为了实现对甲烷和二氧化碳双气体一体化测量,设计了以两个窄带中红外发光二极管(LED)作为甲烷和二氧化碳测量光源、以两个光电二极管(PD)作为探测器敏感元件的双LED-PD光学测量结构,研制了中红外甲烷二氧化碳双气体传感系统。对谱线及光学器件的选择、双LED光源脉冲电流调制、温度补偿算法进行了研究。根据甲烷和二氧化碳气体的红外线吸收光谱特征进行光学测量结构的设计,利用LED器件高速响应特性完成双光源脉冲电流调制时序算法,即采用窄脉冲模式进行电流驱动。在温度实验分析的基础上,采用中值归一数据预处理得到温度影响因子,然后对温度影响因子进行线性拟合得出温度补偿算法。实验结果表明:传感系统的平均功耗低至38.3 mW;甲烷测量误差最小为0.06%(体积分数),二氧化碳测量误差最小为0.05%(体积分数),可满足煤矿中甲烷和二氧化碳双气体浓度低功耗、稳定可靠实时测量的要求。

A mid-infrared methane and carbon dioxide dual-gas sensor system is developed herein to realize the integrated measurement of methane and carbon dioxide. A dual LED-PD(light-emitting diode-photodiode) optical-measurement structure with two narrow-band mid-infrared light-emitting diodes as the light source for methane and carbon dioxide measurements and two photodiodes as the detector sensing elements are designed. Furthermore, the selection of spectral lines and optical devices, pulse current modulation of double LED light source, and the temperature compensation algorithm are studied. The optical measurement structure is designed based on the infrared absorption spectrum characteristics of methane and carbon dioxide gas, and the pulse current modulation timing algorithm of double light sources is completed by using the high-speed response characteristics of LED devices, that is, the current is driven by narrow pulse mode. Based on the analysis of temperature experiment, the temperature influence factors are obtained through the data preprocessing of median normalization, and then the temperature compensation algorithm is obtained by linear fitting. Experimental results indicate that the average power consumption of the sensor system is as low as 38.3 mW; the minimum measurement error of methane is 0.06% (volume fraction), and the minimum measurement error of carbon dioxide is 0.05% (volume fraction). The system can satisfy the requirements of low power consumption and stable and reliable real-time measurement of methane and carbon dioxide concentrations in coal mine.