thermopiles

A thermopile is an electrical device that converts thermal energy into voltage using the Seebeck effect. It consists of a series-connected array of thermocouples, so the small voltage produced by each junction adds up to a usable signal. The overall output is proportional to the temperature difference between the hot junctions and a cold reference, or, in infrared (IR) detectors, to the radiant power heating the front surface.

In infrared thermopile sensors, the front face absorbs incident IR radiation, heating the hot junctions and generating a millivolt-level signal. This voltage is then amplified and conditioned to produce either a calibrated temperature reading or a signal proportional to the incident radiant power. Thermopiles can also be used as heat-flow sensors in non-IR applications, where the temperature difference across the device drives the output.

Applications include non-contact temperature measurement with infrared thermometers and pyrometers, flame sensing in gas appliances, radiometric and solar-energy instrumentation, and portable gas detectors. They are valued for simplicity, ruggedness, low power consumption, and the ability to operate without an external power source for the sensing element.

Typical thermopile outputs are small (millivolts) and require signal conditioning, including amplification and sometimes cold-junction compensation and linearization. Construction emphasizes a balance among sensitivity, response time, and environmental stability, with many devices integrating basic electronics to improve accuracy and ease of use.