Portable High-Precision System for CH4 Concentration Detection in Mines based on the Laser Mode-Hopping
LU Xu-tao1, LI Jing2, Lü Hai-feng3
1. School of Information and Communication Engineering, North University of China, Taiyuan 030051, China 2. School of Computer and Control Engineering, North University of China, Taiyuan 030051, China 3. School of Mechanical and Power Engineering, North University of China, Taiyuan 030051, China
Abstract：In order to detect rapid, portable concentration of methane in the mine, meanwhile, the system includeed a high sensitivity and a long working period, designed differential optical absorption spectroscopy method based on mode-hopping of semiconductor laser, and established wireless detection system for concentration of methane in the mine. Output wavelengths of the semiconductor laser occurred mode-hopping by modulation current of the system, so it obtained the two wavelengths close to the laser, and one is on the characteristic absorption peakof methane, while the other is not substantially absorbed. When the two beamsof light were illuminated test chamber, methane concentration of the gas chamber was solved by Bill Lambert law with the difference of the light intensity between the two beams. Light source used DFB single mode semiconductor laser from Japan Anritsu company. Experimental results show that, when the modulation current increased from 20.0 to 60.0 mA, output wavelength occurred mode-hopping when the modulation current reached 48.3 mA, and output wavelength changed to 1 651.020 nm from 1 650.888 nm. By HITRAN spectrum database, it showed that the position of the wavelength 1 650.888 nm can be used for characteristic absorption peaks, while the wavelength 1 651.020 nm was suitable for reference wavelength. On this basis, the standard concentrations of methane gas was tested in the sealed container, test data of the system was compared to the H-BD5GD410-HC portable methane detector. Test results of the system and the H-BD5GD410-HC portable methane detector were similar, but with the constant concentration increased, the detection error of the system is relatively stable, slightly better than the portable methane detector. Detection error of system were less than 0.050%, under the conditions that there were without the use of expensivephase lock or inspection phase circuit, to achieve the accuracy of better than0.10% concentration of methane detected in the mine.
鲁旭涛1，李 静2，吕海峰3 . 基于模式跳变的井下便携式高精度CH4浓度监测系统设计 [J]. 光谱学与光谱分析, 2015, 35(03): 846-849.
LU Xu-tao1, LI Jing2, Lü Hai-feng3 . Portable High-Precision System for CH4 Concentration Detection in Mines based on the Laser Mode-Hopping . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2015, 35(03): 846-849.
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