文档介绍：基于谐波检测的甲烷气体光纤传感器的研究设计
摘要
本文研究了新型的光纤甲烷气体浓度的检测系统。从甲烷的分子结构出发,研究了甲烷分子的红外吸收谱线并选取合适的吸收峰。根据比尔朗伯定律,建立了谐波检测技术的数学模型。其可以有效将光源波长精确锁定在气体吸收线中心,并消除光强波动等共模噪声带来的误差。
研究了DFBLD的工作原理及其作为系统光源的优点,并针对其特点设计了驱动和温控电路。介绍了光电探测器的特性,设计了一系列信号检测电路(包括正弦波发生电路、倍频电路、前置放大电路和滤波电路)。研究了数字锁相放大器的结构及其工作原理。分析了气室及其与光纤的耦合。最后基于LabVIEW设计了虚拟示波器。
关键词:甲烷;光纤传感器;谐波检测;分子光谱;DFBLD;锁相放大器;虚拟仪器
Abstract
In this paper, a new type of optical fiber methane gas detection system isdiscussed. According to the molecular structure of methane, the infrared absorption spectra of methane molecule are studied and the appropriate absorption peaks is selected. According to the law of beer-lambert, a mathematical model of harmonic detection technology is established. It can lock wavelength in the gas absorption line center effectively, and can eliminate the errors of light intensity fluctuations caused mon mode noises.
Working principle and advantages of DFBLD as the light source is studied. And according to its characteristic, the drive and temperature control circuits are designed. The characteristics of photoelectric detectors are described. A series of signal detection circuits are designed, including sine wave generating circuit, multiplier circuit, pre-amplifier circuit and filter circuit. The structure and working principle of digital lock-in amplifier is studied. Gas chamber and its coupling with fiber is analyzed. Finally the virtual oscilloscope is designed based on the LabVIEW.
Keywords: Methane; Optical fiber sensors; Harmonic detection; Molecular spectra; DFBLD; Lock-in amplifier; Virtual instrument
第一章绪论
甲烷是化工、煤矿生产中引起瓦斯爆炸最直接的有害气体。甲烷是无色无臭的气体,且不溶于水,化学性质稳定,非常不易检测。%,上限为15%,快速、准确检测甲烷气体的体积分数,对工矿安全运行,生产生活有着至关重要的作用。此外,我国许多城市使用甲烷作为生活用气。同时甲烷也被认为将成为温室效应的最主要成分,甲烷的吸收截面要比现在的主要温室气体二氧化碳的吸收截面高出大约23倍,大气中的甲烷浓度大约以每年1%~%的速度递增。如何对矿井甲烷进行可靠、高效、实时监测,一直是矿业生产中的焦点问题,是能源、化工行业安全生产的重要保证,是生态环境保护的可靠手段。快速、准确地对易燃、易爆、有毒、有害气体进行监测、控制已经成为目前全世界亟待解决的首要问题之一。因此开发一种安全、可靠、灵敏度高的甲烷检测报警系统具有巨大的经济和社会意义。
气体检测方法
荧光吸收法、化学材料法、气相色谱法以及