Design of Optoelectric Detection Circuit for Difference Absorption Gas Sensor

Since the gas infrared absorption spectrum source intensity of several in a thousand, it is even less linewidth is only several nanometers occupying the than the noise of light source. The signal of gas absorption is submerged in the noise, so it is impossible to measure the concentration of gas with spectrum absorption directly. According to the principle and parameters of difference absorption system of CH4 gas, a detection circuit consisted of the lock-in amplifier is designed. The experiment results indicated that the detection circuit can satisfy the demand of the whole system, and the limit concentration is 150×10^-6.

因为煤气的红外线的吸收光谱线宽仅仅是在 1000 占据几的来源紧张的几纳米，它是平的不到光的噪音来源。煤气的吸收的信号在噪音被沉没，因此直接与光谱吸收测量气体的集中是不可能的。根据 CH_4 气体的差别吸收系统的原则和参数，一个察觉电路由 lock-inamplifier 组成了被设计。实验结果显示察觉电路能满足整个系统的需求，并且限制集中是 150 X10~(-6) 。