Compact Multigas Sensor Using Laser Absorption Spectroscopy Combined With the Spectral Matrix Compensation Method

Here, a compact multigas sensor using tunable diode laser absorption spectroscopy (TDLAS) combined with the spectral matrix compensation (SMC) method is developed. Each gas measurement unit, assisted with highly integrated circuits and a stable miniaturized gas multi pass cell, can effectively distinguish the types of industrial gases and conduct subsequent inspections. Compared with traditional time-division, frequency-division, and optical multiplexing techniques, this sensor avoids the interference introduced by hardware. Moreover, facing the common problem of mutual interference in gas measurement under complex conditions, a new SMC method is proposed to address the aliasing spectral demodulation of overlapping absorption lines. In a proof-of-concept experiment, the simultaneous detection of oxygen (O2), methane (CH4), acetylene (C2H2), and carbon monoxide (CO) in a complex environment is realized successfully. The measurement results demonstrate that the limits of detection (LODs) of this sensor for O2, CH4, C2H2, and CO are 0.14%, 0.86, 1.01, and 0.31 ppm, respectively, and the precisions for long-term measurement are 0.03%, 1.05, 0.05, and 0.08 ppm, respectively. Meanwhile, in the interference test, with the increase of CH4 concentration, the impact on 10-ppm CO becomes greater, but the fluctuation is no more than 0.6 ppm. In summary, this sensor can not only fulfill multigas measurement and aliasing spectral demodulation but also further expand the application prospects of TDLAS.