Thermopile is a device that converts thermal energy into an electrical signal. A thermopile is composed of several thermocouples connected usually in series or rarely in parallel.
A thermopile is a series of thermocouples interconnected in series, each of which consists of two different materials with a large thermoelectric power and opposite polarities. The thermocouples are placed through 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 an 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.
With a couple of thermocouples connected in series. The two top thermocouples are a connected junction are at temperature T1 while the two bottom thermocouple junction is at temperature T2. The output voltage from the thermopile delta V is directly proportional to the difference in temperature or T1-T2, across the thermal resistance layer and the number of thermocouple junctions pairs.
Applications of thermopiles:
- Non-contact temperature measurement in the process industry
- Handheld non-contact temperature measurement
- Thermal line scanner
- Commercial building HVAC and lighting control
- Security human presence and detection
- Black ice detection and early warning
- Blood glucose monitoring
- Automatic HVAC control
- Fire detection in transportation tunnel
- Aircraft flame and fire detection
- Automatic exhaust gas analysis