【作者】 陈林；

【导师】 周孟然；

【作者基本信息】 安徽理工大学 ， 控制理论与控制工程， 2007， 硕士

【摘要】 随着煤炭工业的发展,瓦斯事故越来越来成为制约煤矿安全的重要因素,瓦斯传感器对监测监控起着决定作用,因此研制开放安全可靠、高灵敏度的瓦斯传感系统具有重大的社会和经济意义。对目前具有广泛应用前景的光纤瓦斯气体传感器进行了研究,光纤气体传感器比传统传感器有无可比拟的优点,本论文旨在设计光纤甲烷气体传感系统以实时、可靠的检测瓦斯气体的浓度。本论文进行瓦斯浓度测量是基于比尔-朗伯(Beer-Lambert)定律,但是直接运用此原理进行测量,由于气体比较微弱,气体吸收较小,加上光源不稳定、光源和探测器等与光纤耦合的损耗,系统固有噪声等对检测灵敏度有很大影响,致使检测效果非常的不理想。为此,我们寻找解决这些问题的方法,本文就这些问题进行分析和研究,并在现有实验条件的基础上设计处合理的使用的光纤瓦斯传感系统,并运用LabVIEW软件平台进行直观显示。利用分子光谱理论对气体近红外选择性吸收的理论分析,给出了气体吸收测量的理论依据。并确定了甲烷气体的吸收谱线,找出适合普通石英光纤进行较长距离低损耗传输的光谱特性。根据比尔-朗伯(Beer-Lambert)定律,直接检测气体时,信号中不仅有光路干扰,还有很大部分与浓度无关,信号难以放大,检测灵敏度受到限制,差分吸收检测和谐波检测是气体吸收检测的两种基本方法。根据光源不同,系统设计有较大不同,本文给出了几种设计方案。但由于实验条件限制,本实验采用SLD产生的宽带光源,通过光纤Bragg光栅和压电陶瓷对其进行波长调制,获得窄带出射光,从而实现瓦斯气体浓度的高灵敏度测量。系统软件采用LabVIEW软件,对数据进行采集和处理,用软件代替了复杂的硬件电路,简化了设计。得到的瓦斯浓度能够在图形界面上显示,并进行保存。图43表3参48更多还原

【Abstract】 Along with the coal industry development, the gas accident more and more becomes to an important factor restricting the coal mine safety. The gas sensor plays very important role of monitoring, therefore it is significant to develop safe reliable, the high sensitivity gas sensing system. It has the great society and the economical significance. The optical fiber gas sensor has found a wide range of applicants by virtue of its various technical merits. The goal of the paper lies in designing the optical fiber methane gas sensing system to examine gas density real-time and reliably.After analyzing the theory of near-infrared selective absorption of gas, we describe the academic base of the measurement of the gas by absorption theory. The absorption spectra of methane are confirmed and the spectrum characteristic, which is fit for low-loss optical fiber to transmit a long way, is also discussed.When the gas is examined directly according to Lambert-beer law, there is not only light route interference, but also no relationship between content and density. Then the signal is very difficult to amplify, and measurement sensitivity is strictly limited. Difference absorption measurement and wavelength modulation harmonic measurement are two fundamental approaches for gas light absorption detection. For different light resource, system designs have great differences. This paper gives several design plans.As a result of experimental condition limit, this paper adopts SLD light source forming ordinary light emitting diode to get narrow band light source through wavelength modulation by Bragg grating and piezoelectric ceramic. It realizes high sensitivity examination of gas density. The software of system adopts LabVIEW software to gather and analyze the data. That simplifies the design by software instead of hardware. The gas density can be displayed in user-friendly interface and saved.更多还原