Uncertainty Evaluation on the Freezing Point of Copper for Calibration of Thermocouples

Abstract

A copper freezing-point furnace and four copper freezing-point cells were constructed in our institute. The furnace was consisted of one main heater and two end-heaters. The copper freezing-point cells were open type cells with high-purity graphite crucibles that contained copper of 99.9999% purity. The uncertainty in realizing freezing-point for thermocouple calibration was evaluated using the Pt/Pd thermocouples. The main sources of the uncertainty investigated were reproducibility of the plateau, the temperature distribution in the cell and the impurity effect of the metal. The combined standard uncertainty was estimated to be 20.2mK.