Theory of Operation B-5
Figure B-3
Flow Schematic for the Electrostatic Classifier with Long DMA
The charged aerosol passes from the neutralizer into the main
portion of the Differential Mobility Analyzer (DMA), shown in
Figure B-3. The DMA contains two concentric metal cylinders. The
polydisperse aerosol (q
a
) and sheath air (q
sh
) are introduced at the
top of the Classifier and flow down the annular space between the
cylinders. The aerosol surrounds the inner core of sheath air, and
both flows pass down the annulus with no mixing of the two
laminar streams. The inner cylinder, the center rod, is maintained
at a controlled negative voltage, while the outer cylinder is
electrically grounded. This creates an electric field between the
two cylinders.