– 9 –
Unit displayed
9
1/min
Rotations per minute.
10
Hz
Frequency of motion per second.
NOTE:
When an external trigger signal is used, the units 1/min (rather
than FPM) or Hz are displayed.
Operating information
11
RANGE External trigger signal is causing the flash frequency to
be too high.
12
EXT
External trigger signal selected.
13
INT
Device is generating flash frequency.
NOTE:
A parameter which has been set to differ from the default
setting flashes during operation.
6.1 Using Special Functions (OT model)
DELAY ms
Adjustment of delay time between the internal trigger signal and
the flash (in milliseconds). This function enables you to set a fixed
delay time between the input signal and the output signal.
Example:
The external trigger signal is generated before the
required observation point (= flash position of the stroboscope). In
this case the connected stroboscope would regularly fl ash too soon.
With the DELAY ms function, you can set the value by which the
output signal should be delayed.
PHASE deg
Phase shift adjustment between the internal trigger signal and the
flash (in degrees, relative to the frequency). This function enables
you to set a fixed angle between the internal trigger signal and the
flash.
Example:
The external trigger signal is generated before the
required observation point (=f lash position of the stroboscope). In
this case the connected stroboscope would regularly fl ash too soon.
With the PHASE deg function, you can adjust the delay so that the
fl ash position of the stroboscope is altered by a set angle. This
setting is independent of the current speed ofrotation, which means
that the stroboscope will flash at the required position even during
the start-up process or when the speed of rotation is fluctuating.
– 12 –
9.0 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 mathe-
matically 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.
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 10.0.
