Simultaneous Detection of C₂H₂ and CO Based on Cantilever-Enhanced Photoacoustic Spectroscopy

Abstract

Gas detection based on photoacoustic (PA) spectroscopy has attracted extensive attention due to high sensitivity and portability. Herein, to achieve the simultaneously detection of the transformer oil carbide gases, C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and CO, a gas-detection system based on one cantilever beam sensor and single-pass PA cell was proposed. The infrared light beams were coupled by the coarse wavelength division multiplexer (CWDM) and fiber coupler, the vibration of the cantilever beam was measured by the vibration meter, and the gas detection experiment was carried out. The results showed that cantilever could distinguish multiple kinds of acoustic waves, in the frequency domain, the simultaneous detection of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and CO can be realized by extracting the fast Fourier transform (FFT) values at 20 and 55 Hz. The system exhibits a good repeatability, and a linear relationship between the pure PA signals and gas concentration was confirmed with the correlation coefficient greater than 0.9. In addition, the pure PA signals also show linear trend with the coupling ratio. The minimum detection limit and resolution of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> are 0.27 and 0.12 per part million (ppm), respectively, when the CWDM is used to couple the light beams, whereas they are 23.42 and 14.94 ppm of CO. Especially, it was found that the PA signals have good superposition whether the modulation frequencies of the external lasers are same or not. This article provides an idea for simultaneous detection of multicomponent in gas mixture.