How to choose the appropriate compensation wire for a thermocouple?

A compensation wire is a connection wire for thermocouples, used to compensate for the potential difference that arises at the cold end of the thermocouple due to changes in ambient temperature. Thermocouples of different types and calibration numbers must use compensation wires that are compatible with their respective calibration numbers. Technical specifications of common compensation wires: Thermocouples, Compensation wires, Positive pole, Negative pole. Thermoelectromotive force in mV when the cold end is at 0 and the hot end at 100. Platinirhodium-platinum: WRP(S); Copper – red; Copper-nickel – green: +0.634; Nichrome-nickel-silicon: WRN(K); Copper – red; Beryllium copper – blue: +4.10; Nichrome-beryllium copper: WRK(E); Nichrome – red; Beryllium copper – yellow: +6.95; Copper-beryllium copper: WRT(T); Copper – red; Beryllium copper – yellow: +4.76

Different thermocouples come with different compensation wires, and these compensation wires also have models corresponding to those of the thermocouples themselves. For example, there are K-type compensation wires and S-type compensation wires. Each type of wire comes in various varieties; generally, there are two types. One is the extension type, whose material is the same as that of the thermal resistor it is paired with, and its thermoelectrical properties are similar to those of the thermocouple. It is suitable for measurements requiring high precision, but it is slightly more expensive. The other type is the compensation type; its material differs from that of the thermocouple it is used with, but its thermoelectrical properties at 0-100 degrees are similar. Although its precision is lower, it is cheaper and sufficient for ordinary measurement requirements