Research On Key Technologies Of Miniaturized Sulfur Dioxide Analyzer

Sulfur dioxide（SO₂）is one of the main pollutants in the atmosphere.Grid monitoring of its concentration is the primary task for the prediction and control of SO2pollution sources.At present,most of the analytical instruments used in atmospheric sulfur dioxide detection are measured by electrochemical sensors,which have problems such as the lowest detection limit and short service life,while the devices used in optical sensors are mostly imported products,which have high cost and difficult maintenance,and cannot meet the requirements of atmospheric grid monitoring technology.In view of the above problems,this paper studies the key technologies of the miniaturized atmospheric sulfur dioxide detection device based on the high-precision and pollution-free ultraviolet fluorescence method.According to the principle of photoluminescence,the mechanism of fluorescence generation was analyzed,and the theory of single-wavelength and multi-wavelength excitation fluorescence analysis was introduced to establish the theoretical unit model of sulfur dioxide detection.On this basis,it is deduced that the fluorescence intensity generated by excitation is positively proportional to the concentration of sulfur dioxide gas,which provides a theoretical basis for the subsequent study of the optical path part and signal acquisition system.The miniaturization optimization design and simulation study of air chamber structure are carried out.ZEMAX software was used to simulate and optimize the fluorescence acquisition optical path of the optical path part of the detection device.The optimized optical path acquisition efficiency was increased by 4.98 times.In order to increase the residence time of the gas to be measured in the main chamber,a photosink is added to the air path of the detection device.The rationality of the design is verified by FLUENT software.On this basis,the structure of the miniaturized testing device and the shading and air tightness of the instrument are preliminarily designed.The circuit part design and system software program part design of miniaturized analysis device.In order to ensure that the fluorescence signal collected in the photoelectric conversion process is not distorted,the hardware circuit is mainly designed for the data acquisition circuit of the photomultiplier tube.The software program part to the single chip computer program,the upper computer program design as the main body.The core part of MCU program is analog-to-digital conversion program,FSMC storage and read,network port communication program;The upper part mainly includes the display and preservation of the waveform of photomultiplier tube.Lab VIEW and Keil u Vision5 software were selected to complete the hardware and software design of the miniaturized analysis equipment.Wavelet threshold optimization variational mode decomposition algorithm is used to reduce the noise of SO₂ detection signal.The miniaturized UV fluorescence detection platform was built and the debugging of each module and the whole device of the system was completed.In order to verify the experimental setup,the same concentration and different concentration experimental tests were carried out.At the same concentration,the standard deviation of the device is less than 1.76ppb;At different concentrations,the fluctuation range was lower than 5.68ppb,the linear correlation coefficient between the measured concentration and the actual concentration was 0.9945,and the return error was less than 1.73ppb.The test results are in line with the test requirements,and the device design is reasonable and feasible.This study is conducive to the miniaturization of sulfur dioxide analysis equipment,the establishment of a grid sulfur dioxide detection system,and the prediction and treatment of sulfur dioxide pollution sources to provide a large number of reliable data support.