What is the difference between a thermocouple, an RTD, and a Thermistor?
A thermocouple is based on the principle that an electromagnetic force (emf) is generated when heat is applied to the junction of two dissimilar metals (sensing junction). At the other end of the wires, usually as part of the input instrument, is another junction, called the reference junction. The temperature is inferred based on the emf difference between the sensing junction and the reference junction, which is at a known temperature. Advantages of thermocouples: Low cost, rugged, small size/fast response, wide temperature range, and reasonably accurate. Disadvantages of thermocouples: Weak emf signal, calibration affected by temperature gradients and material contaminants, affected by electrical interference, calibration drifts following calibration. An RTD is based on the principle that the electrical resistance of a metal increases as its temperature increases. The RTD sensing element consists of pure metal (frequently platinum) and shows a small positive, linear change in resist
