Research And Application Of Dissolved Oxygen Detection Technology Based On Frequency Domain Fluorescence Lifetime

With a combination of optical principles and electronic technology,the application of optical dissolved oxygen detection technology,based on fluorescence quenching technique,has the advantages of high detection accuracy,good stability,and fast response speed compared with traditional dissolved oxygen detection methods.Thus it has received extensive attention and research from domestic and overseas well-known agencies.This method has become a research hotspot in the field of dissolved oxygen detection.An novel approach is proposed for detecting dissolved oxygen by frequency-domain fluorescence lifetime.The single-channel light source is used to detect the concentration of dissolved oxygen in water,which simplifies the optical path and circuit structure,improves the dissolved oxygen concentration detection algorithm and enhances the efficiency of the inspection process.Research results provide a high standard detection method for detection of dissolved oxygen concentration in water,which can be applied to scenarios with high accuracy,strong stability,and fast response,besides,it has certain applications for the fluorescence quenching method in other areas.Main work and research results of this paper are as follows:(1)Design of dissolved oxygen detection optical path and hardware: Firstly,analyze the dissolved oxygen detection method for frequency-domain fluorescence lifetime,determine the actual hardware requirements,and build the overall architecture of the hardware and optical path design.Then,the light path structure of the single-source fluorescence quenching method was designed because of complex structure and large volume of traditional light path structure.According to actual hardware circuit design requirements,a 24-bit resolution sinusoidal signal generating circuit that drives excitation light source and a weak current signal receiving,amplifying,filtering,and biasing circuit are designed.Finally,the mechanical structure of the overall hardware is designed for required tightness and shielding performance.(2)Implementation of Dissolved oxygen detection method research and algorithm: Firstly,based on the improvement of the optical path structure,frequency-domain fluorescence lifetime detection method was optimized,and a calibration fitting method based on the least square method was designed.Then analyze user needs,design the overall software framework and work sequence.Then for the hardware circuit control flow,the functions of driving signal generation,hardware component control and data transmission are designed.Finally,to solve the slow response speed caused by data processing,the functions of data receiving and signal processing jointly designed by the upper and lower computers are designed.(3)Analysis of system test results: Firstly,set up the experimental environment for Dissolved oxygen concentration detection,and configure different Dissolved oxygen environment.Then,test the light source driving and fluorescent signal receiving of the hardware part.Then,the linear calibration,accuracy analysis,response time,stability,and repeatability of the dissolved oxygen concentration detection equipment based on the frequency-domain fluorescence lifetime were tested and analyzed,and the proposed method for detecting dissolved oxygen was verified.Finally,test the influence of temperature and salinity to verify the anti-interference ability of the equipment.