What is a thermocouple/compensation cable?

Generally speaking, a thermocouple can be laid with its base material from the measuring point to the control room. However, the sensor may not be flexible enough or simply too expensive, depending on the diameter, design and type of thermocouple. Just imagine the costs and amount of work required to lay a type R platinum thermocouple over 100 meters across the factory floor, or bending an 8.0mm thermocouple to follow the cable routing.

For this reason, thermocouple or compensation cables are used to bridge the distance between the measuring point or thermocouple and the measuring card. Beyond purely transmitting the signal, the cable is also required for signal generation to ensure the temperature difference between the cold end of the thermocouple and the intrinsic temperature of the measuring card can be compensated. The thermocouple and compensation cables therefore need to possess the same thermoelectric properties as the thermo material in the thermocouple.

While the thermocouple cable has the same thermo material as the inner conductor, only materials that possess identical thermoelectric properties as the thermo material are used for the compensation cable.

Using the same thermo material in the thermocouple cable improves the accuracy of the measuring chain.

That being said, the use of compensation cables remains justified due to their cheaper purchase price. For instance, noble metal thermocouples in particular only use compensation cables, as producing a thermocouple cable is simply not economical.

The color coding for thermocouple and compensation cables is standardized in DIN EN 60584-3.