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. Such a device works on the principle of the thermoelectric effect, i.e., generating a voltage when its dissimilar metals (thermocouples) are exposed to a temperature difference.
Picture of a heat flux sensor that utilizes a thermopile construction to directly measure heat flux. Model shown is the FluxTeq PHFS-01 heat flux sensor. Voltage output is passively induced from the thermopile proportional to the heat flux through the sensor or similarly the temperature difference across the thin-film substrate and number of thermocouple junction pairs. This voltage output from the sensor's thermopile is initially calibrated in order to relate it to heat flux.
A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the Seebeck effect, and this voltage can be interpreted to measure temperature. Thermocouples are widely used as temperature sensors.
Thermocouple connected to a multimeter displaying room temperature in °C
Reference junction block inside a Fluke CNX t3000 temperature meter. Two white wires connect to a thermistor (embedded in white thermal compound) to measure the reference junctions' temperature.
Typical low cost type K thermocouple (with standard type K connector). While the wires can survive and function at high temperatures, the plastic insulation will start to break down at 300 °C.
A thermocouple (the right most tube) inside the burner assembly of a water heater
