test facilities

Fine and ultrafine particles measurement

SMPS: Scanning Mobility Particle Sizer.

Although this equipment may not be used to study in a simple way transitive phenomena, it offers a very good precision in the sub-micron domain : it can measure particle size distribution of an aerosol between 7 nm and 900 nm.

Particles diameters given by this analysis are electrical mobility diameter which may easily be compared to aerodynamics diameters.

Results are usually given as size distribution number (bar-plots or size distribution function) with 64 size classes per decade.

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SMPS: Electrical mobility analysis principle

T he principle of the electrostatic classifier is based on the monotonic relationship between electrical mobility and particle size with singly charged particles.

To ensure a fixed percentage of particles carrying one unit of charge, the particles are introduced to a bipolar charge where they undergo frequent collisions with bipolar ions. This process is known as bipolar charging or "neutralization". As a result, an equilibrium state is obtained, with known percentages of particles carrying no charge, a single charge, or multiple charges. These aerosol particles are then measured with the differential mobility analyzer. The mobility distribution, and hence size distribution, can be determined from the measurement.

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Particle counting

Submicrometer particles are drawn into the Condensation Particle Counter and enlarged by condensation of a supersaturated vapor into droplets that measure several micrometers in diameter. The droplets pass through a lighted viewing volume where they scatter light. The scattered-light pulses are collected by a photodetector and converted into electrical pulses. The electrical pulses are then counted and their rate (calculated) is a measure of particle concentration.

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Contact: frantz.gouriou@certam-rouen.com