X90 mobile modules
250
X90 mobile system User's manual V 1.20 - Translation of the original manual
Amplitude
[mg]
Time [s]
Figure 83: Advanced bearing damage at 600 rpm
To make the actual result, or shock sequence, clearly visible, it is obviously not enough to simply provide the
amplitude spectrum. It is much more important that the process of convolution that took place when the signal
occurred be appropriately reversed so as to separate the excitation function from the natural frequency. This is
what envelope analysis provides.
An amplitude-modulated signal is made up of a high-frequency carrier signal and a low-frequency wanted signal.
The amplitude of the carrier signal changes depending on the wanted signal. In the receiver, the wanted signal is
extracted from the carrier signal by the formation of the envelope curve (demodulation).
In the case of machine resonances caused by periodic impacts, the machine resonances can be viewed as the
carrier signal and the low-pass-filtered shock pulses can be viewed as the low-frequency modulation signal. De-
modulation results in the shock pulses being extracted from the resonance frequencies.
