E – 1777 Principles and methods of Temperature Measurement

Temperature is a principle parameter that needs to be monitored and controlled in most engineering applications such as heating, cooling, drying and storage. Temperature can be measured via a diverse array of sensors. All of them infer temperature by sensing some change in a physical characteristic be it a thermal expansion, thermoelectricity, electrical resistance or thermal radiation. There are four basic types of temperature measuring devices, each working on a different principle:

1. Mechanical (liquid-in-glass thermometers, bimetallic strips, bulb & capillary, pressure type etc.)
2. Thermocouples
3. Thermo-resistive (RTDs and thermistors)
4. Radiative (infrared and optical pyrometers)