Design and implementation of differential mid-infrared carbon monoxide detector

Based on wide-band infrared (IR) light source and dual-channel pyroelectric detector with detection channel of 4.66 μm and reference channel of 3.95 μm, a differential mid-infrared (MIR) carbon monoxide (CO) detector is designed and implemented. In order to reduce the detection limit and improve the detection sensitivity, an open spherical mirror chamber is designed and fabricated according to the divergence angle of the light source. The CO detection system is established using the welded and debugged detection circuits, a series of CO gases with different concentrations are prepared, and gas concentration calibration experiment is carried out. Experimental results indicate that after the amplifying circuit, the signal-to-noise ratios (SNRs) of the two channels are 17.58 dB and 18.46 dB, respectively, and the detection error of this system is less than 9% in 0%–4% measuring range. The detection sensitivity in the low concentration range is approximately 0.05%. 6 h measurement on the 0 ppm sample gas shows that the fluctuation range is about ±0.02%, and the measurement standard deviation is about 0.89%.