Brief Introduction of Temperature Compensation Method for Thermocouple Cold Junction

1. The ice bath method is commonly used in the laboratory, that is, the temperature of the reference junction is kept constant at 0 degrees, but it is costly and difficult to do. 2. The cold junction temperature correction method is commonly used in sites with low requirements, that is, when the cold junction temperature cannot be kept constant at 0 degrees, it is necessary to correct the indicated value of the instrument. It is easy to do but the error is large. 3. The compensation bridge method is rarely used alone, but uses an unbalanced bridge. The ice bath method is commonly used in the laboratory, that is, the temperature of the reference junction is kept constant at 0 degrees, but it is costly and difficult to do. 2. The cold-junction temperature correction method is commonly used in sites with low requirements, that is, when the cold-junction temperature cannot be constant at 0 degrees, it is necessary to correct the indicated value of the instrument. It is easy to do but the error is large. 3. The compensation bridge method is rarely used alone. It uses the electric potential generated by the unbalanced bridge to compensate the thermoelectric potential change value caused by the temperature change of the cold junction of the thermocouple. There are separate products for the compensation bridge, and some are built in the instrument. 4. Compensation wire method This is the most commonly used method, that is, extend the thermocouple to lead the cold junction to a place with a relatively stable temperature (usually a control room), and then manually adjust the temperature of the cold junction, that is, adjust the zero point of the instrument to room temperature. Or it can be automatically compensated by the circuit in the instrument. It is also impossible for precious metal thermocouples to extend thermocouples, because the price is too high to work, so base metals with similar thermoelectric properties are used to extend the wires. The intermediate temperature rule is the theoretical basis for applying compensation wires. The compensation wire cannot automatically compensate for the temperature change of the cold junction of the thermocouple. It only leads the cold junction of the thermocouple to a place where the temperature is relatively stable. The compensation must be performed manually and by an instrument. Therefore, the compensation wire should be called a thermocouple extension wire, so as not to give people a wrong understanding.