Product Overview
1-3
H o w i t W o r k s
The Model 3082 Electrostatic Classifier consists primarily of an impactor to
remove large particles (outside the size range of interest), a charger to
neutralize the charges on particles, a controller to control flows and high-
voltage, and a Differential Mobility Analyzer (DMA) which separates
particles based on their electrical mobility. When using the classifier for
particle sizing, a CPC placed downstream of the classifier counts particles
as they exit the DMA.
Polydisperse submicrometer aerosol passes through a bipolar diffusion
charger (also called an aerosol neutralizer), establishing a bipolar-
equilibrium charge level on the particles. Particles receive either positive,
negative, or zero charge(s). The particles then enter the DMA and are
separated according to their electrical mobility. This parameter is inversely
related to particle size and proportional to the number of charges on the
particles.
In the particle generation mode, the particle size of the monodisperse
aerosol exiting the classifier is selected using the display screen on the
front panel. When using the classifier for particle sizing, it can be operated
in the following modes:
Underpressure
mode
When the flow rate of the polydisperse aerosol is set by
a CPC or any other vacuum source downstream of the
classifier. Air is drawn through the DMA, a useful
practice when sampling from aerosol at or near
atmospheric pressure.
Overpressure
mode
When the flow rate of the polydisperse aerosol is set by
the aerosol source entering the Classifier. The aerosol is
pushed through the DMA. Overpressure operation is
best when generating aerosols from pneumatic
nebulizers or other pressurized systems.
How it works:
1. An impactor removes large particles and measures flow.
2. A neutralizer creates a well-characterized charge distribution on the
particles.
3. Inside a Differential Mobility Analyzer (DMA), the charged particles
experience an electrical field that causes them to move through the
gas in which they are suspended.
4. The number of particles per size exiting the DMA can be measured by
an external particle detector, such as a CPC. A CPC can count single
particles to provide accurate counts, even at low concentrations.
Summary of Contents for 3082
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