Checkline PK2X - Manual (Page 9)

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7.0 PK2X O PERATION
1. Be sure to charge the battery before first use (assuming you plan on operating
using the internal battery). Otherwise, connect the strobe to the AC-Adapter/
Charger and plug it into an AC output to operate.
2. Aim the PK2X at the moving object and turn it on. There will be a delay of 1–2
seconds before the flash begins to operate. If the LOW BAT symbol in the
display is illuminated, charge the battery.
3. Adjust the flash rate by rotating the Flash Adjustment Knob until the image appears
motionless (as you approach the movement frequency, the image appears to move
more slowly). This value will be shown in the LCD display.
IMPORTANT: Motionless images do not only appear when the movement frequency
is reached, but also when multiples and fractions of the movement frequency are
reached.
For additional information on visually slowing down the motion of an object as well as
using your Pocket-Strobe as a tachometer, please refer to the appropriate section(s)
later in this manual.
Helpful Hints:
■ Dim the ambient lights for best results.
■ The flash frequency for which the image of the object appears with the greatest
contrast is the movement frequency.
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14.0 DETERMINING AN OBJECT’S TRUE RPM
The Pocket-Strobe can be used as a digital tachometer to determine the true RPM
and/or the reciprocation rate of an object. This is done by visually “freezing” the
object’s movement and then reading the LCD display. As with all stroboscopes, it is
important to verify that this frozen image is not a harmonic of the object’s actual rate.
Helpful Hints
■ Knowing the approximate rate of the object in advance gives you a useful
starting point.
■ If the object has a uniform shape, like a multi-blade fan or motor shaft, you must
give it an identifying mark (using paint or reflective tape or equivalent) in order
to differentiate its orientation.
■ A singular image always appears at exactly one half of the object’s true RPM.
■ Mathematical harmonic techniques can be used to determine an object’s true RPM
if it is greater than 12,500 (the upper limit of the Pocket-Strobe).
See Example 3 on page 16.
Example 1 (Within Range):
This example shows why identifying marks are important.
Suppose you want to determine the true RPM of this fan.
The only thing you know is that its speed is less than 3,500 RPM.
If you slowly decrease the flash rate starting from 3,500 FPM,
the following “frozen” images appear:
Image No.: 1 2 3 4
Flash Rate: 3.300 1,650 1,100 916.6
Image No.: 5 6 7 8
Flash Rate: 825 733.3 660 550