-
The term "enveloping" spectra plot is
not always a technically correct description of the signal processing involved
but will be the term we use for simplicity sake.
-
An enveloping spectra is the same in
appearance (amplitude vs. frequency) as a conventional spectrum - it simply
displays different information.
-
An enveloping spectra is
not sensitive to sinusoidal motion - unlike the FFT plot
that determines what simple sinusoids combined to generate a complex signal
in displacement, velocity or acclereration units.
-
An enveloping spectra is
sensitive to impact related events.
-
The ability to quantify both the frequency
of impacts and their intensity is very helpful and important to
the vibration analyst. Although there are machines that generate impact
energy normally (i.e. reciprocating equipment), most machines don't. Impacts
are destructive forces and normally indicate some type of problem is developing.
Most typically, this plot is used to detect bearing defects.
|
