甲烷(CH4)是大气环境监测、工业过程控制、煤矿生产安全等多个领域中需重点监测的气体之一, 研制CH4传感器具有广泛的应用价值。利用CH4分子在3.31 μm附近的基频吸收带并选择其在3038.5 cm-1的吸收线作为目标谱线, 研制了一种基于中红外室温、连续、单模带间级联激光器(ICL)的CH4传感器。该传感器采用可调谐激光直接吸收光谱技术以及长光程(54.6 m)吸收光谱技术测定CH4气体浓度。自主研制了高灵敏、低功耗的激光器温度控制器和电流驱动器, 编写了基于LabVIEW的数据产生、采集与处理程序。利用体积分数为2.1×10-6的CH4标准气体和气体稀释系统配备了不同浓度的CH4气体样品, 开展了传感器的性能测试实验。根据传感器标准差的分析结果, 当采样周期为2.5 s时, 传感器的1σ检测下限约为1.1×10-8。利用该传感器对室外大气中CH4浓度进行了连续84 h的监测, 结果证实了所研制CH4传感器的工程实用价值。

Methane (CH4) is one of the most important gases to be monitored in many fields such as atmospheric environment monitoring, industrial process control and coal mine production safety. Developing CH4 sensor has a wide application value. Based on the fundamental frequency absorption band of CH4 molecule near 3.31 μm and its absorption line at 3038.5 cm-1 as the target line, a CH4 sensor based on the mid-infrared room-temperature, continuous and single-mode interband cascaded laser (ICL) is developed. The sensor uses tunable laser direct absorption spectroscopy and long-path (54.6 m) absorption spectroscopy to measure CH4 gas concentrations. A high sensitivity, low power laser temperature controller and current driver are developed independently, and the program of data generation, acquisition and processing based on LabVIEW is coded. The CH4 standard gas with a volume fraction of 2.1×10-6 and a gas dilution system are used to prepare CH4 gas samples with different concentrations. And the performance test of the sensor is conducted. According to the analysis of the standard deviation of the sensor, when the sampling period is 2.5 s, the lower 1σ detection limit of the sensor is about 1.1×10-8. The sensor is used to monitor the concentration of CH4 in the outdoor air for 84 h continuously. The results confirm the engineering practical value of the developed CH4 sensor.