Comparisons of Co–C and Pd–C Eutectic-Point Cells for Thermocouple Calibration Between NMIA and NMIJ

Abstract

Comparisons between NMIA and NMIJ on the melting temperatures of the Co–C eutectic point and the Pd–C eutectic point were performed using an NMIJ high-temperature furnace. The eutectic-point cells were constructed by NMIA and NMIJ following two different specifications. NMIA designed two miniature crucibles, one for Co–C and one for Pd–C eutectic-point cells. NMIJ designed larger eutectic-point cells, one for Co–C and one for Pd–C eutectic-point cells. Prior to performing the comparisons, the effect of conductive heat flow through the thermocouple stem was evaluated during the melting. The comparisons of the Co–C eutectic-point cells and of the Pd–C eutectic-point cells were performed using types R, B and Pt/Pd thermocouples. Despite the different cell designs and different material sources, the melting temperatures of the Co–C and Pd–C eutectic-point cells under investigation agreed within 0.1 \(\,{^{\circ }}\hbox {C}\).