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The measurement tasks described on this page are only available
in the 'Route / Machine template' mode. The measurement param-
eters are set in the OMNITREND PC software.
TrendingSpectrum
A TrendingSpectrum is a measurement template for the route
mode. It can be used to make data collection significantly faster
and more efficient. A TrendingSpectrum is based on a time signal
measurement. Based on the TrendingSpectrum, VIBXPERT first
generates a spectrum, which in turn is used to calculate up to 30
overall values. The overall values result from the frequency bands
defined in OMNITREND and are used for condition monitoring when
recorded in the form of a trend.
Order spectrum
In an order spectrum, the frequencies are recorded and displayed
as a multiple of the shaft rotational frequency (= order). In these
measurements, the RPM is recorded at the same time as the
vibration signal and is taken into account when the order spectrum
is calculated. If short-term, system-related fluctuations in the RPM
occur, the sample rate of the time signal is adjusted accordingly
('resampling') to avoid a 'smearing' of the frequencies.
An order spectrum cannot be converted into a frequency spectrum,
since the time and thus the frequency information are lost through
the resampling procedure.
Order-based spectrum
With this type of spectrum, the frequencies are converted into
orders*.
The RPM is measured, manually entered or passed as a parameter
by the OMNITREND software. The maximum order to be displayed
is also required. Order-based spectra are advantageous when
machines run at different RPMs for process-related reasons because
the spectra are only comparable in relation to the RPM.
Measurement tasks
Note
TrendingSpectrum
(Amplitude)
TrendingSpectrum
(Envelope)
Order spectrum
* Shaft rotational frequency =
1. Order
5-29
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