Simultaneous CH4/CO Measurement at Atmospheric Pressure Using a Single 2.3 μm Laser and a Dual-Gas Cross-Interference Cancellation Algorithm

• Published in: IEEE transactions on instrumentation and measurement Vol. 71; pp. 1 - 9
• Main Authors: Yu, Di, Song, Fang, Zheng, Chuantao, Hu, Lien, Ma, Yanming, Zheng, Kaiyuan, Zhang, Yu, Wang, Yiding, Tittel, Frank K.
• Format: Journal Article
• Language: English
• Published: New York IEEE 2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Absorption; Algorithms; Carbon monoxide; Carbon monoxide (CO); Coal mines; Complexity; cross-interference cancellation; Distributed feedback lasers; Filtration; Fire detection; Gas lasers; Gas sensors; Infrared detectors; Infrared lasers; Interference; laser absorption spectroscopy; Laser applications; Laser modes; Lasers; Methane; methane (CH₄); Mining industry; Near infrared radiation; Occupational safety; Polynomials; Selectivity; Sensors; Signal to noise ratio; Spectroscopy; Temperature sensors; Time measurement; trace gas sensing
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2021.3138105

A simultaneous methane (CH 4 ) and carbon monoxide (CO) dual-gas sensor system for coal mine safety applications is highly desirable and yet challenging, from the perspective of complexity and cost. A single <inline-formula> <tex-math notation="LaTeX">2.3 \mu \text{m} </tex-math></inline-formula> distributed feedback (DFB) laser has been utilized in dual-gas sensor to solve the problems in cost and setup complexity. However, there is dual-gas cross-interference to be addressed in single-laser-based dual-gas sensor. To suppress the interference caused by absorption line overlapping, a novel two-step (<inline-formula> <tex-math notation="LaTeX">2s </tex-math></inline-formula>) second harmonic (<inline-formula> <tex-math notation="LaTeX">2f </tex-math></inline-formula>) algorithm based on polynomial fitting (<inline-formula> <tex-math notation="LaTeX">2s </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">2f </tex-math></inline-formula>-Polyfit) method was proposed for the single DFB laser-based near-infrared dual-gas sensor. A Herriott absorption gas cell was designed with a ~25 m optical path length. Numerical simulations and measurements were carried out to investigate the reported dual-gas cross-interference cancellation method. The signal-to-noise ratio (SNR) with the <inline-formula> <tex-math notation="LaTeX">2s </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">2f </tex-math></inline-formula>-PolyFit algorithm was improved by ~53 dB compared to the scheme without the algorithm. The limit of detection (LoD) of CH 4 was 0.97 parts per million in volume (ppmv) with a 0.4-s averaging time and it was further decreased to 62 parts per billion in volume (ppbv) with a 224-s averaging time. The CO measurement precision is 0.23 ppmv with a 0.4-s averaging time. With increasing averaging time, a measurement precision of 11 ppbv with a 212-s averaging time was obtained. Field experiments were carried out to evaluate the sensor performance for early fire detection and CH 4 gas leakage monitoring. The reported novel <inline-formula> <tex-math notation="LaTeX">2s </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">2f </tex-math></inline-formula>-PolyFit algorithm-based dual-gas sensor with no additional requirement on hardware shows enhanced selectivity and antiinterference ability compared to the infrared dual-gas sensor using a traditional sensing architecture with two lasers.