Since the invention of the mercury thermometer in 1742, a variety of more elaborate thermal sensors have been developed. Various types of sensors are utilized in industrial applications, process control automated machinery and manufacturing processes. Others can be adapted for home use. Each type of temperature sensor can be placed in one of two main categories: contact thermometers and non-contact thermometers.
Contact thermometers describe most traditional thermometers. Mercury thermometers, food thermometers, and many digital thermometers all require surface contact with or immersion in the subject of the measurement. Thermocouples and RTD probes could also be classified as contact thermometers.
Infrared thermal sensors and pyrometers are the two most common types of non-contact thermometers. IR thermometers measure an object’s infrared radiation and calculate the surface temperature of the object based on that measurement. Pyrometers are thermal sensors that require a user to manually match the apparent brightness of an incandescent object (such as molten steel) to an internal filament of known temperature.
Thermal Sensors in Equipment and Machinery
Most machinery relies on temperature sensors to function properly. Generally, a thermometer or thermostat controls the cooling system of most vehicles and appliances, insuring that the engine, bearings, or other internal parts do not overheat.