Thermocouple wire or extension grade wire is recommended to be used to connect thermocouples to the sensing or control instrumentation. The conditions of measurement determine the type of thermocouple wire and insulation to be used. Temperature range, environment, insulation requirements, response, and service life should be considered.

The main technical data of thermocouple extension wire and thermocouple compensating wire as following:
1. Wire grade (Thermocouple wire or extension wire)
2. Calibration (Type J, K, T, E)
3. Insulation material
a. Conductor insulated ( PVC, Fiberglass, Teflon)
b. Overall insulated ( PVC, Fiberglass, Teflon)
c. Overbraided ( Stainless steel or Tinned copper)
4. Color code (ANSI or IEC standard)
5. Wire gauge size (16AWG, 18AWG, 20AWG, ...)
6. Wire shape (Round, Flat or Twisted)
7. Wire type (Solid or Stranded)