Key Comparison CCT-K2: Key Comparison of Capsule-type Standard Platinum Resistance Thermometers from 13.8 K to 273.16 K

Calibrated capsule-style 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 capsules.
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 also 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.