CCT-K2: key comparison of capsule-type standard platinum resistance thermometers from 13.8 K to 273.16 K

Abstract

Calibrated capsule-type standard platinum resistance thermometers were used to compare national realizations of the International Temperature Scale of 1990 (ITS-90) from 13.8033 K, the triple point of equilibrium hydrogen, to 273.16 K, the triple point of water, for seven countries in CIPM Key Comparison CCT-K2. Measurements were made at temperatures close to the eight low-temperature defining fixed points of the ITS-90, using a copper comparison block capable of simultaneously holding nine thermometers. Two separate measurement runs were performed, allowing two different groups of capsules from each laboratory to be examined. The results are used to determine the degree of equivalence of the independent national realizations of the scale for use in the Mutual Recognition Arrangement Appendix B database. In addition, measurements were made with the first group of thermometers at approximately eighty temperatures throughout the cryogenic range, which provide information to evaluate some of the so-called scale non-uniqueness issues inherent in the ITS-90 interpolation scheme.