Temperature Measurement of Pd-C and Ru-C Cells at NIM

The results of the research on two new eutectic fixed point cells, Palladium-Carbon (Pd-C) and Ruthenium-Carbon (Ru-C), conducted by the National Institute of Metrology (NIM) after participating in an international joint study on high-temperature fixed point cells thermodynamic temperatures are reported. Two types of crucibles were designed for Pd-C (1492 °C) and Ru-C (1953 °C), which can be used to calibrate radiation thermometers and high-temperature thermocouples. The International Temperature Scale of 1990 values (T₉₀) of Pd-C and Ru-C are measured extrapolated from a primary standard thermometer, and the thermodynamic temperature (T) is obtained using a precision photoelectric pyrometer LP4 measurement, where LP4 is interpolated and indexed by Co-C (1324 °C), Pt-C (1738 °C) and Re-C (2474 °C) with thermodynamic temperature values. The experimental results show that the differences between T and T₉₀ of Pd-C and Ru-C are 0.25 K and 0.29 K, respectively; the uncertainties of T and T₉₀ of Pd-C are 0.32 K and 0.45 K, and those of Ru-C are 0.49 K and 0.50 K. The results not only promote the application of calibration for high-temperature fixed points, but also establish an important basis for transferring thermodynamic temperature.