what are the properties of thermocouples?

Question

what are the properties of thermocouples?

Answer 1

In 1821, the German–Estonian physicist Thomas Johann Seebeck discovered that when any conductor (such as a metal) is subjected to a thermal gradient, it will generate a voltage. This is now known as the thermoelectric effect or Seebeck effect. Any attempt to measure this voltage necessarily involves connecting another conductor to the "hot" end. This additional conductor will then also experience the temperature gradient, and develop a voltage of its own which will oppose the original. Fortunately, the magnitude of the effect depends on the metal in use. Using a dissimilar metal to complete the circuit creates a circuit in which the two legs generate different voltages, leaving a small difference in voltage available for measurement. That difference increases with temperature, and can typically be between 1 and 70 microvolts per degree Celsius (µV/°C) for the modern range of available metal combinations. Certain combinations have become popular as industry standards, driven by cost, availability, convenience, melting point, chemical properties, stability, and output. This coupling of two metals gives the thermocouple its name.





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Answer 2

Thermocouples are bi-metals which when joint in a junction by crimping or welding and heated by a flame or other hot substance,small voltage in millivolts are generated, the value of which is proportional to the flame temperature, example, iron-constantan, chromel Alumel and other combinations.

Answer 3

Output depends nicely on temperature.

Try http://en.wikipedia.org/wiki/Thermocouple