A thermopile is an electronic device that converts thermal energy into electrical energy. It is composed of several thermocouples connected usually in series or, less commonly, in parallel.
A thermopile is an array of several thermocouples connected in series. A thermopile with N thermocouples will output a voltage N times bigger than the one produced by a single thermocouple, increasing the sensitivity of the transducer. With enough elements in the thermopile, a useful voltage can be generated in order to control another process. This type of transducer is often used to measure heat flux.
Thermopiles do not respond to absolute temperature, but generate an output voltage proportional to a temperature difference or temperature gradient.
Thermopiles are used to provide an output in response to temperature as part of a temperature measuring device, such as the infrared thermometers widely used by medical professionals to measure body temperature. They are also used widely in heat flux sensors and gas burner safety controls.
The output of a thermopile is usually in the range of tens or hundreds of millivolts. As well as increasing the signal level, the device may be used to provide spatial temperature averaging.
Thermopiles are also used to generate electrical energy from, for instance, heat from electrical components, solar wind, radioactive materials, or combustion. The process is also an example of the Peltier Effect (electric current transferring heat energy) as the process transfers heat from the hot to the cold junctions.
Thermopiles are used along with infrared sensors. A black body absorbs the infrared radiation from the source to be measured. This heats up the thermopiles which produces an output in millivolts.
Thermopiles are used in medical applications for measuring the body temperature.
Thermopiles are also used in industrial measurement applications where they are fitted on to a suface, such as that of a bearing. The temperature of the surface can be measured.
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