5-29
VIBXPER
T II 05.2012
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 measure-
ment. 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 OMNI-
TREND and are used for condition monitoring when recorded in the
form of a trend.
Based on the spectrum, VIBXPERT also calculates a time signal ac-
cording to the settings in the OMNITREND software. The measure-
ment quantity of the recorded time signal may differ from the mea-
surement quantity of the measured time signal.
Order spectrum
In an order spectrum, the frequencies are recorded and displayed as
a multiple of the shaft rotational frequency (= order). In these mea-
surements, the RPM is recorded at the same time as the vibration sig-
nal 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.
* Shaft rotational frequency = 1. Order
TrendingSpectrum
(Amplitude)
TrendingSpectrum
(Envelope)
Order spec-
trum
Note
Measurement tasks
Содержание VIBXPERT II
Страница 175: ......