Rotating multi-channel high-sensitivity integrating sphere gas sensing based on NDIR

Non-dispersive infrared (NDIR) gas detection is capable of detecting multiple gases simultaneously and has the advantages of high stability, selectivity and fast response time, making it ideal for greenhouse gas detection. However, in traditional NDIR gas sensors, the infrared detector must be paired with a bandpass filter to select the target gas, and multiple pairs of bandpass filters and detectors are required for mixed-gas testing, which makes the sensor bulky and increases the cost. Here, we propose a gas sensor based on NDIR with a rotating multichannel integrating sphere. Unlike the traditional detector array approach, we utilize the symmetry of the integrating sphere and integrate multiple filter channels along the equatorial direction. By simple rotation, multiple gases can be measured simultaneously, significantly reducing costs. At the same time, relying on the ultra-long equivalent optical range provided by the integrating sphere structure, we are able to achieve ultrahigh sensitivity while miniaturizing the sensor. Experiments show that the detection limits for five common gases at 25 degrees C demonstrate, CO2, C2H2, CH4, N2O, and CO, are 1.87 ppm, 8.52 ppm, 23.4 ppm, 3.64 ppm, and 40.66 ppm, respectively. Furthermore, we have designed a high-precision concentration reconstruction scheme for the spectrally overlapping gases, which can effectively compensate for the errors caused by cross-interference problems through algorithms. The integrating sphere system in this paper has the advantages of miniaturization multi-channel and high sensitivity, which provides a new method for NDIR mixed gas detection.