基于强度调制的液体浓度检测系统

介绍了一种光纤传感器液体浓度实时检测系统，采用了5mW的激光二级管LD、光纤光电耦合器、U型敏感元件以覆PN结型光电二极管（PD）为主要的组成部件。光在U型敏感元件中传输时发生全反射，同时被测液体的浓度对光强进行调制，通过测量输出端电压的变化来测量液体浓度的变化。实验以食盐和蔗糖溶液为测量对象，精度可以达到0．05％，测量结果与理论分析十分相符。这个实验装置的显著优点是体积小、结构简单、测量范围宽，能够实现液体浓度的在线测量与生产的自动化。

Research of Liquid Concentration Testing System Based on Intensity Modulation

Presented a testing system with optical fiber sensor to measure liquid concentration changes in real time.The essential components in the system include a 5 mW laser diode(LD)coupled to a single-mode optical fiber,a optical fiber optoelectronic couplers(OFOC),a U-shaped sense probe,and a silicon photodiode(PD).When the beam passed through the U-shaped sense probe,it occured total internal reflection and was modulated by liquid concentration.The changes of liquid concentration can be gotten by measuring the changes of output voltage.Results were presented for salt and sucrose aqueous solutions,while providing a high resolution on the order of 0.05% concentration or better and with very good agreement with theoretic analysis.The experimental configuration is small,simple with wide measurement range.It can measure liquid concentration in real time and accomplish automatic production.