Checkline QB-LED - Manual (Page 17)

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Which is correct?
Example 2 (no marking required)
To determine the fan’s actual rotational speed, one of the ventilator vanes is
attached with a marking and the test is repeated.
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 eliminates the need for an orientation
marking. The following “frozen” images will appear if the flashing rate of
7,000 is reduced:
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.
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 displaying just one mark. Remem-
ber that a still image always appears exactly 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
Image No. 1 2 3 4
Flashing rate 6.000 4.000 3.000 1.500