What is Thermocouple Extension Wire?

Thermocouples are temperature sensors which measure temperature in a unique way across many industrial applications. A detailed explanation of Thermocouples can be found in our Thermocouples guide.

Thermocouple Extension Wire is used to create a hardwearing connection between the thermocouple probe to a readout instrument and is used to extend a thermocouple signal back to the instrument. At RS, we have many types of thermocouple extension wires suitable for different types of Thermocouples such as:

J
K
L
N
R/S
RTD
S
T

It is important to note that different thermocouple types (e.g. K or S type thermocouple wire) use different mixtures of metals in the cable.

What is thermocouple extension wire made from?

Thermocouple extension wire is made from a lower grade of wire than that used in thermocouple probes, so is more economical when used at length. It's typically made with colour-coded (usually PVC) insulation applied to each wire leg.

The negative lead is usually insulated in red and the positive lead is the colour of the thermocouple. For added durability and flexibility, a metal overbraid is applied to the insulated wire. For PVC wire this is a tinned copper overbraid, and for PFA it's stainless steel. This added layer protects the wire against abrasion.

Why use thermocouple extension wire?

This extension grade wire is used to extend a thermocouple signal from a probe back to the instrument reading the signal.

Thermocouple Extension Wire generally has a lower ambient temperature limit than a thermocouple, therefore it can pass a higher temperature signal as received from the probe, however the wire element cannot be physically exposed to higher temperatures.

Thermocouple Extension Wire is effective for extension purposes in Thermocouple applications, although Thermocouple Extension Wire may not be used in the probe part of the thermocouple.

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