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CALIBRATION HANDBOOK
OF
MEASURING INSTRUMENTS
Alessandro Brunelli
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FIRST EDITION
NoticeThe information presented in this publication is for the general education of the reader. Because neither the author
nor the publisher has any control over the use of the information by the reader, both the author and the publisherdisclaim any and all liability of any kind arising out of such use. The reader is expected to exercise sound professionaljudgment in using any of the information presented in a particular application.
Additionally, neither the author nor the publisher has investigated or considered the effect of any patents on theability of the reader to use any of the information in a particular application. The reader is responsible for reviewing anypossible patents that may affect any particular use of the information presented.
Any references to commercial products in the work are cited as examples only. Neither the author nor thepublisher endorses any referenced commercial product. Any trademarks or tradenames referenced belong to therespective owner of the mark or name. Neither the author nor the publisher makes any representation regarding theavailability of any referenced commercial product at any time. The manufacturer’s instructions on the use of anycommercial product must be followed at all times, even if in conflict with the information in this publication.
Copyright © 2017 International Society of Automation (ISA)All rights reserved.
Printed in the United States of America. 10 9 8 7 6 5 4 3 2
ISBN: 978-1-945541-57-5
No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means,electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher.
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Library of Congress Cataloging-in-Publication Data in process
Disclaimer: Neither the Author nor the Publisher are responsible for the results obtained by the use or possiblemisuse of the spreadsheets used in this handbook or on the CD.
The literary property and all rights of the series of ISA Publications are reserved to the Publisher. The graphicalstructure, the editorial content, and illustrations in this volume cannot be reported, translated, or stored, even partially,without the permission of the Publisher.
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TABLE OF CONTENTS
Preface 5
Part I – Requirements and General Guidelines for Management of Instruments and Measurements 7
1. International System of Units (SI) 92. International Calibration System (ILAC) 153. European Calibration System (EA) 174. Traceability and Compatibility of the Measures 215. Measurement Uncertainty 236. Calibration of Measuring Instruments 297. Requirements in the Quality Management Systems ISO 9001, 14001, 16949, and EN 9100 358. Requirements in the Measurement Management Systems ISO 10012 399. Criteria for Instrument Selection in Relation to the Measurement Requirements 4910. Criteria for Conformity Evaluation of the Measuring Instrument 5311. Notes to Legislative Requirements for Initial and Periodic Calibration Checks 5912. Notes to Technical Requirements on Document Management According to FDA 21 CFR Part 11 65
Part II – Requirements and Criteria for the Management and Calibration of Measuring Instruments 71
1. Physical Quantities 731.1 Pressure 751.2 Flow 871.3 Level 1131.4 Temperature 1191.5 Humidity 1431.6 Viscosity 1531.7 Density 1631.8 Mass 175
2. Chemicals for Liquids 1912.1 pH 1932.2 Redox 1992.3 Turbidity 2052.4 Conductivity 2112.5 Dissolved Oxygen 2172.6 Dissolved Ions 2232.7 Colorimetry 2292.8 Refractometry 235
3. Chemicals for Gases 2413.1 Infrared Analyzers 2433.2 Ultraviolet Analyzers 2473.3 Comburent Gases 2513.4 Combustible Gases 2553.5 Chromatography 2613.6 Spectrometry 267
4. Mechanical Quantities 2734.1 Length 2754.2 Force 2874.3 Torque 2914.4 Velocity (and Rotation) 2954.5 Vibration (and Acceleration) 2994.6 Sound and Noise 305
5. Electrical Quantities 3155.1 Indicators 3175.2 Oscilloscopes 3215.3 Transformers 3255.4 Energy Meters 3295.5 Clamp Meters 3335.6 Multimeters 337
Analytical Index for Acronyms, Terms, and Instruments to be Calibrated 341
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Dedication
To my learned readers, this book combines my so-called HME versus HMS,or How Much is Enough versus How Much it Serves,
in compliance with metrological requirementsimposed by the reference normatives for
calibrating and confirming measuring instruments.
In loving memory of my beloved wife, Romanella, who always encouraged me to give the best of myself.
PREFACE
The Calibration Handbook of Measuring Instruments was commissioned by the Association for the Instrumentation,Control and Automation Company in Italy (GISI) to meet the needs of instrumentation technicians, who stronglyrequested a handbook that clearly and completely explained calibration procedures and periodic metrologicalconfirmation for all the instruments for measurement in industrial applications: chemical, petrochemical,pharmaceutical, food, energy, and custody and transfer for water, oil, and gas.
Published first in the Italian language in 2012, it was outstandingly successful; many companies, professionals, andtraining centers have found this calibration handbook a valuable reference.
FOREWORD
The handbook is mainly dedicated to operators involved in the verification and calibration of measuring instrumentsused in ISO 9001 – Quality management systems, ISO 14001 – Environment applications, ISO 16949 – Automotiveindustry, and EN 9100 – Aviation industry to be a reference and consultation handbook in the main topics for theassurance and management of industrial process measurement, such as:
• The general concepts for managing the measurement equipment according to ISO 10012 concerning themanagement system of instruments and measurements
• The ability of the instrument to perform accurate measurements, by controlling the drift to maintain the qualityof the measurement process
• The criteria and procedures for acceptance, management, and verification of the calibration of the mainindustrial measuring instruments
• The provisions of law and regulations for production and the European marking, CE, of metrologicalinstruments used in commercial transactions and for their periodic verification
The handbook consists of two main parts:
• Part I illustrates the International System of Units (SI) and the international, European, and national calibrationservices (ILAC, EA, and others) and then the performance requirements of the instruments for measuring andthe criteria for assessing the traceability and uncertainty of the measurements. It also covers the technical andregulatory requirements relating to the management of instruments and measurements.
• Part II describes the problems of calibration, verification, and metrological confirmation for the main families ofinstruments for measuring physical, chemical, mechanical, and electrical quantities. Then, for each quantity, itdescribes the specific concepts of the measure and the main reference standards, and then presents the mostcommon types of instruments, simple calibration procedures, and metrological confirmation. This isaccompanied by the format for collecting and processing experimental data, suitable for recording and editingthe calibration report of metrological confirmation.
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GENERAL GUIDELINES
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For the most common measurement instruments, it is possible to determine the best practices for calibrationprocedures suitable for industrial applications, with procedures harmonized on the following points:
• Scope and purpose• Identification and classification• Normative references• Ambient conditions• Initial checks• Calibration method• Calibration verification• Calibration results• Metrological confirmation
Practical report templates useful for recording both the recorded instrument data and the experimental calibration data,to evaluate the conformity of the instrument, are available on the enclosed CD for practical usage.
The report templates are reported in “white” on the enclosed CD for a practice specific use.
Furthermore, the CD contains various spreadsheets in Excel (Reports Calibration) that automatically calculate errorsand the relative uncertainty of measurement. They directly determine the compliance of the calibrated instrumentaccording to the two methods mentioned in this calibration handbook: as a practical method, according to the errorapproach, or an analytical method, according to the uncertainty approach.
Therefore, once again, the author aims to develop and promote the culture of instrumentation in its metrological andapplication aspects, currently the cornerstone of a company’s production as traceability and compatibility ensuremeasurements in the global market.
ABOUT THE AUTHOR
Alessandro Brunelli has worked for more than 40 years in the field of training andcertification in industrial instrumentation at an experimental laboratory. He graduated fromthe Higher Institute of Industrial Technology Mechanical of the Polytechnic (University) ofMilan in 1974 and later became a professor of mechanical and thermal measurement atthe Polytechnic of Milan.
As a technologist, Brunelli participates in the activities of National, European, andInternational standardization for mechanical and electronic equipment. He is responsiblefor the Italian National Unification (UNI) commission on “Metrology of Pressure andTemperature” and is secretary of the technical committee Italian ElectrotechnicalCommittee (CEI) on “Industrial-Processes Measurement, Control and Automation.”
During his career, Brunelli published many papers in the areas of measurement andautomation of industrial processes. He published two monographs relating to humidity andflow measurement, a series of five volumes on measurement and control in industrial applications, a specific volumetitled Industrial Measurements: Physical & Mechanical, and a two-volume Instrumentation Handbook series.
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PART I
Requirements and General Guidelines for Management of Instruments and Measurements
1. International System of Units (SI)
2. International Calibration System (ILAC)
3. European Calibration System (EA)
4. Traceability and Compatibility of the Measures
5. Measurement Uncertainty
6. Calibration of Measuring Instruments
7. Technical Requirements in Quality Management Systems ISO 9001, 14001, 16949, and EN 9100
8. Technical Requirements in Measurement Management Systems ISO 10012
9. Criteria for Instrument Selection in Relation to the Measurement Requirements
10. Criteria for Conformity Evaluation of the Measuring Instruments
11. Notes to Legislative Requirements on Initial and Periodic Calibration Checks
12. Notes to Technical Requirements on Document Management according to FDA 21 CFR Part 11
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INTERNATIONAL SYSTEM OF UNITS (SI)
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1 International System of Units (SI)1
1.1 Introduction
The International System of Units (in French: Système International d’unité), abbreviated SI, is the internationalreference system for expressing measurement results all over the world. The International System was established in1960 as a result of the Metre Convention of 1875, which sought to coordinate all metrological activities at all levels:
• Scientific and diplomatic• International and national
It did this through the General Conference on Weights and Measures (Conférence Générale des Poids et Mesures[CGPM]), which was formed by the delegates of the member states to the Metre Convention and still has these tasks(see figure 1-1):
• Discuss and promote the necessary measures to spread and refine the SI system• Recognize the results of new fundamental metrological determinations• Issue scientific resolutions of international scope• Approve the definition of the SI units
The CGPM uses the work of the International Committee for Weights and Measures (Comité International des Poids etMesures [CIPM]), composed of members appointed by the same CGPM. Their task is to carry out the decisions of theCGPM and oversee the activities of the International Bureau of Weights and Measures (Bureau International des Poidset Mesures [BIPM]).
This latter institution is an international metrological laboratory based in Sèvres near Paris. It is the permanent scientificbody of the CGPM and has the following tasks:
• Preserve the international prototypes of measurement standards• Carry out and coordinate the determination of fundamental physical constants• Make the necessary comparisons to ensure the uniformity of international measures
The units, terminology, and International System recommendations are established by the General Conference ofWeights and Measures, the diplomatic body that is connected with the BIPM.
The International System of quantities and units has thus developed over time:
• 1889: the “MKS system” with only three units (meter, kilogram, second), approved by the first CGPM• 1935: the “MKSΩ system” with a fourth unit (ohm) dedicated to electrical resistance, on the proposal of the
Italian physicist Giovanni Giorgi• 1946: the “MKSA system” with a variation of the fourth unit: ampere electric current, based on the Giorgi
proposal and therefore also commonly called the “Giorgi system”• 1954: the “SI system” with the addition of kelvin and candela, approved by the 10th CGPM• 1971: the “SI system” included a seventh unit, the mole, approved by the 14th CGPM
Therefore, currently the International System:
• Is based on seven fundamental quantities (with the respective units of measurement) (see table 1-1)• Is made up of other so-called derived quantities (and their units) (see table 1-2 for the variables that have
proper names and table 1-3 for other units.)• Includes prefixes to identify the different sizes of the various units of measurement (see table 1-4)
1. The measurement units of the International System (SI) are currently regulated by the International Standards ISO/IEC 80000 series, replacing the previous standard ISO 31 and IEC 60027 series.
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GENERAL GUIDELINES
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The International System is therefore a coherent system in that its magnitudes and derived units are derived as aproduct of magnitudes and fundamental units.
Figure 1-1. International Organization of Metrology
Diplomatic Level
Technical Level
CGPM
METRE CONVENTION
CIPM BIPM
NATIONAL LABORATORY
ADVISORY COMMITTEES(quantities of competence)
1 – Electricity and Magnetism 2 – Photometry and Radiometry 3 – Thermometry 4 – Length 5 – Time and Frequency 6 – Ionizing Radiation 7 – Units of Measurement 8 – Mass and Related Quantities 9 – Quantities of Substance 10 – Acoustics, Ultrasound, and Vibration i i
CGPM = Conférence Génerale des Poids et Mesures (General Conference of Weights and Measures)
CIPM = Comité International des Poids et Mesures (International Committee of Weights and Measures)
BIPM = Bureau International des Poids et Mesures (International Bureau of Weights and Measures)
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INTERNATIONAL SYSTEM OF UNITS (SI)
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1.2 Writing Rules Used in the International System
To standardize the writing and avoid misinterpretation, the SI provides some rules for writing units of measurement andtheir symbols:
a) Units writingA unit of measure should be written:
• In full and without accents or diacritical marks if it is introduced in a discursive text (e.g., leakage current of afew milliamperes and not a few mA)
• With the symbol if included in a formulation with quantitative rather than qualitative value (e.g., 10 mA and not10 milliamperes)
b) Symbols writingUnits of measurement symbols are identified as follows:
• With a small letter, if the unit is derived from the name of a unit (e.g., m for meter, cd for candela)• With a capital letter, if the unit is derived from the name of a person (e.g., A for Ampere, V for Volta, W for Watt)
The only exception is for liter, where both the symbols l and L are acceptable.
c) Quantities writingRegarding quantities detected or identified by units of measure, SI symbols:
• Should never be followed by a period (e.g., write 10 mm and not 10 mm.)• Should be placed after the numeric value (e.g., write 10 mm and not mm 10)• Must be separated from the numeric value by a space (e.g., write 10 mm and not 10mm)• Can be derived quantities written without spaces or interposed by “.” or “/” (e.g., Nm or N.m, ms-2 or m/s2)
d) Numbers writingFinally, regarding separating the numbers of the quantity values:
• Use a space to separate them with the whole numbers in groups of three (no points or commas); for example,1 000 000 and not 1.000.000 or 1,000,000.
• Use a comma as the separator between the whole numbers and decimal ones, except for using the decimalpoint in English-language texts (CGPM of 2003).
The SI should be used in each country. In some of them, such as in Italy, their use is mandatory, in compliance with theEEC Council Directive 18 October 1971 (71/1354/ EEC), as amended on 27 July 1976 (76/770/EEC). Its use ismandatory in drafting acts and documents with legal value, and therefore the failure to comply with the above rules ofwriting could invalidate such documents.
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CALIBRATION OF MEASURING INSTRUMENTS
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6 Calibration of Measuring Instruments
6.1 Introduction
The control of measuring instruments, namely:
• Measuring equipment in the ISO 9001 – Quality management systems• Surveillance equipment in the ISO 14001 – Environmental management systems
ensures, where necessary for valid results, that the measuring instruments are:
• Calibrated and verified, at specified intervals or prior to use, against measurement standards traceable tointernational or national measurement standards. Where no such standards exist, they must be registered withthe criteria used for calibration or verification.
• Adjusted or regulated again, when necessary.
Therefore, all management systems provide the initial calibration and any periodic “adjustment or metrologicalconfirmation” (according to ISO 10012 – Measurement management systems) of the measuring instruments to validatethe various measurement processes to ensure proper traceability of measurements to the International System (SI) (forterminology, see table 6-1).
6.2 General Calibration Conditions
To correctly perform a calibration, one must have infrastructure, means, methods and procedures, and appropriatestaff, or possess the four fundamental pillars:
Ambient ConditionsIf the measurement ambient is industrial, it is appropriate that the measures are carried out within these maximumlimits:
• Temperature : 20 ± 5°C (or 25 ± 10°C)• Relative humidity : 50 ± 25%
This contains the thermal drift of the standard and calibration instruments.
If, however, the measurement is made in a laboratory, it is appropriate that the measures are carried out in controlledconditions, within these maximum limits:
• Temperature : 20 ± 2°C for mechanical measurements, 23 ± 3°C for electrical measurements• Relative humidity : 50 ± 10% (or ± 20%)
This gives better uncertainty, and therefore traceability, of the measuring process.
Measurement EquipmentUse appropriate equipment for the measuring ranges and the desired levels of uncertainty, traceable to the SI units(see point 1) by:
• National calibration laboratories (NCL):o European cooperation for Accreditation (EA) (or extra-European)o International Laboratory Accreditation Cooperation (ILAC)
• National metrological institutes (NMI)
The reference standard instrument should still have a measurement uncertainty of typically better than one-third of thenominal uncertainty of the calibrated instrument (see point 10).
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GENERAL GUIDELINES
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Technical PersonnelTechnical personnel should be specifically trained and operating under the technical and management proceduresregarding the quality manual of the company or the laboratory.
Operating Procedures The operating calibration procedures should be specifically drawn up:
• For each type of provided measurement• For each type of instrumentation with respect to any applicable normatives
In the absence of specific reference normatives, it is good practice to follow the generic operating proceduresdescribed in table 6-1.
6.3 Generic Operational Procedures3
Among the various international normatives available in the field of instrumentation, reference is made hereinafter toIEC 61298 concerning the methods and procedures to evaluate process instrumentation. It provides for the accuracydetermination, namely the error indication, of industrial measurement instrumentation (i.e., pressure, flow, level,temperature). There are essentially two main procedures: calibration and verification.
6.3.1 Calibration Procedure (or Initial Characterization)This is applicable to new instrumentation, and typically also to the standard instrumentation. This first procedureconsists initially in performing three full excursions of the measuring signal up and down, and then follow thismethodology:
a. With input signal of 0%, adjust the initial scale of the instrument being calibrated.b. With input signal equal to 100%, adjust the full scale of the instrument being calibrated.c. Return the input signal to 0%, and check the instrument’s output signal. If this error is more than one-quarter
error of the nominal value specified by the manufacturer or the user of the instrument, readjust the initial scale to fall within the tolerance above.
d. Return the input signal to 100% and check the instrument’s output signal. If this error is more than one-quarter error of the nominal value specified by the manufacturer or the user of the instrument, readjust the full scale up to fall within the tolerance above.
e. Repeat steps (c) and (d) until the initial and the full scale are within the tolerance of one-quarter specified nominal value.
f. Perform the measuring cycle every 20–25% by detecting the instrument output signal, after a sufficient period of stabilization, in the following modes:
• 20/40/60/80/100/80/60/40/20/0%• 25/50/75/100/75/50/25/0%
Usually the complete measuring cycle up and down is expected for instrumentation using sensors at “elasticdeformation” (and therefore with displacement: type dial manometers or dilatation thermometers) while a measuringcycle is carried out up (preferentially) or down for the instrumentation using sensors at the “solid state” (and thus usingsensors without moving, electric type: digital multimeters and sensor thermoelectrics as resistance thermometers andthermocouples that don’t have inherent hysteresis phenomena).
3. See also table 6-3
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CALIBRATION OF MEASURING INSTRUMENTS
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Table 6-1. Main Terms Relating to Measurement Processes (ISO-VIM)
Measurand:Quantity intended to be measured.
Measurement:Process of experimentally obtaining one or more quantity values that can reasonably be attributed to a quantity.
Error:Measured quantity value minus a reference quantity value.
Accuracy:Closeness of agreement between a measured quantity value and a true quantity value of a measurand.
Accuracy class:Class of measuring instruments or measuring systems that meet stated metrological requirements that are intended to keepmeasurement errors or instrumental measurement uncertainties within specified limits under specified operating conditions.
Measurement accuracy:Closeness of agreement between a measured quantity value and a true quantity value of a measurand.
International measurement standard:Measurement standard recognized by signatories to an international agreement and intended to serve worldwide.
Reference measurement standard:Measurement standard designated for the calibration of other measurement standards for quantities of a given kind in a givenorganization or at a given location.
Traveling measurement standard:Measurement standard, sometimes of special construction, intended for transport between different locations.
Primary measurement standard:Measurement standard established using a primary reference measurement procedure, or created as an artifact, chosen byconvention.
Secondary measurement standard:Measurement standard established through calibration with respect to a primary measurement standard for a quantity of thesame kind.
Material measure:Measuring instrument reproducing or supplying, in a permanent manner during its use, quantities of one or more given kinds,each with an assigned quantity value.
Reference material:Material, sufficiently homogeneous and stable with reference to specified properties, that has been established to be fit for itsintended use in measurement or in examination of nominal properties.
Measuring instrument:Device used for making measurements, alone or in conjunction with one or more supplementary devices.
Metrological traceability:Property of a measurement result whereby the result can be related to a reference through a documented unbroken chain ofcalibrations, each contributing to the measurement uncertainty (see point 4.2).
Metrological traceability chain:Sequence of measurement standards and calibrations used to relate a measurement result to a reference (see figure 4-1).
Measurement uncertainty:Nonnegative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on theinformation used (for more details, see point 5 and table 5-1).
Measurement method:Generic description of a logical organization of operations used in a measurement. Measurement methods may be qualified invarious ways, such as:
• Direct measurement method (e.g., manometer calibration with pressure balance)• Indirect measurement method (e.g., manometer calibration with reference manometer)
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6.3.2 Verification Procedure (or Metrological Confirmation)The verification procedure is applicable to instrumentation in operation and therefore particularly suitable for themetrological confirmation of instrumentation in production processes.
This second procedure also begins by executing three complete excursions of the measurement signal up and down;expected, however, only for mechanical-type instrumentation with displacement sensors.
Subsequently, however, it only provides for the execution of the measuring cycle according to the method described inthe preceding calibration procedure in step (f), since the aim of this procedure is to be seen during the metrologicalconfirmation in subsequent times, if the error or uncertainty detected on the instrumentation of the production processis better than the limit expected for the “correct control” of the quality of the “measurement process.”
6.4 General Index of the Operational Procedures
Each operating procedure should be structured on the following points:
1. Scope and purpose2. Identification and classification3. Normative references4. Ambient conditions5. Initial checks6. Calibration method7. Calibration verification8. Calibration results9. Metrological confirmation
The last point is required only in the case of procedures aimed at metrological confirmation.
6.5 General Index of the Calibration Report or Metrological Confirmation4
Following the calibration procedure or metrological confirmation, note and record the results and further elaborations,on a specific report that must contain at least the following information (see also ISO 10012):
a. Applicant (if applicable)b. Subject of the report (calibration or confirmation)c. Name or symbol of the instrumentd. Reference standards and calibration certificatese. Procedures usedf. Ambient conditionsg. Reference values and measured errorsh. Measurement uncertainty resultingi. Uncertainties of measurement requestsj. The result of the declaration of conformityk. Execution date of the calibration or confirmation and date of the next confirmationl. Signature executor and the person responsible for the calibration or confirmation reports
For an example of procedures and reports of calibration or confirmation, see Part II.
4. See also table 6-3
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CALIBRATION OF MEASURING INSTRUMENTS
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6.6 Examination of Internal or External Calibration Feasibility of Measuring Instruments
In order to properly calibrate instruments at home, in the first analysis, a company must have at least the followingelements:
• A metrological chain, composed of at least one standard, for each type of instrument• Any ancillary equipment, according to requirements (e.g., generators, furnaces)• A local or a work area with suitable environmental conditions to the needs• Designed and tested calibration procedures • Trained and qualified personnel
All this represents a significant cost that can be justified by the amount of equipment to be calibrated, and therefore acost/benefit analysis on the convenience of equipping a laboratory or on delegating calibration to an external laboratorymust be done.
Generally, for instruments such as manometers, thermometers, hygrometers, micrometers, calipers, and analog anddigital multimeters, internal calibration is convenient when the group of instruments is referable to a single referencestandard that exceeds at least 10 units. For lesser quantities, it may be more beneficial to contact an externallaboratory.
These figures and tables provide examples:
• Figure 6-1 shows a possible suitable framework to analyze the possibility of internal or external calibration.• Table 6-2 shows the possible advantages and disadvantages of internal and external calibration.• Table 6-3 shows some considerations for the procedures and results of related expressions.
Figure 6-1. Sequential Scheme of Analysis for Choice of the Internal or External Calibration
Accreditedalibration
enter?NOTYES
NOTYES
DEFINITION OF THE QUALITY PLANAND PRODUCT CHARACTERISTICS
TO CHECK
Calibrationinside theompany ?
IDENTIFICATION OF THE INSTRUMENTSTHAT MUST BE CALIBRATED
Qualifythe alibration
enter
RESULTS CONTROL (MADE IN COMPANY)
check that the results are within acceptance criteria
indicate the controller ( aboratory or uality esponsible)
Calibration at a alibration enter:ILAC, EA, etc.
Calibration at aqualified outside center
Calibration in theinternal metrological
laboratory
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GENERAL GUIDELINES
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Table 6-2. Evaluation of the Advantages and Disadvantages of Internal and External Calibration
Evaluation Internal Calibration External Calibration
Purchase costs of the reference standards Yes No
Calibration of the reference standards Yes No
Cost for personnel training Yes No
Cost of procedures Yes No
Locations for the laboratory Yes No
Unavailability time of the instrument hour 2-30 days
Costs to ship the instrument No Yes
Possibility of damage during transport No Yes
Possibility of immediate verifications Yes No
Possibility of checks on the processes Yes No
Laboratory qualification No Yes, if it is not ILAC
Table 6-3. Common Terms Relating Procedures and Results of Expressions (ISO and Others)
Operational procedure:Procedure that tends to define and characterize the metrological characteristics of an instrument, or to adjust or restore thefunctional and metrological characteristics of an instrument or a measuring apparatus. Note: The operational procedure should be specified: measurement, calibration, verification, etc.
Measurement procedure:Detailed description of a measurement according to one or more measurement principles and to a given measurement method,based on a measurement model and including any calculation to obtain measurement results.
Calibration procedure:Procedure performed under the specified conditions that establishes the relationship between the values of a quantity relatedwith the associated measurement uncertainties and the reading of a measuring instrument, which can be expressed by meansof a table or calibration curve, usable for the eventual measurement results correction conducted with the calibrated instrument.Note: This procedure should not be confused with the procedures described below!
Verification procedure:Operation that provides evidence that an instrument meets the specified requirements. (Note: This procedure is normally used inthe sense of “metrological confirmation.”)
Adjustment procedure:Set of operations carried out (of zero and span adjustments) on an instrument so that it provides prescribed information(specified) in relation to the measured value. Note: This procedure is commonly used before the “calibration procedure.”
Maintenance procedure:Process conducted in a systematic manner or as necessary to return the instrument to its normal functional conditions. (Note:This procedure is performed periodically according to the manufacturer’s specifications.)
Calibration curve:Expression of the relation between indication and corresponding measured quantity value (and relative measurementuncertainty).
Calibration certificate:Document that provides a calibration curve of an instrument, issued by a laboratory or an accredited organization (e.g.,accredited ISO 17025: ILAC, EA).
Calibration report:Document that provides a calibration curve of an instrument, issued by a laboratory or an organization that is not accredited forcalibration (e.g., accredited only ISO 9001).
As found report/certificate:Document that provides a calibration curve for an instrument, as found, or as presented to the calibration or metrologicalconfirmation.
As left report/certificate:Document that provides a calibration curve for an instrument, as left, or after making an adjustment procedure (because it wasfound out of the specifications).
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REQUIREMENTS IN THE QUALITY MANAGEMENT SYSTEMS ISO 9001, 14001, 16949, AND EN 9100
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7 Requirements in the Quality Management Systems ISO 9001, 14001, 16949, and EN 9100
7.1 Introduction
The main international normative requirements on calibration of measuring instruments in the quality managementsystems, in the environmental management system, and in the automotive and aeronautic industries are provided.
7.2 ISO 9001 Requirements
ISO 9001:2015 on quality management systems (QMS) states in point 7.1.5:
7.1.5 Monitoring and measuring resources
7.1.5.1 GeneralThe organization shall determine and provide the resources needed to ensure valid and reliable results whenmonitoring or measuring is used to verify the conformity of products and services to requirements.
The organization shall ensure that the resources provided:
a) Are suitable for the specific type of monitoring and measurement activities being undertakenb) Are maintained to ensure their continuing fitness for their purpose
The organization shall retain appropriate documented information as evidence of fitness for the purpose ofmonitoring and measurement resources.
7.1.5.2 Measurement traceabilityWhen measurement traceability is a requirement, or is considered by the organization to be an essential part ofproviding confidence in the validity of measurement results, measuring equipment shall be:
a) Calibrated or verified, or both, at specified intervals, or prior to use, against measurement standardstraceable to international or national measurement standards; when no such standards exist, the basisused for calibration or verification shall be retained as documented information
b) Identified in order to determine their statusc) Safeguarded from adjustments, damage, or deterioration that would invalidate the calibration status and
subsequent measurement results
The organization shall determine if the validity of previous measurement results has been adversely affected whenmeasuring equipment is found to be unfit for its intended purpose, and shall take appropriate action as necessary.
7.3 ISO 14001 Requirements
ISO 14001:2015 on environmental management systems (EMS) states in point 9.1.1:
9.1 Monitoring, measurement, analysis, and evaluation
9.1.1 General
The organization shall monitor, measure, analyze, and evaluate its environmental performance. The organizationshall determine:
a) What needs to be monitored and measuredb) The methods for monitoring, measurement, analysis, and evaluation, as applicable, to ensure valid resultsc) The criteria by which the organization will evaluate its environmental performance, and appropriate
indicatorsd) When the monitoring and measuring shall be performede) When the results from monitoring and measurement shall be analyzed and evaluated
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Part II
Requirements and Criteria for the Management and Calibration of Measuring Instruments
Part II describes the requirements and operating procedures for the management and calibration of measuring instruments for thefollowing measurement quantities:
1.0 Physical quantities: Pressure, flow, level, temperature, etc.
2.0 Chemicals for liquids: pH, redox, turbidity, conductivity, etc.
3.0 Chemicals for gases: Infrareds, ultraviolets, gas chromatographs, etc.
4.0 Mechanical quantities: Length, speed, acceleration, etc.
5.0 Electrical quantities: Indicators, oscilloscopes, multimeters, etc.
For the main types of measuring instruments, the operating procedures of calibration and metrological confirmation for managing thequality of the measurements is presented. They are accompanied by the registry and metrology card, suitable for recording theinstrument identification and the registration of subsequent verification checks and metrological confirmation implemented with thetwo methods explained in Part I, 10.2.1 and 10.2.2:
• Verify that the Maximum Relieved Error (MRE) of the instrument is less than or equal to the Maximum Tolerated Error(MTE). This is generally recommended when using references with uncertainty less than or equal to one-third of that of theinstrument to be calibrated.
• Verify that the Maximum Relieved Uncertainty (MRU) of the instrument is less than or equal to the Maximum ToleratedUncertainty (MTU). This is particularly recommended when using references with uncertainty greater than one-third of thatof the instrument to be calibrated.
Obviously, this must always be done in compliance with any applicable normative references.
At the same time, note that errors and uncertainties are generally expressed:
• In absolute terms in the case of temperatures (°C), lengths (mm), etc.• In relative terms (e.g., percent of full scale for pressure or percent of reading for flow)
Also note that for editorial convenience, all metrological confirmation intervals of different measurement instruments have been setat one year, without regard to the course management criteria of the intervals reported in Part I in:
• 8.5 Definition of Metrological Confirmation Intervals• 8.6 Review of the Metrological Confirmation Intervals• 8.7 Examples of Definition of Metrological Confirmation Intervals
This is unless otherwise specified in any technical requirements or related legislations.
In addition, it points out the importance of reviewing the metrological confirmation intervals with the scale method provided by theinternational document OIML D 10, which in principle should lead to:
• An increase in the interval for the most stable instruments (or scarcely used), type: manometers, thermocouples, etc.• A decrease in the interval for the most critical instruments (or continuous use), type: analyzers, gas chromatographs, etc.
This is unless otherwise specified in the technical requirements and/or related legislations.
Finally, note that for uniformity in the various operating procedures, the document has highlighted the environmental conditions interms of temperature, relative humidity, and atmospheric pressure. This is a practice for a proper independent laboratory. For anindustrial laboratory, always specify the temperature, and specify humidity and pressure if they are influential or prescribed byapplicable normative references.
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INTRODUCTION
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1. Physical Quantities
This first section of Part II describes the requirements and specific criteria for managing and calibrating measuring instruments ofphysical quantities:
1.1 Pressure1.2 Flow1.3 Level1.4 Temperature1.5 Humidity1.6 Viscosity1.7 Density1.8 Mass
For each quantity, the International System (SI) of units, any specific definitions, the main operating principles, and any referencetables will be succinctly presented.
In addition to the main types of instruments, the handbook will present the relative operating procedure of calibration andmetrological confirmation articulated on the following points:
1. Scope and Purpose2. Identification and Classification3. Normative References4. Ambient Conditions5. Initial Checks6. Calibration Method7. Calibration Verification8. Calibration Results9. Metrological Confirmation
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PRESSURE
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1.1 Pressure
Units of Measurement and Definitions
The pressure P is defined as the ratio between the force F acting on a surface and its area A:
P = F / A
The pressure unit in the International System is pascal (Pa):
1 Pa = 1 N / 1 m2
The pressure unit bar is also accepted:
1 bar = 105 Pa
For the relationship with other units, see table 1.
Notes: The standard reference atmospheric pressure at sea level is 1013.25 mbar (101325 Pa). The air pressure decreases byabout 1 mbar for every 10 m above sea level (valid until 4000 m).
The concepts related to the type of the relative and absolute pressures are shown in figure 1.
Table 1. Conversions of the Different Units of Pressure
Pa bar Atm kg/cm2 mm H2O@ 4°C
mm Hg@ 0°C
psiin H2O@ 4°C
in Hg@ 0°C
1 Pa 1 0.00001 0.0000099 0.000010 0.101972 0.00750 0.000145 0.004015 0.000295
1 bar 100000 1 0.986923 1.01972 10197.2 750.062 14.5038 401.463 29.530
1 Atm 101325 1.01325 1 1.03323 10332.3 760 14.6959 406.78 29.921
1 kg/cm2 98066.5 0.980665 0.967841 1 10000 735.559 14,2233 393.701 28.959
1 mm H2O 9.80665 0.000098 0.000097 0.0001 1 0.07355 0.001422 0.03937 0.002896
1 mm Hg 133.322 0.001333 0.001316 0.001359 13.595 1 0.019337 0.53524 0.03937
1 psi 6894.76 0.068947 0.068046 0.070307 703.07 51.715 1 27.68 2.03602
1 in H2O 249.089 0.002491 0.002458 0.002540 25.4 1.86832 0.03613 1 0.073556
1 in Hg 3386.39 0.038639 0.033421 0.034532 345.316 25.4 0.491154 13.5951 1
Figure 1. Concepts Related to the Type of Pressure Measurement
Pressure [bar]
1.013
0
Atmospheric pressure
Absolute pressure above atmospheric P
Related pressure below atmospheric P
(depression)
Limits of variation of atmospheric pressure Absolute pressure
below atmospheric P
Related pressure above atmospheric P
(pressure)
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Main Instruments for Pressure Measurement
The main instruments and most common pressure measurements are as follows:
• Manometers or pressure gauges, according to European standard EN 837• Transmitters or pressure transducers, according to international standard IEC 60770
As an example, the following tables show the features provided by the European standard EN 837 for manometers (i.e., pressuregauges or dial gauges), which standardizes the use of Bourdon tubes, membranes, and capsules: table 2 for standard ranges, table3 for standard nominal diameters, and table 4 for standard accuracy classes.
Notes:(1) The preferred units are the bar and mbar.(2) The maximum measuring range is 25 bar for diaphragm and capsule manometers.(3) Measuring ranges are in mbar only for diaphragm and capsule manometers.
Table 2. Standard Measuring Ranges for Manometers (EN 837)
Instrument Measuring Ranges (1)
Manometers orPressure Gauges
Measuring ranges in bar (2)0 – 0.60 – 1 0 – 10 0 – 100 0 – 10000 – 1.6 0 – 16 0 – 160 0 – 16000 – 2.5 0 – 25 0 – 2500 – 4 0 – 40 0 – 4000 – 6 0 – 60 0 – 600
Measuring ranges in mbar (3)0 – 1 0 – 10 0 – 1000 – 1.6 0 – 16 0 – 1600 – 2.5 0 – 25 0 – 2500 – 4 0 – 40 0 – 4000 – 6 0 – 60 0 – 600
Vacuum Gauges Measuring ranges in bar–0.6 – 0 –1 – 0
Measuring ranges in mbar (3)–1 – 0 –10 – 0 –100 – 0–1.6 – 0 –16 – 0 –160 – 0–2.5 – 0 –25 – 0 –250 – 0–4 – 0 –40 – 0 –400 – 0–6 – 0 –60 – 0 –600 – 0
Pressure and Vacuum Gauges Measuring ranges in bar–1 – 0.6 –1 – 3 –1 – 9 –1 – 24–1 – 1.5 –1 – 5 –1 – 15
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Note:(1) The minimum nominal diameter is 50 for diaphragm and capsule manometers.
Note:(1) The minimum accuracy class is 0.6 for diaphragm and capsule manometers.
Calibration and Metrological Confirmation Procedures
1.1.1 Pressure indicators (manometers) : PI : EN 837
1.1.2 Pressure transmitters : PT : EN 60770
1.1.3 Electromechanical manometers : PE : EURAMET 17
1.1.4 Pressure balances : PB : EURAMET 3
For Other Pressure Gauges
• Manometers for extinguishers use : EN 3-5 with accuracy class 6%• Manometers for welding use : EN 562 with accuracy class 2.5%• Manometers for medical use : EN 738 with accuracy class 2.5%• Manometers for tires use (1) : EN 12645 according to EC Directive 86/217 (with MTE ≤ 2.5%)• Manometers for pressure blood (2) : EN 1060 according to EC Directive 93/42 (with MTE ≤ 3 mm Hg)
For the latter pressure gauges, generally follow the procedure for manometers EN 837 (1.1.1) with calibration points at least every20% (15% for EN 562); however, follow the specific method described in the relevant technical normative references or legalregulations.
Notes:(1) There is also a similar international recommendation, OIML R 23: Tire pressure gauges for motor vehicles.(2) There is also a similar international recommendation, OIML R 16: Sphygmomanometers.
Table 3. Standard Nominal Diameters DN for Manometers (EN 837)
DN Nominal Diameters (1)
(mm) 40 50 63 80 100 150 160 250
Table 4. Standard Accuracy Classes for Manometers (EN 837)
Cl Accuracy Classes (1)
(%) 0.1 0.25 0.6 1 1.6 2.5 4
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1.1.1 Pressure Indicators
1. Scope and PurposeThis procedure applies to all types of pressure indicators or dial manometers with Bourdon tubes or membranes and capsules, withmeasuring ranges between –1 and 1600 bar (or greater).
2. Identification and ClassificationBefore information about the new instrument is used in the application, it must be filed in accordance with the instrument card at theright, defining the procedures, the normative references, and the required checks and results. The instrument must be confirmedmetrologically for the application, including the instrument’s recalibration, if necessary.
3. Normative References• EN 472 (1995) : Pressure gauges – vocabulary• EN 837-1-2-3 (1996) : Pressure gauges – Bourdon tube, membrane, capsule pressure gauges
4. Ambient ConditionsTemperature: (20 ± 2)°C, Relative humidity: (50 ± 25)%, Atmospheric pressure: (1000 ± 25) mbar
5. Initial ChecksBefore starting any operation, check that the instrument does not indicate traces of rupture, wear, or alteration of parts, such asmeasuring scale and fittings. Then install the instrument in the measuring circuit, ensure that there are no leaks, and make threepreload cycles on the whole verification range.
6. Calibration MethodPerform calibration methods by comparing with standard instruments:
• For laboratory manometers, by pressure balance with standard masses (figure A)• For industrial manometers with accuracy class more than 1, with standard manometer (figure B)• For industrial manometers with accuracy class less than 1, with standard calibrator (figure C)
It has a lower measurement uncertainty, possibly one-fourth of that of the manometer in calibration (according to the normativereferences).
If there is a different level Δh between the intake of the standard manometer and the manometer in calibration, it is necessary tocorrect the pressure difference ΔP between the two levels, through the relation: ΔP = ρ ⋅ g ⋅ Δh [Pa], where ΔP = differential pressurein pascal (1 Pa = 10-5 bar), ρ = density of the measurement fluid (for water ≈ 1000 kg/m3), g = local gravitational acceleration (orstandard = 9.80665 m/s2), and Δh = different level between the two manometers in meters
7. Calibration VerificationThe verification should be carried out with increasing/decreasing pressure (i.e., at least every 25% of scale):
25 – 50 – 75 – 100 – 75 – 50 – 25 – 0%Reach every point of measurement without going over, and wait for the indication that the standard and instrument in calibration areperfectly stable. Then read and detect the standard and the instrument indications.
8. Calibration ResultsReport the calibration results in an instrument card to first be processed and then valued against the Maximum Tolerated Error(MTE) or Maximum Tolerated Uncertainty (MTU):
• Verify that the Maximum Relieved Error (MRE) of the instrument is less than or equal to MTE.• Verify that the Maximum Relieved Uncertainty (MRU) of the instrument is less than or equal to the MTU.
If the check is not positive, it will be necessary to recalibrate the instrument, and then repeat the calibration verification (point 7), ordowngrade or alienate the instrument.
9. Metrological ConfirmationRecord on the side of the instrument card:
• The results of the metrological confirmation (positive, negative: declassification or alienation)• The signature of those who made the verification and the next verification date
Also, fill out and attach the positive confirmation label on the instrument, indicating at least the number of the verification/calibrationreport, the instrument serial number, and the next verification date.
Figure A Figure B Figure C
Standard manometer Manometer in calibration
Manual pump or pressure reducer
Δh = 0
Manometer in cal ibration
Standard ca librator Reference leve l
2.500 bar Δh ≠ 0
kPa
43
2
6
5 1
0
Variable volume
Fluid reservoir
Fluid filling valve
Mass Manometer in calibration
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PRESSURE
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Metrological Laboratory
Pressure Indicators(pressure gauges or dial manometers)
Card Number XX-PI
IDENTIFICATION AND METROLOGICAL DATA
Instrument identification PI 11 Measuring range 0–10 barInstrument classification Process Calibration range 0–10 barInstrument denomination Manometer Accuracy class 1%Manufacturer ABC Measure resolution (Eres) 0.05 barModel DN 100 Max Tolerated Error (MTE) 0.10 barSerial number XYZ Max Tolerated Uncertainty (MTU) 0.15 barDate of acquisition 01.02.2010 Reference standard uncertainty (Uref) 0.01 barLocation of installation Process PI 11 Certificate number of standard 1111Installation conditions Vertical Fluid exercise/calibration Air/airUtilization conditions Eventual Fluid filling Eventual
APPLICABLE PROCEDURES AND NORMATIVES
Calibration procedure PP-PI Maintenance procedure Manufacturer spec.Confirmation procedure PP-PI Normative reference EN 837
REQUIRED CONTROLS
Calibration YES NO
Confirmation YES NO
Certification YES NO
Body Control Internal External
TRACEABILITY OF MEASUREMENT
Calibration and ConfirmationInternal traceability to reference standard PS 11
CertificationExternal traceability of certification body
INTERVAL OF METROLOGICAL CONFIRMATION
3 months 6 months 1 year 2 years
RESULTS OF CONFIRMATION
Date of Control
Body Control
Number ofReport
Results of Confirmation
DriftMRE/bar
Signature Vision
Deadline Notes
01.06.2017 Internal XX-PI Positive 0.05 White 01.06.2018
RESULTS OF LAST CONFIRMATION
Was the adjustment made before the verification? YES NO
PressureReference
(bar)
RELIEVED VALUES RELIEVED ERRORS Max Relieved Error
Emax(bar)
Increasing Decreasing Increasing Decreasing
(bar) (bar) (bar) (bar)
0 – 0.05 – 0.052 1.95 2.05 –0.05 0.054 3.95 4.05 –0.05 0.05 0.056 5.95 6.05 –0.05 0.058 7.95 8.05 –0.05 0.0510 9.95 – –0.05 –
RESULTS OF METROLOGICAL CONFIRMATION
MRE < MTE 0.05 bar < 0.10 bar YES NOOR ALTERNATIVELY
MRU < MTU YES NO
THE NEXT VERIFICATION MUST BE CARRIED OUT WITHIN 01.06.2018
MetrologicalFunction
EXECUTOR SIGNATURE RESPONSIBLE SIGNATURE DATE 01.06.2017
barbarEresEUref
MRU 15.006.046,305.0
73.105.0
201.02
3.23max
22
222222
<=
+
+
⋅=
+
+
⋅=
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LEVEL
113
1.3 Level
Units of Measurement and Definitions
The level of liquid and solid products (such as powders, mixtures, and granules) in containers (such as tanks, silos, and vessels) ismeasured in height in meters. In the case of liquids, the level or height measurement is always the effective real average height ofthe liquid content. In the case of solids, the level or height measured is the punctual real actual height of the solid content, a heightwhich is substantially a function of the measuring point (figure 1).
Calibration and Metrological Confirmation Procedures
1.3.1 Pressure (Hydrostatic) : LP: IEC 60770
1.3.2 Reflection (Sonar and Radar) : LX: IEC 60770
Figure 1. Level Measurement of Products in Containers with Sensors (1-2-3) Mounted on Top of the Tanka. Level measurement of liquids: The sensors always detect the same level h (h1 = h2 = h3) given the horizontal liquid level.b. Level measurement of solids: The sensors detect various levels (h1 ≠ h2 ≠ h3) as a function of the content solid surface.
1 2 3 1 2 3
h h1 h2 h3
(a) (b)
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PHYSICAL QUANTITIES
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1.3.1 Measurers at Pressure (Hydrostatics)
1. Scope and PurposeThis procedure applies to the types of pressure level meters, otherwise called hydrostatic, that use relative (for vessels open to theatmosphere) or differential (for pressure vessels) pressure measuring instruments with an analog (mA or mV) or digital (HART orBus) output signal.
2. Identification and ClassificationBefore information about the new instrument is used in the application, it must be filed in accordance with the instrument card at theright, defining the procedures, the normative references, and the required checks and results. The instrument must be confirmedmetrologically for the application, including the instrument’s recalibration, if necessary.
3. Normative References• IEC 60770-1 (2010) : Industrial transmitters – Part 1: Methods for performance evaluation• IEC 60770-2 (2010) : Industrial transmitters – Part 2: Methods for inspection and routine• IEC 60770-3 (2014) : Industrial transmitters – Part 3: Methods for performance evaluation of intelligent transmitters
4. Ambient ConditionsTemperature: (20 ± 2)°C, Relative humidity: (50 ± 25)%, Atmospheric pressure: (1000 ± 25) mbar
5. Initial ChecksBefore starting any operation, check that the instrument does not indicate traces of rupture, wear, or alteration of parts, such ascasings, fittings, and the optional indicator. Then install the instrument in the measuring circuit and ensure that there are no leaks.Make three preload cycles on the whole verification range.
6. Calibration MethodSince the principle of hydrostatic measurement precisely uses the pressure generated by the liquid level in the vessel bottom(according to the note and detailed formula at the bottom of a typical installation in figure A) to perform the calibration locally (byintercepting the transmitter) or elsewhere (by removing the transmitter) for comparison with a standard instrument (calibrators orpressure balances):
• For analog instruments with a pressure calibrator measuring the output signal (figure B)• For digital instruments with a pressure calibrator and digital communicator or configurator (figure C)
In any case, it has a lower measurement uncertainty possibly of one-fourth of that of the instrument in calibration (according to thenormative references).
The hydrostatic pressure exerted by the liquid level of the tank bottom is given by the following relation: P = ρ ⋅ g ⋅ h [Pa], where P =pressure exercised in pascal (1 Pa = 10-5 bar), ρ = density of the measurement fluid (for water ≈ 1000 kg/m3), g = local gravitationalacceleration (or standard = 9.80665 m/s2), h = level height to be measured in meters
7. Calibration VerificationThe verification should be carried out with increasing/decreasing pressure (i.e., at least every 20% of scale):
20 – 40 – 60 – 80 – 100 – 80 – 60 – 40 – 20 – 0%Reach every point of measurement without going over, wait for the indication that the standard and instrument in calibration areperfectly stable, then read and detect the standard and the instrument output or indications.
8. Calibration ResultsReport the calibration results in an instrument card to first be processed and then valued against the Maximum Tolerated Error(MTE) or Maximum Tolerated Uncertainty (MTU):
• Verify that the Maximum Relieved Error (MRE) of the instrument is less than or equal to the MTE.• Verify that the Maximum Relieved Uncertainty (MRU) of the instrument is less than or equal to the MTU.
If the check is not positive, it will be necessary to recalibrate the instrument, then repeat the calibration verification (point 7), ordowngrade or alienate the instrument.
9. Metrological ConfirmationRecord on the side of the instrument card:
• The results of the metrological confirmation (positive, negative: declassification or alienation)• The signature of those who made the verification and the next verification date
Also, fill out and attach the positive confirmation label on the instrument, indicating at least the number of the verification/calibrationreport, the instrument serial number, and the next verification date.
Figure A Figure B Figure C
Output4-20 mA
SupplyConnection
Load250 Ω
Communicatoror ConfiguratorTransmitter
or Transducer
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LEVEL
115
Metrological Laboratory
Measurers at Pressure(Hydrostatics)
Card Number XX-LP
IDENTIFICATION AND METROLOGICAL DATAInstrument identification LP 11 Measuring range (0–10m H2O) 0–100 kPaInstrument classification Process Calibration range (0–10m H2O) 0–100 kPaInstrument denomination Transmitter Accuracy class 0.05%Manufacturer ABC Measure resolution (Eres) 0.01%Model LP Max Tolerated Error (MTE) 0.05%Serial number XYZ Max Tolerated Uncertainty (MTU) 0.10%Date of acquisition 01.02.2010 Reference standard uncertainty (Uref) 0.01%Location of installation Process LP 11 Certificate number of standard 1111Installation conditions Vertical Fluid exercise/calibration Water/airSupply conditions Nominal ± 1% Output load 250 Ω ± 0.1%
APPLICABLE PROCEDURES AND NORMATIVES Calibration procedure PP-LP Maintenance procedure Manufacturer spec.Confirmation procedure PP-LP Normative reference IEC 60770
REQUIRED CONTROLSCalibration
YES NOConfirmation
YES NOCertification
YES NOBody Control
Internal ExternalTRACEABILITY OF MEASUREMENT
Calibration and ConfirmationInternal traceability to reference standard PS 11
CertificationExternal traceability of certification body
INTERVAL OF METROLOGICAL CONFIRMATION 3 months 6 months 1 year 2 years
RESULTS OF CONFIRMATIONDate of Control
Body Control
Number ofReport
Results of Confirmation
DriftMRE/%
Signature Vision
Deadline Notes
01.06.2017 Internal XX-LP Positive 0.03 White 01.06.2018
RESULTS OF LAST CONFIRMATIONWas the adjustment made before the verification? YES NO
PressureReference
(%)
RELIEVED VALUES RELIEVED ERRORS Max Relieved Error
Emax(%)
Increasing Decreasing Increasing Decreasing(%) (%) (%) (%)
0 – 0.00 – 020 19.99 20.01 – 0.01 0.0140 39.98 40.00 – 0.02 0.00 0.0360 59.97 59.99 – 0.03 – 0.0180 79.98 80.00 – 0.02 0.00
100 99.99 – – 0.01 –RESULTS OF METROLOGICAL CONFIRMATION
MRE < MTE 0.03% < 0.05% YES NOOR ALTERNATIVELY
MRU < MTU YES NO
THE NEXT VERIFICATION MUST BE CARRIED OUT WITHIN 01.06.2018MetrologicalFunction
EXECUTOR SIGNATURE RESPONSIBLE SIGNATURE DATE01.06.2017
%10.0%04.046.301.0
73.103.0
201.02
3.23max
22
222222
<=
+
+
⋅=
+
+
⋅= EresEUref
MRU
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PHYSICAL QUANTITIES
116
1.3.2 Measurers at Reflection (Sonar and Radar)
1. Scope and PurposeThis procedure applies to all the types of level measurers at reflection (sonar and radar) with an analog (mA or mV) or digital (HARTor Bus) output signal and a measurement range to 50 m (or more).
2. Identification and ClassificationBefore information about the new instrument is used in the application, it must be filed in accordance with the instrument card at theright, defining the procedures, the normative references, and the required checks and results. The instrument must be confirmedmetrologically for the application, including the instrument’s recalibration, if necessary.
3. Normative References• IEC 60770-1 (2010) : Industrial transmitters – Part 1: Methods for performance evaluation• IEC 60770-2 (2010) : Industrial transmitters – Part 2: Methods for inspection and routine • IEC 60770-3 (2014) : Industrial transmitters – Part 3: Methods for performance evaluation of intelligent transmitters
4. Ambient ConditionsTemperature: (20 ± 2)°C, Relative humidity: (50 ± 25)%, Atmospheric pressure: (1000 ± 25) mbar
5. Initial ChecksBefore starting any operation, check that the instrument does not indicate traces of rupture, wear, or alteration of parts, such ascasings, fittings, and the optional indicator. Then install the instrument in the measurement system and check the electricalfunctionality.
6. Calibration MethodSince the measuring principle of the transmitters in question uses the reflection of waves, use, respectively:
• Sonic for sonar, with propagation velocity of about 300 m/s• Electromagnetic for radar, with velocity of propagation of about 300 • 106 m/s
Therefore, it must be prepared in a “variable level” calibration system in order to verify the measurements obtained by thetransmitters with respect to the calibration system, or between the probe and the level surface.
The calibration, therefore, can be practically performed (see the figure) locally, by intercepting the transmitter, or remotely, byremoving the transmitter. This is provided that this last condition is representative of the process (type of gas, pressure, andtemperature) in terms of the wave propagation speed of measurement and the quality of the reflection, for comparison with standardsystems consisting of ribs or reference lasers, having in each case a lower measurement uncertainty possibly of ¼ of that of theinstrument being calibrated (according to the normative references).
7. Calibration VerificationThe verification must be carried out with progressive levels every 20% of the measuring scale, namely:
0 – 20 – 40 – 60 – 80 – 100%.
8. Calibration ResultsReport the calibration results in an instrument card to first be processed and then valued against the Maximum Tolerated Error(MTE) or Maximum Tolerated Uncertainty (MTU):
• Verify that the Maximum Relieved Error (MRE) of the instrument is less than or equal to the MTE.• Verify that the Maximum Relieved Uncertainty (MRU) of the instrument is less than or equal to the MTU.
If the check is not positive, it will be necessary to recalibrate the instrument, then repeat the calibration verification (point 7), ordowngrade or alienate the instrument.
9. Metrological ConfirmationRecord on the side of the instrument card:
• The results of the metrological confirmation (positive, negative: declassification or alienation)• The signature of those who made the verification and the next verification date
Also, fill out and attach the positive confirmation label on the instrument, indicating at least the number of the verification/calibrationreport, the instrument serial number, and the next verification date.
Depth of the level to be measured
Variable level to be measured
Max level (100%)
Reference level to be measured by comparison with rib metric or laser device
Min level (0%)
Measure wave
Reflected wave
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LEVEL
117
Metrological Laboratory
Measurers at Reflection(sonar and radar)
Card Number XX-LR
IDENTIFICATION AND METROLOGICAL DATAInstrument identification LR 11 Measuring range (0–10m H2O) 0–10 mInstrument classification Process Calibration range (0–10m H2O) 0–10 mInstrument denomination Transmitter Accuracy class 0.05%Manufacturer ABC Measure resolution (Eres) 0.01%Model LR Max Tolerated Error (MTE) 0.05%Serial number XYZ Max Tolerated Uncertainty (MTU) 0.10%Date of acquisition 01.02.2010 Reference standard uncertainty (Uref) 0.01%Location of installation Process LR 11 Certificate number of standard 1111Installation conditions Vertical Fluid exercise/calibration Water/waterSupply conditions Nominal ± 1% Output load 250 Ω ± 0.1%
APPLICABLE PROCEDURES AND NORMATIVES Calibration procedure PP-LR Maintenance procedure Manufacturer spec.Confirmation procedure PP-LR Normative reference IEC 60770
REQUIRED CONTROLSCalibration
YES NOConfirmation
YES NOCertification
YES NOBody Control
Internal ExternalTRACEABILITY OF MEASUREMENT
Calibration and ConfirmationInternal traceability to reference standard LS 11
CertificationExternal traceability of certification body
INTERVAL OF METROLOGICAL CONFIRMATION 3 months 6 months 1 year 2 years
RESULTS OF CONFIRMATIONDate of Control
Body Control
Number ofReport
Results of Confirmation
DriftMRE/%
Signature Vision
Deadline Notes
01.06.2017 Internal XX-LR Positive 0.03 White 01.06.2018
RESULTS OF LAST CONFIRMATIONWas the adjustment made before the verification? YES NO
LevelReference
(m)
RELIEVED VALUES RELIEVED ERRORS Max Relieved ErrorEmax(%) (m) (%)
0 0.000 0.002 1.999 – 0.014 3.998 – 0.02 0.036 5.997 – 0.038 7.998 – 0.0210 9.999 – 0.01
RESULTS OF METROLOGICAL CONFIRMATIONMRE < MTE 0.03% < 0.05% YES NO
OR ALTERNATIVELYMRU < MTU YES NO
THE NEXT VERIFICATION MUST BE CARRIED OUT WITHIN 01.06.2018MetrologicalFunction
EXECUTOR SIGNATURE RESPONSIBLE SIGNATURE DATE01.06.2017
%10.0%04.046.301.0
73.103.0
201.02
3.23max
22
222222
<=
+
+
⋅=
+
+
⋅= EresEUref
MRU
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TEMPERATURE
119
1.4 TEMPERATURE
Units of Measurement and Definitions
The kelvin is the fraction 1/273.16 of the temperature interval from the triple point of water to absolute zero, and can be formulatedas follows:
1 K = 1/273.16 Thermodynamic temperature of the triple point of water
For conversion to other units still in use and for the evolution of the temperature scale, see table 1 and table 2. (Please note that fortemperature intervals, the kelvin K corresponds to the °C.)
• tC = Relative temperature in Celsius degrees (°C): Scale that assigns 0°C and ≅ 100°C at the fusion and boiling point of thewater
• tK = Absolute temperature in kelvin (K): Scale that assigns 0 K = –273.15°C at zero absolute temperature• tF = Relative temperature in Fahrenheit degrees (°F): Scale that assigns 32°F and ≅ 212°F at the fusion and boiling point of the
water• tK = Absolute temperature in Rankine degrees (°R): Scale that assigns 0°R = –459.67°F at zero absolute temperature
(1) Primary fixed point not provided(2) Secondary fixed point providedFor the old International Practice Temperature Scale, IPTS 68 (1968)For the new International Temperature Scale, ITS 90 (1990)
Table 1. Conversion for Temperature Measurement Units
Temperature tC tK tF tR
tC 1 tK – 273.15 5/9 (tF – 32) 5/9 tR – 273.15
tK tC + 273.15 1 5/9 tF + 255.37 5/9 tR
tF 9/5 tC + 32 9/5 tK – 459.67 1 tR – 459.67
tR 9/5 tC + 491.67 9/5 tK tF + 459.67 1
Table 2. Fixed Points of the International Temperature Scales
Substance Fixed Points(@ 101325 Pa)
IPTS 68 ITS 90
Element Symbol (K) (°C) (K) (°C)
HydrogenHydrogenHydrogenNeonNeonOxygenOxygenArgonMercuryWaterWaterGalliumWater (2)IndiumTinZincAntimony (2)Aluminum SilverGoldCopper
H2H2H2NeNeO2O2ArHg
H2OH2OGa
H2OInSnZnSbAlAgAuCu
Triple pointLiquefaction point
Boiling pointTriple pointBoiling pointTriple pointBoiling pointTriple pointTriple pointFusion pointTriple pointFusion pointBoiling pointFusion point
Solidification pointSolidification pointSolidification pointSolidification pointSolidification pointSolidification pointSolidification point
13.8117.04220.282
(1)27.10254.36190.188
(1)(1)
273.15273.16
(1)373,15
(1)505.118692.73903.89
(1)1235.931337.58
(1)
-259.34-256.108-252.868
(1)-246.048-218.789-182.962
(1)(1)0
0.01(1)100(1)
231.968419.58630.74
(1)961.93
1064.43(1)
13.80317.03620.27124.556
(1)54.358
(1)83.806234.316273.15273.16302.915373.124426.749505.078692.677
(1)933.4731234.931337.331357.77
-259.347-256.114-252.879-248.594
(1)-218.792
(1)-189.344-38.834
00.01
29.76599.974
156.599231.928419.527
(1)660.323961.78
1064.181084.62
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The Most Widely Used Temperature Sensors
Standardized Types of Resistance Thermometers (table 3):• Platinum resistance thermometers: According to technical standard IEC 60751• Nickel and copper resistance thermometers: According to legal standard OIML R 84
For the characteristics of standardized resistance thermometers (or thermoresistances), also see table 4 for the tolerance classesand table 5 for the resistance values for the various types of standardized resistance thermometers.
(1) According to international technical standard IEC 60751(2) According to international legal standard OIML R 84(3) Temperature value with sign (t)(4) Coefficient C applicable only under 0° C and multiplied by the factor (t – 100°C)
(0) Or more precisely, resistance thermometer detectors (RTD)(1) According to international technical standard IEC 60751(2) According to international legal standard OIML R 84(3) Temperature module without sign t(4) Equivalent to the drop cap of the type of material followed by the acronym RT (resistance thermometer)
Table 3. Temperature Limits and Interpolating Polynomials for Normalized Resistance Thermometers
MaterialType
TemperatureLimits
(°C)
TemperatureCoefficient
(/°C)
Interpolating Polynomial (3)Rt = Ro (1 + A•t + B•t2 + C•t3)
(Ω)
Platinum (1) – 200 / +850 3.85 • 10-3 A = 3.9083 • 10 –3
B = – 5.7750 • 10 –7
C = – 4.1830 • 10 –12 (4)
Nickel (2) – 60 / +180 6.17 • 10-3 A = 5.485 • 10 –3
B = 6.650 • 10 –6
C = 2.805 • 10 –11
Copper (2) – 180 / +200 4.26 • 10-3 A = 4.260 • 10 –3
Table 4. Temperature Ranges and Tolerance Classes of Standardized Resistance Thermometers (Thermoresistances)
ThermoresistanceType(0)
Commercial Denomination (4)
ToleranceClasses
TemperatureRanges
(°C)
ToleranceValues
(°C)
Platinum – Pt (1) PRT AAABC
– 50 / + 250– 100 / + 450– 200 / + 600– 200 / + 600
± (0.10°C + 1.7•10-3t) (3)± (0.15°C + 2.0•10-3t) (3)± (0.30°C + 5.0•10-3t) (3)± (0.60°C + 10.0•10-3t) (3)
Nickel – Ni (2) NRT CC
0 / + 180– 60 / 0
± (0.20°C + 8.0•10-3t) (3)± (0.20°C + 16.5•10-3t) (3)
Copper – Cu (2) CRT BC
–50 / + 200–50 / + 200
± (0.25°C + 3.5•10-3t) (3)± (0.50°C + 6.5•10-3t) (3)
Table 5. Resistance Values of the Standardized Resistance Thermometers with 100 Ω @ 0°C:Values Ω versus °C in the range –200 to 600°C
Type –200 –150 –100 –50 0 50 100 150 200 250 300 350 400 450 500 600
PRT 18.52 39.72 60.26 80.31 100.00 119.40 138.51 157.33 175.86 194.10 212.05 229.72 247.09 264.18 280.98 313.71
NRT 74.21 100.00 129.17 161.72 198.68
CRT 78.70 100.00 121.30 142.60 163.90 185.20
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Standardized Types of Thermocouples (TC) (table 6):
• Thermocouples of metals in alloy: According to International Electrotechnical standard IEC 60584• Thermocouples of pure metals: According to International Electrotechnical standard IEC 62460
For the characteristics of standardized thermocouples see:
• Table 7 for the tolerance classes of thermocouples alloy• Table 8 for the tolerance classes of extension and compensating cables• Table 9 for the connecting cables in accordance with international standard IEC and national standards• Table 10 for the values of the electromotive force for various thermocouples standardized by IEC
(1) Thermocouples in pure metals (IEC 62460) have no identifying letter, but rather the component metals symbols(2) The Copper-Nickel alloy is commonly called Constantan
(1) Tolerance values are always worth the greater value.(2) For types A, B, C, the Tolerance Class 1 is not foreseen.
Table 6. Temperature Limits of Standardized Thermocouples (IEC 60584-1)
ThermocoupleType(1)
ThermocoupleMaterials Temperature
Range
CommercialDenomination
(2)Positive Conductor Negative Conductor
TEJKNSRBCA
Copper Nickel – ChromiumIron Nickel – ChromiumNickel – Cr – SiPlatinum – 10% RhPlatinum – 13% RhPlatinum – 30% RhTungsten – 5% ReTungsten – 5% Re
Copper – Nickel Copper – Nickel Copper – Nickel Nickel – AluminumNickel – SiliconPlatinumPlatinum Platinum – 6% RhodiumTungsten – 26% RheniumTungsten – 20% Rhenium
– 270 / 400– 270 / 1000– 210 / 1200– 270 / 1300– 270 / 1300– 50 / 1760– 50 / 1760
0 / 18200 / 23150 / 2500
Copper ConstantanChromel Constantan
Iron Constantan Chromel Alumel
Nicrosil Nisil
Table 7. Tolerance Classes of Standardized Thermocouples (IEC 60584-2)
ThermocoupleType
ThermocoupleMaterials
Tolerance Classes (1)
1 2Positive Conductor Negative Conductor
TEJKNSRBCA
Copper Nickel – ChromiumIron Nickel – ChromiumNickel – Cr – SiPlatinum – 10% RhPlatinum – 13% RhPlatinum – 30% RhTungsten – 5% ReTungsten – 5% Re
Copper – Nickel Copper – Nickel Copper – Nickel Nickel – AluminumNickel – SiliconPlatinumPlatinum Platinum – 6% RhodiumTungsten – 26% RheniumTungsten – 20% Rhenium
0.5°C or 0.4%1.5°C or 0.4%1.5°C or 0.4%1.5°C or 0.4%1.5°C or 0.4%1.0°C or 0.2%1.0°C or 0.2%
(2)(2)(2)
1.0°C or 0.75%2.5°C or 0.75%2.5°C or 0.75%2.5°C or 0.75%2.5°C or 0.75%1.5°C or 0.25%1.5°C or 0.25%1.5°C or 0.25%
1.0% > 425°C1.0% > 1000°C
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(1) The extension cable is of the same constituents as the thermocouple materials, used for common thermocouples: T, E, J, K, N.(2) The compensation cable is made of other materials than those constituting the thermocouple, used for precious thermocouples:R, S, B (for the latter, they are usually used for normal copper cables with typical maximum error of 3.5° C).
(*) For type B thermocouples, common copper cables in the range up to 100°C are usually used.(+) Conductor +(–) Conductor –(S) Outer Sheath
Table 8. Tolerance Classes of Extension (X) and Compensation (C) Cables for Thermocouples (IEC 60584-3)
CableType
Cable Symbol
Tolerance Classes Cable Temperature
Range
MeasureJunction
Temperature1 2
EXTENSION(1)
TXEXJXKXNX
± 30 μV (0.5°C)± 120μV (1.5°C)± 85μV (1.5°C)± 60μV (1.5°C)± 60μV (1.5°C)
± 60 μV(1.0°C)± 200 μV(2.5°C)± 140 μV(2.5°C)± 100 μV(2.5°C)± 100 μV(2.5°C)
– 25°C / +100°C– 25°C / +200°C– 25°C / +200°C– 25°C / +200°C– 25°C / +200°C
300°C500°C500°C900°C 900°C
COMPENSATION(2)
NCKCAKCB
RCA/SCARCB/SCB
–––––
± 100 μV(2.5°C)± 100 μV(2.5°C)± 100 μV(2.5°C)± 30 μV (2.5°C)± 60 μV (5.0°C)
0°C / +150°C0°C / +150°C0°C / +100°C0°C / +100°C0°C / +200°C
900°C900°C900°C1000°C1000°C
Table 9. Matching the Colors of Thermocouple Wires between IEC 60584-3 and Other National Standards
Cable forThermocouple
Type
Colors of Sheath and Cables According to:
(INTERNAT.)IEC
(U.S.)ANSI
(U.K.)BS
(D)DIN
(F)NFE
(J)JIS
T
(S) Brown Brown Blue Brown Blue Brown
(+) Brown Blue White Red Yellow Red
(–) White Red Blue Brown Blue White
E
(S) Violet Brown Brown Black Violet Violet
(+) Violet Violet Brown Red Yellow Red
(–) White Red Blue Black Violet White
J
(S) Black Brown Black Blue Black Yellow
(+) Black White Yellow Red Yellow Red
(–) White Red Blue Blue Black White
K
(S) Green Brown Red Green Yellow Blue
(+) Green Yellow Brown Red Yellow Red
(–) White Red Blue Green Violet White
N
(S) Pink Brown Orange
(+) Pink Orange Orange
(–) White Red Blue
R/S
(S) Orange Green Green White Green Black
(+) Orange Black White Red Yellow Red
(–) White Red Blue White Green White
B (*)
(S) Grey Grey Grey Grey
(+) Grey Grey Red Red
(–) White Red Grey White
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Values in mV versus °C, in the range –200 to 1200°C, with thermocouple reference junction @ 0°C
Table 10. Values of the Various Types of Normalized Thermocouples Consisting of Alloy Metals (IEC 60584) and Pure Metals (Au-Pt and Pt-Pd: IEC 62460)
Type – 200 – 100 0 100 200 300 400 500 600 700 800 900 1000 1100 1200
T –5.603 –3.379 0 4.279 9.288 14.862 20.872
E –8.825 –5.237 0 6.319 13.421 21.036 28.946 37.005 45.093 53.112 61.017 68.787 76.373
J –7.890 –4.633 0 5.269 10.779 16.327 21.848 27.393 33.102 39.132 45.494 51.877 57.953 63.792 69.553
K –5.891 –3.554 0 4.096 8.138 12.209 16.397 20.644 24.905 29.129 33.275 37.326 41.276 45.119 48.838
N –3.990 –2.407 0 2.774 5.913 9.341 12.974 16.748 20.613 24.527 28.455 32.371 36.256 40.087 43.846
S 0 0.646 1.441 2.323 3.259 4.233 5.239 6.275 7.345 8.449 9.587 10.757 11.951
R 0 0.647 1.469 2.401 3.408 4.471 5.583 6.743 7.950 9.205 10.506 11.850 13.228
B 0 0.033 0.168 0.431 0.787 1.242 1.792 2.431 3.154 3.957 4.834 5.780 6.786
C 0 1.451 3.090 4.865 6.732 8.657 10.609 12.559 14.494 16.398 18.260 20.071 21.825
A 0 1.336 2.871 4.512 6.203 7.908 9.605 11.283 12.933 14.549 16.127 17.662 19.150
Au-Pt 0 0.778 1.845 3.142 4.633 6.301 8.135 10.132 12.291 14.609 17.085
Pt-Pd 0 0.569 1.208 1.933 2.781 3.787 4.974 6.352 7.917 9.657 11.557 13.601 15.772
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Standardized Types of Thermometers to Radiation (also called pyrometers):
• Pyrometers operating in the red radiation: OIML R18• Pyrometers operating in the red and infrared radiation: IEC 62492
For the measuring characteristics of pyrometers and relative sensors, see respectively:
• Table 11 for the accuracy classes depending on the measurement temperature• Table 12 for the applicable sensors in relation to the measuring range to be detected
For the operating characteristics of pyrometers related to the emissivity of the bodies to be measured and the transmissivity of theinterposed media, see respectively:
• Table 13 for the emissivity (ε) of the bodies to be measured (for black body coinciding with 1)• Table 14 for the transmissivity (τ) of the interposed medium (for pure air N2+O2 coinciding with 1)
(1) Maximum permissible errors in % of the upper limit of the temperature measurement range of the pyrometer(2) Mean deviation values tolerated for five measures between the indicated temperature and the reference(3) Maximum repeatability values tolerated in five measures to the same reference temperature
Table 11. Standardization of Monochromatic Pyrometers Operating @ 0.65 µm (OIML R 18)
AccuracyClass
TemperatureRange
(°C)
Maximum Permissible Errors (1)
Deviation (2)(%)
Repeatability (3)(%)
Normal 400 – 800 800 – 14001400 – 20002000 – 32003200 – 6000
± 1.5± 1.5± 1.5± 2.5± 4.0
11123
Special 400 – 800800 – 1400
1400 – 20002000 – 32003200 – 6000
± 1.0± 0.6± 0.6± 1.2± 2.0
0.500.250.250.501.00
Table 12. Measuring Spectral Bands of Infrared Pyrometers with Various Sensors
SensorSpectral Band
(μm)
Minimum Temperature Measurable
(°C) (K)
Human eye 0.38 – 0.76 > 600 > ≈ 900
Si 0.5 – 1.0 > 400 > ≈ 700
PbS 1 – 3 > 200 > ≈ 500
PbSe 2 – 4 > 100 > ≈ 400
InAs 2 – 4 > 100 > ≈ 400
InSb 2 – 5 > 0 > ≈ 300
HgCdTe 5 – 15 < 0 < ≈ 300
Pyroelectric 0.5 – 20 < 0 < ≈ 300
Thermoelectric 0.5 – 20 < 0 < ≈ 300
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* In these applications, the coefficient of transmissivity is much less than 1, and therefore are bands to avoid.
Calibration and Metrological Confirmation Procedures1.4.1 Glass thermometers : TG : ASTM E 771.4.2 Dial thermometers (and digital) : TD : EN 13190 1.4.3 Thermoresistances : TR : IEC 607511.4.4 Thermocouples : TC : IEC 605841.4.5 Temperature transmitters : TT : IEC 607701.4.6 Temperature calibrators : TU : EURAMET 111.4.7 Calibration furnaces : TF : EURAMET 13 1.4.8 Radiation thermometers : TP : OIML R 18 & IEC 62942
For Other Temperature Meters• Clinical thermometers : OIML R 7 from 35 to 42°C (with MTE +0.1/–0.15°C)• Thermometers for refrigeration : EN 13485 according to EC Directive 92/1 (with MTE ≤ 0.5°C)• Thermometers for sterilization : EN 285 according to EC Directive 93/42 (with MTE ≤ 0.3°C)
The latter thermometers can follow the procedure for dial thermometers, EN 13190 (1.4.2) with at least three calibration pointsdistributed over the measurement range; however, they should follow the specific method described in the relevant technicalnormative references and legal regulations.
Table 13. Typical Emissivity Coefficient ε @ 0.65 μm for Various Materials
Material Type Material State Emissivity Coefficient
Aluminum 0.30
Beryllium 0.61
Carbon 0.80 – 0.95
ChromeNot oxidized 0.35
Oxidized 0.87
CobaltNot oxidized 0.36
Oxidized 0.77
Copper 0.10
Gold 0.14
IronNot oxidized 0.36
Oxidized 0.80 – 0.95
Molybdenum 0.40
NickelNot oxidized 0.36
Oxidized 0.85 – 0.95
Palladium 0.33
Rhodium 0.26
Silver 0.07
SteelNot oxidized 0.35
Oxidized 0.85
Tantalum 0.50
VanadiumNot oxidized 0.35
Oxidized 0.70
Zirconium 0.32
Table 14. Spectral Bands of Atmospheric Absorption in the Infrared (*)
Substance Spectral Band Absorption (μm)
Carbon dioxide 1.3–1.5 – 1.8–2.0 – 2.4–3.2 – 4.2–4.4 – 14–20
Water vapor 0.95–1.05 – 1.1–1.2 – 1.3–1.5 – 1.8–2.0 – 5.0–8.0
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2. Chemicals for Liquids
This second section describes the requirements and specific criteria for the management and calibration of measuring instrumentsof chemical quantities for liquids, that is, for:
2.1 pH2.2 Redox2.3 Turbidity2.4 Conductivity2.5 Dissolved Oxygen2.6 Dissolved Ions2.7 Colorimetry2.8 Refractometry
For each quantity, the handbook will succinctly present its SI units, any specific definitions, the main operating principles, and anyreference tables. In addition to the main types of instruments, it will present the relative operating procedure of calibration andmetrological confirmation articulated on the following points:
1. Scope and Purpose2. Identification and Classification3. Normative References4. Ambient Conditions5. Initial Checks6. Calibration Method7. Calibration Verification8. Calibration Results9. Metrological Confirmation
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2.1 pH
Units of Measurement and Definitions
The pH is the evaluation of hydrogen and its relationship with the concentration or the activity of H+ ions in the liquid. The pH valueis the negative logarithm of the concentration (or activity) of “hydrogen ions” (H+ or H3O+). It generally ranges from 0 for the acids to14 for the bases (7 is neutral for pure water).
Typically, the pH is detected through a chain of measuring and reference electrodes (of the type with two separate electrodes, or twoelectrodes inserted into a combined measurement device, otherwise called mono tubular) that uses the Nernst law:
E = Eo + (RT/nF) • ln “concentration” H+
whereE = measurement potential (function of concentration H+)Eo = zero potential (function of asymmetry of the measuring electrodes of the pH)R = gas constant (8.3144 J/K•mol)F = Faraday constant (96493 C/mol)T = temperature in kelvin (typically 25°C)n = number of ions (1 per H+)ln = natural logarithm (concentration H+)
The Nernst slope is 59.159 mV/pH at 25°C. It is given in table 1 for other temperatures, according to IEC 60746-2.
Table 2 shows by example the typical pH of some common substances of general interest and application.
Table 1. Nernst Slope with Varying Temperature
Temperature Nernst Slope (mV/pH)
0 54.1995 55.19110 56.18315 57.17520 58.16725 59.15930 60.15235 61.14440 62.13645 63.12850 64.120
Table 2. Typical pH Values of Some Substances
Substance pH
Strong acids < 1.0Gastric acid 2.0 Lemon juice 2.4 Cola 2.5 Vinegar 2.9 Orange juice 3.5 Beer 4.5 Coffee 5.0 Tea 5.5 Acid rain 6.0 Milk 6.5 Pure water 7.0 Human spittle 6.5–7.4 Blood 7.35–7.45 Sea water 8.0 Laundry soap 9.0–10.0 Ammonia 11.5 Chlorine bleach 12.5 Caustic soda 13.5
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Calibration Buffer Solutions Normalized
The planned buffer solutions for calibration and periodic testing of pH meters are standardized by reference to IEC 60746-2, or bytable 3 for the compositions of the buffer solutions and table 4 for the values of buffer solutions at different temperature.
Table 3. Compositions of the Reference Buffer Solutions (IEC 60746-2)
Buffer Solution Substance Molecular formulaMolarity
mol • kg–1Mass
g • dm–3
A Potassium tetraoxalate KH3C4O6 • 2H2O 0.1 25.101
B Potassium hydrogen tartrate
KHC4H4O6 Saturated at 25°C 6.4
C Potassium hydrogren phthalate
KHC8H4O4 0.05 10.12
D Disodium hydrogen phosphate&Potassium dihydrogen phosphate
Na2HPO4
KH2PO4
0.025
0.00869
3.533
3.388
E Disodium hydrogen phosphate&Potassium dihdrogen phosphate
Na2HPO4
KH2PO4
0.03043
0.025
4.302
1.179
F Tris*&Tris hydrocholoride
(CH2OH)3CNH2
(CH2OH)3CNH2•HCI
0.01667
0.05
1.999
7.800
G Disodium tetraborate Na2B4O7•10H2O 0.05 19.012
H Disodium tetraborate Na2B4O7•10H2O 0.01 3.806
I Sodium hydrogen carbonate&Sodium carbonate
NaHCO3
Na2CO3
0.025
0.025
2.092
2.640
J Calcium hydroxide Ca(OH)2 Saturated at 25°C 1.5
*Tris (hydroxymethyl) aminomethaneNote: All reagents shall be of analytical grade and the conductivity of the water shall be no greater than 2pS cm–1 (at 25°C).
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Most Used Normalized Calibration Buffer Solutions
In general, the most used buffer solutions for the calibration and periodic testing of pH meters are reported in table 5, derived fromearlier tables 3 and 4, in accordance with the reference standard IEC 60746-2.
Selection of Glass Measuring Electrodes
Figure 1 illustrates the recommended use of glass electrodes for pH as a function of temperature:G – General for each pH and low temperatures E – Particular for low pH and high temperatureS – Standard for low pH and low temperatures L – Special for high pH and high temperature
Calibration and Metrological Confirmation Procedures
2.1.1 pH meters analog and digital: AP: IEC 60746-2
Table 4. Values of the Buffer Solutions (IEC 60746-2)
TamponeBuffer
0°C 5°C 10°C 15°C 20°C 25°C 30°C 35°C 37°C 40°C 50°C 60°C 70°C 80°C 90°C 95°C
A(2) 1.67 1.67 1.67 1.67 1.68 1.68 1.68 1.68 1.69 1.69 1.71 1.72 1.74 1.77 1.75 1.81
B(1) — — — — — 3.557 3.552 3.549 3.548 3.547 3.549 3.55 3.57 3.60 3.63 3.65
C(1) 4.000 3.998 3.997 3.998 4.000 4.005 4.011 4.018 4.022 4.027 4.050 4.06 4.12 4.16 4.21 4.24
D(1) 6.984 6.951 6.923 6.900 6.881 6.865 6.853 6.844 6.841 6.838 6.833 6.84 6.85 6.86 6.88 6.89
E(1) 7.534 7.500 7.472 7.448 7.429 7.413 7.400 7.389 7.386 7.380 7.367 — — — — —
F(2) 8.47 8.30 8.14 7.99 7.84 7.70 7.56 7.43 7.38 7.31 7.07 — — — — —
G(2) 9.51 9.43 9.36 9.30 9.25 9.19 9.15 — 9.09 9.07 9.01 8.93 8.90 8.88 8.84 8.89
H(1) 9.464 9.395 9.332 9.276 9.225 9.180 9.139 9.102 9.088 9.068 9.011 8.97 8.93 8.91 8.90 8.89
I(1) 10.317 10.245 10.179 10.118 10.062 10.012 9.966 9.926 9.910 9.889 9.828 9.75 9.73 9.73 9.75 9.77
J(2) 13.42 13.21 13.00 12.81 12.63 12.45 12.29 12.13 12.07 11.98 11.71 11.45 — — — —
Table 5. Main Buffer Solutions Used for Calibration Verification of pH Meters (IEC 60746-2)
Temperature(°C)
pH Buffers Main Used in Temperature
CKHC8H4O4
DKH2PO4
INaH2CO3
JCa(OH)2
10 3.997 6.923 10.179 13.0015 3.998 6.900 10.118 12.8120 4.000 6.881 10.062 12.6325 4.005 6.865 10.012 12.4530 4.011 6.853 9.966 12.29
Figure 1. Typical Uses of Glass Measurement Electrodes in Relation to pH and to the Measuring Temperature
1 3 5 7 9 11 13 [pH]
[°C]
125
100
75
50
25
0
S
E L
G
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2.1.1. pH Meters Analog and Digital
1. Scope and PurposeThis procedure applies to analog and digital pH meters, to a measuring electrode and a separate reference, or to those integrated inthe same electrode, otherwise called mono tubular.
2. Identification and ClassificationBefore information about the new instrument is used in the application, it must be filed in accordance with the instrument card at theright, defining the procedures, the normative references, and the required checks and results. The instrument must then beconfirmed metrologically for the application, including the instrument’s recalibration, if necessary.
3. Normative References• IEC 60746-1 (2003) : Expression of performance of electrochemical analyzers: General• IEC 60746-2 (2003) : Expression of performance of electrochemical analyzers: pH value• OIML R 54 (1981) : pH scale for aqueous solutions
4. Ambient ConditionsTemperature: (25 ± 2)°C, Relative humidity: (50 ± 25)%, Atmospheric pressure: (1000 ± 25) mbar
5. Initial ChecksBefore starting any operation, check that the instrument does not indicate traces of rupture, wear, or alteration of parts, such aselectrode cleaning, unfilled electrolyte solutions, or indicators. Install and connect the instrument in the measurement system, andmake sure that there is proper ionic contact between the measurement electrodes and the calibration reference measurementsolution.
6. Calibration MethodWhen performing calibration, compare with a reference standard:
• With standard reference solutions in a special dedicated support (figure A)• With standard reference solutions automatically slaved (preferable) (figure B)• With mV generator instruments, only suitable for verification of the indicators of pH meters (figure C)
In any case, it has a lower measurement uncertainty, possibly one-third of that of the instrument in calibration.
7. Calibration VerificationThe verification should be performed on at least three points, distributed with respect to the measuring standard value (STD):
3 pH; STD + 3 pHFor example, for applications at neutral pH: 4 pH; 7 pH; 10 pH, or only on two calibration points, if it generally works with just acidicor basic solutions. At each pH value, wait a few minutes before taking the measurement values of the calibration instrument.
8. Calibration ResultsCalibration results should be reported on the instrument card to first be processed and then valued against the Maximum ToleratedError (MTE) or Maximum Tolerated Uncertainty (MTU):
• Verify that the Maximum Relieved Error (MRE) of the instrument is less than or equal to the MTE.• Verify that the Maximum Relieved Uncertainty (MRU) of the instrument is less than or equal to the MTU.
If the check is not positive, it will be necessary to recalibrate the instrument, repeat the calibration verification (point 7), or downgradeor alienate the instrument.
9. Metrological ConfirmationRecord on the side of the instrument card:
• The result of the metrological confirmation (positive, negative: declassification or alienation)• The signature of those who made the verification and the next verification date
Also, fill out and attach the positive confirmation label on the instrument, indicating at least the number of the verification/calibrationreport, the instrument serial number, and the next verification date.
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Metrological Laboratory
pH Meters(analog and digital)
Card Number XX-AP
IDENTIFICATION AND METROLOGICAL DATA
Instrument identification AP11 Measuring range 0–14 pH
Instrument classification Process Calibration range 4–10 pH
Instrument denomination pH meter Accuracy class 0.2 pH
Manufacturer ABC Measure resolution (Eres) 0.1 pH
Model AP2 Max Tolerated Error (MTE) 0.2 pH
Serial number XYZ Max Tolerated Uncertainty (MTU) 0.3 pH
Date of acquisition 01.02.2010 Reference standard uncertainty (Uref) 0.1 pH
Location of installation Process AP 11 Certificate number of standard 1111
Installation conditions Vertical Fluid exercise/calibration Water/std. solution
Utilization conditions Specify Fluid filling/reference Specify
APPLICABLE PROCEDURES AND NORMATIVES
Calibration procedure PP-AP Maintenance procedure Manufacturer spec.
Confirmation procedure PP-AP Normative reference IEC 60746-2
REQUIRED CONTROLS
Calibration YES NO
Confirmation YES NO
Certification YES NO
Body Control Internal External
TRACEABILITY OF MEASUREMENT
Calibration and ConfirmationInternal traceability to reference standard AS 11
CertificationExternal traceability of certification body
INTERVAL OF METROLOGICAL CONFIRMATION
3 months 6 months 1 year 2 years
RESULTS OF CONFIRMATION
Date of Control
Body Control
Number ofReport
Results of Confirmation
DriftMRE/pH
Signature Vision
Deadline Notes
01.06.2017 Internal XX-AP Positive 0.1 White 01.06.2018
RESULTS OF LAST CONFIRMATION
Was the adjustment made before the verification? YES NOSolution
ReferenceTable 5
(pH)
RELIEVED VALUES RELIEVED ERRORS Max Relieved ErrorEmax(pH)
Indication Elaboration
(pH) (pH)
4.0 ≡ Solution C 4.1 0.1
6.9 ≡ Solution D 7.0 0.1
10.0 ≡ Solution I 10.0 0.0 0.1
RESULTS OF METROLOGICAL CONFIRMATION
MRE < MTE 0.1 pH < 0.2 pH YES NO
OR ALTERNATIVELY
MRU < MTU YES NO
THE NEXT VERIFICATION MUST BE CARRIED OUT WITHIN 01.06.2018
MetrologicalFunction
EXECUTOR SIGNATURE RESPONSIBLE SIGNATURE DATE01.06.2017
2 22 2 2 2max 0.1 0.1 0.12 2 0.16 0.302 2 1.73 3.463 2. 3
Uref E EresMRU pH pH
= ⋅ + + = ⋅ + + = <
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TERMS
345
2. Terms Index for the Management of Measuring Instruments
TERM SYMBOL PAGE
Accuracy 31
Accuracy class Cl 31
Assessment of conformity (CE) 61
Audit Trail 65
Bureau International de Poids et Mesures BIMP 9
Calibration certificate 34
Calibration report 34
Calibration report (As Found) 34
Calibration report (As Left) 34
Characteristic, metrological 42
Characteristic, metrological for measuring equipment MEMC 52
Characteristic, metrological for reference equipment REMC 52
Code of Federal Regulation CFR 65
Comité Internationale des Poids et Mesures CIPM 9
Compatibility of Measures 22
Conference Générale des Poids et Mesures CGPM 9
Conformity assessment modules (CE) 61
Conformity marking (CE) 61
Control chart 46
Coverage factor 28
Customer Metrological Requirement CMR 42
Distribution, normal (or Gaussian) 25
Distribution, rectangular 25
Distribution, triangular 25
Environmental Management System EMS 35
Error E 32
Error, eccentricity Eecc 26
Error, indication (maximum) Emax 26
Error, interpolation Eint 27
Error, parallelism Epar 26
Error, planarity Epla 26
Error, repeatability Erep 27
Error, resolution Eres 26
Essential Safety Requirements ESR 59
European cooperation for Accreditation EA 17
Evidence of conformity instruments 57
Food and Drug Administration FDA 65
Good Automated Manufacturing Practices GAMP 66
Good Practice Guidelines GPG 66
Good Practices GxP 66
International Accreditation Forum IAF 15
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ANALYTICAL INDEX
346
International Laboratory Accreditation Cooperation ILAC 15
International Organization for Accreditation Bodies 15
International System of units SI 9
Italian Body Accreditation ACCREDIA 18
Key Performance Indicators KPI 68
Labels of evidence of conformity instruments 58
Maximum Admitted Error MAE 56
Maximum Permissible Error MPE 63
Maximum Relieved Error MRE 54
Maximum Relieved Uncertainty MRU 55
Maximum Tolerated Error MTE 54
Maximum Tolerated Uncertainty MTU 55
Measurand 31
Measurement 31
Measurement accuracy 31
Measurement equipment selection 50
Measurement Management System MMS 39
Measurement method, direct 31
Measurement method, indirect 31
Measurement process control 42
Measurement traceability 35
Measuring equipment (or measuring instrument) 42
Measuring instrument 31
Measuring instrument (calibration and verification procedures) 33
Measuring instrument (calibration conditions) 29
Measuring instrument (criteria for instrument selection) 49
Measuring Instruments Directive MID 59
Metre convention 10
Metrological confirmation 42
Metrological confirmation intervals (definitions) 43
Metrological confirmation intervals (examples) 47
Metrological confirmation intervals (review) 45
Metrological function 42
Metrological traceability 31
Metrological traceability chain 31
National Accreditation Bodies NAB 17
National Metrological Institutes NMI 20
Procedure, adjustment 34
Procedure, calibration 34
Procedure, maintenance 34
Procedure, measurement 34
Procedure, operational 34
Procedure, verification 34
Product Reference Value (process or service) PRV 52
Product Tolerance Amplitude (process or service) PTA 52
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TERMS
347
Product Tolerance Band (process or service) PTB 52
Quality Management System QMS 35
Reference equipment selection 50
Reference material 31
Reference measurement standard 31
Standard deviation s 27
Standard deviation, equivalent σeq 27
Standard Operation Procedure SOP 66
Standard, primary measurement 31
Standard, reference measurement 31
Standard, secondary measurement 31
Standard, traveling measurement 31
Test Uncertainty Ratio TUR 50
Traceability of measures 21
Type examination (CE) 60
Uncertainty 23
Uncertainty, combined uc 23
Uncertainty, expanded U 23
Uncertainty, type u 23
Uncertainty, type A 23
Uncertainty, type B 23
Verification of conformity of measuring instrument (application methods) 53
Verification of conformity of measuring instrument (process or service) 53
Verification, first (CE) 64
Verification, periodic (CE) 64
Zone, ambiguity 56
Zone, conformity 56
Zone, nonconformity 55
Zone, secure conformity ZSC 56
Zone, secure nonconformity 56
Zone, tolerance (specified) 56
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INSTRUMENTS INDEX
349
3. Instruments Index for the Calibration of Measuring Instruments
INSTRUMENT MEASURE PAGE
Accelerometers Vibration 302
Aerometers by immersion Density 174
Ammeters (see indicators) Electrical quantities 318
Amperometrics (or polarimetrics) Dissolved oxygen 220
Analyzers, amperometric cell Dissolved oxygen 219
Analyzers, catalytic combustion (for gas) Combustible gases 256
Analyzers, electrochemical (for gas) Comburent gases 251
Analyzers, flame ionization (for gas) Combustible gases 255
Analyzers, fluorimetric cell (for oxygen) Dissolved oxygen 219
Analyzers, infrared (IR) Infrared gases 244
Analyzers, paramagnetic (for gas) Comburent gases 251
Analyzers, thermal conductivity (for gas) Combustible gases 256
Analyzers, ultraviolet (UV) Ultraviolet gases 248
Aphrometers (see manometers) Pressure 78
Balance, mass Mass 188
Balance, pressure Pressure 84
Barometers (see manometers) Pressure 78
Calibrators, acoustic Sound and noise 311
Calibrators, humidity (saturated salt solutions) Humidity 146
Calibrators, pressure Pressure 82
Calibrators, temperature Temperature 136
Calipers (analog and digital) Length 284
Chromatographs Gas chromatography 264
Colorimeters Colorimetry 232
Colorimetry Colorimetry 229
Comparators Length 280
Conductivity meters Conductivity 214
Current clamps Electrical quantities 334
Densimeters, immersion (or aerometers) Density 174
Densimeters, pressure Density 170
Densimeters, vibration (or rotation) Density 172
Dew Point (DP) Humidity 148
Dissolved ions Dissolved ions 223
Dissolved oxygen Dissolved oxygen 217
Dynamometers Force 288
Energy meters Electrical quantities 330
Flame Ionization Detector (FID) Gas chromatography 262
Flame Photometric Detector (FPD) Gas chromatography 262
Flowmeters (or measurers of flow) Flow 87
Fluorimeters (or luminescence) Dissolved oxygen 220
Frequency meters (see indicators) Electrical quantities 318
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ANALYTICAL INDEX
350
Frost Point (FP) Humidity 148
Gas chromatographs Gas chromatography 264
Gas chromatography Gas chromatography 261
Gas spectrometers Gaspectrometry 270
Gas spectrometry Gaspectrometry 267
Gauge blocks Length 278
Hydrometers (by immersion) Density 174
Hydrostatics (at pressure) Level 114
Hygrometers, absolute humidity Humidity 148
Hygrometers, relative humidity Humidity 150
Indicators (analog and digital) Electrical quantities 318
Ion Selective Electrodes (ISE) Dissolved ions 223
Level meters (or measurers of level) Level 113
Load cells (or dynamometers) Force 288
Lower Explosive Limit (LEL) Combustible gases 257
Magnetics (or electromagnetics) Flow 98
Manometers, analog (or dial) Pressure 78
Manometers, digital (or numeral) Pressure 82
Manometers, electromechanical Pressure 82
Manometers for blood pressure (sphygmomanometers) Pressure 77
Manometers for extinguishers Pressure 77
Manometers for medical Pressure 77
Manometers for tires Pressure 77
Manometers for welding Pressure 77
Manovacuumeters (see manometers) Pressure 78
Mass (standards) Mass 179
Massics (Coriolis) Flow 108
Measurers for comburent gases Comburent gases 251
Measurers for combustible gases Combustible gases 255
Measurers of chromatography Gas chromatography 261
Measurers of colorimetry Colorimetry 232
Measurers of conductivity (or electrical conductibility) Conductivity 211
Measurers of couple (or torque wrenches) Couple 291
Measurers of density (or volumic mass) Density 163
Measurers of dissolved ions Dissolved ions 226
Measurers of dissolved oxygen Dissolved oxygen 220
Measurers of electrical quantities Electrical quantities 315
Measurers of flow (or flowmeters) Flow 87
Measurers of force Force 287
Measurers of humidity Humidity 143
Measurers of infrareds Infrared gases 243
Measurers of length Length 275
Measurers of level Level 113
Measurers of mass Mass 175
Measurers of pH pH 193
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INSTRUMENTS INDEX
351
Measurers of pressure Pressure 75
Measurers of refractometry Refractometry 238
Measurers of rH rH 199
Measurers of sound and noise Sound and noise 305
Measurers of spectrometry Gaspectrometry 267
Measurers of speed (or rotation) Velocity 295
Measurers of temperature Temperature 119
Measurers of turbidity Turbidity 205
Measurers of ultraviolets Ultraviolet gases 247
Measurers of vibration (or acceleration) Vibration 299
Measurers of viscosity Viscosity 153
Measurers per combustible gases Combustible gases 258
Micrometers Length 282
Mostimeters at immersion Density 174
Multimeters (analog and digital) Electrical quantities 338
Normal Hydrogen Electrode (NHE) rH or pH 200
Nozzle (see orifice plates) Flow 92
Ohmmeters (see indicators) Electrical quantities 318
Orifice plates Flow 92
Oscilloscopes Electrical quantities 321
Oxidation Reduction Potential (ORP) rH 199
Ph meters pH 196
Phonometers Sound and noise 312
Pistonphons Sound and noise 311
Polarimetrics (or amperometrics) Dissolved oxygen 220
Psychrometers Humidity 146
Pycnometers (to weigh) Density 174
Pyrometers Temperature 140
Radar (at reflection) Level 116
Refractometers Refractometry 238
Refractometry Refractometry 235
Rh meters rH 200
Root Mean Square (RMS) Vibration 300
Saccarimeters (at immersion) Density 174
Servoaccelerometers (see accelerometers) Vibration 302
Sonar (at reflection) Level 116
Sonics (or ultrasonics) Flow 106
Sound Exposure Level (SEL) Sound and noise 309
Sound Pressure Level (SPL) Sound and noise 309
Spectrometers Gaspectrometry 270
Sphygmomanometers (see manometers for blood pressure) Pressure 77
Standard masses Mass 186
Tachometers (or velocimeters) Velocity 296
Temperature furnaces Temperature 138
Thermal (flowmeters) Flow 110
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ANALYTICAL INDEX
352
Thermal Conductivity Detector (TCD) Gas chromatography 262
Thermocouples Temperature 132
Thermometers, dial or digital Temperature 128
Thermometers, glass Temperature 126
Thermometers, medical use Temperature 125
Thermometers, pyrometers Temperature 140
Thermometers, refrigeration Temperature 125
Thermometers, sterilization Temperature 125
Thermoresistances Temperature 130
Torque meters Couple 292
Torque wrenches Couple 292
Transducers, pressure Pressure 80
Transformers, measure Electrical quantities 326
Transmitters, pressure Pressure 80
Transmitters, temperature Temperature 134
Turbidimeters Turbidity 208
Turbines Flow 102
Upper Explosive Limit (UEL) Combustible gases 257
Vacuum gauges (see manometers) Pressure 78
Vacuum meters (see manometers) Pressure 78
Velocimeters (see velocity) Velocity 295
Venturi meters (see orifice plates) Flow 92
Vibrometers (see accelerometers) Vibration 302
Viscometers, differential pressure Viscosity 158
Viscometers, vibration (or rotation) Viscosity 160
Voltmeters (see indicators) Electrical quantities 318
Volumetrics Flow 104
Vortex Flow 100
Wattmeters (see indicators) Electrical quantities 318
Weight sets Mass 186
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