Describe construction and working of Resistance Temperature Detector (RTD).
RTD:
Construction and working: Resistance thermometer bulbs consist of a coil of fine wire wound or in a frame of insulating material. The resistance wire itself must be homogeneous in order to avoid any localized emf. Industrial resistance thermometer always employ Pt, Cu or Ni. Resistance thermometer bulbs are generally used with a thermal well. Lead wires are used to connect the resistance bulb with the indicating element (Wheatstone bridge). Lead wires transmit the information regarding the temperature surrounding the bulb to indicating element. The electrical resistance of the sensing element changes with change in temperature surrounding it. Thus RTD is used to measure temperature in terms of change in resistance.