Research On Linux-based Online Monitoring Instrument For Multi-channel Particulate Concentration

With the rapid development of living standards and technology,atmospheric environmental pollution is increasing day by day.Air pollutants emitted from stationary sources are one of the important sources of air pollution.Stationary pollution sources refer to chemical pollutants,thermal power plants and others.According to theoretical and practical investigations,the particle size distribution of aerosols emitted from stationary sources is approximately a single-peak log-normal distribution.Three wavelengths of equipment are required to measure the aerosol concentration and particle size spectrum.In order to select the most suitable combination of incident light wavelengths,this paper designs and implements a multi-channel particle concentration monitoring system based on Mie scattering theory,which provides an important basis for the selection of key optical parameters of three-wavelength equipment.Based on the Mie scattering theory,this paper designed a multi-channel particulate concentration monitoring device that is superior to the single-channel measurement method,and studied the distribution characteristics and physical characteristics of aerosols emitted by stationary sources;on this basis,combined Mie scattering theory and multi-channel particulate concentration measurement,design unique wavelength combination of incident light.The simulation results show that the increase in the number of scattering angles improves the measurement accuracy to a small extent,and cannot compensate for the gap between its design and cost.Thus,the wavelength device and the multi-channel device select a single scattering angle optical path structure,the scattering angle is 40 degrees,and the multi-channel wavelengths are selected as 405 nm,450nm,520 nm,650nm,808 nm,940nm,1064 nm,and 1550 nm.Through the simulation program based on the Matlab,the multi-wavelength combination is simulated and verified to determine the accuracy of measuring the particle concentration and particle size distribution under different wavelength combinations,so as to select the most suitable wavelength combination for the three-wavelength device,and the wavelength combination is 450 nm,940nm,1550 nm.This paper designs the mechanical structure and software system of multi-channel particle concentration monitoring equipment according to the system design requirements and the key parameters selected by simulation.At the same time,the Linux-based upper computer software platform is used to develop the corresponding upper computer software system.The software system can calculate,store and display the measurement data,which has cross-platform characteristics.It can not only run on three wavelength devices but also on multi-channel devices.Finally,the equipment is tested through the experimental platform,and the measurement results of the particle concentration measurement instrument and the particle spectrum measurement instrument on the market are compared and analyzed.The results prove that the incident light wavelength selected in this paper can accurately measure the particle concentration and particle size distribution,the concentration error is only 6.1%,and the errors of the median diameter and standard deviation corresponding to the particle spectrum are 1.6% and 5.1%,respectively.