US 7,592,801 B2
Methods and apparatus for vibration detection
James M. Bailey, Concord, N.H. (US); Michael C. Doogue, Manchester, N.H. (US); and Jay M. Towne, Newbury, N.H. (US)
Assigned to Allegro Microsystems, Inc., Worcester, Mass. (US)
Filed on Mar. 21, 2008, as Appl. No. 12/53,004.
Application 12/053004 is a division of application No. 10/942577, filed on Sep. 16, 2004, granted, now 7,365,530.
Application 10/942577 is a continuation in part of application No. 10/820957, filed on Apr. 08, 2004, abandoned.
Prior Publication US 2008/0164871 A1, Jul. 10, 2008
Int. Cl. G01B 7/14 (2006.01)
U.S. Cl. 324—207.25  [324/207.26] 22 Claims
OG exemplary drawing
 
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
a vibration processor responsive to the first and second output signals from the at least two rotation detectors for detecting the vibration of the object, the vibration processor comprising one or more vibration detectors including a direction-agreement processor, wherein the direction-agreement processor is configured to generate a first signal indicative of a direction of rotation of the object, to generate a second signal indicative of the direction of rotation of the object, to determine whether the first signal indicative of the direction of rotation has an agreement with or a disagreement with the second signal indicative of the direction of rotation, and to generate a direction-agreement output signal in response to the agreement or disagreement.