Study On Particle Generator And Verification System

Many countries in home and abroad use the standard particle to calibrate the PM2.5 monitoring instrument, but the fine particles’physical and chemical properties will change easily in the air, which would lead to a huge deviation between its production and application. As to this problem, on the foundation of normal standard particles, we have studied a nondestructive technology of detection based on Mie scattering to monitor the standard particles’size and mass concentration.First of all, we analyze and derive the fundamental formula of Mie scattering. Then on the basis of fundamental formula of Mie scattering, we do some simulation with MATLAB to study the relationship between the particle’s size and particle’s refractive index and the wavelength of the incident light with the intensity of scattering light. Besides, based on the basic theory of Mie scattering, we deduce the relation of scattering light’s intensity and the particle cloud mass concentration.Based on the theoretical foundation of Mie scattering, we design and develop an instrument which combines photometric measurement of the particle cloud and optical sizing of single particles in a single optical system.With the instrument, we study on particle size monitoring with the polystyrene spheres and the mono disperse aerosol. According to the experimental results, we can get the following conclusion. The instrument’s repeatability is good. As the particle size increases, its discrimination voltage also increases gradually. And the instrument can distinguish the two sizes which are close to each other. At the same time, we study on particle cloud mass concentration monitoring with the mono disperse aerosol. The particle cloud mass concentration is proportionate to its average voltage. Then we get the linear relationship between voltage value and the mass concentration.