Resistance Temperature Detector(RTD) used for temperature measurement -50 to 400 Deg.C. The system accuracy begins with proper primary sensor selection. Various considerations apply to the design of RTD assemblies. The element should be protected from shock and vibration, yet free of expansion stresses that may shift the reading. The element assembly needs to be isolated without obstructing heat flow. The outer sheath has to withstand pressure, erosion and vibration, yet it should be small enough for easy installation and rapid response to temperature changes.