标准铂电阻温度计自热效应的计算公式

Formula for Calculating the Self-Heating Effect of a Standard Platinum Resistance Thermometer

标准铂电阻的量值溯源中,自热效应是非常重要的一项指标。通常使用测温电桥先测量工作电流为1 mA下的温度计的电阻值,再调节电流为 mA并测量温度计的电阻值,计算前后两次电阻值的差,利用偏差函数计算的微分电阻比来换算成温度值。但是由于电阻的焦耳热效应,电流改变后,其电阻发生了变化(增加),调节电流后的热效应功率并不是电流改变前的两倍,因此该计算方式具有一定的误差。在此基础上,笔者通过公式推导,提出新的计算公式。

In the traceability of the magnitude of standard platinum resistance, the self-heating effect is a very important indicator. Generally, a temperature measuring bridge is used to measure the resistance value of the thermometer at 1 mA, then adjust the current to mA and measure the resistance value of the thermometer, calculate the difference between the two resistance values before and after, and convert it into the temperature value by using the differential resistance ratio calculated by the deviation function. However, due to the Joule heating effect of the resistor, the resistance of the resistor changes (increases) after the current changes, and the thermal effect power after adjusting the current is not twice as high as before the current changes, so this calculation method has a certain error. On this basis, the author proposes a new calculation formula through formula derivation.