Bilateral Comparison Between NIM and NMC Over the Temperature Range from 83.8058 K to 692.677 K

A bilateral comparison of local realization of the International Temperature Scale of 1990 between the National Institute of Metrology (NIM) and National Metrology Centre (NMC) was carried out over the temperature range from 83.8058 K to 692.677 K. It involved six fixed points including the argon triple point, the mercury triple point, the triple point of water, the melting point of gallium, the freezing point of tin, and the freezing point of zinc. In 2009, NMC asked NIM to participate in a bilateral comparison to link the NMC results to the Consultative Committee for Thermometry Key Comparison 3 (CCT-K3) and facilitate the NMC’s calibration and measurement capabilities submission. This comparison was agreed by NIM and Asia Pacific Metrology Programme in 2009, and registered in the Key Comparison Database in 2010 as CCT-K3.2. NMC supplied two 25 Ω fused silica sheath standard platinum resistance thermometers (SPRTs) as traveling standards. One of them was used at the Ga, Sn, and Zn fixed points, while the other one was used at the Ar and Hg fixed points. NMC measured them before and after NIM measured them. During the comparison, a criterion for the SPRT was set as the stability at the triple point of water to be less than 0.3 mK. The results for both laboratories are summarized. A proposal for linking the NMC’s comparison results to CCT-K3 is presented. The difference between NMC and NIM and the difference between NMC and the CCT-K3 average reference value using NIM as a link are reported with expanded uncertainties at each measured fixed point.