CH_4传感系统微弱光电信号处理电路的研究

Study on Faint Photoelectric Signal Processing Circuit of CH_4(Methane) Sensing System

为改善以CH4为目标气体的检测系统的信噪比,提高系统的检测灵敏度。基于微弱信号的锁定检测原理,以方波调制系统LED为光源,设计以锁相放大器为核心的微弱信号处理电路和计算机控制电路,将携带浓度信息的光强信号转换为直流电压输出。实验结果表明,电路输出电压与检测甲烷气体浓度呈线性关系。分析表明,理论上电路对甲烷浓度检测极限值为1.5×10-4。系统灵敏度可通过设计光源功率稳定电路和温度控制电路得到进一步提高。

In order to improve the signal noise ratio of the gas detection system with methane as object, and to enhance system ＇ s sensitivity, the processing circuit for faint signal and computerized control circuit with phase lock amplifier as the core are designed based on lock-in detection principle of faint signal. With square wave modulating LED light source, luminous intensity signals carrying concentration value are transferred to DC voltage output. The result indicated that the relationship between output voltage of detective circuit and methane concentration is linear. In theory, the limit concentration value detected is 150×10^-6. The sensitivity can be improved by designing light source power stabling circuit and constant temperature controlling circuit.