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Metrology in Industry The Key for Quality

French College of Metrology

Series Editor

Dominique Placko

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Metrology in Industry

Metrology in Industry The Key for Quality

French College of Metrology

Series Editor

Dominique Placko

First published in Great Britain and the United States in 2006 by ISTE Ltd Translated into English by Jean Barbier Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE Ltd ISTE USA 6 Fitzroy Square 4308 Patrice Road London W1T 5DX Newport Beach, CA 92663 UK USA

www.iste.co.uk

© ISTE Ltd, 2006

The rights of the French College of Metrology to be identified as the authors of this work has been asserted by them in accordance with the Copyright, Designs and Patents Act 1988.

____________________________________________________________________

Library of Congress Cataloging-in-Publication Data Metrology in industry : the key for quality / edited by French College of Metrology. p. cm. Includes bibliographical references and index. ISBN-13: 978-1-905209-51-4 1. Quality control. 2. Metrology. I. Collège français de métrologie. TS156.M485 2006 620'.0045--dc22

2006003530

British Library Cataloguing-in-Publication Data A CIP record for this book is available from the British Library ISBN 10: 1-905209-51-7 ISBN 13: 978-1-905209-51-4

Printed and bound in Great Britain by Antony Rowe Ltd, Chippenham, Wiltshire.

Table of Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Foreword. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Chapter 1. Analysis of the Metrological Requirements Needed to Ensure Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Jean-Yves ARRIAT and Klaus-Dieter SCHITTHELM

1.1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 1.2. Definition of the objectives . . . . . . . . . . . . . . . . . . . . . . . . . . 21 1.3. Choice of the method of measurement . . . . . . . . . . . . . . . . . . . . 22 1.3.1. Accounting for the selection of the method . . . . . . . . . . . . . . 22 1.3.2. Defining the method and the principle to implement . . . . . . . . . 23 1.4. Choice of the means of measurement . . . . . . . . . . . . . . . . . . . . 24 1.4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 1.4.2. Analysis of what is already available . . . . . . . . . . . . . . . . . . 25 1.4.3. Assessment and acquisition of material . . . . . . . . . . . . . . . . . 26 1.4.4. Technical criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 1.4.4.1. Basic characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 27 1.4.4.2. Comportment towards influence quantities. . . . . . . . . . . . . 27 1.4.4.3. Durability of the instruments used . . . . . . . . . . . . . . . . . . 27 1.4.4.4. Homogeneity of the supply of instruments . . . . . . . . . . . . . 28 1.4.4.5. Quality of the supplier’s service . . . . . . . . . . . . . . . . . . . 28 1.4.4.6. Adaptation of the instrument . . . . . . . . . . . . . . . . . . . . . 28 1.4.4.7. Possibility of traceability . . . . . . . . . . . . . . . . . . . . . . . 29 1.4.4.8. Computerization and the speed of taking measurements . . . . . 29 1.4.4.9. Ergonomics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 1.4.4.10. Capability of measuring instruments. . . . . . . . . . . . . . . . 29

6 Metrology in Industry

1.4.5. Economic criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 1.4.6. Grid of the analysis of the choice . . . . . . . . . . . . . . . . . . . . 31 1.4.6.1. Stage 1: primary technical requirements (unavoidably necessary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 1.4.6.2. Stage 2: secondary technical requirements (desirable) . . . . . . 31 1.4.7. Technical assistance for users of measuring instruments. . . . . . . 33 1.4.7.1. The EXERA (France) . . . . . . . . . . . . . . . . . . . . . . . . . 33 1.4.7.2. VDI/VDE-GMA (Germany) . . . . . . . . . . . . . . . . . . . . . 34 1.5. The traceability of the measurements . . . . . . . . . . . . . . . . . . . . 36 1.5.1. The necessity of traceability of the measurements . . . . . . . . . . 36 1.5.2. Calibration requirements . . . . . . . . . . . . . . . . . . . . . . . . . 38 1.5.3. The selection of standards . . . . . . . . . . . . . . . . . . . . . . . . . 39 1.6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Chapter 2. Organization of Metrology: Industrial, Scientific, Legal. . . . . 43 Luc ERARD, Jean-François MAGANA, Roberto PERISSI, Patrick REPOSEUR and Jean-Michel VIRIEUX

2.1. A metrological organization: why? . . . . . . . . . . . . . . . . . . . . . . 43 2.2. Metrology: how?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 2.3. Scientific and technical metrology . . . . . . . . . . . . . . . . . . . . . . 47 2.3.1. The BIPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 2.3.2. Results of the international activities . . . . . . . . . . . . . . . . . . 50 2.3.3. Regional organizations. . . . . . . . . . . . . . . . . . . . . . . . . . . 51 2.3.3.1. EUROMET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 2.3.3.2. European Cooperation for Accreditaton (EA) . . . . . . . . . . . 54 2.3.3.3. Accreditation procedure . . . . . . . . . . . . . . . . . . . . . . . . 58 2.3.4. Organization at the national level . . . . . . . . . . . . . . . . . . . . 59 2.3.4.1. The Laboratoire National de Métrologie et d’Essais (LNE) . . . 59 2.3.4.2. The Italian national calibration system (SNT) . . . . . . . . . . . 63 2.3.4.3. The Swiss national calibration system . . . . . . . . . . . . . . . 65 2.4. Legal metrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 2.4.1. Scope of legal metrology . . . . . . . . . . . . . . . . . . . . . . . . . 67 2.4.2. The International Organization of Legal Metrology (OIML) . . . . 68 2.4.3. The European level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 2.4.3.1. European Union harmonization . . . . . . . . . . . . . . . . . . . 71 2.4.3.2. WELMEC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 2.4.3.3. Other regional bodies . . . . . . . . . . . . . . . . . . . . . . . . . 73 2.4.4. At national level. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 2.4.4.1. Legal metrology in Italy . . . . . . . . . . . . . . . . . . . . . . . . 73 2.4.4.2. Legal metrology in Switzerland . . . . . . . . . . . . . . . . . . . 74 2.4.4.3. Legal metrology in France . . . . . . . . . . . . . . . . . . . . . . 76

Table of Contents 7

Chapter 3. Mastering Measurement Processes Approach to the Setting up of a Metrology Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Marc PRIEL and Patrick REPOSEUR

3.1. What to do at the beginning? . . . . . . . . . . . . . . . . . . . . . . . . . 79 3.2. Goals and role of the measurement management system – metrological function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 3.3. The measurement processes . . . . . . . . . . . . . . . . . . . . . . . . . . 86 3.3.1. Conception and development of a new measurement process. . . . 86 3.3.1.1. Analysis of the requirements . . . . . . . . . . . . . . . . . . . . . 86 3.3.1.2. Transcription of the characteristics of the product in “measurand” form or “characteristics to be measured” form . . . . . . . 87 3.3.1.3. The development of a measurement process can be managed as a project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 3.3.2. Exploitation of a valid process . . . . . . . . . . . . . . . . . . . . . . 88 3.3.3. Continuous improvement of measurement processes . . . . . . . . . 88 3.4. Management of the measuring equipment (metrological confirmation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 3.4.1. Analysis of the requirement and selection of the measuring equipments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.4.1.1. Technical requirements . . . . . . . . . . . . . . . . . . . . . . . . 91 3.4.1.2. Economic and commercial conditions. . . . . . . . . . . . . . . . 93 3.4.1.3. Assessment of the measuring equipment . . . . . . . . . . . . . . 93 3.4.2. Receiving the measuring equipment and putting it into service. . . 93 3.4.2.1. Compliance with the order . . . . . . . . . . . . . . . . . . . . . . 94 3.4.2.2. Identification of the measuring equipment . . . . . . . . . . . . . 94 3.4.2.3. Inventory (description). . . . . . . . . . . . . . . . . . . . . . . . . 94 3.4.2.4. Technical dossier of the equipment . . . . . . . . . . . . . . . . . 94 3.4.2.5. Technical documentation . . . . . . . . . . . . . . . . . . . . . . . 94 3.4.2.6. Basic definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 3.4.3. Calibration and verification operations . . . . . . . . . . . . . . . . . 97 3.4.3.1. Calibration or verification program . . . . . . . . . . . . . . . . . 99 3.4.3.2. Calibration or verification intervals . . . . . . . . . . . . . . . . . 99 3.4.3.3. Supervision of the measuring equipment . . . . . . . . . . . . . . 100 3.4.4. Fitness for use of measuring equipment. . . . . . . . . . . . . . . . . 100 3.4.4.1. Freedom from bias, repeatability, stability . . . . . . . . . . . . . 100 3.4.4.2. Maximum permissible errors . . . . . . . . . . . . . . . . . . . . . 101 3.4.4.3. Demands for an assurance of the quality . . . . . . . . . . . . . . 101

3.5. Setting up a metrological structure within the firm . . . . . . . . . . . . 102 3.5.1. Analysis of the metrological requirements and setting up standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 3.5.2. Traceability of the measuring instrument(s) to the firm’s reference standards . . . . . . . . . . . . . . . . . . . . . . . . . 104 3.5.3. Traceability of the firm’s reference standards to the SI. . . . . . . . 104


3.6. Suggested approach for setting up a metrology function . . . . . . . . . 105 3.7. Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Chapter 4. Handling of a Bank of Measuring Instruments . . . . . . . . . . 109 Jean-Yves ARRIAT

4.1. Acquaintance with the bank . . . . . . . . . . . . . . . . . . . . . . . . . . 110 4.1.1. Inventory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 4.1.2. Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

4.2. Metrological policy of the firm . . . . . . . . . . . . . . . . . . . . . . . . 113 4.2.1. Objective and commitment of the firm’s management . . . . . . . . 113 4.2.2. Plan of actions to launch. . . . . . . . . . . . . . . . . . . . . . . . . . 113 4.2.3. Awareness, training and vocabulary . . . . . . . . . . . . . . . . . . . 113 4.2.4. Selection of the material to be followed periodically . . . . . . . . . 114

4.3. Drafting of the documents . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 4.3.1. Codification of the documents . . . . . . . . . . . . . . . . . . . . . . 115 4.3.2. Work instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 4.3.3. Result-recording documents . . . . . . . . . . . . . . . . . . . . . . . 117 4.3.4. Other documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

4.4. Physical handling of the measuring instruments . . . . . . . . . . . . . . 119 4.4.1. Receipt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 4.4.2. Transfer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

4.4.2.1. Traceability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 4.4.2.2. Transfer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 4.4.2.3. Precautions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

4.4.3. Storing and environment. . . . . . . . . . . . . . . . . . . . . . . . . . 121 4.4.4. Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

4.5. Follow-up of the measuring instruments over time . . . . . . . . . . . . 123 4.5.1. Periodicity of the follow-up. . . . . . . . . . . . . . . . . . . . . . . . 123 4.5.2. Campaign of recall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 4.5.3. Follow-up of the results . . . . . . . . . . . . . . . . . . . . . . . . . . 125

4.6. Software for the handling of the means of measurements . . . . . . . . 125

Chapter 5. Traceability to National Standards . . . . . . . . . . . . . . . . . . 127 Luc ERARD and Patrick REPOSEUR

5.1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 5.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

5.2.1. Traceability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 5.2.2. Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 5.2.3. Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

5.3. Traceability chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 5.4. Traceability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

Table of Contents 9

5.5. Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 5.5.1. Calibration in an accredited laboratory . . . . . . . . . . . . . . . . . 132 5.5.2. Calibration in a non-accredited laboratory . . . . . . . . . . . . . . . 132

5.6. Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 5.6.1. Verification in an accredited laboratory and in its accreditation scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 5.6.2. Verification in a non-accredited laboratory or out of the accreditation scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

5.7. Use of calibration and verification results . . . . . . . . . . . . . . . . . . 133 5.7.1. Use of the results of a calibration . . . . . . . . . . . . . . . . . . . . 134 5.7.2. Use of the results of a verification . . . . . . . . . . . . . . . . . . . . 134

5.8. Particular cases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 5.8.1. “Self-calibrating” or “self-gauging” measuring instruments. . . . . 135 5.8.2. Complex instruments in which components/equipments and software are narrowly combined and large measurement ranges are covered for complex quantities. . . . . . . . . . . . . . . . . . . . . . . . . . 136

5.9. Metrology in chemistry and physical methods of chemical analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

5.9.1. Traceabilty in metrology in chemistry. . . . . . . . . . . . . . . . . . 137 5.9.2. Influence of the principle of the method . . . . . . . . . . . . . . . . 139

5.9.2.1. Absolute methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 5.9.2.2. Relative method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 5.9.2.3. Comparative method . . . . . . . . . . . . . . . . . . . . . . . . . . 140

5.9.3. “Documentary” traceability . . . . . . . . . . . . . . . . . . . . . . . . 141 5.9.4. Control of the reference materials . . . . . . . . . . . . . . . . . . . . 143 5.9.5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

5.10. Assessment of traceability . . . . . . . . . . . . . . . . . . . . . . . . . . 145 5.11. Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

Chapter 6. Calibration Intervals and Methods for Monitoring the Measurement Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Patrizia TAVELLA and Marc PRIEL

6.1. Normative requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 6.2. Methods for monitoring the instruments in use – general criteria . . . . 150

6.2.1. First method: metrological redundancies . . . . . . . . . . . . . . . . 150 6.2.2. Second method: checking the coherence of the results . . . . . . . . 151 6.2.3. Third method: “monitoring standards” and statistical supervision of the measurement processes . . . . . . . . . . . . . . . . . . . 152

6.2.3.1. Statistical control of the measurement processes . . . . . . . . . 152 6.2.3.2. Control charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 6.2.3.3. Use of the monitoring methods. . . . . . . . . . . . . . . . . . . . 157

6.3. The determination of the calibration intervals . . . . . . . . . . . . . . . 158 6.4. Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161


Chapter 7. Measurements and Uncertainties . . . . . . . . . . . . . . . . . . . 163 Marc PRIEL

7.1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 7.2. Measurement of physical quantity . . . . . . . . . . . . . . . . . . . . . . 164 7.3. Analysis of the measurement process . . . . . . . . . . . . . . . . . . . . 166

7.3.1. The cause and effect diagram method . . . . . . . . . . . . . . . . . . 166 7.3.2. Using the list published in the GUM (section 3.3.2) . . . . . . . . . 167 7.3.3. Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 7.3.4. Cutting down the errors . . . . . . . . . . . . . . . . . . . . . . . . . . 169

7.3.4.1. Cutting down random errors by repeating measurements . . . . 170 7.3.4.2. Cutting down systematic errors by applying corrections . . . . . 171

7.4. Modeling of the measurement process . . . . . . . . . . . . . . . . . . . . 172 7.4.1. Measurement procedure and model of the measurement process . . 172 7.4.2. An essential stage for the assessment of uncertainty: modeling the measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

7.5. Assessment of the uncertainty of the input quantities . . . . . . . . . . . 174 7.5.1. Type A methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

7.5.2. Type B methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 7.5.3. Comparing the Type A and Type B methods . . . . . . . . . . . . . 179

7.6. Calculating the combined uncertainty on the result . . . . . . . . . . . . 180 7.6.1. Situation when all the input quantities are independent . . . . . . . 180

7.6.1.1. Situation when the input quantities are independent and the model is a sum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 7.6.1.2. Situation when the model is a product . . . . . . . . . . . . . . . 181

7.6.2. Situation when the input quantities are dependent . . . . . . . . . . 181 7.6.2.1. Assessment of the covariances by assessing a coefficient of correlation ji xxr , . . . . . . . . . . . . . . . . . . . . . . . 181 7.6.2.2. Assessment of the covariances by calculating the terms of covariance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 7.6.2.3. Assessment of the covariances by considering the terms common to two input quantities . . . . . . . . . . . . . . . . . . . . 181

7.7. Use of the performances of the method (repeatability and freedom of bias) to assess the uncertainty of the measurement result . . . . 183

7.7.1. Intra- or interlaboratory approaches . . . . . . . . . . . . . . . . . . . 184 7.7.2. Intra-laboratory approach . . . . . . . . . . . . . . . . . . . . . . . . . 185 7.7.3. Interlaboratory approach. . . . . . . . . . . . . . . . . . . . . . . . . . 186 7.7.4. Data processing for intra- and interlaboratory approaches . . . . . . 187

7.7.4.1. Assessment of the repeatability and the reproducibility . . . . . 187 7.7.4.2. Assessment of the freedom of bias (trueness) . . . . . . . . . . . 188 7.7.4.3. Evaluation of the linearity . . . . . . . . . . . . . . . . . . . . . . . 189 7.7.4.4. The terms ii

i

xuc 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 189

Table of Contents 11

7.8. Reporting of the measurement result . . . . . . . . . . . . . . . . . . . . . 189 7.9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 7.10. Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Chapter 8.The Environment of Measuring . . . . . . . . . . . . . . . . . . . . 195 Jean-Yves ARRIAT and Marc PRIEL

8.1. The premises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 8.1.1. Ambient temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 8.1.2. Relative humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 8.1.3. Handling of the air conditioning systems . . . . . . . . . . . . . . . . 199 8.1.4. Power network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 8.1.5. Radioelectric disturbances. . . . . . . . . . . . . . . . . . . . . . . . . 199 8.1.6. Measurements on-site . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

8.2. The personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 8.2.1. The connection of metrology function . . . . . . . . . . . . . . . . . 200 8.2.2. Staff involved in the metrology function . . . . . . . . . . . . . . . . 201 8.2.3. The qualification of the personnel . . . . . . . . . . . . . . . . . . . . 202

8.3. The documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 8.3.1. Filing of the documents . . . . . . . . . . . . . . . . . . . . . . . . . . 202

8.3.1.1. Documents dealing with the quality system . . . . . . . . . . . . 202 8.3.1.2. Records regarding quality . . . . . . . . . . . . . . . . . . . . . . . 203

8.3.2. Management of the documents . . . . . . . . . . . . . . . . . . . . . . 204 8.4. Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 8.5. Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

Chapter 9. About Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 Claude KOCH

9.1. Preliminary information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 9.1.1. Physical quantity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 9.1.2. The object to be measured. . . . . . . . . . . . . . . . . . . . . . . . . 210 9.1.3. Field of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 9.1.4. Four types of uses of measuring instruments. . . . . . . . . . . . . . 211 9.1.5. Influencing quantities . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

9.2. Choice of a measuring principle. . . . . . . . . . . . . . . . . . . . . . . . 213 9.2.1. Differential measurement . . . . . . . . . . . . . . . . . . . . . . . . . 214 9.2.2. Direct measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 9.2.3. Indirect measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 214


9.3. Practicing in metrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 9.3.1. Implementing the instruments . . . . . . . . . . . . . . . . . . . . . . 216 9.3.2. Precautions before measuring. . . . . . . . . . . . . . . . . . . . . . . 216 9.3.3. Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 9.3.4. Variations and their sign. . . . . . . . . . . . . . . . . . . . . . . . . . 217 9.3.5. The time factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

9.4. Expression of the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 9.4.1. Graphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 9.4.2. Histograms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

9.5. What qualities does a metrologist require? . . . . . . . . . . . . . . . . . 221 9.5.1. Be inquisitive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 9.5.2. Be tidy and methodical . . . . . . . . . . . . . . . . . . . . . . . . . . 222 9.5.3. Be open to doubt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 9.5.4. Be observant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 9.5.5. Be honest. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

Chapter 10. Organization of Metrology at Solvay Research and Technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 José MONTES

10.1. Presentation of the company . . . . . . . . . . . . . . . . . . . . . . . . . 225 10.2. Organization of the metrology sector . . . . . . . . . . . . . . . . . . . . 226

10.2.1. Creation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 10.2.2. Missions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 10.2.3. Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 10.2.4. Geographic localization of the activities . . . . . . . . . . . . . . . 227 10.2.5. Composition of the bank of measuring equipment. . . . . . . . . . 227

10.3. Metrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 10.3.1. Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 10.3.2. Connection of the standards . . . . . . . . . . . . . . . . . . . . . . . 228 10.3.3. Periodicity of the calibrations . . . . . . . . . . . . . . . . . . . . . . 229 10.3.4. Calibration operations . . . . . . . . . . . . . . . . . . . . . . . . . . 229 10.3.5. Documentation of the calibration results . . . . . . . . . . . . . . . 230 10.3.6. Verdict of the metrological confirmation . . . . . . . . . . . . . . . 231 10.3.7. Indication of the state of the calibrations . . . . . . . . . . . . . . . 231 10.3.8. Personnel and subcontracting . . . . . . . . . . . . . . . . . . . . . . 232

Table of Contents 13

Chapter 11. Metrology within the Scope of the ISO 9001 Standard . . . . . 233 Philippe LANNEAU and Patrick REPOSEUR

11.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 11.2. Introduction to the evolution of the standard . . . . . . . . . . . . . . . 234

11.2.1. The concept of continuous improvement . . . . . . . . . . . . . . . 234 11.2.2. The process approach. . . . . . . . . . . . . . . . . . . . . . . . . . . 235

11.3. Measurement control process . . . . . . . . . . . . . . . . . . . . . . . . 236 11.4. The ISO 9001 (2000) standard step-by-step . . . . . . . . . . . . . . . . 238 11.5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

Chapter 12. Training for the Metrology Professions in France . . . . . . . . 247 Bernard LARQUIER

12.1. The metrology function in a firm’s strategy . . . . . . . . . . . . . . . . 247 12.2. Metrology profession . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

12.2.1. Metrological engineer . . . . . . . . . . . . . . . . . . . . . . . . . . 249 12.2.2. Metrological technician . . . . . . . . . . . . . . . . . . . . . . . . . 249 12.2.3. Metrological operator. . . . . . . . . . . . . . . . . . . . . . . . . . . 250

12.3. Initial training. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 12.3.1. Schools for engineers . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 12.3.2. Courses for higher level technicians . . . . . . . . . . . . . . . . . . 251 12.3.3. Vocational high schools . . . . . . . . . . . . . . . . . . . . . . . . . 251

12.4. Continuing education . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 12.5. Long-lasting training courses . . . . . . . . . . . . . . . . . . . . . . . . 253 12.6. The teaching of metrology in secondary schools . . . . . . . . . . . . . 265 12.7. Prospects for the development of long-lasting training courses . . . . 265 12.8. Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

The Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

Preface

Metrology is an essential part of the infrastructure of today’s world. It enters into our lives in a multitude of ways, some direct and some indirect. National and international trade increasingly require demonstrated conformity to written standards and specifications and mutual recognition of measurements and tests. The economic success of most manufacturing industries is critically dependent on how well its products are made, a requirement in which measurement plays a key role. Navigation and telecommunications require the most accurate time and frequency standards. Human health and safety depend on reliable measurements in diagnosis and therapy and in the production and trade in food and food products. The protection of the environment from the short-term and long-term destructive effects of industrial activity can only be assured on the basis of accurate and reliable measurements. Global climate studies depend on reliable and consistent data from many disciplines often over long periods of time and this can be assured only on the basis of measurements traceable to measurement standards that are themselves linked to fundamental and atomic constants.

Metrology is not an activity that is only carried out in specialized institutes or

calibration laboratories. In order to meet the needs of society for accurate and reliable measurements in all its many applications, a strong spirit of metrology must also exist in companies and enterprises that make the instruments and that use them to make measurements.

For this reason I welcome this book. It gives a clear outline of the basic ideas of

metrology, why we need it and how, in an enterprise it can be practiced. I wish it every success.

T.J. Quinn,

Director of BIPM

Foreword

Technically, economically, commercially and, sometimes, statutorily speaking, having relevant and reliable results of measurements, analyses and tests is a real asset for a firm which wishes to make efficacious decisions.

You cannot achieve such an end if you do not have firm control over the

processes of measurement, analysis and testing. Nowadays, however, the measuring techniques, the normative and statutory requirements, the methods of measurement uncertainty assessment or those to secure the traceability of measurements are all complex and it is more necessary than ever to integrate them into a network of competent bodies so as to exchange experience and information. It is on this fundamental principle that the Metrology College was created in 1986, which became the French College of Metrology in 2002. The purpose of this association is obviously much wider:

– to identify which firms and organisms’ needs are to be met from the angle of metrology;

– to spread metrological culture and knowledge through the industrial, scientific and economic fabric;

– to be a form of exchange between people involved in metrology; – to contribute to make the collective national and regional actions coherent in

this sphere; – to perform any action likely to contribute to the development and promotion of

metrology. The permanent evolution of metrology, together with the willingness to impart

all the knowledge acquired so far, have led a working party of the French College of Metrology to write a second edition of the book Metrology in the Firm. Metrologists from various callings (national metrology laboratories, accrediting organisms,


industrial concerns and consulting firms) and from different nationalities make up this working party. This broad range of authors gives the book a pragmatic characteristic and enables it to answer the questions and concerns of organizations, whether they be principals, small or medium firms, laboratories, etc.

The contribution from foreign authors gives the book an unquestionable

international aspect which accurately reflects the current reality. More than ever, as a matter of fact, metrology contributes to the free circulation of goods between countries, thanks to the international organization of metrology and thanks to the international agreements between national metrology laboratories and between accrediting organisms.

Moreover, most of the authors belong to different national or international

standardization committees. As a result, the latest normative evolutions are to be found in this book, whether it is the concept of firm certification developed in the 2000 version of standard ISO 9001, or the approach concerning the competence of activities of measurement, testing or analysis as expounded in standard ISO 17025.

Whether you are involved in your firm’s metrology function, or are simply

interested in a concrete matter of measurement, analysis or testing, I am confident you will find here some clues which will help you progress and improve your processes.

The growing interest you have shown in this book has encouraged us in our

intention of producing this English version. It is my sincere wish that whatever your need and country may be, you can get as much out of it as our French colleagues do.

May you enjoy reading it.

P. LEBLOIS, President of the French College of Metrology

Chapter 1

Analysis of the Metrological Requirements Needed to Ensure Quality

Anybody with a mind to implement (or improve) a metrology function might feel a bit panicky at the thought of all the work to be done if they read this book unwarned, and more particularly this chapter. Let the reader’s mind be put at ease first. All the content is not, fortunately, to be carried out literally. All we want to do is to offer as broad as possible a survey of the subject by pointing out practically all the items that require consideration.

And then, is it not normal to start wondering what one really needs? Experience has taught us, too often alas, that this is not a natural process. Many

industrial difficulties, or many costs, grow out of the inadequacy “means of measurement/real need”.

1.1. Introduction

Before we start any concrete action, it is primordial to analyze the metrological needs carefully. There are two kinds: – The organizational needs for the management of metrology. Are those needs great enough to require the introduction of full-scale metrology? Are premises or qualified personnel needed permanently? What possibilities are there in the region?

Chapter written by Jean-Yves ARRIAT – Ascent Consulting – and Klaus-Dieter SCHITTHELM – Expert in Metrology, Germany.


Does someone want to manage metrology on his or her own, with the help of a someone else, or to handle it to a subcontractor? – The material needs for the realization of the measurements. In order to realize measurements correctly, it is necessary to have appropriate means; these means are found after analysis of the objectives and the possibilities of the instruments and the connection. In order to define the firm’s needs, it is necessary to answer the following questions: 1. What are my industrial needs?

– What do I have to measure and what accuracy shall I expect? 2. How can I meet my needs?

– What are the possible measuring methods? – Which method and principle will be used?

3. Which measuring instruments can be used? – Which instrument shall I use? – Can the selected instrument ensure the required accuracy?

4. How is to be used the selected instrument? – What assembly is to be set up and what procedure is to be followed? – What technical competence do you have to have to use it?

Then a question of a very different magnitude arises: how am I going to

guarantee the quality of my measurements?

Setting up a metrological function

The three key components of a metrological function have to be under control (see Chapter 4):

– adequacy of means to needs; – traceability of the means of measurement to international standards; – administrative management of the equipment (measuring instruments, standards, etc.).

The preliminary analysis of the needs will produce a first set of specifications.

There is a good chance that these analysis are going to be a bit theoretical and take little heed of the notions of profitability. You have to accept the principle which says that the specifications will evolve and obtain agreement from the major actors taking part in the drafting of the specifications. For a new measuring instrument, all the stages from conception to utilization must be taken into account by the specifications. This is fundamentally the concern

Analysis of the Metrological Requirements Needed to Ensure Quality 21

of the manufacturers, but potential users may sometimes take part in the elaboration of the specifications. The specifications for a new measuring laboratory must ignore all of the environmental characteristics of the measurement (see Chapter 8), and take into consideration the problems of maintainability (for instance, the maintenance of air conditioning), of access to the personnel, of user-friendliness, etc. However big or small the problem is, one must always begin by analyzing one’s real meterological need.

1.2. Definition of the objectives

The metrological function must be approached as soon as you start thinking about problems of measurement. Its role may depend on each particular firm (see Chapter 3), but its chief role is to act as a consultant. It examines the need in a logical process based on:

– the functional analysis of the measurement (drafting of specifications); – the analysis of the achievement of the measurement results (and of the level of

accuracy reached);

– the analysis of the risks related to the selected means; – the analysis of the non-conformities which could be encountered.

This process makes it possible to identify and quantify the means (personnel and material) to be implemented to take the intended measurements. It is during these phases that the “tools of quality” will be used. Let us point out that the analysis of the value (fundamental at the outset) is among the most useful tools. In order to clearly define the objective, we strongly recommend to use “brainstorming”, cause/effect diagrams, Pareto, etc., which make analysis and collective participation easier. So as to guarantee the quality of its measurements (i.e. a process of management by quality), the firm sets up a real management of the means of measurement. For this purpose, the metrological function conducts the management of these means according to needs that are clearly defined and regularly updated. This involves examining a large number of actions in order to start up and maintain the supply of measuring instruments necessary to meet the firm’s needs.


The first thing to do regarding the analysis of the supply of material is to work out:

– the list of physical quantities (e.g. temperature, length, electric resistance, etc.); – the ranges which need to be covered for each physical quantity (e.g. length

from 0.1 mm to 1,000 mm); – the permissible uncertainty for each quantity and each range (the uncertainty in

the 0.1 mm to 0.5 mm range will be different from the one which is expected between 100 mm and 1,000 mm).

Then, for each separate case, it will be necessary to consider and define: – the analysis of the needs and the choice of the means of measurement; – the acquisition, the reception and the implementation of these means; – the traceability of the material of measurement (in the case where materials of

measurement are assigned); – the traceability of the measurements (which material do they come from?); – the calibration or the verification of the means and the decisions they entail; – the exploitation of the calibration results; – the operations related to the moving of these means (protection, authorization,

etc.); – the updating of the inventory of these means. The outcome of this is that the intended objectives must not be mixed up to satisfy: – the needs for the management of metrology with; – the needs for the realization of the measurements.

1.3. Choice of the method of measurement

1.3.1. Accounting for the selection of the method

You have to justify the choice of the selected method. It is to be understood by this that the criteria have to possess as little subjectivity as possible. This choice must take possible restraints of qualification into consideration. The fact is that within the scope of some contracts (notably related to safety, public security, health, etc.) you may have to qualify the method of measurement. This means it must be subjected to an authenticated description, officially certified tests, etc., in accordance with the relevant program and by a very precise process. Besides, the ISO/QS 9000 or TS 16 949 certification process also involves a description of the selected method.


Fortunately, it is often possible to hang on to the methods which are known and officially accepted. You must not forget that the great metrology laboratories can be a great help in this area. In France, for example, these are the laboratories of the LNE (Laboratoire National de Métrologie et d’Essais), and in Germany, those of the PTB (Physikalisch-Technische-Bundesanstalt), or calibration laboratories accredited by the DKD (Deutscher Kalibrierdienst). Whether the method is qualified or not, it is important, after the metrological objectives have been set, to make the methodology of the measurement explicit. The different stages, the conditions of the material and the environment, the operations that make it possible to get the measurement, i.e. everything related to the carrying out of these measurements, must be written in a document and will be taken into account particularly when choosing the operators. One of the very first principles of quality assurance is to write down what is being done. This process is simple and allows people to think further about the choice of the method. There must be a clear distinction between chosing a method and chosing a measuring instrument. For example, you may want to measure a dimension on a rubber part: you happen to be close to a three-dimensional measuring machine and your instant reaction may be to go to this machine without thinking whether there may be a more suitable method than this one.

1.3.2. Defining the method and the principle to implement

When there are several methods of measurement, it is often difficult to determine which one will best fit your need if you are not able to classify them. Our advice is to keep only the two (maybe three) most important criteria in mind and to draw a table. Let us consider the example of Table 1.1. It makes it possible to analyze the different methods of measurement that lead to the assessment of the characteristics of industrial robots.

Two criteria have been selected: – the principle of measurement (two groups of them here); – the characteristics measured (two families of them here). As a rule, there are in metrology three great principles of measurement; the three

of them have advantages and drawbacks. They are: – differential measurement; – direct measurement; – indirect measurement.

See Chapter 9 for more details.


Positioning characteristics Trajectory characteristics Local

methods Measurement terminal with cubes

(Peugeot SA and LNE) Measurement terminal on measuring machine (IPA)

Different realizations based on the same principles have been

developed (IBM, General Motors, etc.)

Measurement terminal with materialized trajectories (rule and circle) (LNE)

Measurement terminal with trajectory (broken line) (Peugeot SA)

Big base methods Method of the two theodolites

(Renault) Theodolites with automatic data

(LNE) Selspine system

Photogrammetry (University of Dresden, NEL and SETP-LNE)

Devices with three sensors and wire (Peugeot)

Sweep of two laser beams (University of Surrey, England)

Selspine system Robotest (Polytech, FRG)

Stroboscoped photogrammetry (University of Dresden, NEL and

SETP-LNE) IPA: Institute for Production techniques and Automation, Germany

LNE: National Testing Laboratory NEL: National Engineering Laboratory, England

SETP: Photogrammetric Studies and Works Society

Table 1.1. “Classification of the methods of measurement” (Reproduced with the kind permission of Techniques de l'ingénieur – France)

1.4. Choice of the means of measurement

1.4.1. Introduction

The choice of the material and/or the equipment must be based on specifications. To make this choice, you must take into consideration:

– the technical needs; – the possibilities of calibration; – the assessments already made; – the economic conditions (last, for the technical specifications have to be

seen first).


Practicing metrology is not simply doing plain measurements. To begin with, a special material has to be used, which means that you do not simply use any dimensional comparator lying about on a shelf, you do not borrow a frequency meter from a colleague and you do not hire a “lowborn” multimeter. On the contrary, you use instruments which are well-known and well-regarded, which come with documents and certificates, so as to be sure of their traceability and, therefore, to better guarantee the quality of the measurements.

These instruments (said to be “reference instruments”) have to be acquired after you have seriously studied the criteria of choice. It is known that:

– the ideal instrument does not exist; – the instrument closest to what is ideal is too expensive; – each buyer limits the claims of technical applicants. Moreover, the choice of an instrument depends on its type of use. Four types of

utilization can be distinguished: – for a study (you must look for an instrument that can evolve); – for a site (robustness ought to be favored); – in manufacturing (the “cost” factor will probably prevail); – for a laboratory (your preference will go to a very reliable, strong and proven

instrument).

For further information, see Chapter 9.

1.4.2. Analysis of what is already available

The first thing to do will be to see if there is not already in the firm some available material which can meet your needs. This requires:

– good communication between the various parties concerned with the measurements; and

– a good knowledge of the material available. The latter point is all the more important when there is a risk of technological obsolescence (using a state-of-the-art instrument to its maximum capacity justifies its acquisition and it makes it easier to get new ones), or when the material is very expensive (when you increase the duration of its productive use, you make its amortization easier).


1.4.3. Assessment and acquisition of material

Speaking of compromise about the choice was actually slightly simplistic. Of course, the economic requirements are obviously taken into account; few are the cases when the material is selected without the price being considered (either before or after the purchase!). As for the assessments which are otherwise made, they quite simply depend on the competence and professionalism of the person in charge of the metrological function. He must indeed be on a permanent technological watch. Furthermore, he must make an inventory of what is in store (material and tested material), in order not to have to repeat work endlessly. The companies which take the trouble to check all the electric and electronic material they buy admit that a far from negligible proportion of the instruments delivered is partly defective or does not comply with tolerances on delivery. A few years ago a survey showed that the percentage of rejected instruments could reach 50%. This is partly explained by the fact that the stated characteristics are obtained by the manufacturers, in a laboratory and in ideal conditions of use; and this situation is very remote from the user’s reality. Tests of assessment preliminary to purchase would be greatly recommended. However, in frequent cases, the instruments that can perform the same function are many in number, the parameters of each of them are numerous and, consequently, the tests are long and expensive. So, before launching into testing, any person who is interested in purchasing an instrument is entitled to ask the salesman the following questions:

– Have any tests been done? If the answer is yes, when? Where? By whom? In which domain? Is a report of the tests available?

– How long has the instrument been manufactured? How many copies of it have been produced?

– Has stopping its production been considered? – Who has bought it? Is it possible to consult users?

Once you have got this information, and if tests seem necessary, you have to choose between doing them yourself or subcontracting them to a better-equipped organization whose results cannot be questioned. A distinction must be made between learning about a instrument which is presented by a salesman and having its characteristics verified by a specialized laboratory. Once again, evidence arises of the importance of good relationships (partnership even) with the manufacturers of the instrument and of their obligation to pass on information in a transparent and unrestricted way. However, the role of the buyer is not simple. He must estimate whether the supplier is capable of keeping to the agreed times in general: time of delivery, time of assistance after the sale. Besides, it