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What is a thermocouple?

What is a thermocouple?

  • Thermocouples are used in different temperature-sensing applications in turbines engines they are based on the principle that when two dissimilar metals are joined, a voltage will be generated voltage is directly proportional to the temperature. So, by measuring the amount of electromotive force, the temperature can be determined.

  • The thermocouple consists of two dissimilar metal wires or semiconducting rods welded together at their ends. One of the two junctions: 
1. hot junction - is exposed to the temperature to be measured
2. cold junction - is maintained at a known reference temperature.
  • the negative lead is usually shorter than the positive lead, and the large pin on a thermocouple connector is the negative conductor.
Thermocouple types:
Type J- composed of a positive leg of Iron and a negative leg of Constantan
Type K- thermocouples are composed of a positive leg of Chromel
  • When replacement a thermocouple, it is extremely important to replace it with a thermocouple of the same style and composition as specified in the maintenance manual.

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