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Stopped Image
Flash Rate (FPM)
If the speed is outside the full scale range of the stroboscope (10,000 FPM),
it can be measured using the method of harmonics and multipoint calculation.
Start at the highest flash rate and adjust the flash rate down. You will
encounter multiple images so be aware of these. Note the flash rate of the
first SINGLE image you encounter, call this speed "A". Continue decreasing
the flash rate until you encounter a second SINGLE image. Note this speed
as "B". Continue decreasing the speed until you reach a third SINGLE
image at speed "C".
For a two point calculation the actual speed is given by:
For a three point calculation:
In instances when you can shut down the device and install a piece of
reflective tape, then an optical tachometer is easier to use for RPM
measurement. Stroboscopes must be used when you can't shut down
the device. The human eye is not easily tricked into seeing a stopped image
by a stroboscope when the flash rate is slower than 300 FPM. Therefore,
stroboscopes are just about impossible to use below 300 FPM for inspection
or to measure RPM.
Find Quality Products Online at:
All manuals and user guides at all-guides.com
1/4 times
1/2 times
833
1250
Example: object rotating at 2500 RPM
GlobalTestSupply
www.
1 time
2 times
2500
5000
RPM = AB/(A-B)
RPM = 2XY(X+Y)/(X-Y) 2 where
X = (A-B) and
Y = (B-C)
.com
3 times
4 times
7500
10000
E-5
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