The role of compensation wire

Compensation wires are generally used for thermocouples. They are divided into compensation type and extension type. Their functions are similar. I will not elaborate on the difference between them here. Our company will explain the difference between the two in detail in the next article.

The function of the compensation wire is to extend the cold end of the thermocouple, that is, the mobile thermocouple, and connect it with the display instrument to form a temperature measurement system. The product is mainly used in various temperature measurement devices and has been widely used in petroleum, chemical, metallurgy, power and other departments.

Generally speaking, the thermocouple may be tens of meters away from the temperature meter, and the temperature of the cold end (outlet end) of the thermocouple is different from the ambient temperature of the temperature meter (even up to tens of degrees).

If ordinary copper wires are used, according to the principle of thermocouples, the connection will generate a temperature difference potential, which will cause measurement errors.

The voltage drop problem of long-distance transmission wires, because the input impedance of the temperature meter is high, the temperature difference potential (millivolt level) generated by the thermocouple and the transmission current (micro-A level) are very small, and the voltage drop loss on the wire is very small. Under normal circumstances, it is within the error range. Therefore, there is a thermocouple transmitter, which inputs a thermocouple signal and outputs 4-20ma. This way, there is no need for compensation wires and long-distance transmission is possible.

If a compensation wire is used (it must match the thermocouple graduation number), the metal material used can generate the smallest possible temperature difference potential at the wiring point, minimizing the temperature measurement error. In other words, move the cold end of the thermocouple to the temperature measuring table.