Calibration of Pyrometers by Using Extrapolation and Interpolation Methods at NIM
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High-temperature fixed points (HTFPs) have been thoroughly investigated, and the performance of variable temperature blackbodies (VTBB) has also improved rapidly. These two are beginning to be used in the calibration of pyrometers; however, tungsten strip lamps (STSL) still play a role in the dissemination of the high-temperature scale in China. International Temperature Scale of 1990 values of HTFPs and the lamps were assigned on a primary standard pyrometer (PSP) and were traced to the primary standard of the high-temperature scale at the National Institute of Metrology. In this paper, two pyrometers calibrated by using extrapolation and interpolation methods are reported. The values of the calibration were compared against the STSL values and the PSP values on HTBB, and their uncertainties are calculated as well. Because the stability of the HTFPs was better than that of the lamps, the calibration chains based on the lamps are starting to be replaced by HTFPs and VTBBs in China.