Measurement of Oxygen Concentration Using Tunable Diode Laser Absorption Spectroscopy

Abstract

230031 2 合肥工业大学仪器科学与光电工程学院, 安徽 合肥 230009 摘要 采用可调谐半导体激光吸收光谱(TDLAS)技术， 利用氧气在 760 nm 波段的吸收谱线对氧气浓度进行实时在线 测量。研制了基于 TDLAS 直接吸收技术的氧气检测系统， 采用压控放大器设计了自动增益控制模块， 实现了对光谱 信号幅度的精确控制， 解决了现场测量中信号幅度波动的问题； 采用归一化洛伦兹函数实现 Voigt 函数的近似计算， 并 结合 Levenberg-Marquardt 非线性拟合算法实现了对光谱吸光度曲线的快速 Voigt 线型拟合， 以适应实时在线检测需要。 实验结果表明， 该算法可以实现吸光度曲线的 Voigt 线型拟合， 对固定浓度的氧气进行连续测量得到系统的最低检测 限为 523×10 -6 m， 系统的标准偏差为 1.75%。检测系统稳定可靠， 满足实时在线氧气浓度检测应用。 关键词 光谱学; 可调谐半导体激光吸收光谱; 自动增益控制; Levenberg-Marquardt 非线性拟合; 氧气浓度测量 中图分类号 O657.3 文献标识码 A Abstract The tunable diode laser absorption spectroscopy (TDLAS) technology and oxygen absorption lines near 760 nm are used to realize real-time on-line measurement of oxygen concentration. A detection system based onTDLAS direct absorption technique is designed. In order to solve signal amplitude fluctuation for on-site measurement, an automatic gain control module is designed using voltage controlled amplifier to achieve precise control of the spectrum signal amplitude; generalized Lorentz function is adopted to realize the approximate calculation of Voigt function combining Levenberg-Marquardt nonlinear fitting method to realize fast Voigt profile fitting of the absorbance spectrum curve, to meet the requirement of real-time on-line detection. Experimental results show that the algorithm can achieve Voigt profile fitting of absorbance curve. A fixed concentration of oxygen is continuously measured. Minimum detection limit of the system is 523 × 10 -6 m, and standard deviation is 1.75%.Detection system is reliable and meets the real-time on-line oxygen concentration detection applications.

Evaluation and test of cross interference of coal mine gas sensing equipment

“…Laser technology, also known as TDLAS tunable semiconductor laser absorption spectroscopy technology, is to detect the concentration of target gas by means of tunable light source+harmonic absorption [8] . Its detection principle is similar to the infrared principle, and also according to Lambert Beer law, the concentration of target gas can be obtained by measuring the attenuation energy [9] .…”