Construction and comparison of high temperature fixed points at NRC and CEM

Abstract

Abstract This paper describes the collaborative project between National Research Council of Canada (NRC) and Centro Español de Metrología (CEM) for the construction and comparison of high temperature fixed points (HTFPs). A hybrid-type crucible that uses the piston method for filling has been jointly developed. A series of 12 high temperature fixed point blackbodies (HTFPBBs) have been constructed, including Cu, Ru-C, Ir-C, Re-C and WC-C covering the temperature range from 1084°C to 2750°C. All these cells were filled in NRC facilities by CEM and NRC staff. Two cells of each type of fixed point were constructed (except for the WC-C cells), using crucibles from two different suppliers in order to study the influence of the density and emissivity of the crucible in the HTFPs’ performance. Moreover, four WC-C cells were made using tungsten powder from two different suppliers, covering all the possible combinations of tungsten powder and crucibles acquired for this project. All cells, and additionally a Pt-C HTFPBB belonging to NRC, have been measured firstly at NRC and, afterwards, at CEM. Both laboratories have calculated the ITS-90 temperatures from their respective measurements and the results have been compared. Differences on the ITS-90 temperatures of the HTFPBBs measured at each lab are within uncertainties of the comparison. After the comparison, CEM kept one Cu cell, one Ru-C cell, one Re-C cell and two WC-C cells. The rest of the fixed points involved in the comparison were sent back to NRC.