Research On Measurement Method Of Dust Concentration Signal Based On Forward Scattering

With the acceleration of China’s industrialization process,the factory’s dust emission is gradually increasing,and the resulting environmental problems are very serious,directly jeopardizing people’s health.Therefore,it is very important to quickly and accurately detect the dust concentration in the air.In view of the above background,this thesis studies the signal measurement method of dust concentration based on forward scattering theory.The main research content of this thesis is as follows:Based on the Mie scattering theory,the scattering properties of dust particles were simulated and analyzed.We selected three kinds of typical particles including dust particles,soot particles and water-soluble particles for the scattering characteristics analysis.Then we studied the variation of three typical particle efficiency factors at different wavelengths and different scale parameters,and demonstrated the feasibility of the forward scattering measurement method.This paper presents a dust concentration measurement model.For the dust particle group satisfying the uncorrelated scattering,the angle integral of the forward scattering light intensity is calculated for the dust particles in the photosensitive region within a certain solid angle,and the concentration measurement model of the particle to be tested is obtained by combining the distribution function of the dust particles.A two-light path dust concentration measurement platform based on forward scattering was built to convert the scattered light flux to the sensor voltage.In addition,A red laser with a wavelength of 650 nm was selected as the scattering source according to the simulation calculation.This paper designs an I-V conversion circuit,a regulated power supply circuit,and a weak signal amplification circuit to complete the amplification of the weak photoelectric signal of the dust particles.This article uses the acquisition card NI-PXI-6251 of LabVIEW to complete the collection of dust voltage signals.The measurement signal includes detector noise and stray light noise,and the wavelet transform method is used to denoise the collected scattering light voltage signal to extract the real dust concentration voltage signal.We use dust particles for calibration experiments of output voltage values and standard fractal concentrations.The experimental results show that the dust concentration has a significant linear relationship with the output voltage.The relative error between the measured concentration and the standard concentration calculated using the calibration equation is less than 10%,within the limits of the international standard error.Experiments have demonstrated the effectiveness of the forward scattering method for measuring dust concentration.