SM0486
Figure 7.
The Stroboscope
(1) The stroboscope is simple to operate. The light from the stroboscope
is directed upon the part to be measured and the large knob is adjusted until the
part appears to stop. The rpm of the part is then read directly from the scale.
This action adjusts the frequency of the internal oscillator so that it is firing
the stroboscopic light once for each rotation of the part.
If the internal
oscillator is firing the light slightly faster than the part is rotating, the part
will appear to be turning slowly in the reverse direction.
(2) If the part is uniform or symmetrical, place an identification mark
with chalk or crayon on the portion to be viewed. If approximate speed is known,
turn to appropriate portion of dial scale and adjust large knob until part appears
stopped. The dial scale will read in revolutions per minute. If speed is unknown,
start at the highest end of the dial scale and work downward until a single
stationary image is obtained.
(3) When stroboscope speed exceeds that of the moving object, multiple
images will be seen; the first single stationary image will be seen at fundamental
frequency.
If the stroboscope is operated at a speed less than the fundamental
frequency, single images will be seen at 1/2, 1/3, 1/4, . .
of the speed of the
moving part.
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