Image Number 5 for United States Patent #5922963.
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.