9
3. Turn the tuning knob to adjust the location (phase) of the reference
mark.
4. Press the PHASE DELAY button again to turn the “Phase” Delay
mode off.
4.2 Internal Mode - TACH Frequency Generator
In the Internal Mode, the strobe can be used as a frequency generator
(outputting TTL pulses) without having the strobe flash. The pulse
output will still occur at the flash rate; the strobe is just not flashing.
To stop flashing:
1. Press the ALT FUNCTION button and then the TACH button.
2. The TACH icon will be displayed.
To start flashing again:
3. Press the ALT FUNCTION button and then the TACH button.
4. The TACH icon will go away and the strobe will start flashing
again.
4.3 External Input Mode
The strobe is in the External Input Mode whenever there is a plug in
the input jack. When the strobe is in the External Input Mode, EXT
will be displayed.
In the External Input Mode the user can’t make any flash rate
adjustments. The flash rate is a function of the input trigger signal.
This mode is used to synchronize the flash to an external event (for
example, from an optical sensor) to stop or freeze motion. The flash
will be triggered on the rising or falling edge (menu selectable) of the
external input pulse.
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Example: object rotating at 5000 RPM
If the speed is outside the full scale range of the stroboscope (20,000 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:
RPM = AB/(A-B)
For a three point calculation:
RPM = 2XY(X+Y)/(X-Y)
2
where
X = (A-B) and
Y = (B-C)
If a Remote Optical Sensor or Magnetic Sensor is used to sense one pulse
per revolution (External mode), the readout will display directly in RPM
(FPM) without any adjustment required.
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.
Stopped Image 1/4 times 1/2 times 1 time 2 times 3 times 4 times
Flash Rate (FPM) 1250 2500 5000 10000 15000 20000
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