Ultra sensitive magnetic field sensors

Abstract

A magnetic sensor and magnetic field sensing method for ordnance, comprising locating a magnetoresistance detector within the ordnance and detecting magnetic fields with the detector. Also other sensing method and sensors employing such detectors.

What is claimed is:  
     
         1 . A magnetic field sensing system for locating defects in objects in two or three dimensions, said system comprising a sensor comprising a magnetoresistance detector and means for sensing at a plurality of frequencies.  
     
     
         2 . The system of  claim 1  wherein said means for sensing provides for sensing defects at a plurality of depths in the objects.  
     
     
         3 . The system of  claim 2  wherein the objects are printed circuit boards.  
     
     
         4 . A magnetic field sensing system for imaging objects comprising a magnetoresistance detector, means for non-magnetic imaging, and means for analyzing images produced by both said magnetoresistance detector and said means for non-magnetic imaging.  
     
     
         5 . The system of  claim 4  wherein said means for non-magnetic imaging comprises optical imaging means.  
     
     
         6 . A system for mechanical system identification comprising a magnetoresistance detector.  
     
     
         7 . The system of  claim 6  wherein said system comprises a system for vehicle identification.  
     
     
         8 . The system of  claim 6  additionally comprising means for analyzing output of said magnetoresistance detector and comparing results to known characteristics of items selected from the group consisting of: perturbations of the earth's field by a moving metallic object or vehicle; fields associated with electric motors; fields associated with generators and alternators; fields associated with spark plugs, wires and coils; fields related to rapidly moving metallic parts; and fields associated with large masses of metals.  
     
     
         9 . The system of  claim 6  wherein said system comprises at least three magnetoresistance detectors.  
     
     
         10 . The system of  claim 6  wherein said magnetoresistance detector detects perturbations of the earth's magnetic field by the mechanical system.  
     
     
         11 . The system of  claim 6  wherein said magnetoresistance detector detects magnetic fields generated by electromagnetic components of the mechanical system.  
     
     
         12 . The system of  claim 6  wherein said magnetoresistance detector detects radio waves generated by the mechanical system.  
     
     
         13 . A magnetic field sensing method for locating defects in objects in two or three dimensions, the method comprising the steps of providing a sensor comprising a magnetoresistance detector and sensing at a plurality of frequencies.  
     
     
         14 . The method of  claim 13  wherein the sensing step senses defects at a plurality of depths in the objects.  
     
     
         15 . The method of  claim 14  wherein the objects are printed circuit boards.  
     
     
         16 . A magnetic field sensing method for imaging objects, the method comprising the steps of providing a magnetoresistance detector, employing means for non-magnetic imaging, and analyzing images produced by both the magnetoresistance detector and the means for non-magnetic imaging.  
     
     
         17 . The method of  claim 16  wherein the means for non-magnetic imaging comprises optical imaging means.  
     
     
         18 . A method for mechanical system identification, the method comprising the steps of providing a magnetoresistance detector and using the detector to sense characteristics of a passing mechanical system.  
     
     
         19 . The method of  claim 18  wherein the passing mechanical system is a vehicle.  
     
     
         20 . The method of  claim 18  additionally comprising the step of analyzing output of the magnetoresistance detector and comparing results to known characteristics of items selected from the group consisting of: perturbations of the earth's field by a moving metallic object or vehicle; fields associated with electric motors; fields associated with generators and alternators; fields associated with spark plugs, wires and coils; fields related to rapidly moving metallic parts; and fields associated with large masses of metals.  
     
     
         21 . The method of  claim 18  wherein the providing step comprises providing at least three magnetoresistance detectors.  
     
     
         22 . The method of  claim 18  wherein in the using step the magnetoresistance detector detects perturbations of the earth's magnetic field by the mechanical system.  
     
     
         23 . The method of  claim 18  wherein in the using step the magnetoresistance detector detects magnetic fields generated by electromagnetic components of the mechanical system.  
     
     
         24 . The method of  claim 18  wherein in the using step the magnetoresistance detector detects radio waves generated by the mechanical system.