RTDs serve as the standard for precision temperature measurements due to their excellent repeatability and stability characteristics. RTDs provide the designer with an absolute result that is fairly linear over limited temperature ranges. RTD’s cuasi-linear relationship between resistance and temperature simplifies the implementation of signal-conditioning circuitry.
RTDs are constructed by one of two different manufacturing configurations. Wire-wound RTDs are constructed by winding a thin wire into a coil. A more common configuration is the thin-film element, which consists of a very thin layer of metal laid out on a plastic or ceramic substrate. Thin-film elements are cheaper and more widely available because they can achieve higher nominal resistances with less platinum. To protect the RTD, a metal sheath encloses the RTD element and lead wires connected to it.
RTDs are able to sense temperatures with extreme repeatability and low drift error from –200°C to +850°C. The temperature coefficient of the RTD element is positive. This is in contrast to the NTC thermistor, which has a negative temperature coefficient.
Figure. 2 More industrial RTDs
Wed, 2010-09-01 06:03
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