High accuracy wide range CO2 detection method based on difference optical path NDIR

A single-channel wide-range CO2 detection method based on difference optical path NDIR (Non-Dispersive Infrared Spectroscopy) is proposed. With only one channel, multiple groups of data including variable influencing factors (such as temperature, sensor responsivity, etc.) and parameters are obtained by changing the optical path for multiple measurements. These data are processed and calculated through the Goertzel algorithm. By the differential operation in the theoretical derivation, the temperature and humidity drift of the sensor response can be calibrated. The C−∆L model is proposed to illustrate the relationship among gas concentration C, optical path length difference∆L, and sensor response. The experimental data of seven gas concentrations (0–6000 ppm) and the corresponding nine optical path lengths show that the model determination coefficient is 0.9929, and the predicted root mean square error is 0.0136. Compared with the traditional dual-channel measurement approaches, this detection method has the advantages of simple structure, high accuracy, wide range, and insensitivity to the interference caused by environmental temperature and humidity.