5-19
VIBXPERT 11.2010
Measurement tasks
Cepstrum analysis
A cepstrum is the 'spectrum of a spectrum' and is particularly suitable
for detecting regular structures in a frequency spectrum. Above all, in
the case of complex patterns with many harmonics and sidebands -
that frequently occur if roller bearings or gearings are damaged- a
cepstrum simplifies the evaluation of the measurement data.
User-defined measurement variables
As well as measurement tasks with fixed specified measurement
variables, VIBXPERT provides measurement tasks where the mea-
surement variables can be freely defined. The voltage (±30V, AC/
DC) or current (±30mA, AC/DC) can be connected as an input signal
and recorded as a characteristic value, as a time waveform* or as a
spectrum*. The assignment of the input signal to the measurement
variable is specified by the 'Measurement Variable' and 'Unit' parame-
ters in the transducer setup (see P. 2-20).
Examples of user-defined measurement variables:
- Measurement of the pressure as a current level (4-20mA, DC).
Connection to pressure transmitter.
- Measurement of the flow rate as a current or voltage signal (4-
20mA / 0-10V, DC). Connection to flow rate measuring device.
- Measurement of the sound pressure as a time signal or spectrum.
Connection to a microphone.
- Displacement measurement (inductive sensor VIB 6.640).
Only the following cables can be used as sensor cables:
VIB 5.433 - Connection cable for low voltage signals
VIB 5.434 - Connection cable for low current signals
These cables may not be used in an explosive environment!
Overall v. Overall v.
Sensor parameters for
sound pressure measurement
VIB 5.433 /
VIB 5.434
Pressure
Flow rate
Attention!
Time wf. Spectrum
* DC measurement for time waveform,
spectrum, see page 5-30.
Cepstrum
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