Patent ID: 7772838

Claim:
Apparatus for detecting a vibration of an object adapted for rotation, comprising: a plurality of magnetic field sensors for generating an RDIFF signal proportional to a magnetic field at a first location relative to the object and an LDIFF signal proportional to a magnetic field at a second location relative to the object; at least two rotation detectors, wherein a first one of the rotation detectors is coupled to at least one of the magnetic field sensors and is responsive to the RDIFF signal for providing a first output signal indicative of rotation of the object and wherein a second one of the rotation detectors is coupled to at least one of the magnetic field sensors and is responsive to the LDIFF signal for providing a second output signal indicative of rotation of the object; and a vibration processor responsive to the first and second output signals of the at least two rotation detectors for detecting the vibration of the object, the vibration processor comprising one or more vibration detectors comprising a direction-change processor coupled to at least one of the rotation detectors to detect the vibration of the object in response to a change in the direction of rotation of the object as indicated by the output signal of the at least one rotation detector and to generate a direction-change output signal indicative of the vibration, wherein the direction-change processor comprises: a first comparator configured to compare the first output signal to a first threshold to generate a first intermediate signal having an edge; a second comparator configured to compare the second output signal to a second threshold to generate a second intermediate signal having an edge; and an edge comparison circuit configured to compare relative positions of the edges of the first and second intermediate signals.