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A thermocouple is a device consisting of two different conductors (usually metal alloys) that produce a voltage proportional to a temperaturedifference between either end of the pair of conductors. Thermocouples are a widely used type of temperature sensor for measurement and control[1] and can also be used to convert a heat gradient into electricity. They are inexpensive[2], interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. 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 and system errors of less than one degree Celsius (C) can be difficult to achieve.[3]
Any junction of dissimilar metals will produce an electric potential related to temperature. Thermocouples for practical measurement of temperature are junctions of specific alloys which have a predictable and repeatable relationship between temperature and voltage. Different alloys are used for different temperature ranges. Properties such as resistance to corrosion may also be important when choosing a type of thermocouple. Where the measurement point is far from the measuring instrument, the intermediate connection can be made by extension wires which are less
