5-8 Model 3321 Aerodynamic Particle Sizer
Spectrometer
Event 2
Is a valid particle event and occurs only when two zero crosses happen
during a gate window. Both the time of flight and light-scatter intensity are
recorded for this event.
Event 3
Is a coincident event, and occurs when three zero crosses happen during a
gate window. This is caused by a second particle entering the
measurement area before the previous one has left.
Event 4
Is an over range event and occurs when a second zero cross does not
occur and the window does not go away until after the timer over-ranges,
exceeds 4.096 s. This happens when a very large particle or a
recirculating particle travels very slowly through the measurement area.
Detection
Threshold
4.096µs
The second PAL is the Counting PAL, and is used by the address PAL to
record all events. Events 1, 3, and 4 each have their own location in
memory and are reported in the headers of the A, B, C, D, and S records.
The events are recorded in bins of the accumulator as reported in the A
record as follows: Event 1 in bin 32, Event 3 in bin 33, Event 4 in bin 34.
Event 2 can be totaled by adding bins 100 through 1023 of the
accumulator. Event 2 is recorded in memory according to the time of flight
reported. The side scatter intensity is also recorded for each Event 2.
The APS™ spectrometer can be configured to record data in two different
modes: uncorrelated and correlated.
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