Abstract
This report describes key comparison CCT-K4 held under the auspices of the Consultative Committee for Thermometry (CCT). For the first time, local realizations of ITS-90 temperatures were compared by directly circulating aluminium and silver freezing-point cells. Twelve national metrology institutes (BNM/INM, IMGC, KRISS, NIM, NIST, NMIJ, NMi/VSL, NML, NPL, NRC, PTB, VNIIM), organized into three subgroups, American, European and Asian/Australian, contributed to the results. The American subgroup used an exemplary bilateral and the other subgroups a round-robin procedure. Key comparison reference values (KCRV) for both freezing points were calculated as the weighted average temperatures using the squared sum of the combined standard uncertainties of the laboratories and an uncertainty representing the stability of the circulated cells to set the weights. For the aluminium freezing point, the absolute temperature differences from the corresponding KCRV varied between 0.13 mK and 4.35 mK with expanded uncertainties between 1.08 mK and 4.16 mK (95 % level of confidence). For the silver freezing point, the absolute differences ranged from 0.74 mK to 13.03 mK and the expanded uncertainties were between 1.01 mK and 12.89 mK.
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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 www.bipm.org/kcdb.
This Final Report has been peer-reviewed and approved for publication by the CCT according to the provisions of the Mutual Recognition Arrangement (MRA).