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Analysis of key comparisons

Working Group 8.42


Key comparisons are interlaboratory comparisons carried out regularly between National Metrology Institutes (NMIs) within the framework of the CIPM Mutual Recognition Arrangement (Opens external link in new windowMRA). Key comparisons enable the mutual recognition of calibrations, measurements, and test certificates of the NMIs and mark a major step in supporting international trade, commerce and regulatory affairs. The final report and the supporting technical data of each key comparison are stored and made publicly available at the key comparison data base  Opens external link in new windowKCDB of the Bureau International des Poids et Mesures (Opens external link in new windowBIPM). Fig. 1 shows a typical example of key comparison data.

Fig.1 Example data of a key comparison along with the key comparison reference value (KCRV). The blue results indicate control measurements made by the so-called pilot laboratory.


The analysis of key comparisons can be seen as a Opens external link in new windowMeta-Analysis in which the results reported by the participating laboratories are assessed. Fixed effects or random effects models are popular models applied in meta-analysis. One focus of research of PTB’s Working Group 8.42 is the development of Bayesian methods for the estimation of fixed and random effects models. This includes the assignment of vaguely informative or appropriate non-informative priors and the exploration of the properties of the resulting inference. Other topics of research are situations in which the common measurand shows a drift, or where the explanatory power of key comparisons is assessed in dependence on the stability of the common measurand and the uncertainties reported by the participating laboratories.



Publication single view


Title: Linking the results of the regional key comparison APMP.AUV.V-K1 to those of the CIPM key comparison CCAUV.V-K1
Author(s): H.-J. von Martens, C. Elster, A. Link, W. Wöger and P. J Allisy
Journal: Metrologia
Year: 2004
Volume: 41
Issue: 1A
Pages: 09002
DOI: 10.1088/0026-1394/41/1A/09002
Web URL: http://stacks.iop.org/0026-1394/41/i=1A/a=09002
Tags: 8.42,KC
Abstract: During 1996 and 1997, eight national metrology institutes (NMI) took part in a vibration accelerometer comparison, identifier APMP.AUV.V-K1 [http://www.bipm.org/utils/common/pdf/final_reports/AUV/V-K1/APMP.AUV.V-K1.pdf] . Two NMIs ultimately withdrew from the comparison and the results of the remaining six NMIs have been approved by the CCAUV. Four NMIs subsequently took part in the 2001 CIPM key comparison for the same quantity, identifier CCAUV.V-K1. The results of these four CIPM participants have been used to link the results of the remaining two NMIs to the results in the CIPM key comparison using the reference frequency of 160 Hz. The CCAUV nominated the PTB to propose the methodology for the link and subsequently approved the linked results as presented in this report. The degrees of equivalence between each result and the key comparison reference value (KCRV), and between each NMI have been calculated and the results are given in the form of a matrix and graph for six NMIs. As two results from the APMP can now be linked to the published CCAUV.V-K1 comparison [http://www.iop.org/EJ/abstract/0026-1394/40/1A/09001] , the updated graph for the key comparison database is also given. Main text. To reach the main text of this paper, click on Final Report [http://www.bipm.org/utils/common/pdf/final_reports/AUV/V-K1/CCAUV.V-K1_APMP.AUV.V-K1.pdf] . The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the Mutual Recognition Arrangement (MRA).

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