Thermopile Sensor Circuit

Cross section through a thermopile sensor showing all relevant parts table 1.

Thermopile sensor circuit.

The sensor reads the temperature over the entire area it sees. The thermopile sensor consists of a series of 116 thermoelements forming a sensitive region size of 545 µm diameter. If the open circuit test reads below 400 millivolts then the thermopile likely requires service or replacement. 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.

Parts of a thermopile sensor and their function part function thermopile chip sensing element converts radiation into voltage reference sensor measures the temperature of the sensor package i e. The sensor must only see the object being measured and nothing else to get an accurate temperature reading. A healthy thermopile in an open circuit test will read between 650 to 850 millivolts or somewhere in between. I account for this in the sketch with a constant called verr.

Thermopile infrared ir non contact temperature measurement sensors are available with various lens and filters allowing use in multiple applications from industrial pyrometers to climate controls and medical devices. The temperature of the cold contacts window filter and or lens. The circuit itself seems to add about 0 6mv to the thermopile raw reading.