Yuan Feng, Hu Mai, He Yabai, Chen Bing, Yao Lu, Xu Zhenyu, Kan Ruifeng
Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China.
Rev Sci Instrum. 2020 Aug 1;91(8):083106. doi: 10.1063/5.0004742.
This paper reports the development of a compact in situ real-time concentration analysis system for methane dissolved in seawater by using a continuous-wave cavity ringdown spectroscopy (CRDS) technique. The miniaturized design of the system, including optical resonance cavity and control and data acquisition-analysis electronics, has a cylindrical dimension of 550 mm in length and 100 mm in diameter. Ringdown signal generation, data acquisition and storage, current driver, and temperature controller of the diode laser are all integrated in the miniaturized system circuits, with an electrical power consumption of less than 12 W. Fitting algorithms of the ringdown signal and spectral line are implemented in a digital signal processor, which is the main control chip of the system circuit. The detection sensitivity for methane concentration can reach 0.4 ppbv with an approximate averaging time of 240 s (or 4 min). Comparing the system's measurement of ambient air against a high-quality commercial CRDS instrument has demonstrated a good agreement in results. In addition, as a "proof of concept" for measuring dissolved methane, the developed instrument was tested in an actual underwater environment. The results showed the potential of this miniaturized portable instrument for in situ gas sensing applications.
本文报道了一种利用连续波腔衰荡光谱（CRDS）技术开发的用于海水中溶解甲烷的紧凑型原位实时浓度分析系统。该系统的小型化设计，包括光学共振腔以及控制和数据采集分析电子设备，其圆柱尺寸为长550毫米、直径100毫米。衰荡信号产生、数据采集与存储、电流驱动器以及二极管激光器的温度控制器均集成在小型化系统电路中，功耗小于12瓦。衰荡信号和谱线的拟合算法在数字信号处理器中实现，该处理器是系统电路的主控制芯片。甲烷浓度的检测灵敏度可达0.4 ppbv，平均时间约为240秒（即4分钟）。将该系统对环境空气的测量结果与高质量的商用CRDS仪器进行比较，结果显示出良好的一致性。此外，作为测量溶解甲烷的“概念验证”，所开发的仪器在实际水下环境中进行了测试。结果表明了这种小型便携式仪器在原位气体传感应用中的潜力。
