a “ periodic signal parameter ” indicates periodic patterns in an autocorrelated vibration waveform and potential faults in a monitored machine . the psp is calculated based on statistical measures derived from an autocorrelation waveform and characteristics of an associated vibration waveform . the psp provides an indication of periodicity and a generalization of potential fault , whereas characteristics of the associated waveform indicate severity . a “ periodic information plot ” is derived from a vibration signal processed using two analysis techniques to produce two x - y graphs of the signal data that share a common x - axis . the pip is created by correlating the y - values on the two graphs based on the corresponding x - value . the amplitudes of y - values in the pip is derived from the two source graphs by multiplication , taking a ratio , averaging , or keeping the maximum value .