What is a Thermopile?

A thermopile is a serially-interconnected array of thermocouples, each of which consists of two dissimilar materials with a large thermoelectric power and opposite polarities. The thermocouples are placed across the hot and cold regions of a structure and the hot junctions are thermally isolated from the cold junctions. The cold junctions are typically placed on the silicon substrate to provide effective heat sink. In the hot regions, there is a black body for absorbing the infrared, which raises the temperature according to the intensity of the incident infrared. These thermopiles employ two different thermoelectric materials which are placed on a thin diaphragm having a low thermal conductance and capacitance.

Thermopile Features
The thermopile has some unique properties not offered by other detectors:
• Response to broad infrared spectrum
• No source of bias voltage or current needed
• Inherently stable response to DC radiation