New Focus 3501 - Front Panel Operation; Wheel; Sync

10
Wheel
The user may select from single or double slot wheels to perform single or
dual path experiments. Different wheel apertures may be selected to accom-
modate the chopping frequency of interest. The table below summarizes
wheel choices and chopping frequency ranges.
Wheel Type Lowest Frequency Highest Frequency
(slots) (F
outer
) (F
outer
)
60 120 Hz 6.40 kHz
42/30 84 Hz 4.48 kHz
7/5 14 Hz 746 Hz
2 4 Hz 213 Hz
F
outer
is the chopping frequency as measured by an optical pick-up on the
chopper head. If a wheel has two sets of slots, F
outer
refers to the chopping
frequency of the slots on the outer edge of the wheel.
To change the wheel type, push the Wheel key until the LED lights under the
desired wheel type.
Sync
The user may synchronize the chopping frequency to the chopper's internal
synthesizer (INT), or the rising edge (EXT+) or falling edge (EXT-) of an
externally-supplied Sync Input signal. When V
ext
is selected, the user may
drive the motor directly with an analog voltage applied at V
ext
on the back
panel. When using V
ext
or INT, a signal applied to the Sync Input has no
effect on the chopper.
To change the Sync source, press the Sync key until the LED under the desired
Sync source lights.
Front Panel
Operation
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