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Last updated: June 1, 2020

What Does Thermocouple Mean?

A thermocouple is a temperature-measuring device consisting of two dissimilar conductors that contact each other at one or more points. It produces a voltage when the temperature of one of the points differs from the reference temperature at other parts of the circuit.

Thermocouples are used for temperature measurement and control, and can also convert a temperature gradient into electricity. Thermocouples are used in many industrial, scientific and OEM applications, such as:

  • Power generation
  • Oil/gas
  • Pharmaceutical
  • Biotech
  • Cement
  • Paper & pulp
  • Appliances (stoves, furnaces, toasters, etc.)

Corrosionpedia Explains Thermocouple

A thermocouple consists of two different types of metals, joined together at one end. When the junction of the two metals is heated or cooled, a voltage is created that can be correlated back to the temperature. Thermocouple alloys are commonly available as wire.

Thermocouples are simple and resilient, can be used over a wide range of temperatures (from -330°F to 4170°F (-200°C to 2300°C)), and permit great precision.

Thermocouple applications include:

  • Temperature sensors in thermostats in home appliances
  • Flame sensors in safety devices for gas-powered appliances
  • Temperature measurement for kilns, gas turbine exhaust, diesel engines and other industrial processes

In contrast to most other methods of temperature measurement, thermocouples are self-powered and require no external form of excitation. The main limitation with thermocouples is accuracy; system errors of less than 34°F (1°C) can be difficult to achieve.

The following criteria are used in selecting a thermocouple:

  • Temperature range
  • Chemical resistance of the thermocouple or sheath material
  • Corrosion, abrasion and vibration resistance
  • Installation requirements

Thermocouples are available in different combinations of metals or calibrations. The most common types of thermocouples are base metal thermocouples, while noble metal thermocouples are used in high-temperature applications. Each calibration has a different temperature range and environment, although the maximum temperature changes with the diameter of the wire used in the thermocouple.


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