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3.1 Internal Mode - Standard Strobe Operation
In the INTERNAL Mode the stroboscope generates its own signals
and functions like a tunable stroboscope. The strobe is in the internal
mode when nothing is plugged into the input jack.
The flash rate can be adjusted using the black knob on the left of the
unit. The current flash rate is displayed. Turn the knob counter clockwise
to increase the flash rate and clockwise to decrease it. If an attempt to
change a value would cause the flash rate to exceed the minimum or
maximum, the value remains unchanged. Refer to section 1.1 above
for more detail on changing flash rates.
The flash rate can be doubled or halved instantly by pressing the x2
or ÷2 buttons respectively up to the maximum or minimum allowed.
Once the flash rate has been adjusted to give a stopped motion image,
the Phase + and Phase - buttons may be used to increase or decrease
the phase of the image. Press and hold the Phase + button to have the
image appear to slowing rotate in the direction the object is actually
rotating. Press and hold the Phase - button to rotate the image in the
opposite direction the object is actually rotating. Use the phase buttons
to bring a reference mark , such as a key way, into your line of sight.
The Store button stores the current flash rate into the last preset location
viewed.
The Preset button will cycle through six different preset flash rates.
These rates are set at the factory to be: 100, 500, 1000, 3600, 7200
and 14000 FPM. Each time this button is pressed, the flash rate and
display is changed to the next preset. The presets can be changed by
the user using the Store button. The Store button stores the current
flash rate into the last preset location the user has viewed.
See section 3.3 for more features.
3.2 External Mode - External Input Required
The strobe is in the external mode whenever there is a plug in the input jack.
The External chevron comes on automatically to indicate this mode.
In the EXTERNAL mode there are no flash rate adjustments the user
can make. The Flash rate is a function of the input 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 edge of the external input pulse. The Alt Function mode
and chevron is automatically set in this mode, since the primary function
of the buttons have no use in this mode.
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If the speed of rotation is within the range of the stroboscope, start at the
highest flash rate and adjust the flash rate down. At some point you will stop
the motion with only a single image of the object in view. Note that at a flash
rate twice the actual speed of the image you will see two images. As you
approach the correct speed you may see three, four or more images at
harmonics of the actual speed. The first SINGLE image you see is the true
speed. To confirm the true speed, note the reading and adjust the
stroboscope to exactly half this reading, or just press the ÷2 button. You
should again see a single image (which may be phase shifted with respect
to the first image seen).
For example, when viewing a shaft with a single key way you will see one
stationary image of the key way at the actual speed and at 1/2,1/3,1/4, etc,
of the actual speed. You will see 2 images of the key way at 2 times the
actual speed, 3 key way at 3 times, etc. The FPM equals the shafts
Revolutions Per Minute (RPM) at the highest flash rate that gives only one
stationary image of the key way.
Example: object rotating at 3000 RPM
If the speed is outside the full scale range of the stroboscope (14,000 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.
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