Comparisons of some NIST fixed-point cells with similar cells of other standards laboratories

Abstract

In this paper we present results of international comparisons of fixed-point cells of some of the defining fixed-point materials of the International Temperature Scale of 1990. These comparisons involved cells from seven national laboratories, although in some cases only one type of fixed-point material was compared. Except for silver cells, the agreement among cells of the same defining fixed-point material from the various laboratories was to within 1 mK. The expanded uncertainties (k = 2) of the comparison measurements were 12 µK for Ga, 18 µK for H2O, 27 µK for Sn, 35 µK for In, 37 µK for Zn, 42 µK for Al, and 55 µK for Ag.