Change of the thermoelectric voltage of type R thermocouples in the freezing points of aluminum and silver cells with the heat treatment methods

R형 열전대의 열처리 방법에 따른 알루미늄과 은 응고점에서의 기전력 변화

In order to investigate the effects of heat treatment on the thermoelectric motive force (EMF) of type R thermocouples, the changes of EMF in the freezing points of aluminum and silver cells were measured with the immersion depth of themocouples. With the variation of heat treatment methods before use, it was found that the EMF values were different from each other, maximum $17.1{\mu}V$ at $660.323^{\circ}C$ and $18.1{\mu}V$ at $961.78^{\circ}C$. Additionally a thermocouple, which was not heat-treated fully, showed an EMF difference with the immersion depth even though it was located on the region maintained at the constant temperature. The measured differences were about maximum $7.8{\mu}V$ at the Al freezing point and $18.9{\mu}V$ at the Ag freezing point. It was recongnized that a thermocouple for the precise temperature measurement should be heat-treated carefully before service. In this report, the proper heat treatment methods for the type R thermocouple were given on the basis of the obtained experimental results.

R형 열전대의 열기전력에 미치는 열처리효과에 대하여 살펴보기 위하여 알루미늄 및 은 금속 응고점 셀에서 깊이에 따른 열기전력의 변화를 조사하였다. 사용전 열처리 방법에 따라 최대기전력 차이는 $660.323^{\circ}C$ 에서 $17.1{\mu}V$, $961.78^{\circ}C$ 에서 $18.1{\mu}V$ 를 보였다. 또한 충분한 열처리를 거치지 않은 열전대는 동일한 온도로 유지되고 있는 응고점 셀내에서도 삽입깊이에 따라 기전력 차이를 나타냈으며, 그 정도는 알루미늄 응고점에서 최대 $7.8{\mu}V$은 응고점에서 $18.9{\mu}V$를 보였다. 따라서 열전대를 사용하여 정확한 온도를 측정하기 위해서는 충분한 열처리를 거쳐야 함을 알 수 있었으며, 본 논문에서 얻어진 실험결과를 바탕으로 R형 열전대의 열처리방법을 제시하였다.