The working principle of compensating leads is that within a certain temperature range, a lead with thermoelectric properties very similar to those of a thermocouple is called a compensating lead for the thermocouple.
According to the thermocouple intermediate temperature rule, the total potential value of the thermocouple temperature measurement circuit depends only on the temperatures of the hot junction and the reference junction, and is not affected by changes in the intermediate temperature. Therefore, compensating leads matching the thermocouple material can be used to replace the expensive thermocouple material that needs to be extended, extending the reference junction from the thermocouple junction box to the instrument terminal, with the compensating lead compensating for the original reference junction temperature.
Besides reducing measurement errors, compensating leads also have the following advantages: they can improve the physical and mechanical properties of the thermocouple temperature measurement circuit. For example, using multi-strand cores or small-diameter compensating leads can improve the flexibility of the circuit, making connections easier and facilitating shielding against external interference; they can also reduce the cost of the measurement circuit.
