基于可调谐激光吸收光谱技术的免校准硫化氢气体传感器

Calibration-free Sensor for hydrogen sulfide detection based on tunable laser absorption spectroscopy technique

为了提供一种快速、敏感的硫化氢(H_2S)气体检测装置,本文基于可调谐二极管吸收光谱技术,利用分布反馈式激光器作为光源建立了一种传感器。所选激光器的波长扫描范围覆盖了H_2S的近红外强吸收波段,1578.128nm波数处被选为H_2S目标检测谱线。利用锁相放大器同时解调一次谐波(1f)和二次谐波(2f)信号,且1f信号相对于2f信号的归一化处理使传感器达到免校准测量的效果,从而抑制由于光路、电路及光强振动等因素产生的干扰。质量流量计被用来配置0~100 ppm H_2S标准气体,以此验证该传感器特性。实验结果表明,该传感器具有良好的线性度和稳定性,同时,响应时间约为20s,通过阿伦方差分析得到传感器在30s最佳积分时间内检测限为160ppb。这一敏感的H_2S气体传感器能够应用于开放光程下环境监测,同时对于其他领域的实时监测有着重要意义。

In order to provide a fast, accurate and sensitive hydrogen sulfide （H2S） detection device, the paper built a sensor based on tunable diode laser absorption spectroscopy （TDLAS） through a distributed feedback laser （DFB） as optical source. The laser wavelength scanning range covers the strongest absorption band of H2S. H2S ab- sorption line at 1578. 128nm is selected as target detection spectral line. A digital lock-in amplifier is used to demodu- late the first harmonic （If） and the second harmonic signal （2f） signals simultaneously. Normalization of the 2f signal by If signal enables the sensor for calibration-free measurement so that the interference from light path, circuit and vi- bration can be restrained. Mass Flow Controller is used to configure 0-100ppm （parts-per-million） H2S standard gas for validating sensor performance. The results show the sensor has good linearity and stability, and the response time is about 20s. Moreover, the detection limit achievement by Allan variance is 160ppb （parts-per-billion） with an integra- tion time of 30s. The sensitive H2S sensor can be applied to environmental monitoring in opening light path, and it is meaningful for real-time detection in many other fields.