Development Of Particle Concentration Detecting System Using The Light Scattering Method

With the increase of smog in the production and living environment,dust pollution has increasingly attracted people's attention.At present,particulate matter concentration is an important indicator in atmospheric environmental monitoring.Therefore,it is of great significance to protect the environment and prevent the occurrence of diseases,by studying efficient and reliable dust concentration monitoring methods and mastering the distribution and variation of atmospheric dust.The light scattering method can carry out real-time online measurement at a long distance,and has been widely used in the field of particulate measurement because of its wide applicability,high precision,and good repeatability.In this paper,a particle concentration detection system based on light scattering method is designed.According to Mie scattering theory analysis and experimental research,the particle concentration detection system is optimized from the aspects of photosensitive area,background noise and detection system.For the optical system,the photo-modulation template is used to optimize the structure of the photosensitive region;light traps are optimized by the tapered structure;and the scattered light collection system is optimized by the combination of collecting lens and iris.With the above optimized structure,the system background noise is reduced,and the signal-to-noise ratio of the system for the measurement at low concentration is improved.For the signal acquisition system,S2386 photodiode and LF353,OPA277 operational amplifier were selected,and a three-stage amplification signal processing system was designed,to add the functions of offset and gain adjustment.Offset adjustment cancels the dark current signal interference of ambient light and photodiode.Gain adjustment improves the signal-to-noise ratio of the system at low concentration measurements.It realizes high(H)and low(L)two-speed detection,and achieves high accuracy and high reliability of the particle concentration detection system.In terms of signal processing,combined with single-particle pulse signal processing methods and group particle photometric voltage processing methods,and considered the influence of Brownian motion on the fluctuation of dust particle concentration,this article establishes a theoretical model for inverting the mass concentration of dust particles with the combination of pulsed signals and photometric signals,to improve the accuracy and sensitivity of the system at low concentrations.In accordance with the requirements of the"Light Scattering Digital Dust Tester Verification Procedure",the correction and measurement of the dust meter's K value were completed by the weighing method,and then the consistency and linear correlation were analyzed.Through the calibration,the measurement range of the L-speed of the measuring instrument reaches 0-1.5g/L with the precision of 2mg/L;the measurement range of H-speed concentration reaches 0-20mg/L,and the precision is 20mg/m~3.The measurement results show that the method used in this paper has high accuracy and reliability,which meets the actual measurement requirements,so it can be widely used in real-time monitoring of dust concentration within ambient air in industrial and mining enterprises and public places.Therefore,the research results of this paper greatly reduce the cost of dust quality measurement instruments and provide a type of instrument used in a large range for the prevention and control of atmospheric pollution.