afrimets supplementary comparison programme calibration of … · 2015-08-31 · calibration of...

AFRIMETS L.S3 Final report Calibration of Gauge Blocks by Mechanical Comparison Method

1

AFRIMETS Secretariat Private Bag X34 Lynnwood Ridge 0040

AFRIMETS

Supplementary Comparison Programme

Calibration of Gauge Blocks

by Mechanical Comparison Method

AFRIMETS.L–S3

Final Report Giza, Egypt, March 2015 M. Amer, F. Abdel Aziz


2

Contents Page No.

Abstract ................................................................................................................................. 3

1. Introduction ......................................................................................................................... 3

2. Aim of the Programme ........................................................................................................ 4

3. Participants .......................................................................................................................... 4

4. Design of the Programme ................................................................................................... 4

5. Reporting .............................................................................................................................. 6

6. Measurement equipment used by the participants ........................................................... 6

7. Stability of the travelling standards ................................................................................... 6

8. Analysis of results ................................................................................................................. 9

9. Reference Values ................................................................................................................ 11

10. Results as reported by the Participants ......................................................................... 12

11. Discussion of measurements results ............................................................................... 18

12. Conclusions ....................................................................................................................... 21

13. List of References ............................................................................................................. 21


3

Abstract:

A round robin comparison in calibration of gauge blocks by mechanical comparison method

between NMIs of Arab countries in addition to the NMI of South Africa was carried out during

the period of November 2011 to July 2013, The Arab Federation for Metrology (AFM)

identification number for this comparison is: ARABMET L.S.1. NIS-Egypt acted as the pilot

laboratory. One set of gauge blocks, with nominal size: 1 mm, 5 mm, 10 mm, 40 mm, 90 mm

were circulated. This comparison was registered in the BIPM KCDB in June 2012 as an

AFRIMETS supplementary comparison under the identifier AFRIMETS.L-S3. The results

obtained are represented in this report. Coordination of the programme has been done by the

AFM technical support unit.

1- Introduction:

The Technical Support Unit (TSU) of the Arab Federation for Metrology (AFM) developed a

questionnaire to assist the Arab Metrology Programme ARABMET to develop appropriate

protocols and schedules for an intended intercomparisons schemes. In May 2011 the TSU

distributed the questionnaire among Arab Metrology Institutions. Positive response was

received from 5 Arab NMIs requesting the participation in two fields, namely Length and Mass

Measurements. The comparison programme proposed for length was of the Round Robin type

on Gauge Blocks calibration, up to 100 mm, by mechanical means.

It was then decided that the AFM, the observer member of the Intra-Africa Metrology System

(AFRIMETS), would extend its invitation to the National Metrology Institutes, NMIs to participate

in measurement comparison programmes in the prescribed metrological fields. The comparison

programmes were designed, organized and coordinated by AFM TSU under technical support

of the National Institute for Standards (NIS) of Egypt being an active member of both the

Programme and the Federation at the time. The comparison programme was open for NMIs of

the members and non members Arab states of the Federation. The comparisons were to be

conducted following appropriate measurement protocols.

The objectives of the comparison programmes are to provide the participating laboratories with

the means for comparing their measurement results, opportunities for technical capability

improvements and recognition of Calibration and Measurements Capabilities (CMCs). AFM,

being an observer member of the AFRIMETS, worked through concerned AFRIMETS

authorities to submit the comparison programmes for registration as AFRIMETS supplementary

comparisons on the BIPM KCDB. Thus, the National Metrology Institute of South Africa

(NMISA) has been invited to join the round robin scheme.

Five gauge blocks, with nominal size 1 mm, 5 mm, 10 mm, 40 mm and 90 mm are chosen as

the artifacts for the comparison. All of them are made of steel according to ISO 3650:1998. The

Engineering and Surface Metrology laboratory (ESML) of NIS - Egypt provided the travelling

standards and the comparison protocol. The measurements in this comparison were carried out

from November 2011 to July 2013.


4

The measurements were carried out according to a protocol approved by the concerned

Regional Metrology Organization technical authorities, namely AFRIMETS.TCL.

2- Aim of the Programme:

The aim of this comparison is to give confidence in the technical capacity of the AFM members

and non members as a step towards the publication of CMCs in the BIPM KCDB to gain

international Statement of Equivalence in accordance with the mutual recognition arrangement

(CIPM MRA). The participation of NIS - Egypt and NMISA – South Africa would help in

achieving these goals through their active participation in Sub Regional Metrology Organizations

(SRMOs) members of AFRIMETS.

The comparison gives objective evidence on the technical competence of the participated

laboratories, and it assists in identifying opportunities to improve the metrological capacity of the

Laboratories.

3- Participants:

Table 3.1 shows the participating NMIs, their affiliations and the planned time schedule.

Country - Laboratory – Abbreviation

Date Planned Metrology region

1- EGYPT - National Institute of Standards – NIS-ESML

November 2011

Pilot Lab; AFM Member, AFRIMETS Member (NEWMET), APMP associate

member and EURAMET Corresponding Member

2- IRAQ - Central Organisation for Standardisation and

Quality Control - COSQC December 2011 AFM Member

3- SYRIA - National Standards and Calibration Laboratory -

NSCL January 2012

AFM Member and APMP Associate Member

4- JORDAN - Jordan National Metrology Institute - JNMI

February 2012 AFM Member and APMP Associate

Member

5- TUNISIA - Central Laboratory for Testing and Analysis-

Metrology Center - LCAE-CME March 2012 AFRIMETS Member (MAGMET)

6- SOUTH AFRICA - National Metrology Institute of South

Africa - NMISA SOUTH AFRICA - National Metrology Institute of

South Africa - NMISA

April 2012 Coach Lab. – AFRIMETS Member (SADCMET) and APMP Associate

Member

1- EGYPT - National Institute of Standards – NIS-ESML

May 2012

Pilot Lab; AFM Member, AFRIMETS Member (NEWMET), APMP Associate

Member and EURAMET Corresponding Member


5

4- Design of the Programme:

The program was designed according to the guidelines for CIPM (Comité International des Poids et Mesures) key comparisons. Five travelling gauge blocks of nominal size 1 mm, 5 mm, 10 mm, 40 mm and 90 mm were provided as artifact by NIS-ESML. They are made of steel according to ISO 3650:1998. The travelling standards were circulated between the participants as shown in table 4.1. As pilot laboratory, NIS-ESML of Egypt determined the length deviation of the travelling standards at the beginning and the end of the comparison.

The transportation sequence and measurements of the travelling standards has been done as shown in figure 4.1. NIS-ESML of Egypt acted as the pilot laboratory regarding the measurements which were conducted starting in November 2011 at NIS-ESML. Then the artifact moved to Institute number 2 and so on. No significant accident has been reported during the comparison. However, the artifacts stayed for a longer period than planned at NIS-ESML at the end of the round waiting for their measurement standard to be calibrated to ensure traceability to SI units.

Serial NMI – Country Artefact Received Report Delivered

1 NIS – Egypt November 2011 15 March 2012

2 COSQC – Iraq 14 December 2011 7 February 2012

3 NSCL – Syria 21 January 2012 26 February 2012

4 JNMI – Jordan 11 March 2012 15 March 2012

5 LCAE – Tunis 6 June 2012 10 December 2012

6 NMISA - South Africa 17 October 2012 16 November 2012

7 NIS – Egypt 30 November 2012 7 July 2013

Table 4.1:- Sequence of the measurements


6

Figure (4.1) shows the transportation sequence and measurements of the travelling standards.

5- Reporting:

The measurement results were sent to the AFM in a final report. A list of the equipment used as gauge block comparator, environmental conditions, details of measurement procedure and uncertainty analysis were included as well as the reference standard used in order to see the traceability at each laboratory.

6- Measurement Equipment used by Participants:

Lab Measurement Device Tip material

Tip diameter Measuring Force

Upper

tip

Lower

tip

Upper

tip

Lower

tip

NIS-ESML Mitutoyo, GBCD-250 Tungsten

Carbide 40 mm 10 mm 0.8 N 0.3 N

COSQC MAHR 826 Tungsten


NSCL Tsugami - ECHD Tungsten

Carbide 20 mm - 3.2 N -

JNMI Mitutoyo, GBCD250 Tungsten


LCAE MAHR 826 Tungsten


NMISA TESA Tungsten 40 mm 40 mm 0.63 N 0.63 N

NIS-Egypt

NSCL - Syria

JNMI - Jordan

LCAE - Tunis

NMISA - South Africa

COSQC - Iraq


7

Table 6.1.: Measurement equipment used in comparison

7- Stability of the traveling standards:

The pilot laboratory NIS-ESML of Egypt assures the stability of the traveling standards during a period of months before beginning of the laboratory measurements. Statement on the instability has been found, so that, the measured gauge block length values of the traveling standards were stable during this period. The travelling standards were circulated among five participating laboratories without any incident that required any return to the pilot laboratory to re-measure the travelling standards. Figures 7.1 to 7.5 show graphs indicating the stability of gauge blocks.

7.1. Stability of 1 mm gauge block

Figure 7.1. Stability of 1 mm gauge block


-30

-20

-10

0

10

20

30

40

50

Dev

iati

on

fro

m n

om

inal

len

gth

, nm

NIS- Nov.2011 NIS - July 2013

1 mm gauge block


8





-20

0

20

40

60

80

100

120

Dev

iati

on

fro

m n

om

inal

len

gth

, nm


10 mm gauge block


9




-150

-100

-50

0

50

100

Dev

iati

on

fro

m n

om

inal

len

gth

, nm


90 mm gauge block


10

8. Analysis of results: The weighted mean is used as the reference value in the comparison. For each laboratory (i) the normalized weight, wi was calculated by the following formula:

𝑤𝑖 = 𝑐.1

𝑢2(𝑥𝑖) (1)

where u(xi) is the standard uncertainty given by the laboratory “i” and C is the normalizing factor and is calculated by the following formula:

𝑐 = 1

∑1

𝑢2(𝑥𝑖)𝑛𝑖=1

(2)

where n is the number of the laboratories. The weighted mean (reference value) is:

�̅�𝑤 = ∑ 𝑤𝑖 . 𝑥𝑖𝑛𝑖=1 (3)

The uncertainty of the deviation from the weighted mean is:

𝑢(𝑥𝑖 − �̅�𝑤) = √𝑢2(𝑥𝑖) − 𝑢𝑖𝑛𝑡2 (�̅�𝑤) (4)

To avoid bias, only the first set of measurements from the pilot laboratory was included in reference value determination and the analysis of the results of each participant can be done by calculating the deviation of the given result from the weighted mean and the uncertainty of this deviation. The statistical consistency of the results with the uncertainties given by the participants can be checked by the En value for each laboratory.

𝐸𝑛 = xi−x̅w

2√u2(xi)−uint2 (x̅w)

(k = 2) (5)

where 𝑥𝑖 − �̅�𝑤 is the deviation from the weighted mean for a result of a laboratory, uint is the so called internal standard deviation that is based on the estimated standard uncertainties as reported by the participants:

𝑢𝑖𝑛𝑡 (�̅�𝑤) = √𝐶 (6)

En values for consistent measurement results are expected to be between -1 and 1 for a coverage factor of k = 2.


11

The statistical consistency of the comparison can be analyzed by the so called Birge ratio test. The Birge ratio compares the observed spread of the results with the spread expected from the individual reported uncertainties. The Birge ratio is:

𝑅𝐵 = 𝑢𝑒𝑥𝑡 (�̅�𝑤)

𝑢𝑖𝑛𝑡 (�̅�𝑤) (7)

where uext is the so called external standard deviation and can be calculated by the following formula:

𝑢𝑒𝑥𝑡(�̅�𝑤) = √ 1

𝐼−1 .

∑ (𝑥𝑖−�̅�𝑤)

2

𝑢2(𝑥𝑖)𝐼𝑖=1

∑ 1

𝑢2(𝑥𝑖)𝐼𝑖=1

. (8)

where I is the number of the results that are taken in the calculation.

For an infinite population size, the Birge ratio has an expectation value of RB = 1, when

considering standard uncertainties. For a coverage factor of k = 2, the expectation value is increased and the data in a comparison are consistent provided that

𝑅𝐵 < √1 + √8/(𝐼 − 1) . (9)

For a limited population size, the Birge criterion is given by:

𝑅𝐵 𝐶𝑟𝑖𝑡 = √1 + √8/(𝐼 − 1) (10)

If the calculation of a gauge shows inconsistent dataset, the largest consistent subset is determined by elimination, starting with excluding the result having the largest En value that makes the largest contribution to the overall chi-squared value. The iteration runs until RB < RB crit. For six laboratories, RB is equal to 1.5. The criterion is recalculated if any results are excluded. A Birge ratio much larger than the criterion implies that some data contain systematic offsets or alternately that some uncertainties have been underestimated. A ratio much less than the criterion implies that uncertainties have been overestimated. The results will point to calculations that may need further investigation and possibly reassessment. The reference value will be selected that best reflects the population. For a population with a number of results of En greater than 1 and the Birge ratio greater than the Birge criterion, the result with the largest En was removed and the weighted mean, the


12

uncertainty of the mean, all En values, the Birge ratio and Birge criterion were recalculated. This iteration process was repeated until the Birge ratio became less than the Birge criterion and the exclusion process was stopped. When a result xi is excluded from the reference value, it is not correlated to it and its En value is calculated by:

𝐸𝑛 = 𝑥𝑖−�̅�𝑤

2√𝑢2(𝑥𝑖)−𝑢𝑖𝑛𝑡2 (�̅�𝑤)

(11)

9 – Reference Value: In this comparison, to meet the requirements of the Mutual Recognition Arrangement, the Key Comparison Reference Values (KCRV) has been evaluated according to the method described in section 8. The weighted mean was determined and the deviations from the weighted mean were calculated. The uncertainty of the weighted mean is based on the internal standard deviation of the final measurement results. The stability measurements of the gauge blocks, performed by the pilot laboratory were excluded. The results of the pilot laboratory contribute only once in the calculation of the reference values. Table 9.1 shows the Key Comparison Reference Values and their standard uncertainties.

Table 9.1 Key Comparison Reference Values and associated standard uncertainty (k = 1).

Nominal Length

(mm)

Reference value

(nm)

Reference value

uncertainty (nm)

1 25.6 13.7

5 66.2 14.4

10 42.9 15.5

40 -57.2 22.5

90 -55.1 36.5

10 – Results as reported by the Participants:

On receipt of the reports from all participants the coordinator asked the participants to revise their results regarding the units and uncertainties quoted. Among the received answers, the JNMI asked to withdraw the results of 40 mm and 90 mm gauge blocks for technical reasons. This withdrawal of results was made before Draft A was released, i.e. with the results still ‘blind’.


13

Overview of measurement results as they were reported by the participating laboratories is given in Table 10.1. Weighted mean and its difference from reported results were calculated, along with corresponding En values (k = 2), for each gauge block. A statistical consistency check was performed as described in section 8. Results of 90 mm gauge block which belongs to COSQC were excluded from calculation in order to form a consistent subset, and their En values are given according to:

𝐸𝑛 = 𝑥𝑖−�̅�𝑤

2√𝑢2(𝑥𝑖)+𝑢𝑖𝑛𝑡2 (�̅�𝑤)

(12)

NIS- ESML

COSQC NSCL JNMI LCAE NMISA

∆L uc ∆L uc ∆L uc ∆L uc ∆L uc ∆L uc

1 mm 10 28.7 50 48.2 34 27 30 90 28 30 20 30

5 mm 70 31.5 80 48.1 53 29 70 90 56 32 80 30

10 mm 60 35.1 20 48.1 47 35 10 90 17 34 60 30

40 mm -40 56.4 -10 48.3 -59 49 NA NA -126 45 -30 55

90 mm -20 91.9 100 49.3 -121 91 NA NA -45 64 -50 61

Table 10.1. Reported measurement results, in nm, k = 1

10.1. Results of 1 mm gauge block

Table 10.1.1. Results as reported by the participants

Nominal

1 mm

NIS- ESML COSQC NSCL JNMI LCAE NMISA


10 28.7 50 48.2 34 27 30 90 28 30 20 30


14

Figure 10.1.1. Graphical representation of results

Table 10.1.2. Results calculated from participant’s values

1 mm Xi - Xw En

NIS- ESML -15.6 -0.31 uint, nm 13.66

COSQC 24.4 0.26 uext, nm 5.08 NSCL 8.38 0.18 RB 0.37 JNMI 4.38 0.02 Xw, nm 25.62

LCAE 2.38 0.04

NMISA -5.62 -0.11



Nominal

5 mm

NIS-ESML COSQC NSCL JNMI LCAE NMISA


70 31.5 80 48.1 53 29 70 90 56 32 80 30

-80

-60

-40

-20

0

20

40

60

80

100

120

140

160

NIS COSQC NSCL JNMI LCAE NMISA

De

viaa

tio

n f

rom

no

min

al le

ngt

h, n

m 1mm gauge block standard uncertainty (k = 1)


15



5 mm Xi - Xw En

NIS- ESML 3.8 0.07 uint, nm 14.38 COSQC 13.8 0.15 uext, nm 5.06 NSCL -13.2 -0.26 RB 0.35 JNMI 3.8 0.02 Xw, nm 66.2

LCAE -10.2 -0.18

NMISA 13.8 0.26



Nominal

10 mm



60 35.1 20 48.1 47 35 10 90 17 34 60 30

-40

-20

0

20

40

60

80

100

120

140

160

180

200


De

viaa

tio

n f

rom

no

min

al le

ngt

h, n



16



10 mm Xi - Xw En

NIS- ESML 17.1 0.27 uint, nm 15.51 COSQC -22.9 -0.25 uext, nm 8.54 NSCL 4.1 0.07 RB 0.55 JNMI -32.9 -0.19 Xw, nm 42.9

LCAE -25.9 -0.43

NMISA 17.1 0.33



Nominal

40 mm



-40 56.4 -10 48.3 -59 49 NA NA -126 45 -30 55

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

140


De

viaa

tio

n f

rom

no

min

al le

ngt

h, n



17



40 mm Xi - Xw En

NIS- ESML 17.2 0.17 uint, nm 22.45 COSQC 47.2 0.55 uext, nm 21.39

NSCL -1.8 -0.02 RB 0.95 JNMI - - Xw, nm -57.2

LCAE -68.8 -0.88

NMISA 27.23 0.27



Nominal

90 mm



-20 91.9 100 49.3 -121 91 NA NA -45 64 -50 61

-200

-160

-120

-80

-40

0

40

80


De

viaa

tio

n f

rom

no

min

al le

ngt

h, n



18

Figure 10.5.1. Graphical representation of results for 90 mm gauge block with standard uncertainty

(k = 1)

Table 10.5.2. Results calculated from participants values

90 mm Xi - Xw En

NIS -ESML -19.8 -0.11 uint, nm 29.32 COSQC 100.2 1.27 uext, nm 39.05

NSCL -120.83 -0.70 RB 1.33 JNMI - - Xw, nm -0.17

LCAE -44.83 -0.39

NMISA -49.83 -0.47

Table 10.5.3. Results calculated from largest consistent subset

90 mm Xi - Xw En

NIS - ESML 35.1 0.21 uint, nm 36.47

COSQC 155.1 1.27 uext, nm 17.64 NSCL -65.95 -0.40 RB 0.48 JNMI - - Xw, nm -55.05

LCAE 10.05 0.10

NMISA 5.05 0.05

-260

-220

-180

-140

-100

-60

-20

20

60

100

140

180

220


De

viaa

tio

n f

rom

no

min

al le

ngt

h, n



19

In table 10.5.2., the results calculated from all the participants’ values. After the statistical consistency check was performed as described in section 8. Results of 90 mm gauge block which belongs to COSQC were excluded from calculation in order to form a consistent subset and the results in table 10.5.3 are calculated.

11 - Discussion of measurement results: Table 11.1 shows the differences of measured values with respect to Key Comparison Reference Values and the expanded (k = 2) uncertainties of these differences, calculated by:

𝑈(𝑥𝑖 − �̅�𝑟𝑒𝑓) = 2√𝑢2(𝑥𝑖) − 𝑢2 (�̅�𝑟𝑒𝑓) (12) where u(xi) is the standard uncertainty of the laboratory result xi and u(xref) is the standard uncertainty of the reference value xref.

Table 11.1 Differences of measured values and KCRV’s, with expanded uncertainties (k = 2)

Gauge block \ Lab NIS – ESML COSQC NSCL JNMI LCAE NMISA

1 mm xi-xref -15.6 24.4 8.4 4.4 2.4 -5.6 U(xi-xref) 50.5 92.4 46.6 177.9 53.4 53.4

5 mm xi-xref 3.8 13.8 -13.19 3.81 -10.19 13.81 U(xi-xref) 56.2 91.8 50.4 177.7 57.2 52.7

10 mm xi-xref 17.1 -22.9 4.13 -32.87 -25.87 17.13 U(xi-xref) 63.0 91.1 62.8 177.3 60.5 51.4

40 mm xi-xref 17.2 47.2 -1.8 --- -68.8 27.2 U(xi-xref) 103.5 85.5 87.1 --- 78.0 100.4

90 mm xi-xref 35.1 155.1 -65.9 --- 10.1 5.1 U(xi-xref) 168.7 122.6 166.7 --- 105.2 97.8

Figures 11.1 through 11.5 show the graphs of Degrees of Equivalence for the five gauge blocks.


20

Figure 11.1 Degrees of Equivalence for 1 mm gauge block with expanded uncertainty (k = 2)


-200.00

-150.00

-100.00

-50.00

0.00

50.00

100.00

150.00

200.00

250.00


-200

-150

-100

-50

0

50

100

150

200

250



21



-250

-200

-150

-100

-50

0

50

100

150

200


-200

-150

-100

-50

0

50

100

150

200



22


12 – Conclusion:

Participation of NMISA of South Africa, a non member of Arab Federation for Metrology

(AFM), enriched the inter-comparison programme and contributed to its recognition on

the international level.

Measurements reports provided by participants show a well established scientific

discipline in length metrology in the participant laboratories.

Data, equipments, procedures followed and traceability listed in the participant’s reports

show a very good infra- structure for length metrology in the participant laboratories

except for NSCL where a single probe comparator was used which does not comply with

ISO 3650:1998.

The inter-comparison programme assures the ability of the participant laboratories to

provide a world class results in length metrology except for COSQC for 90 mm gauge

block, also, JNMI does not participate for 40 mm and 90 mm gauge blocks.

13 – List of References

1. ISO 3650:1998(E), Geometrical Product Specification (GPS) – Length Standards –

Gauge Blocks, International Organization for Standardization, Geneva, Switzerland.

2. Guide to the Expression of Uncertainty in Measurement (JCGM 100:2008, GUM 1995

with minor corrections)

3. Decker J.E., Brown N. et al., Recent recommendations of Consultative Committee for

Length (CCL) regarding strategies for evaluating key comparison data. Metrologia 43

(2006) L51-L55.

4. EURAMET comparison of gauge blocks by interferometry, EURAMET

#1138,EURAMET.L-K1.2 ,Final report, Zagreb, December 2011, V. Mudronja, M. Katic.

-200

-150

-100

-50

0

50

100

150

200

250

300



23

5. Asia-Pacific Metrology Programme; developing Economies‘ Committee (DEC)

Intercomparison on gauge blocks by Mechanical Comparison Method (APMP.L-S3; 2006

– 2009)

6. Measurement comparisons in the CIPM MRA; CIPM MRA-D-05 Version 1.2.

7. International comparison of surface roughness, APMP.L-K8, final report, NMIA 2013,

Andrew Baker.

afrimets supplementary comparison programme calibration of … · 2015-08-31 · calibration of...

Documents