1 1 Wolfgang Brunnhuber , Dr. Friedhelm Schneider GRIMM Aerosol Spectrometer GRIMM Aerosol Spectrometer and Dust Monitors and Dust Monitors Measuring principle Measuring principle by Eng. Wolfgang Brunnhuber by Eng. Wolfgang Brunnhuber Grimm Aerosol-Technik 2 Wolfgang Brunnhuber , Dr. Friedhelm Schneider Part A physical background general principles of optical particle detection Part B Nanoparticles counting and sizing Agenda 3 Wolfgang Brunnhuber , Dr. Friedhelm Schneider Scale [nm] Fields: Media Materials Ions Molecules Macro Mol. Micro Particle Macro Particle Impurities Sievable 1 10 100 1,000 10,000 100,000 Light Metal Ions Saccharose Virus Activated Carbon Dust Colour Pigments Bacteria Human Hair Asbestos Diesel Soot Grimm SMPS+C Grimm SMPS+C(DMA+CPC) [nm] Grimm SMPS+E Grimm SMPS+E(DMA+FCE) models Grimm 1.108 / 1.109 Grimm 1.108 / 1.109 physical background: particle size range [µm] 1 10 100 0.1 0.01 0.001 Scale [µm] Fungal spores 4 Wolfgang Brunnhuber , Dr. Friedhelm Schneider physical background: Interaction of radiation and aerosol particles [Seinfeld & Pandis, 1998] α = π d p /λ with d p = particle diameter and λ = incident wavelength note: π d p = particle circumference, for spherical particles The interaction between incident light and a particle (solid, droplet and or gas molecules!) is strongly dependent on the particles size and the wavelength. To show this dependency, the parameter α is used. 5 Wolfgang Brunnhuber , Dr. Friedhelm Schneider physical background: dependency of particle size and wavelength on scattering [Baron & Willeke, 2001] For particle sizes much smaller than the incident wavelength (α << 1) RAYLEIGH-scattering: the oscillating electric field of the light waves induce an oscillating dipole in the particle, causing symmetrical scattering (in forward and backward directions). The Intensity of the scattered light is proportional to the sixth power of particle diameter (I ~ d p 6 ) Example: Sunlight hits gas molecules in the atmosphere, blue sky effect! α = π d p /λ with d p = particle diameter; and λ incident wavelength note: π d p = particle circumference, for spherical particles 6 Wolfgang Brunnhuber , Dr. Friedhelm Schneider physical background: dependency of particle size and wavelength on scattering [Baron & Willeke, 2001] For particle sizes in the size range as the incident wavelengt (depending on the light source! say 0.1µm-1µm) MIE-scattering: strong interaction between the particle and the incident beam, depending although on particle refractive index. No simple relation between scattered intensity and particle diameter (Mie-programs, spherical particles) α = π d p /λ with d p = particle diameter; and λ incident wavelength note: π d p = particle circumference, for spherical particles Gustav Adolf Feodor Wilhelm Ludwig Mie * 1868 † 1957
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GRIMM Aerosol Spectrometer and Dust Monitors Measuring … · 2014-07-28 · 1 1 Wolfgang Brunnhuber, Dr. Friedhelm Schneider GRIMM Aerosol Spectrometer and Dust Monitors Measuring
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