A dual-gas sensor for simultaneous detection of methane and acetylene based on time-sharing scanning assisted wavelength modulation spectroscopy

Abstract

Methane (CH₄) and acetylene (C₂H₂) are important bioscience and chemical gases. The real-time monitoring and analysis of them have important research value in industrial process control. The time-sharing scanning assisted wavelength modulation spectroscopy (WMS) technique is developed for real-time and simultaneous detection of CH₄ and C₂H₂. This system involves two near-infrared distributed feedback (DFB) lasers and a compact multipass cavity with an effective optical path of 52.2 m. The selected strong absorption lines of methane and acetylene are located at 6046.96 cm-1 and 6531.7 cm-1, respectively. The experiment environment is conducted at room temperature 23 °C and pressure 760 Torr. The sensor performance, including the minimum detection limit (MDL) and the stability, was improved by eliminating the influence of light intensity fluctuation using the WMS-2f/SAW technique. Allan deviation analysis indicates that a MDL of 0.1 ppm for CH₄ and 0.2 ppm for C₂H₂ are achieved with 1-s integration time. And the instrument response time is about 44 s through the continuous analysis of standard gases. This sensitive, simple, reliable, and lowcost dual-gas sensor is very suitable for applications in the field environment, chemical process, and many other gas-phase analysis areas.

Keywords: Acetylene (C(2)H(2)); Allan deviation; Dual-gas sensor; Methane (CH(4)); Time-sharing scanning assisted wavelength modulation spectroscopy.