光纤气体分析传感技术的研究

Research on gas Sensing Technique by optical fiber

本文报导开发了一个光纤气敏传感系统。采用Φ5发光二极管作光源,硅光电二极管作检测器,以大芯径、大数值孔径的Y型分叉光纤束作传感介质,可用于大气及水质环境中NH_3/NH_4^+、SO_2的检测。根据不同的检测对象,选择不同的指示剂及其固定方法,采用相应的探头结构,仅用一套系统(包括一套光路,一套电路和一套计算机软件系统)即可检测不同的分析参数。系统中提出了双LED双光束补偿的设计思想,对两个气敏探头的传感机理做了系统性推导。整个系统体积小,价格低廉,性能稳定,检测灵敏度达到甚至超过了采用复杂仪器结构的光纤传感器。系统对水中NH_4^+的检测限为2μmol/L;对SO_3~2检测限为2×10^(-4)mol/L。

A gas sensing system by optical fiber is reported in this paper. According to the necessary of biochemical and biomcdical research work and detection technique, we have designed and developed a gas sensing system by optical fiber for NH3/NH4+ and SO2. In the developed system, two light emitting diodes are used as light sources, a silicon photo-diode is used as light detector, a multimould stepped bifurcate optical fiber bundle with big core diameter and great numeric aperture is used as light transmissive medium, the dyestuff is coupled to fiber with two different methods. For different gas detection, the same optical system, the same electronic circuit and one set of computer hard/and software are used coupled with corresponding fiber probes. Different from the research and development work abroad, we have presented a new design idea with double LED and double beams compensation, a new advanced gas sensing system with new optical, electronic and computerized techniques was developed. The new analytical system is compact, cheap, stable and useful, it's detective limits is the same as or better than those gas sensing systems with more complex instrument construction developed abroad. The detective limit with our system for NH4+ in water is 2μmol/L,and 2×10-4mol/L for SO2 In the paper,the systematic analysis for two gas sensing probes are introduced, the design of double beams compensation system is discussed, the response characteristics and different influences from various factors to the NH3/NH4+ and SO2 probes are reviewed in details, the experimental methods and resultants are presented.