3502
Optical Chopper System
19
WARNING
The moving wheel may inflict injury. The operator should ensure the
safety of personnel who may be exposed to this hazard.
3.2.4
Mounting the Wheel Cover
WARNING
The wheel cover is provided for safety and its installation is
encouraged. The Chopper wheel can cause injury if it is touched while
rotating. This is especially critical if you find yourself reaching into your
optical set-up with the lights off. You may want to use the Chopper
wheel cover to reduce the chance of injury.
The wheel cover attaches to the Chopper Head with four screws. The wheel cover
is made of 0.031” (0.80 mm) aluminum with an anti-reflective black anodized
coating. Two concentric slots, etched in both faces of the cover, allow apertures
of various sizes according to the table below. The wheel cover dimensions are 5”
x 5” x 0.5”.
Wheel Type
Model Number
Largest Beam Diameter
Inner Cover Slot
Outer Cover Slot
2-slot
3511
0.295” (7.50 mm)
0.394” (10.00 mm)
7/5-slot
3512
0.295” (7.50 mm)
0.394” (10.00 mm)
42/30-slot
3513
0.135” (3.44 mm)
0.138” (3.51 mm)
60-slot
3514
-
0.107” (2.71 mm)
100-slot
3515
-
0.064” (1.62 mm)
60/2-slot
3516
0.295” (7.50 mm)
0.107” (2.71 mm)
The wheel cover is also provided to reduce the generation of stray light that could
interfere with your measurements. The Chopper head uses an IR sensor to detect
Chopper wheel motion. The source in this sensor emits light of approximate
wavelength 950 nm. The wheel cover will greatly reduce the amount of sensor-
radiated stray IR light picked up by your experiment detector.
To install the wheel cover, first install a wheel on the Chopper hub. Then, slide
the wheel cover over the wheel. Please note that it can require some force to
separate the wheel cover’s mounting flanges far enough to fit over the motor
housing. Once the mounting flanges are lowered past the motor, align one of the
four flange holes with a threaded hole in the motor base and loosely attach the