0.012 0.012 0.004 0.006
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.080 0.080 0.080 0.080 0.081 0.081 0.080 0.080
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.23 0.22
Type A standard uncertainty due to reproducibility of difference results 0.015 0.023
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.082 0.084
I column
Difference between 2 means (each the mean of 4 results) 0.450 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** -0.005 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.059 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -30 °C Lab name NIM China
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Output
(mV)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -30.17 88.228 -29.98 -0.19 -30.17 -304.31 -30.43 0.26
Meas 2 -30.14 88.225 -29.99 -0.15 -30.14 -304.02 -30.40 0.26
Meas 3 -30.07 88.264 -29.89 -0.18 -30.07 -303.24 -30.32 0.25
Meas 4 -30.16 88.243 -29.94 -0.22 -30.16 -304.18 -30.42 0.26
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.060 0.060 0.060 0.060 0.060 0.060 0.060 0.060
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.013 0.008 0.006 0.007 0.008 0.006 0.004 0.003
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.062 0.061 0.061 0.061 0.061 0.061 0.060 0.060
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.19 0.26
Type A standard uncertainty due to reproducibility of difference results 0.020 0.004
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.064 0.061
I column
Difference between 2 means (each the mean of 4 results) 0.450 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.035 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.044 (uncertainty in the parameter being compared)
99
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -10 °C Lab name NIM China
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Output
(mV)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -10.14 96.099 -9.97 -0.17 -10.14 -103.71 -10.37 0.23
Meas 2 -10.15 96.121 -9.91 -0.24 -10.15 -103.19 -10.32 0.17
Meas 3 -10.15 96.116 -9.93 -0.22 -10.15 -103.54 -10.35 0.2
Meas 4 -10.25 96.058 -10.07 -0.18 -10.25 -104.77 -10.48 0.23
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.002 0.015 0.01 0.004 0.002 0.007 0.009 0.002
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.060 0.062 0.061 0.060 0.060 0.061 0.061 0.060
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.20 0.21
Type A standard uncertainty due to reproducibility of difference results 0.028 0.023
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.066 0.064
I column
Difference between 2 means (each the mean of 4 results) 0.410 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.005 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.046 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 1 °C Lab name NIM China
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Output
(mV)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 1.04 100.442 1.13 -0.09 1.04 8.33 0.83 0.21
Meas 2 0.94 100.430 1.10 -0.16 0.94 7.10 0.71 0.23
Meas 3 0.96 100.441 1.13 -0.17 0.96 7.51 0.75 0.21
Meas 4 1.14 100.491 1.26 -0.12 1.14 9.30 0.93 0.21
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.009 0.01 0.009 0.008 0.006 0.01 0.009 0.002
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.040
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.14 0.22
Type A standard uncertainty due to reproducibility of difference results 0.030 0.008
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.051 0.041
I column
Difference between 2 means (each the mean of 4 results) 0.360 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.040 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.033 (uncertainty in the parameter being compared)
100
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 20 °C Lab name NIM China
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Output
(mV)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 19.83 107.761 19.92 -0.09 19.83 196.31 19.63 0.2
Meas 2 19.84 107.780 19.97 -0.13 19.84 196.40 19.64 0.2
Meas 3 19.83 107.750 19.90 -0.07 19.83 196.25 19.63 0.2
Meas 4 19.89 107.783 19.97 -0.08 19.89 197.20 19.72 0.17
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.003 0.023 0.026 0.012 0.007 0.011 0.012 0.006
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.040 0.046 0.044 0.041 0.041 0.041 0.041 0.040
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.09 0.19
Type A standard uncertainty due to reproducibility of difference results 0.019 0.011
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.042 0.041
I column
Difference between 2 means (each the mean of 4 results) 0.290 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.050 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.029 (uncertainty in the parameter being compared)
101
VNIIFTRI ESB
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: -50 °C Lab name VNIIFTRI ES
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 -50.23863 80.230185 -50.19161 -0.0471 -50.23017 80.173120 -50.33529 0.1051
Meas 2 -49.81143 80.398098 -49.76879 -0.0426 -49.80320 80.351449 -49.88626 0.0831
Meas 3 -49.89061 80.366741 -49.84776 -0.0429 -49.88891 80.271832 -50.08675 0.1978
Meas 4 -50.00567 80.314387 -49.97959 -0.0261 -50.00485 80.253659 -50.13250 0.1279
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.0248 0.0220 0.0224 0.0227 0.0248 0.0220 0.0224 0.0227
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.0050 0.0063 0.0078 0.0039 0.0070 0.0052 0.0072 0.0052
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.0253 0.0229 0.0237 0.0230 0.0258 0.0226 0.0235 0.0233
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.0397 0.1285
Type A standard uncertainty due to reproducibility of difference results 0.0093 0.0497
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.0046 0.0249
I column
Difference between 2 means (each the mean of 4 results) -0.168 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.044 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.013 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON
Nominal
value: -30 °C Lab name VNIIFTRI ES
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied
dew point
(°C)
Resistanc
e output
(ohms)
Output in
°C
Difference
(applied
dp - meas
dp) in °C
Applied
dew point
(°C)
Resistanc
e output
(ohms)
Output in
°C
Difference
(applied
dp - meas
dp) in °C
Meas 1 -29.60836 88.390700 -29.57142 -0.0369 -29.60719 88.315073 -29.76317 0.1560
Meas 2 -29.74895 88.325140 -29.73764 -0.0113 -29.74665 88.260019 -29.90274 0.1561
Meas 3 -30.34831 88.096864 -30.31635 -0.0320 -30.34592 88.002911 -30.55450 0.2086
Meas 4 -29.95452 88.227280 -29.98575 0.0312 -29.95270 88.183068 -30.09783 0.1451
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.0222 0.0201 0.0197 0.0220 0.0222 0.0201 0.0197 0.0220
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A)0.0082 0.0063 0.0062 0.0042 0.0090 0.0125 0.0107 0.0134
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.0237 0.0211 0.0207 0.0224 0.0240 0.0237 0.0224 0.0257
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.0122 0.1664
Type A standard uncertainty due to reproducibility of difference results 0.0310 0.0286
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.0155 0.0143
I column
Difference between 2 means (each the mean of 4 results) -0.179 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.077 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.011 (uncertainty in the parameter being compared)
102
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON
Nominal
value: -10 °C Lab name VNIIFTRI ES
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp)
in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in
°C
Meas 1 -11.10640 95.673620 -11.05152 -0.0549 -11.10443 95.567779 -11.32142 0.2170
Meas 2 -11.30619 95.593573 -11.25565 -0.0505 -11.27519 95.498638 -11.49773 0.2225
Meas 3 -11.24888 95.624613 -11.17649 -0.0724 -11.24655 95.532276 -11.41195 0.1654
Meas 4 -11.28372 95.612975 -11.20617 -0.0776 -11.28173 95.516799 -11.45142 0.1697
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.0250 0.0136 0.0152 0.0149 0.0250 0.0136 0.0152 0.0149
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.0015 0.0014 0.0024 0.0015 0.0018 0.0008 0.0022 0.0020
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.0250 0.0137 0.0154 0.0150 0.0251 0.0136 0.0154 0.0150
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.0638 0.1937
Type A standard uncertainty due to reproducibility of difference results 0.0131 0.0303
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.0066 0.0151
I column
Difference between 2 means (each the mean of 4 results) -0.257 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.065 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.008 (uncertainty in the parameter being compared)
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON Nominal value: 1 °C Lab name VNIIFTRI ES
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp) in °C
Meas 1 1.06886 100.423079 1.08269 -0.0138 1.08514 100.335072 0.85744 0.2277
Meas 2 0.96621 100.401048 1.02630 -0.0601 1.00193 100.309507 0.79201 0.2099
Meas 3 1.08839 100.446285 1.14208 -0.0537 1.08968 100.341697 0.87440 0.2153
Meas 4 1.21559 100.507623 1.29908 -0.0835 1.21885 100.383155 0.98050 0.2384
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.0127 0.0143 0.0137 0.0142 0.0127 0.0143 0.0137 0.0142
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.0004 0.0003 0.0002 0.0003 0.0004 0.0003 0.0003 0.0003
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.0127 0.0143 0.0137 0.0142 0.0127 0.0143 0.0137 0.0142
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) -0.0528 0.2228
Type A standard uncertainty due to reproducibility of difference results 0.0290 0.0128
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.0145 0.0064
I column
Difference between 2 means (each the mean of 4 results) -0.276 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.085 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.008 (uncertainty in the parameter being compared)
103
REPORTING TEMPLATE FOR DEW-POINT KEY COMPARISON
Nominal
value: 20 °C Lab name VNIIFTRI ES
Results
Hygrometer 1(Michell) Hygrometer 2 (MBW)
Applied dew
point (°C)
Resistance
output
(ohms)
Output in
°C
Difference
(applied dp -
meas dp)
in °C
Applied dew
point (°C)
Resistance
output (ohms)
Output in
°C
Difference
(applied dp -
meas dp) in
°C
Meas 1 19.86280 107.735573 19.85091 0.0119 19.88897 107.6534408 19.63953 0.2502
Meas 2 19.90056 107.737380 19.85488 0.0457 19.90921 107.6484400 19.62600 0.2832
Meas 3 20.31663 107.910350 20.30005 0.0166 20.31795 107.8150393 20.05475 0.2632
Meas 4 20.04904 107.815613 20.05622 -0.0072 20.05249 107.7046259 19.77059 0.2819
Uncertainties (in °C) Hygrometer 1 Hygrometer 2
Meas 1 Meas 2 Meas 3 Meas 4 Meas 1 Meas 2 Meas 3 Meas 4
Standard uncertainty of applied condition 0.0152 0.0147 0.0149 0.0155 0.0152 0.0147 0.0149 0.0155
Std uncert due to short-term stability (from standard deviation) of measurements of travelling standard (type A) 0.0014 0.0002 0.0004 0.0005 0.0027 0.0002 0.0008 0.0005
Std uncert due to long-term drift of travelling standard [if needed]
Std uncert due to resolution of travelling standard [if needed]
Std uncert due to non-linearity of travelling standard [if needed]
Covariance between applied and measured values of dew/frost-point [if needed]
Combined standard uncertainty (8 values) 0.0153 0.0147 0.0149 0.0155 0.0154 0.0147 0.0149 0.0155
Aggregation of results
Hyg 1 Hyg 2
Mean of 4 dew-point differences (for 2 instruments) 0.0167 0.2696
Type A standard uncertainty due to reproducibility of difference results 0.0219 0.0159
two values (each derived from standard deviation of 4 values on same instrument)
Uncertainty of mean dew point difference for each instrument (2 values) 0.0109 0.0079
I column
Difference between 2 means (each the mean of 4 results) -0.253 (consistency indicator - all labs should hope to get the same value for this)
Average (mid-point) of 2 means (each the mean of 4 results) ** 0.143 (aggregated result - parameter to be compared between institutes)
Uncertainty in average ** 0.007 (uncertainty in the parameter being compared)
104
APPENDIX 3: UNCERTAINTY ANALYSES OF PARTICIPANTS
Uncertainty budgets of each participant are shown on the following pages. These were
reported either in the MS Excel template provided for comparison reporting or as tabulated
information giving a suitable level of detail to cover the main sources of uncertainty. Where
the template was used, included here are selected pages detailing uncertainty calculations at
+20 °C and -50 °C, the extremes of the comparison. The protocol required participants to
report the effective number of degrees of freedom of the uncertainty estimates. In cases
where this was sufficiently large, a coverage factor of 2 is used to obtain an interval for
confidence probability of 95 %. In the few cases where a larger coverage factor was needed,
the detail is included in this Appendix.
105
NPL
The uncertainty routinely reported for calibrations is based on the combined standard
uncertainty of the standard applied condition, together with an allowance for the resolution
and short-term stability of the instrument being calibrated. The result is reported with an
expanded uncertainty at a coverage factor k=2 giving a coverage probability of approximately
95 %.
106
NMIJ
Uncertainty analysis of dew-point standardNominal
value: -50 °C Lab name: NMIJ
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty Unit of u (Qi)
(symbol) uncertainty components evaluated coefficient contribution and/or
by a type A method * comment
Qi u (Qi) n i u i in °C
Primary dew-point generator Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.00236567 infinite 1 0.002 °C
Long-term stability (sensor and indicator) 0.00866179 2.001422222 1 0.009 °C
Self-heating and residual heat fluxes (sensor) 0.00500076 2.001216794 1 0.005 °C
Resolution and accuracy or linearity (indicator unit) 0.00289749 146126.5652 1 0.003 °C
Saturator:
Temperature homogeneity 0.0057735 2 1 0.006 °C
Temperature stability 0.003 8 1 0.003 °C
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 1.59058426 infinite 8.0068E-05 0.000 Pa
Long-term stability (sensor and indicator) 20.9808492 infinite 8.0068E-05 0.002 Pa
Resolution and accuracy or linearity (indicator unit) 0.57735027 infinite 8.0068E-05 0.000 Pa
Pressure differences in the saturator cell 37.9248709 2 8.0068E-05 0.003 Pa
Stability of the pressure 0.55555556 8 8.0068E-05 0.000 Pa
Effect of the tubing between the saturator and the pressure gauge 1.17710124 18.12897416 8.0068E-05 0.000 Pa
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 1.59058426 infinite 8.0068E-05 0.000 Pa
Long-term stability (sensor and indicator) 20.9808492 infinite 8.0068E-05 0.002 Pa
Resolution (indicator unit) 0.57735027 infinite 8.0068E-05 0.000 Pa
Stability of the pressure 0 0.000 This uncertainty is included in the uncertainty due to stability of saturation pressure because gas pressure at the generator outlet is almost same as saturation pressure in our two-temperature generator.
Effect of the tubing between the saturator and the pressure gauge 0.81139293 6.30353879 8.0068E-05 0.000 Pa
Flow measurement:
Flow meter
Stability of the flow 0.01154701 8 0.05 0.001 L/min
Reproducibility 0.02886751 8 0.05 0.001 L/min
Saturation efficiency
Saturation efficiency 0.00103957 6.128943835 8.097518522 0.008 Non-dimentional. Relative uncertainty of efficiency
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant 0 0.000 Not relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e) 1.509E-05 2.142975853 8.097518522 0.000 Non-dimentional. Relative uncertainty of vapour pressure due to uncertainty of formula(e)
Water vapour enhancement formula(e) 1.2535E-06 8 8.097518522 0.000 Non-dimentional. Relative uncertainty of vapour pressure due to uncertainty of formula(e)
Other uncertainties
vapor pressure change in tubing, mainly due to water adsorption and desorption0.02236068 4.411764707 2.057404355 0.046 Pa
resistance of PRT in the travelling standard 0.00601458 264630.4746 2.5 0.015 ohm
Combined standard uncertainty 0.051
Effective degrees of freedom 6.61045735
Expanded uncertainty 0.102
107
Uncertainty analysis of dew-point standardNominal
value: 20 °C Lab name: NMIJ
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertainty components evaluated coefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator Saturation temperature
Thermometer:
t1-1 Calibration uncertainty (sensor and indicator unit) 0.0070 0.98467 0.007
t1-2 Long-term stability (sensor and indicator) 0.0028 0.98467 0.003
t1-3 Self-heating and residual heat fluxes (sensor) 0.0013 0.98467 0.001
t1-4 Resolution and accuracy or linearity (indicator unit) 0.0045 0.98467 0.004
Saturator:
t1-5 Temperature homogeneity 0.0020 99 0.98467 0.002
t1-6 Temperature stability 0.0010 99 0.98467 0.001
Saturation pressure
Pressure gauge:
p1-1 Calibration uncertainty (sensor and indicator unit) 10.4 0.000140856 0.001
p1-2 Long-term stability (sensor and indicator) 76.9 0.000140856 0.011
p1-3 Resolution and accuracy or linearity (indicator unit) 32.2 0.000140856 0.005
p1-4 Pressure differences in the saturator cell
p1-5 Stability of the pressure 4.0 29 0.000140856 0.001
p1-6 Effect of the tubing between the saturator and the pressure gauge 0.0 0.000140856 0.000
Gas pressure at the generator outlet:
Pressure gauge:
p2-1 Calibration uncertainty (sensor and indicator unit) 5.0 0.000159349 0.001
p2-2 Long-term stability (sensor and indicator) 22.9 0.000159349 0.004
p2-3 Resolution (indicator unit) 6.8 0.000159349 0.001
p2-4 Stability of the pressure 1.6 29 0.000159349 0.000
Effect of the tubing between the saturator and the pressure gauge
p2-5
Effect of the tubing between the pressure gauge and the measuring
instrument 29.0 0.000159349 0.005
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e)
Water vapour enhancement formula(e)
Relative Uncertainty due to formulae/calculations
e Saturation vapour pressure formula(e), e(t1),e(td) 0.000071 16.142 0.001
f Water vapour enhancement formula(e), f(p1,t1), f(p2,td) 0.000312 16.142 0.005
Other uncertainties
Combined standard uncertainty 0.017
Effective degrees of freedom 508000
Expanded uncertainty 0.034
108
VSL
Uncertainty analysis of dew-point standardNominal
value: -50 °C Lab name: NMi-VSL
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertainty components evaluated coefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator Infinite if not specified
Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.005 1 0.005
Long-term stability (sensor and indicator) 0.010 1 0.010
Self-heating and residual heat fluxes (sensor) 0.005 1 0.005
Resolution and accuracy or linearity (indicator unit) 0.00003 1 0.000
Saturator:
Temperature homogeneity 0.004 1 0.004
Temperature stability 0.005 9 1 0.005
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit)
Long-term stability (sensor and indicator)
Resolution and accuracy or linearity (indicator unit)
Pressure differences in the saturator cell
Stability of the pressure
Effect of the tubing between the saturator and the pressure gauge
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit)
Long-term stability (sensor and indicator)
Resolution (indicator unit)
Stability of the pressure
Effect of the tubing between the saturator and the pressure gauge
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency 0.008 1 0.008
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e)
Water vapour enhancement formula(e)
Other uncertainties
Contaminations 0.001 1 0.001
Pressuredrop over generator /Pa 43 0.00015 0.00645
Pressuredrop over dewpointmeters /Pa 130 0.00015 0.0195
Combined standard uncertainty 0.026
Effective degrees of freedom 95.5
Expanded uncertainty (95.45 %) 2.03 0.053
109
Uncertainty analysis of dew-point standardNominal
value: 20 °C Lab name: NMi-VSL
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertainty components evaluated coefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator Infinite if not specified
Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.007 1 0.007
Long-term stability (sensor and indicator) 0.011 1 0.011
Self-heating and residual heat fluxes (sensor) 0.005 1 0.005
Resolution and accuracy or linearity (indicator unit) 0.00025 1 0.000
Saturator:
Temperature homogeneity 0.005 1 0.005
Temperature stability 0.012 8 1 0.012
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit)
Long-term stability (sensor and indicator)
Resolution and accuracy or linearity (indicator unit)
Pressure differences in the saturator cell
Stability of the pressure
Effect of the tubing between the saturator and the pressure gauge
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit)
Long-term stability (sensor and indicator)
Resolution (indicator unit)
Stability of the pressure
Effect of the tubing between the saturator and the pressure gauge
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency 0.008 1 0.008
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e)
Water vapour enhancement formula(e)
Other uncertainties
Contaminations 0.001 1 0.001
Pressuredrop over generator /Pa 43 0.00015 0.00645
Pressuredrop over dewpointmeters /Pa 130 0.00015 0.0195
Combined standard uncertainty 0.029
Effective degrees of freedom 4.5
Expanded uncertainty (95.45 %) 2.86931517 0.084
110
MIKES
Uncertainty analysis of dew-point standardNominal
value: -50 °C Lab name: MIKES
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertainty components evaluated coefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.006 50 1 0.006
Long-term stability (sensor and indicator) 0.01 1 0.01
Self-heating and residual heat fluxes (sensor) 0.003 1 0.003
Resolution and accuracy or linearity (indicator unit) 1.00E-06 125.8 0.0001
Saturator:
Temperature homogeneity 0.0060 1 0.0060
Temperature stability 1.43E-06 9 125.8 0.0002
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 2 50 7.94E-05 0.0002
Long-term stability (sensor and indicator) 2.3 7.94E-05 0.0002
Resolution and accuracy or linearity (indicator unit) 1 7.94E-05 0.0001
Pressure differences in the saturator cell (eli Pes) 14.13 7.94E-05 0.0011
Stability of the pressure 2.89 7.94E-05 0.0002
Effect of the tubing between the saturator and the pressure gauge 12 7.94E-05 0.0010
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 2 50 7.94E-05 0.0002
Long-term stability (sensor and indicator) 2.3 7.94E-05 0.0002
Resolution (indicator unit) 1 7.94E-05 0.0001
Stability of the pressure 2.89 7.94E-05 0.0002
Effect of the tubing between the dew-point cell and the pressure gauge 10.68 7.94E-05 0.0008
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency 0.017 1 0.017
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e)
Water vapour enhancement formula(e)
Other uncertainties
Combined standard uncertainty 0.022
Effective degrees of freedom 8668
Expanded uncertainty 0.044
Effective degrees of freedom including type B components 44
111
Uncertainty analysis of dew-point standardNominal
value: 20 °C Lab name: MIKES
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertainty components evaluated coefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.007 50 1 0.007
Long-term stability (sensor and indicator) 0.002 1 0.002
Self-heating and residual heat fluxes (sensor) 0.003 1 0.003
Resolution and accuracy or linearity (indicator unit) 0.000 128.5 0.0001
Saturator:
Temperature homogeneity 0.007 1 0.007
Temperature stability 2.59E-06 9 128.5 0.0003
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 2 50 0.0002 0.0003
Long-term stability (sensor and indicator) 2.3 0.0002 0.0004
Resolution and accuracy or linearity (indicator unit) 1 0.0002 0.0002
Pressure differences in the saturator cell, Pes 15.48 0.0002 0.0024
Stability of the pressure 2.89 0.0002 0.0004
Effect of the tubing between the saturator and the pressure gauge 12 0.0002 0.0018
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 2 50 0.0002 0.0003
Long-term stability (sensor and indicator) 2.3 0.0002 0.0004
Resolution (indicator unit) 1 0.0002 0.0002
Stability of the pressure 2.89 0.0002 0.0004
Effect of the tubing between the dew-point cell and the pressure gauge 48.35 0.0002 0.0074
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency 0.017 1 0.017
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e) 0.004
Water vapour enhancement formula(e)
Other uncertainties
Combined standard uncertainty 0.022
Effective degrees of freedom 4732
Expanded uncertainty 0.044
Effective degrees of freedom including type B components 44
112
INTA
Uncertainty analysis of dew-point standardNominal
value: -50 Lab name INTA
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Saturator temperature (ºC) -42.04
Saturator pressure (Pa) 264402
Chamber pressure (Pa) 101310
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertainty components evaluated coefficient contribution
by a type A method *
Qi u(Qi) n i u i in °C
Primary dew-point generator Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.002 50 0.932 0.0019
Long-term stability (sensor and indicator) 0.005 50 0.932 0.0047
Self-heating and residual heat fluxes (sensor) 0.001 50 0.932 0.0009
Resolution and accuracy or linearity (indicator unit) 0.001 50 0.932 0.0009
Saturator:
Temperature homogeneity 0.012 50 0.932 0.0108
Temperature stability 0.003 30 0.932 0.0028
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 6 50 -3.020E-05 -0.0002
Long-term stability (sensor and indicator) 112.4 50 -3.020E-05 -0.0034
Resolution and accuracy or linearity (indicator unit) 1 50 -3.020E-05 0.0000
Pressure differences in the saturator cell 20 50 -3.020E-05 -0.0006
Stability of the pressure 60 30 -3.020E-05 -0.0018
Effect of the tubing between the saturator and the pressure gauge 10 50 -3.020E-05 -0.0003
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 6 50 7.948E-05 0.0005
Long-term stability (sensor and indicator) 90.8 50 7.948E-05 0.0072
Resolution (indicator unit) 0.6 50 7.948E-05 0.0000
Stability of the pressure 20 30 7.948E-05 0.0016
Effect of the tubing between the saturator and the pressure gauge 6 50 7.948E-05 0.0005
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(es) 0.0022 50 7.99 0.0176
Water vapour enhancement formula(fs) 0.001 50 8.10 0.0065
Saturation vapour pressure formula(ed) 0.0026 50 -8.10 -0.0211
Water vapour enhancement formula(fd) 0.0003 50 -8.10 -0.0026
Other uncertainties
Pressure drop in sampling line 5.77 50 7.948E-05 0.0005
0.0000
0.0000
Combined standard uncertainty 0.032
Effective degrees of freedom 168
Expanded uncertainty 2.01 0.064
113
Uncertainty analysis of dew-point standardNominal
value: 20 Lab name INTA
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Saturator temperature (ºC) 30.01
Saturator pressure (Pa) 184503
Chamber pressure (Pa) 101322
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) coefficient
Qi
Primary dew-point generator Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.002 50 0.927 0.0019
Long-term stability (sensor and indicator) 0.005 50 0.927 0.0046
Self-heating and residual heat fluxes (sensor) 0.001 50 0.927 0.0009
Resolution and accuracy or linearity (indicator unit) 0.001 50 0.927 0.0009
Saturator:
Temperature homogeneity 0.012 50 0.927 0.0107
Temperature stability 0.003 30 0.927 0.0028
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 6 50 -8.703E-05 -0.0005
Long-term stability (sensor and indicator) 112.4 50 -8.703E-05 -0.0098
Resolution and accuracy or linearity (indicator unit) 1 50 -8.703E-05 -0.0001
Pressure differences in the saturator cell 100 50 -8.703E-05 -0.0087
Stability of the pressure 60 30 -8.703E-05 -0.0052
Effect of the tubing between the saturator and the pressure gauge 10 50 -8.703E-05 -0.0009
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 6 50 1.587E-04 0.0010
Long-term stability (sensor and indicator) 90.8 50 1.587E-04 0.0144
Resolution (indicator unit) 0.6 50 1.587E-04 0.0001
Stability of the pressure 20 30 1.587E-04 0.0032
Effect of the tubing between the saturator and the pressure gauge 6 50 1.587E-04 0.0009
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(es) 5.000E-05 50 16.057 0.0008
Water vapour enhancement formula(fs) 1.122E-04 50 16.138 0.0018
Saturation vapour pressure formula(ed) 5.000E-05 50 -16.138 -0.0008
Water vapour enhancement formula(fd) 6.858E-05 50 -16.138 -0.0011
Other uncertainties
Pressure drop in sampling line 5.77 50 1.587E-04 0.0009
0.0000
0.0000
Combined standard uncertainty 0.0240
Effective degrees of freedom 226
Expanded uncertainty 2.01 0.048
114
INRIM
Uncertainty analysis of dew-point standardNominal
value: -50 Lab name: INRIM
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertainty components evaluated coefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.005 50 1 0.005
Long-term stability (sensor and indicator) 0.006 50 1 0.006
Self-heating and residual heat fluxes (sensor) 0.005 50 1 0.005
Resolution and accuracy or linearity (indicator unit) 0.003 50 1 0.003
Saturator:
Temperature homogeneity 0.020 50 1 0.020
Temperature stability 0.004 40 1 0.004
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 20 50 7.5E-05 0.002
Long-term stability (sensor and indicator) 50 50 7.5E-05 0.004
Resolution and accuracy or linearity (indicator unit) 0.2 50 7.5E-05 0.000
Pressure differences in the saturator cell 10 20 7.5E-05 0.001
Stability of the pressure 11 40 7.5E-05 0.001
Effect of the tubing between the saturator and the pressure gauge 20 20 7.5E-05 0.002
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 3.3 50 7.5E-05 0.000
Long-term stability (sensor and indicator) 2.5 50 7.5E-05 0.000
Resolution (indicator unit) 0.4 50 7.5E-05 0.000
Stability of the pressure 7 20 7.5E-05 0.001
Effect of the tubing between the saturator and the pressure gauge 0 20 7.5E-05 0.000
Flow measurement:
Flow meter
Stability of the flow 0 10 3.0E-03 0.000
Resolution 0.05 50 3.0E-03 0.000
Saturation efficiency
Saturation efficiency 0.005 50 1 0.005
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e)
Water vapour enhancement formula(e)
Other uncertainties
Desorption Effect 0.004 50 1 0.004
Saturator thermometer interpolation curve 0.006 50 1 0.006
Combined standard uncertainty 0.025
Effective degrees of freedom 113
Expanded uncertainty 0.049
Additional uncertainty in applied condition at point of use
Pressure drop between point of realisation and measuring instrument 7 20 7.5E-05 0.001
Other
* for type B method the number of degrees of freedom will be considered as being larger than 50.
(Degrees of freedom of 50 for a component of type B corresponds 10 % in relative uncertainty of the uncertainty estimate u Qi; see Annex G of the ISO Guide)
Combined uncertainty 0.025
Effective degrees of freedom 113
Expanded uncertainty 0.049
115
Uncertainty analysis of dew-point standardNominal
value: 20 °C Lab name: INRiM
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertainty components evaluated coefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.005 50 1 0.005
Long-term stability (sensor and indicator) 0.012 50 1 0.012
Self-heating and residual heat fluxes (sensor) 0.005 50 1 0.005
Resolution and accuracy or linearity (indicator unit) 0.003 50 1 0.003
Saturator:
Temperature homogeneity 0.005 50 1 0.005
Temperature stability 0.001 40 1 0.001
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 20 50 1.5E-04 0.003
Long-term stability (sensor and indicator) 50 50 1.5E-04 0.007
Resolution and accuracy or linearity (indicator unit) 0.2 50 1.5E-04 0.000
Pressure differences in the saturator cell 35 20 1.5E-04 0.005
Stability of the pressure 32 40 1.5E-04 0.005
Effect of the tubing between the saturator and the pressure gauge 20 20 1.5E-04 0.003
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 3.3 50 1.5E-04 0.000
Long-term stability (sensor and indicator) 2.5 50 1.5E-04 0.000
Resolution (indicator unit) 0.4 50 1.5E-04 0.000
Stability of the pressure 3.1 20 1.5E-04 0.000
Effect of the tubing between the saturator and the pressure gauge 0 20 1.5E-04 0.000
Flow measurement:
Flow meter
Stability of the flow 0 10 0.006 0.000
Resolution 0.05 50 0.006 0.000
Saturation efficiency
Saturation efficiency 0.005 50 1 0.005
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e)
Water vapour enhancement formula(e)
Other uncertainties
Desorption Effect 0 50 1 0.000
Saturator thermometer interpolation curve 0.004 50 1 0.004
Combined standard uncertainty 0.020
Effective degrees of freedom 264
Expanded uncertainty 0.040
Additional uncertainty in applied condition at point of use
Pressure drop between point of realisation and measuring instrument 40 50 1.5E-04 0.006
Other
* for type B method the number of degrees of freedom will be considered as being larger than 50.
(Degrees of freedom of 50 for a component of type B corresponds 10 % in relative uncertainty of the uncertainty estimate u Qi; see Annex G of the ISO Guide)
Combined standard uncertainty 0.021
Effective degrees of freedom 301
Expanded uncertainty 0.042
116
NIST
Uncertainty of dew/frost-point standard
Nominal
value: -10 °C Lab name: NIST/USA
CCT-K6
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertaintycomponents evaluatedcoefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator
Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.001°C 0.8 0.001
Long-term stability (sensor and indicator) 0.001 °C 0.8 0.001
Self-heating and residual heat fluxes (sensor) 0.000 °C 0.8 0.000
Resolution and accuracy or linearity (indicator unit) 0.000 °C 0.8 0.000
Saturator:
Temperature homogeneity 0.001 °C 0.8 0.001
Temperature stability 0.001 °C 50 0.8 0.001
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 39 Pa 0.00004 0.002
Long-term stability (sensor and indicator) 7 Pa 0.00004 0.000
Resolution and accuracy or linearity (indicator unit) 7 Pa 0.00004 0.000
Pressure differences in the saturator cell 7 Pa 0.00004 0.000
Stability of the pressure 9 Pa 50 0.00004 0.000
Effect of the tubing between the saturator and the pressure gauge0 Pa 0.00004 0.000
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 18 Pa 0.00011 0.002
Long-term stability (sensor and indicator) 7 Pa 0.00011 0.001
Resolution (indicator unit) 1 Pa 0.00011 0.000
Stability of the pressure 7 Pa 50 0.00011 0.001
Effect of the tubing between the saturator and the pressure gauge0 Pa 0.00011 0.000
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency 0.002 °C 0.002
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e) .06 Pa 0.044 0.002
Water vapour enhancement formula(e) 0.0005 11 0.007
Other uncertainties
Combined standard uncertainty 0.008
Effective degrees of freedom
Expanded uncertainty 0.017
117
Uncertainty of dew/frost-point standard
Nominal
value: 20 °C Lab name: NIST/USA
CCT-K6
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertaintycomponents evaluatedcoefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator
Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.001°C 1 0.001
Long-term stability (sensor and indicator) 0.001 °C 1 0.001
Self-heating and residual heat fluxes (sensor) 0.000 °C 1 0.000
Resolution and accuracy or linearity (indicator unit) 0.000 °C 1 0.000
Saturator:
Temperature homogeneity 0.001 °C 1 0.001
Temperature stability 0.000 °C 50 1 0.000
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 18 Pa 0.00016 0.003
Long-term stability (sensor and indicator) 7 Pa 0.00016 0.001
Resolution and accuracy or linearity (indicator unit) 7 Pa 0.00016 0.001
Pressure differences in the saturator cell 7 Pa 0.00016 0.001
Stability of the pressure 9 Pa 50 0.00016 0.001
Effect of the tubing between the saturator and the pressure gauge0 Pa 0.000
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 18 Pa 0.00016 0.003
Long-term stability (sensor and indicator) 7 Pa 0.00016 0.001
Resolution (indicator unit) 1 Pa 0.00016 0.000
Stability of the pressure 7 Pa 50 0.00016 0.001
Effect of the tubing between the saturator and the pressure gauge0 Pa 0.00016 0.000
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency 0.002 °C 1 0.002
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e) .15 Pa 0.007 0.002
Water vapour enhancement formula(e) 0.0002 16 0.004
Other uncertainties
Combined standard uncertainty 0.007
Effective degrees of freedom
Expanded uncertainty 0.014
118
NMC
Uncert
ain
ty o
f 4500 fro
st
poin
t genera
tor
Td
(°C
)
Ts
(°C
)
DTs
(°C
)
u(T
s)
(°C
)P
s(P
a)
DP
s
(Pa)
u(P
s)
(°C
)P
c (
Pa)
DP
c
(Pa)
u(P
c)
(°C
)
Es(T
s)
(Pa)
DE
s(T
s)
(form
ula
)
(Pa)
u(E
s(T
s))
(°C
)f(Ts,P
s)
D(fs)
u(fs)
(°C
)f(Td,P
c)
D(fd)
u(fd)
(°C
)
Es(T
d)
(Pa)
DE
s(T
d)
(form
ula
)
(Pa)
u(E
s(T
d))
(°C
)
Effe
ct
of
perm
eation
(°C
) u_c(T
d)
-50
-44.9
0.0
17
0.0
16
186848
103
-0.0
04
100663
14
0.0
01
7.3
0.0
20.0
19
1.0
100
0.0
006
0.0
05
1.0
055
0.0
003
-0.0
03
3.9
0.0
102
0.0
21
0.0
09
0.0
35
-50
-40.0
0.0
17
0.0
16
332120
103
-0.0
03
100663
14
0.0
01
12.8
0.0
30.0
17
1.0
172
0.0
010
0.0
08
1.0
055
0.0
003
-0.0
03
3.9
0.0
102
0.0
21
0.0
09
0.0
34
-50
-35.0
0.0
17
0.0
15
588123
103
-0.0
01
100663
14
0.0
01
22.3
0.0
40.0
15
1.0
293
0.0
017
0.0
13
1.0
055
0.0
003
-0.0
03
3.9
0.0
102
0.0
21
0.0
09
0.0
34
-50
-33.5
0.0
17
0.0
15
685339
103
-0.0
01
100663
14
0.0
01
26.3
0.0
50.0
14
1.0
337
0.0
020
0.0
15
1.0
055
0.0
003
-0.0
03
3.9
0.0
102
0.0
21
0.0
09
0.0
35
-30
-24.9
0.0
17
0.0
16
168232
103
-0.0
06
100663
14
0.0
01
63.9
0.0
90.0
13
1.0
074
0.0
004
0.0
04
1.0
045
0.0
002
-0.0
02
38.0
0.0
608
0.0
15
0.0
00
0.0
27
-30
-20.0
0.0
17
0.0
16
277307
103
-0.0
04
100663
14
0.0
01
103.2
0.1
10.0
10
1.0
117
0.0
006
0.0
06
1.0
045
0.0
002
-0.0
02
38.0
0.0
608
0.0
15
0.0
00
0.0
25
-30
-15.0
0.0
17
0.0
15
444712
103
-0.0
02
100663
14
0.0
01
165.3
0.1
40.0
08
1.0
181
0.0
009
0.0
09
1.0
045
0.0
002
-0.0
02
38.0
0.0
608
0.0
15
0.0
00
0.0
25
-30
-10.0
0.0
17
0.0
14
705334
103
-0.0
01
100663
14
0.0
01
259.9
0.1
60.0
06
1.0
277
0.0
014
0.0
13
1.0
045
0.0
002
-0.0
02
38.0
0.0
608
0.0
15
0.0
00
0.0
26
-10
-5.0
0.0
17
0.0
16
155822
103
-0.0
07
100663
14
0.0
02
401.7
0.1
40.0
04
1.0
060
0.0
003
0.0
03
1.0
040
0.0
002
-0.0
02
259.9
0.1
559
0.0
07
0.0
00
0.0
20
-10
0.0
0.0
17
0.0
14
239455
103
-0.0
05
100663
14
0.0
02
611.2
0.0
30.0
01
1.0
087
0.0
003
0.0
03
1.0
040
0.0
002
-0.0
02
259.9
0.1
559
0.0
07
0.0
00
0.0
17
Note
:1
23
45
67
89
Td
Fro
st
or
dew
poin
t
Ts
Satu
ration t
em
pera
ture
DTs U
ncert
ain
ty in s
atu
ration t
em
pera
ture
measure
ment
as in t
he u
ncert
ain
ty a
naly
sis
for
the s
atu
ration t
em
pera
ture
Ps
Satu
ration p
ressure
DP
sU
ncert
ain
ty in s
atu
ration p
ressure
measure
ment
as in t
he u
ncert
ain
ty a
naly
sis
for
the s
atu
ration p
ressure
Pc
Cham
ber
pre
ssure
DP
cU
ncert
ain
ty in c
ham
ber
pre
ssure
measure
ment
as in t
he u
ncert
ain
ty a
naly
sis
for
the c
ham
ber
pre
ssure
1,7
The w
ate
r satu
ration v
apor
pre
ssure
is c
alc
ula
ted b
ased o
n B
ob H
ard
y ITS
-90 form
ula
tion
2,8
Assum
e u
ncert
ain
ty o
n t
he w
ate
r satu
ration v
apor
pre
ssure
form
ula
tion is 0
.005%
for
t>=
0 a
nd (
0.0
1-0
.005*t
)% for
t<0
3,5
The e
nhancem
ent
facto
r is
calc
ula
ted b
ased o
n G
reenspan form
ula
tion
4,6
The u
ncert
ain
ty o
f th
e e
nhancem
ent
facto
r is
calc
ula
ted b
ased o
n J
ere
my L
ove
ll-S
mith's
fit t
o t
he o
rigin
al uncert
ain
ty o
f th
e G
reenspan form
ula
tion
9
The fitte
d v
alu
e o
f diff
ere
nces in s
atu
ration v
apor
pre
ssure
is c
onsid
ere
d a
s u
ncert
ain
ty a
nd c
om
bin
ed w
ith a
ll oth
er
uncert
ain
ty c
om
ponents
. N
o c
orr
ection is d
one.
Uncert
ain
ty o
f 2500 h
um
idity g
enera
tor
Td
(°C
)
Ts
(°C
)
DTs
(°C
)
u(T
s)
(°C
)P
s (
Pa)
DP
s
(Pa)
u(P
s)
(°C
)P
c (
Pa)
DP
c
(Pa)
u(P
c)
(°C
)
Es (
Ts)
(Pa)
DE
s (
Ts)
(form
ula
)
(Pa)
u(E
s(T
s))
(°C
)
Es(T
d)
(Pa)
DE
d
(form
ula
)
(Pa)
u(E
s(T
d))
(°C
)fs
(Ts,P
s)
D(fs)
u(fs)
(°C
)fd
(Td,P
c)
D(fd)
u(fd)
(°C
)E
s(T
s)
(Pa)
Des (
sat-
eff)
(Pa)
u(s
at-
eff)
(°C
)u_c(T
d)
-10
00.0
36
0.0
30
236835
145
-0.0
07
100663
14
0.0
02
611.2
10.0
30561
0.0
01
259.8
70.0
12994
0.0
07
1.0
0861
0.0
003
0.0
03
1.0
04
0.0
0018
-0.0
02
611.2
1291
0.8
7403446
0.0
16
0.0
35
12
0.0
36
0.0
36
107903
145
-0.0
19
100663
14
0.0
02
705.9
70.0
35299
0.0
01
657.0
80.0
32854
0.0
01
1.0
0408
0.0
001
0.0
02
1.0
0383
0.0
0011
-0.0
01
705.9
7325
1.0
0954175
0.0
20
0.0
45
115
0.0
36
0.0
32
262070
145
-0.0
08
100663
14
0.0
02
1705.7
0.0
85286
0.0
01
657.0
80.0
32854
0.0
01
1.0
0885
0.0
002
0.0
03
1.0
0383
0.0
0011
-0.0
01
1705.7
228
2.4
3918354
0.0
20
0.0
39
121
0.0
36
0.0
31
383280
145
-0.0
05
100663
14
0.0
02
2488.2
0.1
24408
0.0
01
657.0
80.0
32854
0.0
01
1.0
1228
0.0
003
0.0
04
1.0
0383
0.0
0011
-0.0
01
2488.1
697
3.5
5808263
0.0
20
0.0
37
20
21
0.0
36
0.0
36
106800
145
-0.0
22
100663
14
0.0
02
2488.2
0.1
24408
0.0
01
2339.3
0.1
16963
0.0
01
1.0
0417
7E
-05
0.0
01
1.0
0397
6.8
E-0
5-0
.001
2488.1
697
3.5
5808263
0.0
23
0.0
48
20
40
0.0
36
0.0
31
318676
145
-0.0
07
100663
14
0.0
02
7385.3
0.3
69265
0.0
01
2339.3
0.1
16963
0.0
01
1.0
103
0.0
003
0.0
05
1.0
0397
6.8
E-0
5-0
.001
7385.2
991
10.5
609777
0.0
23
0.0
40
Note
12
34
56
78
910
Ts
Satu
ration t
em
pera
ture
DTs U
ncert
ain
ty in s
atu
ration t
em
pera
ture
measure
ment
as in t
he u
ncert
ain
ty a
naly
sis
for
the s
atu
ration t
em
pera
ture
Ps
Satu
ration p
ressure
DP
sU
ncert
ain
ty in s
atu
ration p
ressure
measure
ment
as in t
he u
ncert
ain
ty a
naly
sis
for
the s
atu
ration p
ressure
Pc
Cham
ber
pre
ssure
DP
cU
ncert
ain
ty in c
ham
ber
pre
ssure
measure
ment
as in t
he u
ncert
ain
ty a
naly
sis
for
the c
ham
ber
pre
ssure
1,3
,9The w
ate
r satu
ration v
apor
pre
ssure
is c
alc
ula
ted b
ased o
n B
ob H
ard
y ITS
-90 form
ula
tion
2,4
Assum
e u
n u
ncert
ain
ty o
n t
he w
ate
r satu
ration v
apor
pre
ssure
form
ula
tion o
f 0.0
05%
for
t>=
0
5,7
The e
nhancem
ent
facto
r is
calc
ula
ted b
ased o
n G
reenspan form
ula
tion
6,8
The u
ncert
ain
ty o
f th
e e
nhancem
ent
facto
r is
calc
ula
ted b
ased o
n J
ere
my L
ove
ll-S
mith's
fit t
o t
he o
rigin
al uncert
ain
ty o
f th
e G
reenspan form
ula
tion
10
The s
atu
ration e
fficie
ncy is t
aken fro
m T
hunder
Scie
ntific
's e
stim
ation w
hic
h is 0
.143 %
of satu
ration p
ressure
The e
ffect
of perm
eation is v
erifie
d b
y g
enera
ting t
he s
am
e fro
st
poin
t at
diff
ere
nt
com
bin
ations o
f satu
ration t
em
pera
ture
and s
atu
ration p
ressure
. The o
bta
ined d
iffere
nces in fro
st
poin
t are
conve
rted t
o
equiv
ale
nt
diff
ere
nces in s
atu
ration v
apor
pre
ssure
. The d
iffere
nce in s
atu
ration v
apor
pre
ssure
is fitte
d a
gain
st
the s
atu
ration t
em
pera
ture
by a
lin
e a
nd e
xtr
apola
ted t
o s
atu
ration t
em
pera
ture
of -5
0°C
.
119
Uncertainty analysis for Michell at -50 point when minimum degree of freedom occurs
Sources of uncertainty [U](°C) kstd. uncertainty (u) u 2 degree of freedom u 4/DOF
1
Standard uncertainty of applied condition except
type A (average of 6 measures) 0.0345 1 0.0345 1.1902500E-03 100000000 1.4166951E-14
2
Standard uncertainty of applied condition type A
(average of 6 measures) (total 13 records and each
record has 20 rdgs) 0.0022 1 0.002233 4.9877778E-06 259 9.6053773E-14
3
Std uncert due to short-term stability (from
standard deviation) of measurements of traveling
standard (type A) (average of 6 measures) (total 13
records and each record has 120 rdgs) 0.0282 1 0.028193 7.9486607E-04 1559 4.0526752E-10
4
Std uncert due to the resistance measurement
uncertainty of traveling standard 0.0005 1 0.0005 2.5000000E-07 100000000 6.2500000E-22
5 Std uncert due to resolution of traveling standard 0.0003 1 0.0003 9.0000000E-08 100000000 8.1000000E-23
6 Reproducibility (6 measures) 0.0250 1 0.024982 6.2410913E-04 5 7.7902441E-08
sum u 2 0.00261455 sum u 4/DOF 7.83078186E-08
Combined Uncer. (Uc) 0.05113270 EDOF 87.29507964
k 2
120
NIM
-50
Quantity Estimate Standard
Uncertainty
Sensitivity
Coefficient
Contribution to
standard
uncertainty
ts -40.05 0.018 0.9/ 0.0162
ps 334256Pa 313Pa -0.00002 /Pa -0.0063
po 101405Pa 62Pa 0.00008/Pa 0.0050
es 13Pa 0.03Pa 0.63/Pa 0.0189
ed 4Pa 0.01Pa -2.06/Pa -0.0206
fs 1.017 0.001 8.0 0.0080
fd 1.006 0.0003 -8.1 -0.0024
td -50 0.0344
Permeation
& leaks 0.03 1/ 0.03
Saturator
efficiency 0.05 1/ 0.05
Combined uncertainty of generator 0.068
Sources of uncertainty uncertainty degree of
freedom
Standard Uncertainty of applied condition except type A 0.068 ∞
Standard Uncertainty of applied condition type A 0.019 11
Standard Uncertainty due to short-term stability of measurement of
traveling standard (type A) 0.012 11
Standard Uncertainty due to the resistance measurement of traveling
standard 0.005 ∞
Standard Uncertainty due to resolution of traveling standard 0.003 ∞
Combined uncertainty 0.072 EDOF
Expanded uncertainty(k=2) 0.15 1956
121
+20
Quantity Estimate Standard
Uncertainty
Sensitivity
Coefficient
Contribution to
standard
uncertainty
ts 30.02 0.018 0.9/ 0.0162
ps 184512 Pa 156Pa -0.00009/Pa -0.0140
po 101425Pa 62Pa 0.00016/Pa 0.0099
es 4247Pa 0.21Pa 0.01/Pa 0.0021
ed 2339Pa 0.12Pa -0.01/Pa -0.0012
fs 1.007 0.0002 16 0.0032
fd 1.004 0.0001 -16.1 -0.0016
td 20 0.0241
Permeation
& leaks 0.02 1/ 0.02
Saturator
efficiency 0.02 1/ 0.02
Combined uncertainty of generator 0.038
Sources of uncertainty degree of
freedom
Standard Uncertainty of applied condition except type A 0.038 ∞
Standard Uncertainty of applied condition type A 0.012 11
Standard Uncertainty due to short-term stability of measurement of
traveling standard (type A) 0.026 11
Standard Uncertainty due to the resistance measurement of traveling
standard 0.005 ∞
Standard Uncertainty due to resolution of traveling standard 0.003 ∞
Combined uncertainty 0.048 EDOF
Expanded uncertainty(k=2) 0.10 122
122
VNIIFTRI ESB
Uncertainty analysis of dew-point standardNominal
value: -50°C Lab name: VNIIFTRI ES
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Meas 4 14.02.2009 00:24-00:34 (19)
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertainty components evaluated coefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.005581 0.68149 0.0054
Long-term stability (sensor and indicator)
Self-heating and residual heat fluxes (sensor)
Resolution and accuracy or linearity (indicator unit)
Saturator:
Temperature homogeneity 0.006 0.681490 0.0058
Temperature stability
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 77.2868 2.67512E-05 0.0043
Long-term stability (sensor and indicator)
Resolution and accuracy or linearity (indicator unit)
Pressure differences in the saturator cell
Stability of the pressure
Effect of the tubing between the saturator and the pressure gauge
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 49.731775 3.92423E-05 0.0041
Long-term stability (sensor and indicator)
Resolution (indicator unit)
Stability of the pressure
Effect of the tubing between the saturator and the pressure gauge
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency 0.002 1 0.0020
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e) (saturation) 0.002 0.68149 0.0161
Water vapour enhancement formula(e) (saturation) 0.000187 3.864181 0.0015
Other uncertainties
Saturation vapour pressure formula(e) (at generator outlet) 0.002156 0.68149 0.0119
Water vapour enhancement formula(e) (at generator outlet) 0.0002 3.863028 0.0016
Std uncert due to short-term stability generaror (type A) 0.002097 9 1 0.0021
Combined standard uncertainty 0.0227
Effective degrees of freedom infinity
Expanded uncertainty (p=99.97) 0.0680
123
Uncertainty analysis of dew-point standardNominal
value: 20°C Lab name: VNIIFTRI ES
CCT Key Comparison in humidity (dew-point temperature) CCT-K6
- each participant submits one spreadsheet summary per nominal dew point measured in the comparison (5 sheets in total)
Meas 3 12.02.2009 21:23-21:30 (14)
Quantity Components Standard Degrees of freedom Sensitivity Uncertainty
(symbol) uncertainty components evaluated coefficient contribution
by a type A method *
Qi u (Qi) n i u i in °C
Primary dew-point generator Saturation temperature
Thermometer:
Calibration uncertainty (sensor and indicator unit) 0.005626 0.743459 0.0054
Long-term stability (sensor and indicator)
Self-heating and residual heat fluxes (sensor)
Resolution and accuracy or linearity (indicator unit)
Saturator:
Temperature homogeneity 0.006 0.743459 0.0058
Temperature stability
Saturation pressure
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 77.064546 0.018085 0.0094
Long-term stability (sensor and indicator)
Resolution and accuracy or linearity (indicator unit)
Pressure differences in the saturator cell
Stability of the pressure
Effect of the tubing between the saturator and the pressure gauge
Gas pressure at the generator outlet:
Pressure gauge:
Calibration uncertainty (sensor and indicator unit) 49.385668 0.024325 0.0081
Long-term stability (sensor and indicator)
Resolution (indicator unit)
Stability of the pressure
Effect of the tubing between the saturator and the pressure gauge
Flow measurement:
Flow meter
Stability of the flow
Reproducibility
Saturation efficiency
Saturation efficiency 0.002 1 0.0020
Correlation between pressure and temperature measurement (if relevant)
Correlation between pressure and temperature measurement if relevant
Uncertainty due to formulae/calculations
Saturation vapour pressure formula(e) (saturation) 0.000045 0.743458608 0.0007
Water vapour enhancement formula(e) (saturation) 0.00005 2391.902523 0.0008
Other uncertainties
Saturation vapour pressure formula(e) (at generator outlet) 0.000043 0.743458608 0.0005
Water vapour enhancement formula(e) (at generator outlet) 6.6667E-05 2391.902523 0.0011
Std uncert due to short-term stability generaror (type A) 0.000526 9 1 0.0005
Combined standard uncertainty 0.0149
Effective degrees of freedom infinity
Expanded uncertainty (p=99.97) 0.0448