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棱镜气室相较于传统渐变折射率透镜(GRIN)气室在灵敏度调节性及抑制干涉噪声方面优势明显。基于比尔-朗伯(Beer-Lambert)定律在气体弱吸收时的近似表述,以大气环境为背景,利用背景扣除和谐波检测技术,实现了常压下甲烷不同体积分数水平(0~20%)的检测。依据实测的甲烷在不同体积分数时的直接吸收谱,结合现有分布反馈式激光二极管(DFB-LD)光源选择2ν3带的R5支(1648.212 nm)作为被测吸收峰。气体配置过程中的在线实验表明系统示值与体积分数变化间线性关系良好,而且系统的稳定性和动态响应特性理想。该系统可根据不同现场环境的甲烷体积分数水平,通过步进电机调节气室内有效吸收光程,动态调整系统灵敏度,可作为煤矿巷道或天然气管道沿线的瓦斯监测仪器。
Prism cells have a significant advantage over sensitivity and interference suppression noise when compared to traditional graded index lens (GRIN) cells. Based on the approximate expression of Beer-Lambert’s law in weak gas absorption, using background subtraction and harmonic detection technology, atmospheric volume fraction (0-20% ) Of the test. According to the measured direct absorption spectra of methane in different volume fractions, R5 branch (1648.212 nm) of 2ν3 band was chosen as the measured absorption peak in combination with the existing DFB-LD light source. In-line experiments in the process of gas configuration show that the linear relationship between the system indication and the change of volume fraction is good, and the stability and dynamic response of the system are ideal. The system can dynamically adjust the sensitivity of the system by adjusting the effective absorption optical path of the gas chamber by a stepper motor according to the methane volume fraction level in different site environments and can be used as a gas monitoring instrument along a coal mine roadway or a natural gas pipeline.