T 90 Measurement of Co-C, Pt-C, and Re-C High-Temperature Fixed Points at the NIM

Abstract

The blackbodies of high-temperature fixed points (HTFPs), namely, Co-C, Pt-C, and Re-C eutectic points, were gradually established at the National Institute of Metrology (NIM) of China after 2007, and their characteristics were studied. Recently, the primary standard pyrometer was improved with the lower size-of-source effect, distance effect, and partial temperature controls. The pyrometer was characterized at the new facility for the calibration of the spectral responsivity. The measurement of its nonlinearity extended to a primary standard pyrometer (PSP) reading of approximately 2680 °C for the HTFP measurements. The International Temperature Scale of 1990 above the silver point was realized at the NIM by an improved scheme, the fixed-point blackbody pyrometer assembly. Two cells each for Co-C, Pt-C, and Re-C points were assigned associated uncertainties (k = 2) of 0.22 °C, 0.37 °C, and 0.75 °C, respectively, in accordance with the NIM scale. These HTFP blackbodies are being adopted for the study and calibration of radiation thermometers at the NIM.