What are Thermocouples?


Thermocouples, of T.C. for short, is a device that is used to convert heat into electricity. It can also work reversely by converting electric current into heat.

How do Thermocouples Work?

There are 2 wires made of dissimilar metals connected at one end to form a junction. When the said junction is heated, electricity will flow through the wire. Heated electrons will begin to cross the junction on their own. The electrons will lose potential energy and gain kinetic energy because of the properties of the different metals. Thermocouple creates a very small voltage but many thermocouples can be combined together in order to produce a larger voltage. This is also known as thermopile.

Thermocouples do not only produce electricity from heat; they can also produce heat from electricity, and even cold from electricity like a refrigerator. When 2 dissimilar wires are connected at both ends, some voltage source will make current flow through the loop and this will lead to one junction getting hot and the other becoming cold. The electrons gain kinetic energy as they cross the hot junction. This is why the metal is hot. On the other hand, the electrons lose kinetic energy as they cross the cold junction and this is what makes the junction cold.

It is indeed not easy to measure the accurate voltage that a thermocouple produces when heat is applied to the junctions, because the voltmeter wires that are connected to the thermocouple is definitely made of a different metal than the thermocouple’s wires. This means the connection between a voltmeter and thermocouple is another thermocouple itself.

Uses of Thermocouples

One of the most popular examples for the use of thermocouples is gas heaters with pilot flames. The thermocouples are stacked in order to form a thermopile so that it can generate sufficient voltage from the heat of the pilot flame to keep the gas valve open so that it can supply gas to the pilot flame. Once the gas runs out, the flame will extinguish and the voltage across the thermopile decreases tremendously, which brings about the closing of the electric gas valve. Other ways in which thermocouples are used are CPUs, as well as to monitor temperatures in freezers and air conditioners.


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