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. It is also used in diesel engines & ships, process control and laboratories for temperature measurement and control.  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.

Ceramic Beaded  A thermocouple consists of two dissimilar metallic Wires joined at one end known as hot junction. When the hot junction is heated, an emf is produced which depends on the difference between the temperature of the hot junction and the temperature of free ends known as cold junction. This thermo emf is measured by galvanometric/potentiometer metric/digital instruments, to display temperature. Read more... MINERAL INSULATED  Mineral Insulated Thermocouples & Resistance Temperature Detectors comprise of a metal sheath in which the thermo-electric elements/RTD element with conductors are embedded in highly compressed magnesium Oxide (MgO) insulation, thus providing the elements complete protection against oxidation and corrosion.  Thermocouples are available in type K, J, T, E, R, S, W, W3 and W5, simplex or duplex, in sheath diameters from 1mm to 19.05mm and length from a few cm to 200 meters or more. The hot junction is TIG welded and could be grounded (element hot junction welded to sheath tip giving faster response) or ungrounded (element insulated from sheath), one of which can be used as per control system requirement. Read more...