X90 mobile modules
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X90 mobile system User's manual V 1.20 - Translation of the original manual
A harmonic oscillation can be clearly described by its amplitude, frequency and phase angle.
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The amplitude in the path, velocity or acceleration indicates the instantaneous value.
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The frequency describes how often an oscillation changes within one second. In oscillation diagnostics,
this plays an important role since many frequencies can be assigned to one cause.
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The phase angle refers to the starting point of the oscillation. This is usually not that important since in
most cases several oscillations are present.
Fast Fourier transforms (FFT)
Oscillation signals generally consist of a number of oscillations that occur simultaneously and overlap. Individual
frequencies are not directly evident from a timing diagram.
Time [s]
Amplitude
[mg]
Figure 72: Timing diagram of an oscillation
Calculating a line spectrum is suitable for analyzing a mixture of oscillations of different frequencies where each
participating oscillation and their frequencies and amplitudes are represented by a single line.
Within the scope of condition monitoring, spectra are a valuable aid in finding the cause of a failure. Many frequen-
cies can be traced back to individual components so that damaged components can be identified.
