Text: Defines the ratio of the peak value of a signal to the RMS value. As the vibration becomes more impulsive, or more random, the crest factor increases. This simple relationship is easily calculated with a simple vibration meter equipped with RMS and peak facilities. When making wide-band measurements on a machine's bearing housing, an increase in a single vibration component caused by a faulty bearing may be undetectable in the RMS measurement, but might be indicated by an increase in the crest factor. Hence by monitoring the growth of the crest factor, it is possible to predict a breakdown or element fault. Another example of the utility of crest factors can be found in structural testing techniques. The crest factor of the input signal to the structure can reveal important information about the excitation. If the crest factor is very high, as can be the case with hammer excitation, the structure may be driven into non-linear dynamic behavior. A high crest factor also indicates that the input may not contain sufficient energy to obtain a good signal-to-noise ratio. On the other hand, a high crest factor is an indication that the input has a wide frequency range.

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