As stated in the combinations of two dissimilar metals is known as thermocouple.

Thermo-couples are usually employed for measurement of temperatures. This is achieved by connecting an indicating instrument to the thermo-couple, as shown in and measuring thermo e.m.f. In this circuit thermo-couple acts in the form of energy and indicating instrument as a load. this arrangement in the pyro-meter. Such pyro-meters are cheap in cost and can be used to measure temperature up to 1,400⁰C.

The materials used in practices depend upon the temperature range to be measured ; thus, copper-constantan couples are suitable for temperatures up to about 400⁰C, iron-constantan couples up to about 900⁰C and a couple made of platinum and platinum iridium alloy is suitable for measurement of temperatures up to about 1,400⁰C,

Thermo-couples are also used for operation of relays or electronic control.


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