Operating instructions
RT STROBE pocketLED LASER
11
8. Accessories, optional
▪ Belt bag with clip
▪ Mounting kit for tripod or articulating arm
▪ Articulating arm including mounting kit
▪ Tripod, 3-way adjustable
▪ Recalibration
▪ Trigger cable
9. Determining the actual rotational speed of
an object
The stroboscope can be used as a digital revolution indicator to de
-
termine an object’s actual rotational speed and/or the frequency of
cyclical movements. The stroboscope does this by visually “freezing”
the object’s movement and then taking a reading of the rotational
speed or frequency from the LCD display. As is the case with all stro
-
boscopes, it is vital to ensure that this “frozen” image is not a harmonic
of the object’s actual rotational speed.
Useful information:
▪ It’s helpful to have a rough idea of the object’s rotational speed
beforehand.
▪ Regular shaped objects, e.g. a fan with several vanes or a motor
shaft, must be affixed with an identification marking (using color
or a reflective strip etc.) in order to be able to differentiate its
orientation of movement.
▪ A still image always appears exactly at integer division of the
speed of the object’s actual rotational speed!
Example 1 (marking required):
This example shows the importance of using identification
markings. Say you want to determine the actual rotational
speed of this ventilator.
The only thing you know is that its rotational speed is less
than 3,500 rpm. The following “frozen” images will appear
if you reduce the flashing rate based on 3,500 FPM (fla
-
shes per minute):
Image no.
1
2
3
4
Flashing rate
3,300
2,200
1,650
1,320
Image no.
5
6
7
8
Flashing rate
1,100
825
733.3
550
What is the actual rotational speed of the fan? Images 1, 3, 5, 6
and 8 correspond to the original one, which means the rotational
speed could be 3,300, 1,650, 1,100, 825 or 550 rpm.
Which is correct?
To determine the fan’s actual rotational speed, one of the
ventilator vanes is attached with a marking and the test is
repeated.
Image no.
1
2
3
4
Flashing rate
3,300
2,200
1,650
1,320
Image no.
5
6
7
8
Flashing rate
1,100
825
733.3
550
The orientation marking confirms that the images at 3,300, 1,650
and 825 rpm are harmonic multiple images. Three identification
marks appear in each of these images.
Still images appear at 1,100 rpm and again 550 rpm, each display
-
ing just one mark. Remember that a still image always appears ex-
actly at integer division of the speed of the actual rotational speed
of an object. 550 is half of 1,100. This means that the rotational
speed of the ventilator must be 1,100 rpm.
Example 2 (no marking required):
This example shows how the actual rotational speed of an object
can be determined without using an orientation marking. This is
only possible for suitably shaped objects.
Let’s assume the only thing we know about this cam is
that it rotates at less than 7,000 rpm. Its clear shape elimi
-
nates the need for an orientation marking. The following
“frozen” images will appear if the flashing rate of 7,000 is
reduced:
Image no.
1
2
3
4
Flashing rate
6,000
4,000
3,000
1,500
The images showing 6,000 and 4,000 rpm are double or multiple
images rather than single images. Still images appear at 3,000
and again at 1,500 rpm. 1,500 is half of 3,000. This means that the
actual rotational speed is 3,000 rpm.
Printed CE declaration of conformity is available on request.
Subject to technical changes without prior notification. Although
the content of these instructions was compiled with the greatest
care, we cannot accept liability for any errors.