5-9
VIBXPERT 11.2010
Measurement tasks
F
C.3 'Phase - RPM' measurement type
This type of measurement records the phase amplitude and the phase
angle in dependence on the RPM. Points of resonance are indicated
by RPMs with increased amplitude and a simultaneous jump in phase
angle by (ideally) 180°. The results are displayed either in a Bode
diagramor in a Nyquist diagram.
Bode diagram
The upper curve shows the amplitude progression and the phase is
displayed in the lower screen. The Zoom function applies to both
diagrams.
If the ‘Continuous Phase’ option in the display setup is enabled, a
number of dotted horizontal lines may appear in the phase
diagram under certain circumstances. These lines represent the
‘360° - 0°’ transition that can occur any number of times due to the
constant continuation of the phase progression (see P. 4-17, 5-6)
Changing the type of diagram
Press the F key and click with the joystick.
Averaging cancellation if rpm deviation > 10%
VIBXPERT records a time signal block per shaft rotation and
combines multiple blocks to an average signal, depending on the
averaging number. If the rotational speed varies by more than 10%
during averaging, VIBXPERT aborts the averaging and uses the
averaged signal to calculate the amplitude and the phase angle.
These values are only saved if the rpm deviation set in the measure-
ment setup is reached.
Note
Runup / Coastdown:
Left:
Phase - RPM (Bode diagram)
Right:
Phase - RPM (Nyquist diagram)
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