TSI Instruments 3082, Operation And Service Manual, Page: 196 / 225

B-14 Electrostatic Classifier Model 3082 and SMPS Spectrometer Model 3938
A particle with a certain mobility may exist as a small particle with a single
charge or as a larger particle with multiple charges. Either has the same
mobility and is removed by the system with the monodisperse air flow.
Refer to Wang and Flagan (1990) for the effect of multiply charged
particles on the data analysis. Figure B-6 shows the relationship between
the diameter of particles with a single charge and collector rod voltage for a
Model 3081A Long DMA.
q = 20 lpm
q
10000
1000
100
10
0.001 0.01
0.1
1
Particle Diameter, Dp, µm
sh
= q
a
< 4 lpm
s
C
o
ll
e
c
to
r
R
o
d
Vo
lta
g
e
V
,
Vo
lts
Figure B-6
Collector Rod Voltage as a Function of Particle Diameter for Normal Operating
Conditions of the Long DMA [Agarwal and Sem, 1978]
The Equations listed above do not account for diffusion broadening. This is
an important factor in particles below 50 nm. For the more comprehensive
formulas, refer to work by Stoltzenburg [1988].
Once the particles are classified according to electrical mobility, their
concentration is measured by a CPC or Electrometer.