Senba Sensing Technology Co., Ltd.
Analysis of Common Thermopile Sensors and Operational Amplifiers for Infrared Temperature Measurement

Analysis of Common Thermopile Sensors and Operational Amplifiers for Infrared Temperature Measurement

Thermopile sensor is often used in non-contact infrared temperature measurement, because any object higher than absolute zero can emit infrared, and the energy radiated by the object increases with the increase of the surface temperature of the object. Based on this relationship, thermopile sensor can measure the energy radiated by the object and accurately measure the surface temperature of the object.


The output of thermopile sensor only increases 50-100uv for every 1°C change of the measured object, and the output voltage change corresponding to the resolution of 0.1°C is only 5-10uv, so it's better to choose the high-sensitivity thermopile probe. In addition, according to different temperature measurement distance, probes of different field angle are selected, because the actual output voltage value of thermopile probe is the average temperature value of the object in the whole field angle range. In order to improve the signal-to-noise ratio of thermopile probe output, the equivalent resistance value inside the thermopile is also one of the key factors. The larger the resistance value is, the greater the thermal noise output will be.


Because the output signal of thermopile sensor is so weak, the voltage error after amplification also needs to be very small. This kind of operational amplifier has a main amplifier and an auxiliary amplifier, which is used to calibrate the offset voltage automatically every US level time interval, as well as clock synchronization circuit, to ensure the offset voltage as the minimum value in real time, especially for the amplification and adjustment of VLF signals.


It should be noted that the larger the offset voltage is, the greater the introduced error will be. If the impact of offset voltage is to be calibrated, the design complexity of hardware will undoubtedly be increased, the process and complexity of production line processing will be increased, and the cost will also be raised and the production efficiency will be reduced.


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