TDLAS气体检测系统及其集成化研究

发布时间：2018-04-30 22:09

本文选题：TDLAS + 集成化　；参考：《电子科技大学》2017年硕士论文

【摘要】：随着我国近年来大气污染问题越来越严重,如何对大气污染物实时检测成为国家治理环境污染问题的首要核心。在众多检测方法中,可调谐半导体激光光谱吸收(TDLAS)技术凭借其高灵敏度和高精度等优点逐渐在气体检测领域得到广泛的应用。现有的TDLAS气体检测系统多为采用分离式仪器搭建的系统,系统构成复杂,不能移动并且操作繁琐。本文在分离式TDLAS气体检测系统的基础上,将系统的主要功能模块(激光器及)驱动电路部分、气室、光电探测及调理电路部分和数据处理部分)进行单板集成或模块化,主要工作包括以下就几个方面:首先,利用FPGA设计一个基于DDS的频率、幅值和相位均可调的波形发生器,并以此完成对激光器驱动电流的调制;基于FPGA实现对激光器工作温度的控制,并测试了电流源与温控源模块功能特性。其次,在光电探测与调理电路部分,为了提高信号的信噪比,减小后端数字滤波的压力,运用了抗混叠滤波和过采样技术,对前端数据进行调理,并对设计细节进行了描述。再次,在数据处理部分中,利用FPGA来实现改进型直接数字采样式数字锁相放大器,详细的描述了该锁相放大器中的滤波器和开方运算模块的设计,并对数据截断引起滤波器滤波效果差异进行了仿真测试。最后,完成集成化TDLAS气体检测系统测试平台的搭建,对直接吸收和波长调制情况下系统对甲烷-氮气混合气体浓度测量的稳定性和精度进行测试,并且分析了温度对谐波信号的影响。
[Abstract]:With the more and more serious problem of air pollution in China in recent years, how to detect the air pollution in real time has become the primary core of national environmental pollution control. Among many detection methods, tunable semiconductor laser absorption spectroscopy (TDLAS) technology has been widely used in the field of gas detection due to its high sensitivity and high accuracy. Most of the existing TDLAS gas detection systems are built with separate instruments. The system is complex, unable to move and cumbersome to operate. Based on the separated TDLAS gas detection system, the main function modules (laser and drive circuit, gas chamber, photoelectric detection and conditioning circuit and data processing part) of the system are integrated or modularized. The main work includes the following aspects: firstly, using FPGA to design a waveform generator which can adjust the frequency, amplitude and phase based on DDS, and to modulate the driving current of the laser; The operating temperature of the laser is controlled based on FPGA, and the functional characteristics of the current source and the temperature control source module are tested. Secondly, in the part of photoelectric detection and conditioning circuit, in order to improve the signal-to-noise ratio and reduce the pressure of back-end digital filtering, anti-aliasing filtering and over-sampling techniques are used to adjust the front-end data, and the design details are described. Thirdly, in the part of data processing, we use FPGA to realize the improved digital phase-locked amplifier of direct digital sampling style, and describe the design of filter and square operation module in the phase-locked amplifier in detail. The filter effect difference caused by data truncation is tested by simulation. Finally, the test platform of integrated TDLAS gas detection system is built, and the stability and accuracy of methane nitrogen mixture gas concentration measurement under direct absorption and wavelength modulation are tested. The influence of temperature on harmonic signal is analyzed.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN249

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