1. 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 at least one of: 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 in response to the vibration; a phase-overlap processor to identify a first signal region associated with the RDIFF signal and a second signal region associated with the LDIFF signal, and to identify an overlap of the first signal region and the second signal region and to generate a phase-overlap output signal in response to the overlap; and a direction-agreement processor coupled to the at least two rotation detectors to detect the vibration of the object in response to a disagreement in the direction of rotation of the object as indicated by output signals of the at least two rotation detectors and to generate a direction-agreement output signal in response to the vibration.