Technical Note
Details
Temperature Definition
Temperature describes the hot or cold state of an object. It is measured indirectly through physical properties that change with temperature. A temperature scale defines the reading origin and unit. Common scales include Fahrenheit, Celsius, Kelvin and international practical temperature scales.
Temperature Measurement Instruments
Temperature instruments can be contact or non-contact devices. Industrial control systems most often use thermocouples and resistance temperature detectors because they are robust and can be connected directly to controllers.
Thermocouples
A thermocouple uses the thermal electromotive force generated by two different conductors. It is suitable for a wide temperature range and harsh industrial environments, but selection depends on the target temperature range, atmosphere and accuracy requirement.
Resistance Temperature Detectors
Resistance temperature detectors measure temperature through the change in electrical resistance of a material, commonly platinum. Pt100 sensors are widely used where higher accuracy and stability are required.