What is a thermocouple? How does it work?

Instrumentation Temperature
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What is a thermocouple?

Two dissimilar metals are welded (joined) at one end to form a ‘hot junction’ and the other end to form a ‘cold junction’.

When there is a temperature difference between the ‘hot’ and ‘cold’ junction a mv is produced in the loop proportional to the temperature difference.

The amount mv production by a thermo-couple depends on the characteristic and type of thermocouple like ‘j’ , ‘k’ type etc.

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Thermocouple is a pair of dissimilar metal wires joined at one end, which generate a net thermoelectric voltage between open pair according to the temperature difference between the ends.

Working:

  • A thermocouple is made of two or more metals joined together to form two junctions.
    • One junction is connected to an object whose temperature is to be measured called as measuring junction.
    • Other junction is connected to an object of known temperature called as reference junction.
    • This is how Thermocouple measures unknown temperature of the object with reference to the known temperature of another object.