《光纤甲烷气体传感研究》》-毕业论文.doc

光纤甲烷气体传感研究 摘 要：瓦斯爆炸严重威胁到煤矿作业人员的生命安全，影响矿井的正常生产。矿井中瓦斯的主要成分是甲烷，有效准确地预测甲烷爆炸的相关信息关系重大。本文以甲烷为目标气体，针对光谱吸收型光纤气体传感器的解调系统进行研究。在分析甲烷气体的近红外吸收谱线的基础上，利用DFBLD光源和光纤设计了低浓度气体谐波检测系统。文中讨论了甲烷气体吸收光谱原理，并对甲烷气体吸收谱线进行了选择。分析了光谱吸收型光纤气体传感器的两种检测方法——差分吸收检测法和波长调制谐波检测法并选择了波长调制谐波检测法。建立了基于波长调制谐波检测技术的吸收型光纤气体传感器解调系统的实验模型，并对该模型进行了实验研究。结果表明甲烷气体浓度与二次谐波信号电压值成线性关系。其线性度拟合系数为0.9903，灵敏度为0.0457V/%。根据光电微弱信号检测的原理以及波长调制谐波检测的光纤气体检测模型，设计了光电微弱信号检测系统。完成了谐波检测微弱信号处理的锁相放大、高频正弦调制和倍频等电路的设计。对电路的功能及性能进行了测试，结果表明解调系统稳定性高，重复性好，灵敏度高且结构简单成本低廉。 关键词：甲烷；光纤气体传感器；谐波检测；锁相放大；倍频电路 Research on Fiber-optic Sensing of Methane gas Abstract：The gas explosion seriously threatens the security of the coal miners as well as the mine pit regular production. In the mine pit methane is the principal constituent gas, accurately and effectively forecast the information of methane explodes is very significant. In this paper, the methane gas is considered as investigated gas, and author focused on the investigation of the absorption spectra fiber-optic gas sensor demodulation systems. Based on the analysis of the near-infrared absorption lines of methane gas, a low concentration of the gas detection harmonic wave system has been designed by using the DFBLD fiber-optic light source. The principle of absorption spectra of methane gas is discussed in this paper and the absorption lines of methane gas are carefully chosen. Two detection methods of spectra absorption fiber gas sensor have been analyzed which are differential absorption detection method and wavelength modulation harmonic wave detection method which is finally chosen. A model which is based on wavelength modulation harmonic wave analysis technique has been established and the experiments have been done. The result shows that there are linear rela