Abstract: The disclosed invention senses a machine's vibration spectrum, converts the vibration signal into a frequency-domain vibration spectrum, and analyzes the vibration spectrum to generate a narrowband alarm limit envelope against which the vibration spectrum of a previously uncharacterized machine may be compared. The limit envelope is generated from the test vibration spectrum of the machine which is the subject of the test, thus providing a performance benchmark against which to compare the vibration level of the previously uncharacterized machine. A limit envelope is also generated from a test vibration spectrum which has been designated as a reference or baseline spectrum. Further, a limit envelope is generated based upon a mean spectrum which is generated by combining several test vibration spectra. A limit envelope is also generated based upon mean and standard deviation spectra when a statistically significant number of test spectra are available.

Abstract: The operational condition of a machine is evaluated when the machine's vibration spectrum deviates from an acceptable state, where an acceptable state is defined by an alarm limit envelope. The amplitude of individual peaks within the machine's vibration spectrum is compared to the alarm limit envelope, and a deviation severity value characterizing the severity of the machine's deviation from an acceptable state is determined for each deviating peak. The deviation severity value represents the severity of deviation when at least one individual peak within the machine's vibration spectrum exceeds the alarm limit envelope. The deviation severity value is obtained by determining the peak excess magnitude for each vibration peak, where the peak excess magnitude is the amount by which the amplitude of each deviating vibration peak exceeds the alarm limit envelope level. The peak excess magnitude is then normalized by a frequency-dependent normalization factor.