Checkline PK2X - Manual (Page 10)

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8.0 EXTERNAL TRIGGERING
The Pocket-Strobe can be externally triggered.
The EXTERNAL TRIGGER jack (F) is DTL/ TTL compatible. It detects a square-
wave signal of 0 to +5 volts which is at least 800 nsec in duration. The signal delay
(the time it takes for the signal to cause the strobe to flash) is less than 5 µsec.
The EXTERNAL TRIGGER jack uses a standard 1/ 8” phono plug with the
configuration shown below:
NOTES: Turn the Pocket-Strobe off when inserting or removing a trigger cable.
Whenever an external trigger is used, the ON/OFF switch and the
Flash Adjustment Knob are disabled.
WARNING: Do not trigger the device with signals over 208 Hz.
1. The outer connection (barrel) is common.
2. The middle connection provides a
+5 V DC output to drive external
sensors which are not self-powered.
3. The center connection is the input signal,
which triggers the flash.
External
Trigger
EXT illuminates when the External Trigger function is activated.
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13.0 HARMONICS
If you continuously increase the flash rate while strobing an object, it may appear to
freeze, slow down, speed up, go forward, freeze again, go backwards, form multiple
images, etc. These images appear at mathematically determined multiples or
harmonics of the object’s actual speed.
Example: Assume you wish to slow the motion of the fan used in the last example,
but you want it to be brighter.
Technique: Starting from 1,000 FPM, slowly increase the flash rate. At 1,500 FPM
the image will appear to freeze again. Continue to increase the rate.
The image will appear to freeze again at 3,000 FPM. At this rate, the fan
appears to be very bright. You can now use the FINE ADJUSTMENT
knob to vary the rate above and below’3,000 to make the fan appear to
move both clockwise and counterclockwise.
Helpful Hint:
■ Harmonic images appear at both whole number multiples as well as fractional
intervals of the object’s actual rate. For example, a fan rotating at 1,000 RPM will
appear to be frozen at the whole number multiples of 2,000 (2x), 3,000 (3x),
4,000 (4x) etc., as well as at the fractional rates of 500 (1/2x), 750 (3/4x),
833 (5/6x) and 1,500 (1 1/2x), etc.
■ Some of the harmonic images are “singular” in appearance while others
are “multiple.” This becomes important if you want to determine the objects
actual rate as discussed in section 12.