Research On Key Technologies Of Miniature Atmospheric Ozone Analyzer

Ozone has become one of the main air pollutants,and accurate monitoring of its concentration is the primary task for ozone pollution warning and treatment.At present,although there are atmospheric ozone analysis instruments in China,the instruments used in grid atmospheric monitoring are mainly electrochemical sensors,and there are problems such as low detection accuracy and insufficient service life.The instruments used in optical methods are mostly dependent on imports and have high cost,which cannot meet the needs of grid atmospheric monitoring in China.In order to solve these problems,this thesis studies the key technologies of miniature atmospheric ozone analyzer based on high-precision and non-pollution UV absorption method.Based on the UV absorption strategy,the Beer-Lambert absorption law was modified by introducing interference factors such as Rayleigh scattering and Mie scattering.The theoretical model of the actual instrument for ozone detection was deduced,and the relationship between the response of the photoelectric detector and the atmospheric ozone concentration was obtained.On this basis,the calculation method of the minimum detection limit of ozone concentration and the main factors affecting the minimum detection limit of ozone concentration were obtained.Finally,the factors affecting the ozone detection accuracy and the detector noise were studied.It lays a theoretical foundation for the subsequent research on optical system and signal processing.The most important key technology to realize miniaturization is the miniaturization of analyzer chamber.In order to achieve the purpose of miniaturization,White chamber is used as the chamber of the miniaturization analyzer.ZEMAX software is used for optical simulation and optimization in the study of optical path of the gas chamber.The optimized optical path can meet the accuracy of the national standard under the premise of 50 % reduction of the gas chamber volume.The simulation also provides a solution to the problem of low mirror utilization in White’s chamber,and lays a foundation for further study of larger optical path and smaller chamber.On this basis,the preliminary design of micro-gas chamber structure and instrument gas path is carried out.The second and third key technologies studied in this thesis are the core hardware circuit of the micro-analysis instrument and the detection program of the system.This is the key to ensure the accuracy of instrument detection,especially the minimum detection limit.The hardware circuit aims to improve the acquisition accuracy of ozone signal and reduce power consumption,and focuses on the optimization design of the signal acquisition circuit of photoelectric detector.The core part of the software is high precision A / D conversion program.The noise in ozone signal is removed by ensemble mode decomposition.Using Altium Designer18,STM32 Cube MX and other software,the hardware and software design of the instrument are completed.The circuit simulation software and ST-Link hardware simulator are used to simulate and verify the performance of the amplification circuit of the photodetector and the execution of the program.This study is helpful to realize the miniaturization of instruments,to build a grid-based atmospheric ozone monitoring system,and to provide accurate data support for the early warning and management of air pollution.