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How Does a CO2 Sensor Work?

A CO2 sensor works by the carbon dioxide gas molecules absorbing infrared light in accordance with the Beer-Lambert Law. Non-dispersive infrared (NDIR) sensor modules apply this principle per the schematic shown here. An infrared source emits energy through a gas sample wave, or a waveguide. A tuned optical filter eliminates all but the target wavelength for the gas of interest. In the case of CO2, this is approximately 4.3 µm. The greater the gas concentration of CO2, the lower the infrared energy reaching the detector. An onboard microprocessor evaluates the electrical signal from the detector in relation to the sensor calibration constants and other parameters and provides a signal-conditioned gas concentration output in ppm.

PTM Published on: 2021-04-26