Investigation Of Dust Density Measurement Based On Scattering Theory

Dust density measurement based on the principle of light scattering by individual particles is developed, i.e the flux scattered from dust which is illuminated under definitely intensity incident beam in the air is proportional to the dust density. The dust density is an important index which signs the quality of air, meanwhile, it is widely used in many fields such as environmental protection, petrochemicals, coal, ocean, water conservancy, metallurgy, building materials and geology, etc.After analyzing the bane of the air pollution, the text elucidates the necessity of the dust test, then introduces the application and development of optical dust test, compares a few method which is generally used in dust test, after analyzing these method, some related physical concepts, formulas and meanings in Mie Scattering Theory are summarized and illustrated, which will lay a solid foundation for further theory research. Furthermore, based on classical Mie's theory ,analysis the effect of particle diameters,index of refraction and incident wavelength on the light scattered light intensity, compare with Rayleigh scattering and Mie scattering, its error will low of 1% in the condition of particulate in the air is smaller, the density is lower, more even, which is the literature[1] discussed. So by Rayleigh scattering formula, we deduce the theories basis of density test under certain condition, which is applied in choosing suitable sensor, designing dust test system. In physically applied, the system had measured the dust relative density outside the Suzhou University of physical experiment center for 36 days, compare with API (converse to the density of PM10), which is forecast by national environmental protection bureau everyday. Meanwhile, it shows that the system test value is quite consistent to the PM10 density. Finally, The test analyzes the system errors. Because the system takes the semi-conductor laser machine as light source, takes the light electricity diode as light electricity receiver, with MCU to measure and control, having the advantage of smaller, lighter, operating simple, low power etc. Therefore, it is widely used in mineral business enterprise and public place etc to real time test.