Report on the key comparison EUROMET-PR-K6: Spectral regular transmittance

Abstract

The EUROMET-PR-K6 key comparison on spectral regular transmittance was carried out in the framework of the Mutual Recognition Arrangement by 17 laboratories: BEV (Austria), CMI (Czech Republic), GUM (Poland), IFA (Spain), INM (Romania), INRIM (Italy), IPQ (Portugal), LNE–INM (France), METAS (Switzerland), MKEH (Hungary), MIKES (Finland), NPL (United Kingdom), PTB (Germany), SMU (Slovakia), SP (Sweden), UME (Turkey), VSL (The Netherlands), with the LNE–INM acting as the central and reporting laboratory. The link to CCPR-K6 is ensured by six link laboratories (IFA, LNE–INM, MIKES, NPL, PTB, SMU)The aim of the comparison was restricted to checking the accuracy of the radiometric scale of spectrophotometers, using coloured glass filters with nominal transmittance of approximately 92%, 56%, 10%, 1% and 0.1%. The wavelengths of measurement were 380 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm and 1000 nm. The comparison was a star type comparison with the samples provided by the pilot laboratory and sent out to all the participants at the same time.The report describes in detail the measurements made at the LNE–INM and summarizes the reports submitted by the participants. The comparison of the results of measurements carried out by the pilot laboratory before and after the circulation of the filters points out that the stability of most of the filters was rather poor. Moreover, for the coloured glass filters (filters B to E), the drift was wavelength dependent. As a consequence, for many results, the uncertainty due to the drift of the filters during the comparison is the major cause of uncertainties, much larger than the measurement uncertainty of the measurements reported by the laboratories.Measurement results from participants and their associated uncertainties were analysed in this report according to the Guidelines for CCPR Comparison Report Preparation but with some adjustment for taking into account that transmittance measurements have unit 1. Across the spectral region (380 nm to 1000 nm) there were eight wavelengths at which a comparison was made. These were treated entirely independently and thus the report describes eight comparisons for each type of filter.The linkage of this RMO key comparison to the CCPR-K6 key comparison takes a particularly simple form because (a) the pilot laboratory was also the pilot laboratory for the CCPR-K6 comparison and (b) the five other laboratories serving as links between the two contributed the same measurements on the same artefacts in each comparison. It follows from (a) and (b) that the same result is obtained by linking through any one of these five laboratories or any combination of them. The degrees of equivalence of participants in this RMO key comparison have hence been evaluated by linking through values measured by the pilot laboratory. Because the CCPR KCRV is defined relative to the values obtained by the pilot laboratory and the ΔX,i (the difference between participant measurement and the pilot laboratory measurement) are also defined relative to measurements by the same pilot laboratory, the unilateral degree of equivalence Di of the national metrological institute i takes the simple form: Di = Δi − ΔKCRV Ui = k[u2(Δi) + u2(ΔKCRV)]1/2; k = 2.All the results and a graphical representation of the unilateral degrees of equivalence with k = 2 are proposed in the final report.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).