【作者】 王杰；

【导师】 王莉田；

【作者基本信息】 燕山大学 ， 测试计量技术及仪器， 2001， 硕士

【摘要】 随着世界经济的发展，环境污染日趋严重，环境保护已经成为各国主要研究课题。因此，近年来气体浓度检测仪成为各国传感技术领域研究的热点和重点。本课题就是基于保护环境的目的，利用近红外光谱吸收理论，研究大气污染监测仪器。它在环境监测、电力系统、油田矿井等场合有着广泛的应用前景。 由于光纤传感器本身具有的优点，使得红外光谱吸收式光纤气体传感器成为气体浓度检测的主流方向。本文通过对以往研究成果的综合和分析，指出了造成气体浓度检测灵敏度和精度不高的主要原因，提出了单谱全宽调制技术并论证了其可行性。在深刻分析乙炔光谱精细吸收谱线线型、位置和线宽的基础上，利用压电陶瓷的电致伸缩效应，对光纤光栅的中心波长进行调制，选择乙炔气体在石英光纤低损耗传输区域的最大吸收峰进行单谱线全宽扫描。通过检测光纤光栅反射谱光强和透射谱光强，并把两者进行比值运算，以消除光源波动的影响。在微弱信号检测电路设计上，采用锁定放大器提取二次谐波，检测一次谐波和二次谐波的比值，可以得到气体浓度。 本系统主要的创新点如下：1、提出单谱全宽调制的概念、理论依据和实现方法；2、首次提出利用光纤光栅的反射谱作为信号通道和透射谱作为参考通道的光强比值作为检测方法；3、通过分析单谱全宽调制，提出二次谐波检测理论以及相应的锁定放大技术。 在本课题的研究中，侧重于气体检测理论分析、方案设计和可行性分析。设计了光路、电路，并进行了部分相关实验。通过资料查阅、理论分析和系统模型设计等工作，作者认识到：光纤气体浓度检测，涉及到的理论是多学科的，有着很深的内涵，要设计一个好的气体检测系统，还有很多实际要做的工作。本论文就是给出了这样一个基本的乙炔气体浓度检测系统的基本模型，为今后高性能光纤气体传感器的研究和研制打下坚实的理论基础和提供积极的参考价值。更多还原

【Abstract】 With the development of global economy, environment pollution has been increasingly serious. Therefore environment protection is the major research project all over the world. It is worth to mention that the study on instrumentation for gas concentration detection has been research focus in sensor technology field among many nations. Based on environment protection, the present graduate project makes use of existent theories and instrumentation facilities to develop monitoring sensor for atmospheric pollution. This monitoring sensor has widespread application prospect in environment monitoring, power system, oil and mine fields. Because of intrinsic advantages of optical fiber sensor, spectrum absorption optical fiber sensor has been the mainstream of gas concentration detection. By means of comprehension and analysis of former research achievements, the present paper presents the main reason for not high sensibility and precision of gas concentration detection and advances single-spectrum full-width modulation technology. It means that, based on the thorough analysis of the fine line type, position and correspondent line width of spectrum, sinusoidal modulation voltage is employed on piezoelectricity ceramic. With piezoelectric converse effect of piezoelectricity ceramic, the center wavelength of optical fiber grating can be modulated. The maximum peak value of C2H2 at low-loss transmission area of quartz optical fiber can be selected to conduct single-spectrum full-width scan. Meanwhile reflection spectrum intensity and transmission spectrum intensity of optical fiber grating are detected simultaneously. Thus the negative effect of illuminant vibration can be eliminated by their ratio. In the circuit design for weak signal detection, the lock-in amplifier is employed to extract quadratic harmonic. Through the ratio of linear harmonic and quadratic harmonic, the gas concentration can be measured. The present graduate project has multitude innovations as following: 1. The conception, theoretic foundation and implementation method of single-spectrum full- width modulation is advanced. 2. For the first time presented is the detection approach -U- Abstract of light intensity ratio of reflection spectrum from signal channel and transmission spectrum from reference channel of optical fiber grating. 3. The detection theory of quadratic harmonic and its correspondent lock-in amplifier technology are propounded by means of single-spectrum full-width modulation. During the development of this project, the author has been mainly engaged in the task of theoretic research, scheme design and feasibility analysis for gas concentration detection. Implementation of detection circuit and experiment of theoretic demonstration are achievements of the whole research group. The author has assisted the research group leader to complete many positive assignments. From the starting involvement to material finding and system model design, the author holds an opinion that optical fiber gas concentration detection relates to multidisciplinary knowledge. In order to develop a better detection system, there are still a lot of practical works to accomplish. The present paper advances the basic system model of C2H2 concentration detection. It has played a solid foundation and provided a valuable reference for the research of high-performance optical fiber gas sensor in the future.更多还原