French College of Metrology’s scientific contributions

The need to know the values of the flow rates measured with ever less uncertainty led the Compagnie Nationale du Rhǒne, with the help of CETIAT, to carry out an in-depth study on the uncertainty of the flow rates measured by two main methods, i.e. current meter and ADCP (Acoustic Doppler Current Profiler). Standards NF EN ISO 748 and NF ENV 13005 are applied to the current meter. Then the uncertainty of the flow rate measured by ADCP is estimated by a comparative study between ADCP and the current meter (ISO 5725). This study has led CNR to choose an uncertainty of ± 7% for current meter gauging and ± 5% for ADCP gauging.

The supplement 1 to the GUM, dealing with the evaluation of uncertainty using the propagation of distributions, will be published this year. This supplement, based on a Monte Carlo method (MCM), allows us to deal with the evaluation of uncertainty even when the hypotheses of the law of propagation of uncertainty (LPU) are not verified. We describe the different steps of the MCM and its advantages. Then to illustrate the method, we present two examples in the fields of metrology and testing and we compare the results given by both methods.

The certified reference materials (CRMs) are among the most appropriate tools for the traceability and validation of analytical methods. Although their number seems to be high 20,000, they only cover a small part of the analytical needs for environmental monitoring. Until now, none were available for analyzing pesticides in water. After an intralaboratory feasibility study and an evaluation of the behavior of this material during interlaboratory testing, the LNE has produced and certified a CRM for the triazine and phenylurea analysis in water samples.

There has been a strong increase in proficiency testing (PT) as a powerful tool to the quality assessment of testing and measurement activities. Many providers propose Interlaboratory Comparisons in various domains such as environment agri-food and health. In the classical former methods exploitation of results enabled the evaluation of each participant comparing their measurement results to their peers, calculating a performance statistic such as the “z-score”. Since the advent of the Guide to the expression of Uncertainty in Measurement (GUM) in 1995 founding the principles of uncertainty evaluation, numerous projects have been carried out to develop alternate practical methods, easier to implement notably when it is impossible to model the measurement process for technical or economical aspects. Besides the method described in Chapter 8 of the GUM so-called “modeling” exploitation of results to the “validation of method” was presented during the Metrology Congress of 2003. In 2005 the “performance of method” approach was presented and in 2007 another alternate method is presented in this paper based on the exploitation of proficiency testing and internal quality assessments. Further considerations drawn from activities in the domain of health for the evaluation of measurement uncertainty will be presented in this paper. The example of the determination of total concentration of glucose in human serum will be described. GUM and Proficiency Testing approaches will be compared.

Measurement results are very often used as the starting point for decision-making processes, whenever a suitable action must be pursued according to the measured values. This requires the comparison of measurement results with each other or with a given threshold. The result of this comparison is useful only if measurement uncertainty is considered. Unfortunately, few and unsatisfactory indications are available on how to take into account uncertainty in a comparison. This paper proposes an original approach, based on the Theory of Evidence, for comparing measurement results when they are expressed in terms of Random-Fuzzy Variables.

Metrological characteristics of measurement processes and the aims of their industrial application are described. The need for validation of measurement processes is justified, as well as clarification of the principles of carrying it out. The main assumptions of the project carried out, are presented. The purpose of this project is the development and improvement of the information system – CAMPV (Computer Aided Measurement Processes Validation). This system contains the metrological database, among others, and is intended for regional metrological centers.

Acquaintance with the bank Metrological policy of the firm Drafting of the documents Physical handling of the measuring instruments Follow-up of the measuring instruments over time Software for the handling of the means of measurements

Introduction Measurement of physical quantity Analysis of the measurement process Modeling of the measurement process Assessment of the uncertainty of the input quantities Calculating the combined uncertainty on the result Use of the performances of the method (repeatability and freedom of bias) to assess the uncertainty of the measurement result Reporting of the measurement result Example Bibliography

Introduction Definition of the objectives Choice of the method of measurement Choice of the means of measurement The traceability of the measurements Conclusion

Introduction Introduction to the evolution of the standard Measurement control process The ISO 9001 (2000) standard step-by-step Conclusion