NDIR-based low-cost integrated three-component gas detection system

In this study, a low-cost miniature non-dispersive infrared (NDIR) three-component gas detector is developed, consisting of an infrared light source, a four-channel thermopile detector, a signal processing circuit, and an optical gas chamber. A low-noise conditioning filter circuit and a low-power 24-bit Σ∆ADC sampling circuit are designed to achieve a compact structure and real-time measurement of multiple gases. The concentration calculation model was derived using a non-linear least squares fit based on the Levenberg-Marquardt optimisation algorithm. The experimental results show that with an accuracy of 1.96% FS in the range of 0-2.5% vol for CH4 and 1.77% FS in the range of 0-3% vol for CO2, the system is capable of measuring gas concentrations relatively accurately and in real time while reducing cost.