Abstract：The high-temperature primary standard system was gradually improved through the continuing research work at the National Institute of Metrology (NIM) in China. Based on the developed primary standard pyrometer, an improved scheme, the “fixed-point blackbody pyrometer” assembly, was applied to realize and disseminate the International Temperature Scale of 1990 (ITS-90) above the silver point. The new scheme can correct the drifts of the pyrometer and extend the highest temperature range from 2 200 ℃ to 2 474 ℃. The expanded uncertainties of the scale were 0.08~0.62 ℃ between the temperature range 961.78~2 474 ℃.The uncertainties of the temperature scale are strongly supported by the international comparison of the high temperature fixed points’ ITS-90 values among China, the U K and Spain in 2009. The new method could be not only applied in the highest level calibration of the precise pyrometers, but also in the calibration of the 900 nm infrared thermometers.
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2014, Vol. 35 
