红外与激光工程, 2017, 46 (8): 0817003, 网络出版: 2017-11-07   

锯齿波调制半波扫描技术对甲烷检测系统的性能改进

Methane detection system performance improvement based on sawtooth modulation half-wave scanning technology
作者单位
1 吉林大学 仪器与电气工程学院, 吉林 长春 130012
2 山东省科学院自动化研究所, 山东 济南 250014
摘要
为了能够在复杂的环境下实现甲烷气体浓度的高精度和高稳定性检测, 在基于光谱吸收原理的光纤甲烷检测系统的基础上, 提出了利用锯齿波调制的半波扫描技术, 较大程度改进了系统的性能指标。采用锯齿波调制光源的方式, 同时对光信号进行波长调制和强度调制, 实现对甲烷气体的洛伦兹吸收线型扫描。锯齿波调制的方式能够解决信号链路噪声、环境噪声等随机信号对光强造成的干扰, 消除光源波长漂移对检测带来的影响, 且实现了积分处理, 进一步提高检测精度; 但由于甲烷吸收光谱的对称性, 采用通用的全波扫描方式, 气体吸收光强后进行微分处理会出现正弦型曲线, 无法准确确定吸收的光强所对应的数字量; 而采用半波扫描方式, 气体吸收光强后进行微分处理只出现凹型曲线, 可以准确确定吸收的光强所对应的数字量。实验结果表明: 采用锯齿波调制的半波扫描方式, 可以准确测得甲烷气体浓度; 测量范围为0%~10%, 精度由100 ppm提升到10 ppm(1 ppm=10-6), 稳定性由0.3%提升到0.01%。该系统经过改进后在复杂环境下受温度影响小, 精度高, 稳定性好, 抗干扰能力强。
Abstract
In order to achieve high accuracy and high stability of methane gas concentration in complex environment, this paper proposed the half-wavelength scanning detection method which using sawtooth modulation based on spectral absorption principle, and this method greatly improved the performance index of the system. In the process of detection, the method of sawtooth modulation realized wavelength modulation and intensity modulation of Distributed Feedback(DFB) laser, scanned Lorentizen absorption linear of methane gas. And it improved the accuracy of detection through eliminating the measurement error and the influence of laser wavelength drifting. Due to the symmetry of methane absorption spectra, relative to full-wave scanning would appears sine curve after differential circuit and could not establish the relation between absorption intensity and digital value, the half-wave scanning would appear concave curve after differential circuit, and could establish the relation between absorption intensity and digital value. The experimental results show that this method could accurately measure methane gas concentration, and the measurement range of methane gas concentration is 0%-10%, the accuracy increased from 100 ppm to 10 ppm(1 ppm=10-6), stability is increased from 0.3% to 0.01%. The system was not affected by temperature in complex environment and has high accuracy, good stability, and strong anti-interference capacity after improvement.

曾祥豹, 王海旭, 王忠民, 周天水, 崔洪亮, 常天英. 锯齿波调制半波扫描技术对甲烷检测系统的性能改进[J]. 红外与激光工程, 2017, 46(8): 0817003. Zeng Xiangbao, Wang Haixu, Wang Zhongmin, Zhou Tianshui, Cui Hongliang, Chang Tianying. Methane detection system performance improvement based on sawtooth modulation half-wave scanning technology[J]. Infrared and Laser Engineering, 2017, 46(8): 0817003.

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