Ultra sensitive magnetic field sensors

Abstract

A magnetic sensor and magnetic field sensing method for ordnance, comprising locating a giant 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 sensor for ordnance, said sensor comprising a magnetoresistance detector and said sensor being located within the ordnance.  
     
     
         2 . The sensor of  claim 1  additionally comprising means for counting turns of spinning ordnance.  
     
     
         3 . The sensor of  claim 2  additionally comprising autonulling means.  
     
     
         4 . The sensor of  claim 3  wherein said autonulling means injects a charge into a circuit comprising said magnetoresistance detector.  
     
     
         5 . The sensor of  claim 4  wherein said injecting means is triggered when a rate of spin of the ordnance exceeds a predetermined rate.  
     
     
         6 . The sensor of  claim 1  additionally comprising means for arming ordnance a pre-determined time after exit of the ordnance from a weapon firing the ordnance.  
     
     
         7 . The sensor of  claim 6  wherein said arming means comprises means selected from the group consisting of means for determining exit of the ordnance from a weapon firing the ordnance, means for determining exit velocity, means for determining proximity to metallic targets, and means for determining direction to metallic targets.  
     
     
         8 . The sensor of  claim 7  wherein said exit determining means detects concentrated earth's magnetic field lines at an opening of a weapon firing the ordnance.  
     
     
         9 . The sensor of  claim 1  wherein said detector is fabricated on a device selected from the group consisting of printed circuit boards, hybrid circuits, and integrated circuits.  
     
     
         10 . The sensor of  claim 1  wherein said sensor detects incoming munitions.  
     
     
         11 . The sensor of  claim 10  wherein said sensor additionally comprises a biasing magnet.  
     
     
         12 . The sensor of  claim 10  additionally comprising means for providing an oscillation frequency.  
     
     
         13 . The sensor of  claim 10  wherein said providing means comprises a coil proximate a nose of the ordnance.  
     
     
         14 . The sensor of  claim 10  comprising multiple detectors and triangulation means.  
     
     
         15 . The sensor of  claim 10  comprising an array of detectors.  
     
     
         16 . The sensor of  claim 1  additionally comprising means selected from the group consisting of means for outputting a signal characteristic of impact of the ordnance, means for employing a map of local magnetic fields to determining position and direction of an object, means for detecting flying objects by looking for response to an emitted magnetic field, and means for determining eddy currents output by flying object traversing earth's magnetic field.  
     
     
         17 . A magnetic field sensing method for ordnance, the method comprising the steps of locating a magnetoresistance detector within the ordnance and detecting magnetic fields with the detector.  
     
     
         18 . The method of  claim 17  additionally comprising the step of counting turns of spinning ordnance.  
     
     
         19 . The method of  claim 18  additionally comprising the step of employing autonulling means.  
     
     
         20 . The method of  claim 19  wherein the employing step comprises injecting a charge into a circuit comprising the magnetoresistance detector.  
     
     
         21 . The method of  claim 20  wherein the injecting step is triggered when a rate of spin of the ordnance exceeds a predetermined rate.  
     
     
         22 . The method of  claim 17  additionally comprising the step of arming ordnance a pre-determined time after exit of the ordnance from a weapon firing the ordnance.  
     
     
         23 . The method of  claim 22  wherein the arming step comprises a step selected from the group consisting of determining exit of the ordnance from a weapon firing the ordnance, determining exit velocity, determining proximity to metallic targets, and determining direction to metallic targets.  
     
     
         24 . The method of  claim 23  wherein the exit determining step comprises detecting concentrated earth's magnetic field lines at an opening of a weapon firing the ordnance.  
     
     
         25 . The method of  claim 17  additionally comprising the step of fabricating the detector on a device selected from the group consisting of printed circuit boards, hybrid circuits, and integrated circuits.  
     
     
         26 . The method of  claim 17  additionally comprising the step of detecting incoming munitions.  
     
     
         27 . The method of  claim 26  wherein the detecting step comprises employing a biasing magnet.  
     
     
         28 . The method of  claim 26  wherein the detecting step comprises providing an oscillation frequency.  
     
     
         29 . The method of  claim 26  wherein the detecting step comprises employing a coil proximate a nose of the ordnance.  
     
     
         30 . The method of  claim 26  wherein the locating step comprises locating multiple detectors and triangulation means.  
     
     
         31 . The method of  claim 26  wherein the locating step comprises locating an array of detectors.  
     
     
         39 . The method of  claim 24  additionally comprising a step selected from the group consisting of outputting a signal characteristic of impact of the ordnance, employing a map of local magnetic fields to determining position and direction of an object, detecting flying objects by looking for response to an emitted magnetic field, and determining eddy currents output by flying object traversing earth's magnetic field.