How to use the intermediate temperature law to compensate the cold end temperature of thermocouples?

There are two main methods for using the intermediate temperature law to compensate the cold end temperature of thermocouples: the calculation correction method and the cold end constant temperature method. The following is a detailed introduction: Calculation correction method to measure the cold end temperature: Use a high-precision thermometer to accurately measure the temperature of the environment where the cold end of the thermocouple is located \(T_c\). Determine the corresponding thermoelectric potential: According to the thermocouple graduation table, find the thermoelectric potential \(E(T_c,0)\) generated by the thermocouple at the cold end when the cold end temperature is \(T_c\). Here \(E(T_c,0)\) represents the thermoelectric potential when the cold end temperature is \(T_c\) and the hot end temperature is \(0℃\). Measure the total thermoelectric potential: Use a measuring instrument to measure the total thermoelectric potential \(E(T,T_c)\) of the thermocouple circuit, where T is the actual temperature of the hot end. Calculate the hot end temperature: According to the intermediate temperature law, the total thermoelectric potential \(E(T,T_c)\) is equal to the thermoelectric potential \(E(T,0)\) when the hot end temperature is T and the cold end temperature is \(0℃\) minus the thermoelectric potential \(E(T_c,0)\) when the cold end temperature is \(T_c\) and the hot end temperature is \(0℃\), that is, \(E(T,0)=E(T,T_c)+E(T_c,0)\). After calculating \(E(T,0)\) by this formula, the corresponding actual hot end temperature T is then retrieved from the thermocouple graduation table. The cold end constant temperature method uses a constant temperature device: the cold end of the thermocouple is placed in a constant temperature device, such as a constant temperature bath, ice bath, etc., to keep the cold end temperature \(T_c\) constant. Generally speaking, an ice bath can keep the cold end temperature at \(0℃\), which is an ideal cold end temperature compensation method. According to the intermediate temperature law: Since the cold end temperature is constant, according to the intermediate temperature law, the thermoelectric potential generated by the thermocouple is only related to the hot end temperature and the constant cold end temperature. In this case, the hot end temperature can be accurately obtained by matching the measured thermoelectric potential with the corresponding hot end temperature according to the thermocouple graduation table, without considering the impact of the cold end temperature change on the measurement result. In practical applications, the calculation correction method is suitable for occasions where the cold end temperature cannot be kept constant and requires precise measurement, while the cold end constant temperature method is simple to operate and has high accuracy, and is often used in laboratories and other environments that require high temperature measurement accuracy.