Thermocouple Wire

Thermocouples allow for accurate temperature measurement in a range of industrial applications. Thermocouple wire or cable is a crucial component for their function. Our range, comprising popular variants such as T and K type thermocouple wire as well as thermocouple extension wire, has all you need to guarantee reliable temperature readings.

We stock products from leading manufacturers including Olympic Wire and Cable Corp., Belden, and our own quality, cost-efficient RS PRO line. You're ensuring high performance by selecting thermal coupling wire from any one of our carefully chosen stocked brands.

Browse our thermocouple wire types below, apply relevant filters to narrow down your options, and tap the PDF icons for in-depth technical information. You can then place online orders for quick and convenient shipping.

Alternatively, read more about this product's function, types, and uses below, and get in touch if you have any questions.

What is thermocouple wire?

Used for measuring temperature in a range of applications including extreme environments, thermocouples rely on high-quality wiring to produce reliable readings. They feature two thermocouple wires made from different metals or metal alloys.

These wires are joined at the 'hot' end of a thermocouple to create a temperature measurement junction, with the 'cold' end known as the reference junction. The measuring junction may be exposed or covered by a metal sheath.

There are various types of thermocouple wire to suit different thermocouples and applications. Their function is different from electrical wire, which is used to carry current and communication signals.

How do thermocouples work?

Knowing how thermocouples work helps with understanding the function of thermocouple wire.

In short, heating the connection point of both wires at the hot end creates a thermoelectric current called a Seebeck current. Heat then transfers from the hot end, or measuring junction, to the cold end, or reference junction.

This current, typically small enough to be measured in microvolts, then gets translated into a precise temperature reading. One thermocouple wire needs to be positively charged and the other negatively charged for a thermocouple device to function correctly.

What are the different thermocouple wire types?

There is a broad range of thermocouple wire types, all classified differently depending on their metal composition, stability, accuracy, and temperature range. The most common types include:

• K type thermocouple wire, which uses chromel - a nickel and chromium alloy - and alumel, a nickel, aluminum, manganese, and silicon alloy. These wires typically measure temperatures from -328°F to 2300°F.
• J type thermocouple wire, which uses iron and constantan, a nickel and copper alloy. They measure temperature within a range of -346°F to 1400°F.
• T type thermocouple wire, which features copper and constantan and measures a range of -454°F to 698°F.
• E type thermocouple wire, using chromel and constantan to measure between -454°F to 1598°F.

Other available types include B, N, R, and S. Thermocouple color can aid with identifying types, as the negative wire is typically red and the positive wire is color-coded according to type. Different countries use different codes, however. Importantly, your thermocouple wire type should match your thermocouple type for correct function.

Thermocouple grade wire vs. thermocouple extension wire

Thermocouple wire and thermocouple extension wire may both form part of a thermocouple device. But while the former is used at the measuring junction to read the temperature, the latter is used to extend the signal to where it can be safely read. This is because thermocouples are often used in harsh environments not suitable for people, with the temperature display placed far from the measuring junction.

Thermocouple extension cable is insulated to protect against environmental factors, though they aren't as extreme as those encountered at the measuring junction. This allows for the use of lower specification, lower price extension wire.

Thermocouple compensating cable has a similar function and is usually a cheaper option. It's also less accurate, however, and cannot withstand the same temperature range as extension wire.

Where is thermocouple cable used?

Thermocouple wire is, by extension, used wherever thermocouples are used to measure temperatures. This might include extreme heat environments, such as automobile and aerospace diagnostics, plus extreme cold, such as freezers.

Other examples include food preparation, smelting, and power generation plants.

Why choose the RS range of thermocouple wire?

Stability and precision are essential for thermocouples, so it's important to use the best wires possible. Our vast range of types and trusted manufacturers allows you to take dependable readings wherever you may need them.

We've made it easy to select the most suitable products and order them online. As North America's largest automation and control distributor, you're ensured quick and convenient shipping too.

Browse our thermocouple cable selection below and get in touch if you have questions about our products or processes. Be sure to explore our expert advice hub too for relevant guides on all things electronics and automation.