基于一次谐波的光谱吸收式甲烷气体传感器设计

Design of a spectrum absorptive methane gas sensor based on the first harmonic signal

甲烷气体检测是工业生产、环境监测和科学研究领域中的一个重要研究课题.该文在基于波长调制技术的光谱吸收式光纤气体检测方法的基础上,分析了一次谐波信号的数学模型,提出了一种基于一次谐波设计的光纤甲烷气体传感器的实施方案,设计精确的电流和温度电路控制垂直腔面发射激光器,利用锁相放大器AD630提取一次谐波信号幅度,实现对不同浓度的甲烷气体进行测量.实验结果表明,一次谐波信号幅度与浓度存在着很好的线性关系,分辨率达到20ppm.该系统消除了光源波动的影响,工作稳定,简化了结构,调试简便.

Methane gas detection is one of the most important research subjects in industrial production, environmental monitoring and scientific research. This paper analyzed the mathematical model of the first harmonic signal based on wavelength modulation of spectrum absorption and optical fiber gas detection method, and proposed an implementation plan of optical fiber methane gas sensor based on the first harmonic signal. Accurate current and temperature circuit were designed to control vertical cavity surface emitting laser （VCSEL） and lock-in amplifier AD630 was used to extract the first harmonic information to measure different concentrations of methane gas. Extensive experiment results showed that there is a good linear relationship between the concentration and the first harmonic signal; the resolution ratio is 20 ppm. This system eliminated the influence of light source fluctuation, worked stably, simplified the structure, and debugged easily.