Development of a Homemade Chopper and Its Application to
Photoacoustic Spectroscopy for CO2 Measurement
PENG Jie1, 2, WANG Rui-feng1, CAO Yuan1*, MEI Jiao-xu1, WANG Gui-shi1, LIU Kun1, GAO Xiao-ming1, 2, CHENG Gang3
1. Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
2. University of Science and Technology of China, Hefei 230026, China
3. State Key Laboratory of Ming Response and Disaster Prevention and Control in Deep Coal Mines (Anhui University of Science and Technology), Huainan 232001, China
Abstract：In photoacoustic spectroscopy, periodic modulation of light sources is one of the necessary conditions for generating photoacoustic signals. The modulation can only be realized using mechanical choppers for some light sources, such as infrared radiation sources applied in broadband photoacoustic spectroscopy. However, a commercial chopper is unsuitable for miniaturized photoacoustic spectroscopy instruments due to its large size and high cost. In this paper, we carried out the design and development of a homemade chopper and its application to carbon dioxide (CO2) detection by photoacoustic spectroscopy. The chopper control circuit was designed based on the STM32 microcontroller technology, and a comparison experiment between the homemade chopper and the commercial chopper was conducted. The experimental results showed that the photoacoustic signals produced by both had a good consistency, verifying the feasibility and reliability of the homemade chopper, which can satisfy the application requirements of photoacoustic spectroscopy. Then, the research of photoacoustic spectroscopy for measuring CO2 was carried out based on the homemade chopper, and the effect of humidity on the CO2 photoacoustic signal was analyzed. It has been shown that water vapor significantly accelerates the molecular relaxation rate of CO2, thus improving the amplitude of the photoacoustic signal of CO2. The Allan deviation result showed that the detection sensitivity for CO2 of the photoacoustic spectroscopy system was found to be 5 μL·L-1 at an average time of 200 s. Compared with the CO2 before humidification, the minimum detection limit of CO2 was improved by a factor of 2.4 after humidification. The homemade chopper is characterized by easy integration and has reference or application value for developing high-sensitivity photoacoustic spectroscopy instruments.
Key words：Photoacoustic spectroscopy; Optical chopper; Carbon dioxide; Trace gas
彭 杰，王瑞峰，曹 渊，梅教旭，王贵师，刘 锟，高晓明，程 刚. 斩波器研制及其应用于光声光谱测量CO2的研究[J]. 光谱学与光谱分析, 2024, 44(12): 3364-3370.
PENG Jie, WANG Rui-feng, CAO Yuan, MEI Jiao-xu, WANG Gui-shi, LIU Kun, GAO Xiao-ming, CHENG Gang. Development of a Homemade Chopper and Its Application to
Photoacoustic Spectroscopy for CO2 Measurement. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2024, 44(12): 3364-3370.
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