B-1
A P P E N D I X B
T h e o r y o f O p e r a t i o n
The Model 3090 Engine Exhaust Particle Sizer
TM
(EEPS
TM
) spectrometer
builds on a tradition of TSI electrical-based measurements including the
Electrical Aerosol Analyzer (EAA 3030) and Electrostatic Classifier (3071,
3080/3081/3085). The EEPS spectrometer extends this line of instruments
based on a technique developed over the last two decades by the
University of Tartu
– Estonia. This chapter gives a brief description of the
instrument and theory of operation.
E l e c t r i c a l M o b i l i t y H i s t o r y
The first electrical mobility
instrument was the
Whitby Aerosol Analyzer,
developed in the late
1960’s (1). This was
followed a few years later
by a similar but smaller
version called the EAA
(Electrical Aerosol
Analyzer) (2). These
instruments both used a
unipolar charger
assembly to place a
positive charge on the
particles. The level of
charge depends on
particle size and is
correlated by the
instrument calibration so
that the instruments can
report number
concentrations.
Figure B-1
Schematic of a Differential Mobility Analyzer
An improvement over the EAA was the development of the Differential
Mobility Analyzer (DMA) column (Figure B-1).
