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  • The Working Principle of Thermopile Infrared Sensor – Thermoelectric Effect

    The Working Principle of Thermopile Infrared Sensor – Thermoelectric Effect

    Thermoelectric Effect(Seebeck Effect)

      If two different materials or objects A and B which have the same material while with different work function, when connected at the hot end (Hot Junction Area), opened at the cold end (Cold Junction Area), and the temperature gradient between the hot end and cold end is ΔTHC, so at the cold end there is going to be a thermoelectromotive force Vout.

    yysensor- sensor structure

      When the external infrared radiation irradiates the absorption area of the detector, the absorption zone absorbs the infrared radiation and converts it into heat energy. A temperature gradient will be generated in the hot junction area and the cold junction area. Through the Seebeck Effect of thermocouple material, the temperature gradient can be converted into voltage signal output.


    Thermoelectric Effect (Seebeck Effect)

    Filter (the characteristic of IR filter is optional): select infrared band, avoid other wavelength of light to affect the sensor.

    Cap: the supporting mechanical structure of IR filter.

    TPS Chip: to sense the infrared signal which passing through the IR filter.

    Header: the supporting mechanical structure of chip.

    Chip Thermistor(Optional): monitor the cold junction area temperature of TPS chip.

    ASIC processing circuit chip (optional, conditioning signal output ): conditioning the analog output signal of TPS chip.


      It can be seen that the working principle of the thermopile sensor chip is the twice physical conversions of "light-thermal-electricity". Any object above absolute zero (including the human body) emits infrared rays, if select the appropriate wavelength through the infrared filter (5-14μm band window), when the infrared sensitive material on the chip absorbs the infrared heat and turns the light into heat, resulting in the temperature rise of the absorption region, the temperature difference between the absorption zone and the cold junction zone is converted into a voltage output through hundreds of sets of micro thermocouples series connection, and the infrared signal is detected after the voltage output is generated.


      Seeing from the structure, the Sunshine Technologies's thermopile infrared sensor is different from ordinary products, its structure is "hollow out". There is a key technical difficulty for this structure, that is, how to lay a layer of 1μm thick suspension film on an area of only 1 mm2, and ensure that the film can have enough conversion rate to convert infrared light into electrical signal output, so as to meet the signal strength requirements of the sensor. It is precisely because the Sunshine Technologies has conquered and mastered this core technology that it can break the long-term monopoly of foreign products at one stroke.

    Post time: Dec-01-2020