Practical AM-4 module circuit schematic designed using TGS4160 sensor

By using the TGS4160 sensor and amplifying it with an op amp with high input impedance and low bias current, and then doing some simple calculations, the signal can be measured in the range of CO2 concentration of 300 to 5000 ppm. The signal range is from 0 to several hundred ppm. The millivolt voltage signal can be used for high-precision A/D sampling. If the AM-4 CO2 sensor module provided by Figaro is used, it can be directly applied to automatic ventilation systems or CO2 gas monitoring. This module has an internal A/D converter, and the data has been sampled and processed. The voltage signal it outputs has a linear relationship with the CO2 concentration value. The output voltage signal is 0~3.0V, which is equivalent to a CO2 concentration of 0~3000ppm. In addition, this module also provides relay transfer control signals. When the CO2 concentration is higher than the set value, the output transfer control signal is high level 5V, which can make the red LED light up; otherwise, it will transfer the control signal to low level 0V to make the LED light up. However, the setting value of this module is step-by-step rather than continuously adjustable. It is divided into four levels (can be realized through jumpers on the circuit board). Table 1 and Table 2 respectively provide the concentration value of the threshold switch signal and the jumper connection method. The practical circuit schematic diagram of the AM-4 module is shown in Figure 1.

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