For temperature measurement in the range, -200°C to + 850°C Resistance Temperature Detector (RTD) is preferred to thermocouple and other sensors because of its higher accuracy, reliability, compact size and faster response. RTDs find use in almost all industries like plastic and rubber processing, food industries, pharmaceuticals, chemical & petrochemical plants, and power plants.

RTDs are available with single or double resistance elements and in 2, 3 or 4 wire circuits. Various types of protection sheaths for protection of the element and screw-in threaded bushes either fixed (welded) or adjustable by screws (for non-pressure application) or by compression fitting (for pressure application) for mounting are available.

RTD normally consists of spring-loaded insert, outer protecting sheath with mounting connections and cast aluminum terminal head. The insert assembly consists of Pt 100 element with silver/copper connection leads, insulated by ceramic multibore insulating tube/beads in a brass or stainless steel sheath with ceramic terminal block and brass terminals attached to a spring loaded arrangement.