What is the difference between thermocouple wire and compensation wire?

In a thermocouple, the line used from the sensing point to the cold junction compensation point (cjc junction) where the signal is measured. A thermocouple is a sensor that measures temperature and consists of two dissimilar metals joined at the sensing end. Different types of thermocouples (such as J, K, T, E, etc.) use different metal wire combinations. At the cold junction compensation end, the millivolt value provided by the thermocouple represents the temperature difference between the sensing end and the cold junction compensation end (also called the reference end).
The insulation of the thermocouple wire is identified by color coding. Common guidelines include the negative lead in the insulated thermocouple compensation wire being red, and the positive lead being the same overall color as the compensation wire. Thermocouple wire jackets are usually brown. High temperature wires are usually white.
Standard and special error limits are related to the temperature of the wire. Special error limited wires are the same as standard error limited wires, but have a higher temperature. Thermocouple accuracy varies with the type of thermocouple. For example, the lower temperature range T-type, which consists of positive copper wire and negative constantan (copper-nickel mix), has good accuracy specifications.
Thermocouple wire is the wire used to create the sensing point of a thermocouple. Compensating wires are used only to extend the thermocouple signal to the meter that reads this signal. The compensation wire usually has a lower ambient temperature limit, that is, it can pass the higher temperature signal obtained from the probe, but it is not exposed to the higher temperature itself. Thermocouple wire can be used as compensation wire, but compensation wire cannot be used to make the sensing point (or probe part) of the thermocouple. The product numbers for compensating conductors usually begin with the prefix "EX".