RESISTANCE TEMPERATURE DETECTORS (RTDs) Temperature DetectorsRTDConstructionThe RTD incorporates pure metalsFigure 1 Electrical Resistance-Temperature Curvesor certain alloys that increase inresistance as temperature increasesand, conversely, decrease inresistance as temperaturedecreases. RTDs act somewhatlike an electrical transducer,converting changes in temperatureto voltage signals by themeasurement of resistance. Themetals that are best suited for useas RTD sensors are pure, ofuniform quality, stable within agiven range of temperature, andable to give reproducibleresistance-temperature readings.Only a few metals have theproperties necessary for use inRTD elements.RTD elements are normally constructed of platinum, copper, or nickel. These metals are bestsuited for RTD applications because of their linear resistance-temperature characteristics (asshown in Figure 1), their high coefficient of resistance, and their ability to withstand repeatedtemperature cycles.The coefficient of resistance is the change in resistance per degree change in temperature, usuallyexpressed as a percentage per degree of temperature. The material used must be capable of beingdrawn into fine wire so that the element can be easily constructed.IC-01 Page 2 Rev. 0
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