Magnetic shunt device for hall effect applications

Abstract

A magnetic shunt device for use in a Hall effect sensor application wherein the shunt device is positioned and located relative to the Hall effect element and is shaped and dimensioned so as to shield and null the influence of the magnetic field when such field is substantially parallel to the sensitive plane of the Hall effect element. The present shunt device ensures that the null output voltage of the Hall effect element in a particular sensor application is consistent for a large number of such sensors despite misalignment problems and mechanical uncertainties in accurately arranging the magnetic devices that generate the magnetic field relative to the Hall effect element at the null or "no action" position of the sensor. The present device also obviates the requirement to use additional electronic circuitry to adjust the output voltage of the Hall effect element at the null or "no action" position.

What is claimed is:  
     
       1. A shunt device for use in a Hall effect sensor having a Hall effect element and at least one magnetic device generating a magnetic field, the Hall effect element having a sensitive plane detecting the magnetic field generated by the at least one magnetic device, said shunt device being positioned and located adjacent to said Hall effect element and being shaped and dimensioned so as to shield the sensitive plane of the Hall effect element from the magnetic field generated by the at least one magnetic device when said magnetic field is parallel to the sensitive plane of said Hall effect element. 
     
     
       2. The shunt device, as set forth in claim  1 , wherein the at least one magnetic device generating a magnetic field includes an electromagnetic device. 
     
     
       3. The shunt device, as set forth in claim  1 , wherein the at least one magnetic device generating a magnetic field includes at least one magnet. 
     
     
       4. The shunt device, as set forth in claim  1 , wherein the at least one magnetic device generating a magnetic field includes a pair of magnets positioned and located in opposed relationship to each other. 
     
     
       5. The shunt device, as set forth in claim  1 , wherein the magnetic field generated by the at least one magnetic device is angularly rotatable about the sensitive plane of the Hall effect element between an angle of 0° wherein the magnetic field is parallel to the sensitive plane of the Hall effect element, and an angle of at least !90° wherein the magnetic field is perpendicular to the sensitive plane of the Hall effect element, said shunt device shielding the sensitive plane of the Hall effect element from the affects of the magnetic field when said magnetic field is located at the 0° angular orientation, and said shunt device exposing the sensitive plane of the Hall effect element to the affects of the magnetic field when said magnetic field is located at some angular orientation other than 0°. 
     
     
       6. The shunt device, as set forth in claim  5 , wherein the magnetic field generated by the at least one magnetic device is further angularly rotatable about the sensitive plane of the Hall effect element between an angle of !90° wherein the magnetic field is perpendicular to the sensitive plane of the Hall effect element, and an angle of !180° wherein the magnetic field is again parallel to the sensitive plane of the Hall effect element, said shunt device shielding the sensitive plane of the Hall effect element from the affects of the magnetic field when said magnetic field is located at the !180° angular orientation, said shunt device exposing the sensitive plane of the Hall effect element to the affects of the magnetic field when said magnetic field is located at some angular orientation other than 0° and other than !180°. 
     
     
       7. The shunt device, as set forth in claim  5 , wherein said shunt device nulls the magnetic field due to any misalignment of the Hall effect element and the at least one magnetic device at the 0° orientation. 
     
     
       8. The shunt device, as set forth in claim  5 , wherein said shunt device nulls the magnetic field due to any misalignment of the Hall effect element and the at least one magnetic device at the ±180° orientation. 
     
     
       9. The shunt device, as set forth in claim  1 , wherein at least the width of that portion of the shunt device positioned to shield the sensitive plane of the Hall effect element from the affects of the magnetic field when the magnetic field is parallel to said sensitive plane is greater than the width of the Hall effect element located adjacent thereto. 
     
     
       10. The shunt device, as set forth in claim  1 , wherein at least the width of that portion of the shunt device positioned to shield the sensitive plane of the Hall effect element from the effects of the magnetic field when the magnetic field is parallel to said sensitive plane is less than or equal to the width of the at least one magnetic device. 
     
     
       11. The shunt device, as set forth in claim  1 , wherein the width of said shunt device is greater than the width of the Hall effect element but less than the width of the at least one magnetic device. 
     
     
       12. The shunt device, as set forth in claim  1 , wherein said shunt device is made of a magnetic material. 
     
     
       13. A magnetic shunt device for use in a Hall effect sensor wherein the Hall effect sensor includes a Hall effect element and a pair of magnetic devices, the magnetic devices being positioned in opposed relationship to each other and generating a magnetic field, the Hall effect element being positioned and located between the pair of opposed magnetic devices and having a sensitive plane which is affected by the magnetic field generated by said magnetic devices, said pair of magnetic devices being rotatable about the Hall effect element between a first position wherein the magnetic field generated by said magnetic devices is parallel to the sensitive plane of the Hall effect element, and a second position angularly related thereto, said shunt device being positioned and located so as to null the affect of the magnetic field on the sensitive plane of the Hall effect element when the magnetic devices are located at their first position, and said shunt device exposing the sensitive plane of the Hall effect element to the affects of the magnetic field when the magnetic devices are located at their second position. 
     
     
       14. A magnetic shunt device for use in a Hall effect sensor wherein the Hall effect sensor includes a Hall effect transducer and a pair of magnetic devices, said pair of magnetic devices being positioned in opposed relationship to each other and each generating a magnetic field, the Hall effect transducer being positioned and located between said opposed pair of magnetic devices and having a sensitive plane which is influenced by the magnetic field generated by said pair of magnetic devices, said pair of magnetic devices being rotatable about the Hall effect transducer in the range of 
       
         
           −90 °[[90° 
         
       
       where  is the angle between the magnetic field generate by said pair of magnetic devices and the direction of current flow through the Hall effect transducer, said magnetic shunt device shielding the sensitive plane of the Hall effect transducer from the influence of the magnetic field when =0° and exposing the sensitive plane of the Hall effect transducer to the influence of the magnetic field when 
       
         
           0 <[90° and when −90°[<0.  
         
       
     
     
       15. A magnetic shunt device for use in a Hall effect sensor wherein the Hall effect sensor includes a Hall effect transducer and a pair of magnetic devices, said pair of magnetic devices being positioned in opposed relationship to each other and each generating a magnetic field, the Hall effect transducer being positioned and located between said opposed pair of magnetic devices and having a sensitive plane which is influenced by the magnetic field generated by said pair of magnetic devices, said pair of magnetic devices being rotatable about the Hall effect transducer in the range of 
       
         
           −180 °[[180 °0  
         
       
       where  is the angle between the magnetic field generate by said pair of magnetic devices and the direction of current flow through the Hall effect transducer, said magnetic shunt device shielding the sensitive plane of the Hall effect transducer from the influences of the magnetic field when =0° and when =!180°, and said magnetic shunt device exposing the sensitive plane of the Hall effect transducer to the influence of the magnetic field when 
       
         
           0<[180° and when−180°[<0.