TSI Instruments SIZER EEPS 3090, Руководство по эксплуатации и обслуживанию

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B-2 Model 3090/3090AK Engine Exhaust Particle Sizer
TM
Spectrometer
Rather than using a unipolar charger, a very stable and predictable
Krypton-85 radioactive bipolar charger was used (3,4). When combined
with a Condensation Particle Counter (CPC), the DMA can be stepped
through various voltages, to detect different particle sizes (5-9). Using a
computer, the voltages can be automatically stepped to generate a particle
size distribution. This was the basis for the Differential Mobility Particle
Sizing (DMPS) systems. An improvement in resolution is obtained by
continuously scanning the rod voltage with an exponential voltage ramp
and counting to generate a size distribution (10,11). This is the basis for
the current Scanning Mobility Particle Sizer (SMPS
™) system that is
commonly used to obtain high resolution size distributions of engine
exhaust particles. Unfortunately, the SMPS
™ method has a drawback in
that it takes a significant amount of time (30 seconds minimum with 60 or
120 seconds being more commonly used) to obtain a single size
distribution. This makes it unsuitable for measuring engine transients on a
second-by-second basis. This led to designs for an improved sizing
instrument that could give complete size distributions in one second or
less. The EEPS spectrometer is such an instrument.
S i z e D i s t r i b u t i o n s
The basic idea upon which the Model 3090 is based was developed at
Tartu University in Estonia. The Tartu instrument, the Electrical Aerosol
Spectrometer (EAS), was originally described in Russian Journals in the
early 1980’s (12) but was more recently published in English language
journals (13, 14, 15). The EAS was developed for ambient monitoring and
has 2 columns to cover a large size range. The EAS did not originally have
a very fast time resolution because it wasn’t needed for ambient
measurement applications. However, it was modified for fast response
(4 second time resolution) for fire detection research in the mid-1990s.
(16, 17, 18). The EEPS spectrometer is based on this fast-response
instrument. Conceptually these instruments are similar to a DMA. But,
rather than particles being drawn to the center, as in a DMA, the particles
are repelled outward to electrodes.
The EEPS spectrometer performs particle size classification based on
differential electrical mobility classification (as with the SMPS). The
charged aerosol enters the analyzer column near on-axis and above the
central rod. The particles are deflected radially outward and collected on
electrically isolated electrodes that are located at the outer wall (see
Figure B-2). The particle number concentration is determined by
measurement of the electrical current collected on a series of electrodes.