Thermocouple Wire & Extension Wire

Thermocouple wire

Thermocouples have normally standard lead wires of 12 inches but can also be ordered with longer lead wires. Thermocouples are perishable items and the controller where they connect to may be many feet away, so it makes sense to replace just the thermocouple with the standard leads.
When ordering thermocouple wire, you need to specify:

calibration, wire gauge, solid or stranded, insulation

Standard thermocouple wire can be ordered with high temperature insulation, while for the thermocouple extension wire there is usually no need for the high temp protection. Thermocouple extension wire should not be used in the sensing point, because of this lower ambient temperature limit. A thermocouple extension wire has often a brown outside insulation. The maximum length of an extension wire should not exceed 100ft with 20 AWG and avoid electromagnetic interferences. Subzero and vacuum application should also be mentioned when ordering thermocouple wire.

Thermocouple wires are sold in several versions:

1. with standard limits of error
2. with special initial limits of error (with certification)
3. Sub-zero applications

Thermocouple extension wire

Thermocouple extension wire for base metal types (example: type J, K or T) has the same composition as the corresponding thermocouple wire. For noble metal compositions (like type B,R, S), a different composition is used due to high pricing of the noble material. (example: Platinum) Jack's and plugs are also color coded, matching the calibration. For easier installation, wires can be stranded instead of solid. If installing thermocouple wires close to other electrical conduits (which is actually not recommanded...), use a shielded thermocouple cable. The longer the wire, the less accurate temperature readings you'll achieve and you may have to consider thermocouple wire with special limits.