Magnetic differential field sensor using hysteresis field in AMR films

• US 20040075430A1
• Filed: 10/21/2002
• Published: 04/22/2004
• Est. Priority Date: 10/21/2002
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Haji-Sheikh, Michael J., Chandler, Ronald W.
• Granted Patent: US 6,831,458 B2
• Time in Patent Office: Days
• US Class Current: 324/252
• CPC Class Codes: G01R 33/09 Magnetoresistive devices

Abstract

A method and system for detecting a magnetic field utilizing a magnetoresistor of a magnetic sensor is disclosed. A normalized magnetoresistance associated with the magnetoresistor can be calculated such that the magnetoresistor comprises an initial magnetization direction thereof. The magnetic field is generally permitted to exceed an ability of the magnetoresistor to remain pointed in the initial magnetization direction, thereby enabling the magnetoresistor to experience a magnetization reversal thereof. The normalized resistance can be placed into a new state in response to the magnetization reversal thereof, thereby permitting the normalized resistance to be utilized as a switch thereof and allowing the magnetic sensor to detect changes in the magnetic field associated with the magnetoresistor.

Claims

1. A method for detecting a magnetic field utilizing a magnetoresistor of a magnetic sensor, said method comprising the steps of:

calculating a normalized magnetoresistance associated with said magnetoresistor, wherein said magnetoresistor comprises an initial magnetization direction thereof;

permitting said magnetic field to exceed an ability of said magnetoresistor to remain pointed in said initial magnetization direction, thereby enabling said magnetoresistor to experience a magnetization reversal thereof; and

placing said normalized resistance into a new state in response to said magnetization reversal thereof, thereby permitting said normalized resistance to be utilized as a switch thereof and allowing said magnetic sensor to detect changes in said magnetic field associated with said magnetoresistor.

2. The method of claim 1 further comprising the step of altering said normalized resistance in response to a change in said magnetic field.

3. The method of claim 1 wherein said magnetic field comprises a one-dimensional zero crossing magnetic field.

4. The method of claim 1 further comprising the step of identifying a switching field associated with said magnetization reversal thereof.

5. The method of claim 4 wherein said magnetic field associated with said magnetoresistor comprises a sinusoidally varying field.

6. The method of claim 5 further comprising the step of converting said sinusoidally varying field into a pulse train, such that a value of said switching field, which produces said pulse train thereof, is dependent on a geometry of said magnetoresistor.

7. The method of claim 6 further comprising the steps of associating a differential Wheatstone bridge circuit with said magnetic sensor, such that said differential Wheatstone bridge circuit produces an output comprising said pulse train.

8. The method of claim 7 further comprising the step of configuring said differential Wheatstone bridge circuit to comprise at least one comparator and at least one D-flip-flop circuit to create a digital representation of said magnetic field, such that said magnetic field comprises a one-dimensional zero crossing magnetic field.

9. The method of claim 1 wherein said magnetic sensor comprises a permalloy sensor.

10. The method of claim 1 wherein said magnetic sensor comprises an AMR sensor.

11. A method for detecting a magnetic field utilizing a magnetoresistor of a magnetic sensor, said method comprising the steps of:

calculating a normalized magnetoresistance associated with said magnetoresistor, wherein said magnetoresistor comprises an initial magnetization direction thereof;

permitting said magnetic field to exceed an ability of said magnetoresistor to remain pointed in said initial magnetization direction, thereby enabling said magnetoresistor to experience a magnetization reversal thereof;

altering said normalized resistance in response to a change in said magnetic field, wherein said magnetic field comprises a one-dimensional zero crossing magnetic field;

placing said normalized resistance into a new state in response to said magnetization reversal thereof, thereby permitting said normalized resistance to be utilized as a switch thereof and allowing said magnetic sensor to detect changes in said magnetic field associated with said magnetoresistor; and

identifying a switching field associated with said magnetization reversal thereof.

12. A magnetic sensor for detecting a magnetic field, said magnetic sensor comprising:

a magnetoresistor comprising an initial magnetization direction thereof, such that a normalized magnetoresistance associated with said magnetoresistor is calculable thereof;

a magnetic field altering mechanism which permits said magnetic field to exceed an ability of said magnetoresistor to remain pointed in said initial magnetization direction, thereby enabling said magnetoresistor to experience a magnetization reversal thereof; and

wherein said normalized resistance is placed into a new state in response to said magnetization reversal thereof, thereby permitting said normalized resistance to be utilized by the magnetic sensor as a switch thereof and allowing the magnetic sensor to detect changes in said magnetic field associated with said magnetoresistor.

13. The system of claim 12 wherein said normalized resistance is alterable in response to a change in said magnetic field.

14. The system of claim 12 wherein said magnetic field comprises a one-dimensional zero crossing magnetic field.

15. The system of claim 12 further comprising a detector for identifying a switching field associated with said magnetization reversal thereof.

16. The system of claim 15 wherein said magnetic field associated with said magnetoresistor comprises a sinusoidally varying field.

17. The system of claim 16 further comprising a converter for converting a sinusoidally varying field into a pulse train, such that a value of said switching field, which produces said pulse train thereof, is dependent on a geometry of said magnetoresistor.

18. The system of claim 17 wherein a differential Wheatstone bridge circuit is associated with said magnetic sensor, such that said differential Wheatstone bridge circuit produces an output comprising said pulse train.

19. The system of claim 18 wherein said differential Wheatstone bridge circuit comprises at least one comparator and at least one D-flip-flop circuit to create a digital representation of said magnetic field, such that said magnetic field comprises a one-dimensional zero crossing magnetic field.

20. The system of claim 12 wherein said magnetic sensor comprises a permalloy sensor.

21. The system of claim 12 wherein said magnetic sensor comprises an AMR sensor.

22. A magnetic sensor for detecting a magnetic field, said magnetic sensor comprising:

a magnetoresistor comprising an initial magnetization direction thereof, such that a normalized magnetoresistance associated with said magnetoresistor is calculable thereof;

a magnetic field altering mechanism which permits said magnetic field to exceed an ability of said magnetoresistor to remain pointed in said initial magnetization direction, thereby enabling said magnetoresistor to experience a magnetization reversal thereof;

wherein said normalized resistance is alterable in response to a change in said magnetic field, such that said magnetic field comprises a one-dimensional zero crossing magnetic field;

wherein said magnetic field associated with said magnetoresistor comprises a sinusoidally varying field; and

wherein said normalized resistance is placed into a new state in response to said magnetization reversal thereof, thereby permitting said normalized resistance to be utilized as a switch thereof and allowing said magnetic sensor to detect changes in said magnetic field associated with said magnetoresistor.

23. A sensor for detecting a magnetic field, said sensor comprising:

a permalloy magnetoresistor comprising an initial magnetization direction thereof, such that a normalized magnetoresistance associated with said permalloy magnetoresistor is calculable thereof;

a magnetic field altering mechanism that permits said magnetic field to exceed an ability of said permalloy magnetoresistor to remain pointed in said initial magnetization direction, thereby enabling said permalloy magnetoresistor to experience a magnetization reversal thereof;

a converter for converting a sinusoidally varying field into a pulse train; and

wherein said normalized resistance is automatically placed into a new state in response to said magnetization reversal thereof, thereby permitting said normalized resistance to be utilized as a switch thereof which permits said sensor to detect changes in said magnetic field associated with said magnetoresistor via said pulse train.