基于Mid-IR LED的甲烷气体浓度检测方法研究

Study of CH_4 detection method based on Mid-IR LED

在矿井和隧道中,甲烷(CH4)气体的浓度监测极为重要.首次设计了一种以中红外发光二极管作为光源的基于光谱吸收原理的高精度CH4气体浓度检测方法.该方法采用5.8kHz的交流恒流源对中红外发光二极管进行激励,中红外发光二极管产生的中红外光在气室被甲烷吸收后,照射在接收端的中红外光电二极管上,产生光电流.用高增益跨阻放大器对光电流进行选频预放大,并用锁相放大器对与气体浓度相关的电信号做进一步的检测,最后,采用由单片微处理器构成的数据采集系统对检测结果进行数据化,对数据进行降噪处理,修正检测系统的非线性误差,最终将气体浓度检测结果显示出来.该方法还对中红外发光二极管以及中红外光电二极管的工作温度进行了恒温控制,保证了中红外器件中心波长的稳定性.同时构建了以低成本中红外发光二极管器件为基础、结合微弱信号检测技术的方法验证系统.结果显示,该方法具有检测时间短、操作简单、精度高和环境适应性强等特点,是一种可行的、优点明显的CH4气体浓度测量方法.

Monitoring methane（CH4）gas concentration is very important in mines and tunnels.This paper proposes a method of CH4 gas concentration detection based on the principle of absorption spectrum,taking Mid-infrared light emitting diode（Mid-IR LED）as the light source.The method adopts 5.8kHz AC constant current source to excite the infrared light emitting diode,The middle infrared light generated by the middle infrared light emitting diode is absorbed by methane in the air chamber,and is irradiated on the middle infrared photoelectric diode,Due to the extremely weak of light current generated by photodiode,it must be preamplifier by high gain amplifier.The center frequency of the amplifier is 5.8kHz,and the bandwidth is 0.5kHz.In order to eliminate the noise,improve the sensitivity of methane detection,we designed lock-in amplifier circuit to amplify the voltage associated with the gas concentration,the lock-in amplifier bandwidth is set to 10 Hz,which can satisfy with the change of gas concentration effectively.Finally,The data acquisition system,which is composed of a single chip microprocessor,is used to make the data of the detection result,The data is processed,the nonlinear error of the detection system is corrected,and thegas concentration detection results are displayed.Moreover,the verification system based on this method was built,by using low cost Mid-IR LED devices and weak signal detection technology.The experiment displays that the proposed method has the advantages of short detection time,simple operation,high accuracy and strong adaptability to the environment,being a feasible measurement one.