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Electrostatic Classifier Model 3082 and SMPS Spectrometer Model 3938
Differential Mobility Analyzer (DMA)
The Model 3082 Electrostatic Classifier can be used with a Model 3081A
Long DMA, a Model 3085A Nano DMA, or a Model 3086 1nm-DMA. If you
have a previous-model DMA (3081 or 3085), you can purchase an upgrade
kit from TSI to make it compatible with the Model 3082.
A filtered flow loop recirculates the sheath flow. Sheath air enters the
Sheath Flow + port on the top of the DMA and passes to an annular
chamber at the top of the DMA. The flow then goes through a Dacron
®
mesh to straighten the flow. The air flows downward axially through the
classifier region. The Polydisperse Flow enters the DMA though an inlet
tube from the top and flows in an axial direction between two narrow
concentric cylinders to evenly distribute the concentric flow and
concentration distribution. This thin annular flow is introduced into the
classifier region and smoothly merged with the laminar sheath air flow.
Particles with negative charge stick to the outer electrode, whereas,
noncharged (neutral) particles are removed unaffected with the exiting
sheath flow. Positively charged particles are carried axially downward with
the sheath airflow while also being attracted radially toward the center
electrode due to the electric field. Particles with a narrow range of electrical
mobility reach a circumferential slit within the center electrode and exit the
DMA as the Monodisperse Flow. If the optional positive polarity High
Voltage is used, negatively charged particles exit the DMA.
The size-classified aerosol continues to the external CPC (if used) to be
counted.
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Summary of Contents for 3082
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