| With the rapid development of my country’s economy,the society’s extensive use of oil,coal caused many harmful gas emissions.The "14th Five-Year Plan",outline has put forward new requirements for environment.Sulfur dioxide is a common polluting gas,which has a great impact on human life and health.The real-time monitoring of sulfur dioxide is the prerequisite for its governance.However,the detectors commonly used in the market will be interfered by the common component gases(H2O,CO2)and DOAS-based detectors are expensive and mostly used experimental research in universities and research institutes.Therefore,the development of a new type of sulfur dioxide detector that is not interfered by other component gases and is convenient for real-time monitoring has important social significance.Based on this background,this paper proposes a detection scheme for UV LED light source modulation combined with phase-locked amplification signal processing technology,and develops a wide-spectrum SO2 detector.The system has little interference from component gases,low cost,and high sensitivity.The minimum detection concentration is 10ppm,and the average detection error is about 5%.It meets the standards of the national environmental protection department and can be used for actual detection and application of SO2.Because it is not affected by moisture,in the future,it can be applied in the SO2 detection of herbal medicines.The main work and innovations of the thesis are as follows:1.Introduced several related sulfur dioxide gas detection methods,analyzed some of the advantages and disadvantages of these methods,pointed out their application limitations,proposed the value and significance of the project research,and discussed the development status of sulfur dioxide detection methods at home and abroad.2.Through the introduction of the SO2 molecular spectrum absorption theory,it is explained that the use of infrared bands for SO2 detection cannot avoid the absorption interference of water,and the phenomenon,mechanism,linear function and the formula derivation of Beer-Lambert law are introduced.It provied a theoretical basis for the development of gas spectrum detection and detector.3.According to the relevant design requirements of the instrument,the development and design of the detector were carried out.Discussed and determined the UV detection band of SO2,proposed a new detection scheme combining ultraviolet LED light source modulation and phase-locked amplification technology,explained the advantages of this detection scheme,and carried out the structural design of the detection system.4.According to the design requirements and the developed detection system plan,the demonstration design of the system optical path and circuit is completed.The main components of the system were selected for the survey,including light source,lens,and detector;the mechanical modules of the whole machine were designed,the relevant size parameters of each module were introduced.Processing requirements and three-dimensional diagrams of the main structure;the design of the hardware circuit system,including drive modulation circuit,signal processing circuit based on AD630,data acquisition and processing system based on LPC1758,and introduced the main circuit module functions,circuit diagrams and the basic inspection process of the detector.5.Research and comparison of instrument detection signal and related detection performance.The function and signal of the main circuit are monitored and analyzed;the gas calibration experiment is carried out under the existing experimental conditions,and the inversion formula for concentration detection is obtained;the measurement accuracy of the detector and the stability of the light source are obtained.Important performances such as the influence of water vapor and water vapor have been tested.It has advantages over infrared detectors on the market in terms of light source stability and water vapor interference,which verifies the performance of the detector’s SO2 concentration detection. |
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