Comparison report of the ITS-90 realization at the freezing point of silver between NIM and CMS

Abstract

The APMP key comparison APMP.T-K4.1 was initiated on the request of the Center for Measurement Standards, Taiwan (CMS) to link their standards to the Consultative Committee for Thermometry (CCT) Key Comparison (KC) and facilitate the CMS CMC submission. National Institute of Metrology, China (NIM) provided the linkage to the CCT-K4 at the temperature of the freezing point of silver. In the APMP.T-K4.1, one high temperature standard platinum resistance thermometer (HTSPRT) was chosen as the transfer instrument and was calibrated at the freezing point of silver. The comparison was carried out in a participant-pilot-participant sequence where NIM served as the pilot. The linkage was based on the temperature of CMS reference Ag fixed point relative to the key comparison reference value (KCRV) of CCT-K4 at the Ag fixed point via the difference in temperature between the NIM reference Ag fixed point and NIM reference Ag fixed point (links to the KCRV of the CCT-K4). The temperature difference between the standards of CMS and the KCRV of the CCT-K4 was within the evaluated comparison uncertainties of the ATPM.T-K4.1. This report provides detailed information on the comparison results, linkage mechanism, and the Degree of Equivalence of the CMS relative to the institutes having participated in the CCT-K4. 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 https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).