What is happening in the animation
here ?
-
The transducer is mounted vertically
so the movement (vibration) being measured is vertical only.
-
The red dot represents the "at-rest"
position of the shaft.
-
The black dot represents the center
point of the shaft.
-
There is a "heavy" spot on the rotor
that causes a centrifugal force to be generated that results is causing
the shaft center point (the black dot) to rotate around the 'at-rest' center
point (the red dot).
-
The "+"peak' occurs when the bearing
is displaced the maximum amount towards the transducer. In other
words, as the black dot passes the 12:00 position (passes the transducer).
-
The location of the heavy spot can be
determined at any moment in the shaft's rotation by imagining a line drawn
from the red dot directly through the black dot. This is, of course, not
able to be seen in real life on a real machine.
-
What we can see is some
"mark" (usually a key) that becomes visible under the flash of the strobe
light once per revolution (the yellow dot). This is our reference mark.
The mark is 45° behind the heavy
spot.
-
In real life, we would not know where
the mark is located
relative to the heavy spot. However, we do know
that unless we do something to change the location or size of the heavy
spot, those two positions will not change relative to one another
as we move the transducer. They will remain 45°
apart.
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