Resistance Temperature Detectors (RTDs)

RTDs are sensors used to measure temperature by associating the resistance of the RTD element with temperature. The RTD element is made from pure material, most commonly platinum, but also nickel and copper. Platinum is a noble metal and has the most stable resistance-temperature relationship over a large temperature range.


A thermocouple is a temperature sensing element that operates on the principle that when two dissimilar metals are junctioned and the junction is heated, they produce a low voltage (millivoltage) which is proportional to the temperature. Thermocouples have a predictable and repeatable relationship between temperature and voltage. They are used widely in higher temperature applications because they can withstand greater temperatures than resistance temperature detectors (RTDs), and are less expensive in most cases.