Resistance thermometers , also called resistance temperature detectors
( RTDs ), are sensors used to measure temperature. Many RTD elements
consist of a length of fine wire wrapped around a heat-resistant ceramic or
glass core but other constructions are also used. The RTD wire is a pure
material, typically platinum (Pt), nickel (Ni), or copper (Cu). The material
has an accurate resistance/temperature relationship which is used to provide
an indication of temperature. As RTD elements are fragile, they are often
housed in protective probes.
RTDs, which have higher accuracy and repeatability, are slowly replacing
thermocouples in industrial applications below 600 °C.
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