Kurtosis
One mathematical representation of the deviation of an amplitude distribution from Gaussian is the so-called "fourth moment", or kurtosis. The Gaussian distribution has a kurtosis of 3, and higher values of kurtosis indicate increased crest factor of the vibration signal. Kurtosis is a valid measure of the degradation of a machine, but it does not give any indication of the diagnosis of the problem. It has been reported that kurtosis is especially well suited to monitoring of reciprocating machines for fault detection.
One possible advantage of using kurtosis as a fault detection parameter is that it does not need to be trended over time to be effective. A kurtosis of 3 generally is taken as indicating a healthy machine, with higher values indicating progressive states of fault progression.
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