Temperature Control of Innert Gas Furnace by B₄C/C Thermocouple

Abstract

A Method for temperature-controlling of an innert gas furnace equipped with a B₄C/C thermocouple has been proposed. The thermocouple was consisted of a graphite tube and a B₄C rod connected to one another by a conical fitting. In the temperature range between 1300° and 2000°C, the thermoelectric voltage rose almost linearly and at 2000°C it was at ca. 450mV. The electric resistance of the thermocouple decreased slightly with increasing furnace temperature, reached a minimum at ca. 250°C, increased remarkably with a further increase of the temperature, and at 2000°C it was at ca. 4.4kΩ. Because of the high thermoelectric voltage and the violent variation of electric resistance, the temperature controlling unit was equipped with a volte-current converter having a high impedance, additionally.