In order to solve the cold junction processing of the thermocouple , keep the thermocouple cold junction temperature constant, and transmit the thermoelectric potential signal remotely to obtain the thermoelectric potential at any cold junction temperature, in the actual thermocouple application, it is necessary to perform cold junction treatment and compensation on the thermocouple . There are three common methods:
又称延伸热电极法)为了使热电偶冷端的温度保持不变，可以把热电偶延长，使冷端延伸到温度比较稳定的地方，远离被测温度的影响，为了减小贵金属热电偶延伸的成本，可以采用在一定温度范围内与需延伸热电偶热电特性相近的廉价金属代替贵金属，实现冷端延伸。 Compensation wire extension method: In order to keep the temperature of the cold end of the thermocouple unchanged, the extension method of the compensation wire ( also known as the extension of the hot electrode method ) can be extended to extend the cold end to a place where the temperature is relatively stable, away from Impact, in order to reduce the cost of noble metal thermocouple extension, a cheap metal with similar thermoelectric characteristics to that of the thermocouple to be extended can be used to replace the noble metal within a certain temperature range to achieve cold end extension.
，但稳定在t0时，可修正仪表指示值，得到冷端在0℃的热电势E(t,0),通过查分度表确定被测温度t 。 Cold junction temperature correction method: When the temperature of the cold junction of the thermocouple is higher than 0 ° C but stable at t0 , the indicator value of the instrument can be modified to obtain the thermoelectric potential E (t, 0) of the cold junction at 0 ° C. Measured temperature t .
时，这种方法也被称为冰点法或冰浴法，为了防止短路，这种方法要做好绝缘工作。 Cold end constant temperature method: The cold end constant temperature method is to place the cold end of a thermocouple in a constant temperature device. When the temperature of the thermostat is 0 ° C , this method is also called the freezing point method or the ice bath method. This method should do a good job of insulation. Because this method uses a constant temperature device such as a freezing point tank, it is relatively cumbersome, and it is mostly used for laboratory measurement. Industrial measurement is generally not used.