The high-temperature primary standard system was gradually improved at the National Institute of Metrology (NIM) in China after 2004. A new primary standard pyrometer (PSP) was developed, one with a size-of-source effect of 1 × 10 −4 , and regional thermostats for interference filters, photoelectric detectors, and I/V converters. The relative spectral responsivity of the entire PSP was calibrated by means of a new facility. A new LED-based measurement facility and novel systematic error correction model were utilized to characterize the PSP nonlinearity and extend the photocurrent to PSP temperature readings of about 2680 • C. As an improved scheme, the fixed-point blackbody pyrometer assembly was utilized to realize and disseminate the International Temperature Scale of 1990 above the silver point. This scheme can avoid the influences of instability and inhomogeneity of tungsten strip lamps and corrects pyrometer drifts, thereby improving the realization uncertainty and simplifying the transfer chain. The expanded uncertainties of the scale realization ranged from 0.04 • C at the silver point to 0.48 • C at 2474 • C.
In this paper, impurity parameters m i and k i have been calculated for a range of impurities I as detected in the eutectics Co-C and Pt-C, by means of the software package Thermo-Calc within the ternary phase spaces Co-C-I and Pt-C-I . The choice of the impurities is based upon a selection out of the results of impurity analyses performed for a representative set of samples for each of the eutectics in study. The analyses in question are glow discharge mass spectrometry (GDMS) or inductively coupled plasma mass spectrometry (ICP-mass). Tables and plots of the impurity parameters against the atomic number Z i of the impurities will be presented, as well as plots demonstrating the validity of van't Hoff's law, the cornerstone to this study, for both eutectics. For the eutectics in question, the uncertainty u T E − T liq in the correction T E − T liq will be derived, where T E and T liq refer to the transition temperature of the pure system and to the liquidus temperature in the limit of zero growth rate of the solid phase during solidification of the actual system, respectively. Uncertainty estimates based upon the current scheme SIE-OME, combining the sum of individual estimates (SIE) and the overall maximum estimate (OME) are compared with two alternative schemes proposed in this paper, designated as IE-IRE, combining individual estimates (IE) and individual random estimates (IRE), and the hybrid scheme SIE-IE-IRE, combining SIE, IE, and IRE.
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 fixedpoint 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.
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