If a vibration signal is measured and displayed it might look like Figure 10.26 A vibration signal as a function of time. The overall sinusoidal shape is visible, along with a significant amount of ’noise’. When this is considered in greater detail it can be described with the given function. To determine the function other tools are needed to determine the frequencies, and magnitudes of the frequency components.
Figure 10.26 A vibration signal as a function of time
A signal spectrum displays signal magnitude as a function of frequency, instead of time. The time based signal in Figure 10.26 A vibration signal as a function of time is shown in the spectrum in Figure 10.27 The spectrum for the signal in Figure 10.26. The three frequency components are clearly identifiable spikes. The height of the peaks indicates the relative signal magnitude.
Figure 10.27 The spectrum for the signal in Figure 10.26 A vibration signal as a function of time