A Practical Handbook on Measurement Uncertainty: FAQs and fundamentals for metrologists

by Swanand Rishi

Overview

In the field of metrology, measurement uncertainty has a special place of its own since “No measurement result is complete without explicit statement about its uncertainty”. Hence for all accredited laboratories, evaluation of measurement uncertainty is a mandatory requirement. The purpose of the book is to clarify the rationale behind certain assumptions or ideas in measurement uncertainty, present the concepts from practical perspective, help readers arrive at a realistic uncertainty figure and be a ready-reference hand-book. The book can serve as a quick reference book on basic concepts in measurement uncertainty. The book is written in a manner so that practicing metrologists can open any chapter and start reading. The topics covered are applicable across all fields of scientific measurements.

Key Features:

• A ready-reference practical hand-book
• Clarifies the rationale behind certain assumptions or ideas
• Presents the concepts from practical perspectives
• Provides insight, examples and case studies
• Helps readers get answers to FAQs

Product Details

ISBN-13:	9780750364621
Publisher:	Institute of Physics Publishing
Publication date:	07/29/2024
Series:	IOP ebooks
Sold by:	Barnes & Noble
Format:	eBook
File size:	3 MB

About the Author

Swanand Rishi graduated in Electrical Engineering with Distinction in 1986, (with specialization in Power Electronics) from College of Engineering, Pune, India, and completed a Diploma in Business Management (DBM) with Gold medal in 1998. After graduation until 1995, Swanand worked in several manufacturing industries with products such as UPS/Power conditioners, Capacitors and Lightning Arrestors. In those companies, he served in various sections including Production, Quality, R&D, Testing and Marketing. He was instrumental in bringing down rejection of certain capacitors from over 40% down to 5% by radical changes in manufacturing process through measurement assurance and using QC tools. In a UPS manufacturing firm, he was Project manager for supply of a unique UPS to India’s ambitious missile system. Since 1995, Swanand has been with the Electronics Test & Development Centre (ETDC), Pune, India; a Test and Calibration laboratory under STQC Directorate, Ministry of Electronics & IT, Government of India. He was In-charge of Calibration lab when ETDC got its first accreditation in 2002 for Electrical and Thermal calibration and significantly contributed to establishing the Quality system as per ISO/IEC 17025. Currently he is working as Head (QA & Training) in ETDC, Pune. Since 1998 he has taught in courses and seminars conducted by ETDC on Calibration (Electrical and Thermal), Laboratory Management per ISO/IEC 17025, Measurement Uncertainty and Certified Calibration Professional. He has published a few papers in national and international journals/conferences. He was also a faculty member for a Contact-Session courses on Statistical Process Control (SPC) for MS (Quality Management) programme for post-graduate students of Birla Institute of Technology & Science, Pilani, India. He was a regular guest-lecturer in engineering colleges on subjects such as Measurements, Testing and Calibration; QMS and was also an external Project examiner. He was a member of ‘Syllabus Review committee’ for engineering courses and is also an ISO 9000 Lead Assessor.

Table of Contents

Preface

Acknowledgements

Author biography

List of abbreviations

List of symbols

How to read this book

Part A Understanding the fundamentals of measurement uncertainty

1 Using correct terminology

2 Why do we need to estimate uncertainty?

3 Should we talk about the ‘evaluation’ or ‘calculation’ of uncertainty?

4 What uncertainty is not

5 Various error terms and bias

6 The Guide to the expression of uncertainty in measurement—the new approach

7 The law of propagation of uncertainty

8 Why is standard deviation used instead of variance?

9 Using pooled standard deviation

10 Some uncommon uncertainties

Part B Dealing with distributions

11 The normal distribution, the t-distribution, and the standard normal distribution

12 Do Type A and Type B evaluations correspond to random and systematic errors?

13 Reproducibility in uncertainty evaluation

14 How is it that we can combine different distributions?

15 Guidelines for the selection of triangular and trapezoidal distributions

16 Is a higher confidence level compatible with a larger expanded uncertainty?

17 Mind the correlations

Part C Sample size and analysis

18 Sampling distributions

19 The sample size dilemma

20 Sample size—another approach

21 Addressing the uncertainty of a single measurement

Part D Decoding degrees of freedom

22 Why are the degrees of freedom generally (n−1) in the Type A method of evaluation?

23 Why are the degrees of freedom generally ‘∞’ in the Type B method of evaluation?

24 Effective degrees of freedom—some considerations

Part E Some contiguous concepts

25 What is the significance of the sensitivity coefficient?

26 Dealing with corrections

27 The test uncertainty ratio: use only as a guiding phenomenon

28 Guarding conformity decisions

Part F Delving a little deeper

29 Treating dominant non-Gaussian components

30 Sample analysis—how normal is the normal?

31 Sample analysis—detecting the outliers

32 Analyzing the results

33 The proper reporting of uncertainty

34 Alternative approaches in uncertainty evaluation

35 Some important notes in the GUM

Further references

Appendix A: Coefficients for the Shapiro–Wilk test and the W statistic for various p-values

Appendix B: Some useful web sites