RH Thermocouple

Abstract

RH thermocouple is so designed that it conduct the continuous measurement of temperature up to 1, 650°C. It consists of a pair of Platinum and Rhodium at the rate of 70 and 30 per cent respectively, while minus side the same materials but at 94 and 6 per cent. This thermocouple gives the thermo-emfs of 10.718 millivolts at Palladium point (1, 552°C) and 5.623 millivolts at copper point (1, 083°C) and about 10 microvolts per deg. in the temperature range of 1, 000 to 1, 800°C.
After this thermocouple was continuously used for total 300 hours in an electric furnace with temperatures kept at 1, 500°C, 1, 550°C and 1, 600°C for 100 hours each, no crystallization of the wire was recognized and emf variation measured at Palladium point indicated only puls 4 microvolts. Furthermore, when the same thermocouple was tested again being kept at 1, 750°C for 30 minutes, 45 microvolts of emf variation was recognized at Palladium point. The above temperature of 1, 750°C is believed maximum for RH thermocouple measurement. For information, protection tube used in this test was of sinter corund.