A diagnostic apparatus and method for sensing a signal emanating from a machine
and determining a periodic machine event based on the emanated signal. The apparatus
includes analog to digital processing components for digitizing the sensed signal,
producing a digitized signal. The apparatus also includes a transform algorithm,
memory, an analysis algorithm, and a display. The transform algorithm transforms
the digitized signal to generate power spectral density and autocorrelation data
which is stored in the memory. The analysis algorithm includes criteria for analyzing
the stored power spectral density and autocorrelation data to determine a period
machine event based at least in part upon the autocorrelation data. The display
displays the periodic machine event to a user. In the event of a suspected defect
or fault, the device alerts the user. The user may then elect to proceed with repairs
or undertake advanced analysis of the suspected fault as economy dictates.