Magnetoresistive sensor with reduced output signal jitter and temperature compensation

• US 6,246,233 B1
• Filed: 05/27/1997
• Issued: 06/12/2001
• Est. Priority Date: 12/30/1994
• Status: Expired due to Fees

• Current Assignee: Northstar Technologies Incorporated (Brunswick Corporation)
• Original Assignee: Northstar Technologies Incorporated (Brunswick Corporation)
• Inventors: Griffen, Neil C., Stokes, Richard S.
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US08/863,339
• Time in Patent Office: 1,477 Days
• Field of Search: 324/207.21, 324/207.22, 324/207.25, 324/173, 324/174, 324/252, 324/207.12, 324/207.24, 324/225, 338/32.R, 327/510, 337/06, 337/08
• US Class Current: 324/207.21
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01P 3/487 delivered by rotating magnets

Abstract

A magnetoresistive sensor for use in a rotary encoder with a drum having a circumference covered with a magnetic track at a predetermined pitch includes a plurality of magnetoresistive elements positioned opposite the drum and connected in a bridge circuit such that when the drum rotates an output signal from the bridge indicates a rotary angle of the drum. The magnetoresistive elements include one or more complementary pairs of elements positioned 180° out of phase. Each of such pair of complementary magnetoresistive elements is connected in one leg of a bridge circuit such that jitter effects caused by asymmetric magnetic fields and physical differences between sensor elements are cancelled. Magnetoresistive sensor element configurations for minimizing the impact of temperature gradients across the magnetoresistive sensor are also disclosed.

Claims

1. A frequency doubling sensor array to detect the motion of a magnetic pattern generated by a moving magnetic source magnetized at a pitch λ

, comprising;

a first pair of sensor elements separated by 2½

λ and

connected to form a first half-bridge;

a second pair of sensor elements separated by 2½

λ and

connected to form a second half-bridge, the first sensor element of the first and second pairs being separated by 3λ

/8;

a third pair of sensor elements separated by 2½

λ and

connected to form a third half-bridge, the first sensor element of the third pair being separated by 3λ

/8 from the first sensor element in the second pair and by 3λ

/4 from the first sensor element in the first pair;

a fourth pair of sensor elements separated by 2½

λ and

connected to form a fourth half-bridge, the first sensor element of the fourth pair separated by 3λ

/8 from the first sensor element in the third pair and by 3λ

/4 from the first sensor element in the second pair; and

plural complementary sensor elements, each complementary sensor element separated by λ

from and connected to a corresponding sensor element of the first through fourth pairs of sensor elements.

2. The sensor array in claim 1, wherein the first through fourth pairs of sensor elements are connected in parallel or in series.

3. The sensor array in claim 1, wherein the complementary sensor elements are connected in parallel or in series to their corresponding elements in the first through fourth half-bridges.

4. The sensor array in claim 1, further comprising:

a fifth pair of sensor elements separated by 2½

λ and

connected to form a fifth half-bridge, the first sensor element of the fifth pair being separated by 3λ

/8 from the first sensor element in the fourth pair and by 3λ

/4 from the first sensor element in the third pair.

5. The sensor array in claim 1, wherein sensor elements in at least one of the half-bridges are placed in close proximity to minimize an effect of a temperature difference across the one half-bridge.

9. A frequency doubling sensor array to detect the motion of a magnetic pattern generated by a moving magnetic source magnetized at a pitch λ

, comprising;

a first pair of sensor elements separated by 3½

λ and

connected to form a first half-bridge;

a second pair of sensor elements separated by 3½

λ and

connected to form a second half-bridge, the first sensor element of the first and second pairs being separated by 5λ

/8;

a third pair of sensor elements separated by 3½

λ and

connected to form a third half-bridge, the first sensor element of the third pair being separated by 5λ

/8 from the first element in the second pair and by 1¼

λ

from the first element in the first pair;

a fourth pair of sensor elements separated by 3½

λ and

connected to form a fourth half-bridge, the first sensor element of the fourth pair separated by 5λ

/8 from the first sensor element in the third pair and by 1¼

λ

from the first sensor element in the second pair;

plural complementary sensor elements, each complementary sensor element separated by λ

from and connected to each sensor element of each of the first through fourth pairs of sensor elements.

6. The sensor array in claim 9, further comprising:

a fifth pair of sensor elements separated by 3½

λ and

connected to form a fifth half-bridge, the first sensor element of the fifth pair of sensor elements being separated by 5λ

/8 from the first sensor element in the fourth pair of sensor elements and by 1¼

λ

from the first sensor element in the third pair of sensor elements.

7. The sensor array in claim 6, wherein the first through fifth pairs of sensor elements are connected in parallel or in series.

8. The sensor array in claim 7, wherein the complementary sensor elements are connected in parallel or in series to their corresponding elements in the first through fifth half-bridges.

10. The sensor array in claim 9, wherein sensor elements in at least one of the half-bridges are placed in close proximity to minimize an effect of a temperature difference across the one half-bridge.

11. A frequency doubling magnetoresistive sensor array to detect the motion of a magnetic pattern generated by a moving magnetic source magnetized at a pitch λ

, comprising;

a first pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, where n is an integer;

a second pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of the first and second pairs of sensor elements being separated by (n+3/8)λ

;

a third pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of the third pair of sensor elements being separated by (n+3/8)λ

from the first sensor element in the second pair of sensor elements;

a fourth pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of the fourth pair of sensor elements being separated by (n+3/8)λ

from the first sensor element in the third pair of sensor elements; and

complementary sensor elements corresponding and electrically connected to sensor elements for at least some of the first through fourth pairs of sensor elements, each complementary and corresponding sensor element spaced apart by (2n−

1)λ

.

12. The sensor array in claim 11, wherein the integer value of n differs for the first through the fourth pairs of sensor elements.

13. The sensor array in claim 11, further comprising:

a fifth pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of this pair separated by 3λ

/8 from the first sensor element in the fourth pair of sensor elements.

14. The sensor array of claim 11, wherein each pair of sensor elements is connected serially or in parallel in a half-bridge configuration.

15. The sensor array of claim 14, wherein complementary sensor elements are connected in a series or parallel to their corresponding sensor elements.

16. The sensor array in claim 11, wherein sensor elements in at least one of the half-bridges are placed in close proximity to minimize an effect of a temperature difference across the one half-bridge.

17. A frequency doubling magnetoresistive sensor array to detect the motion of a magnetic pattern generated by a moving magnetic source magnetized at a pitch λ

, comprising;

a first pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, where n is an integer;

a second pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of the first and second pairs of sensor elements being separated by 3λ

/8;

a third pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of the third pair of sensor elements being separated by 3λ

/8 from the first sensor element in the second pair of sensor elements;

a fourth pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of the fourth pair of sensor elements being separated by 3λ

/8 from the first sensor element in the third pair of sensor elements; and

complementary sensor elements corresponding and electrically connected to sensor elements for at least some of the first through fourth pairs of sensor elements, each complementary and corresponding sensor element spaced a distance of (2m−

1)λ

, where m is an integer other than one.

18. The sensor array in claim 17, further comprising:

a fifth pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of the fifth pair of sensor elements being separated by 3λ

/8 from the first sensor element in the fourth pair of sensor elements.

19. The sensor array in claim 17, wherein sensor elements in at least one of the half-bridges are placed in close proximity to minimize an effect of a temperature difference across the one half-bridge.

20. A frequency doubling magnetoresistive sensor array to detect the motion of a magnetic pattern generated by a moving magnetic source magnetized at a pitch λ

, comprising;

a first pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, where n is an integer other than zero;

a second pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of the first and second pairs of sensor elements being separated by 5λ

/8;

a third pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of the third pair of sensor elements being separated by 5λ

/8 from the first sensor element in the second pair of sensor elements;

a fourth pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of the fourth pair of sensor elements being separated by 5λ

/8 from the first sensor element in the third pair of sensor elements; and

complementary sensor elements corresponding and electrically connected to sensor elements for at least some of the first through fourth pairs of sensor elements, each complementary and corresponding sensor element spaced apart by (2n−

1)λ

.

21. The sensor array in claim 20, further comprising:

a fifth pair of sensor elements separated by (n+½

)λ and

connected to form a half-bridge, with the first sensor element of this pair separated by 5λ

/8 from the first sensor element in the fourth pair of sensor elements.

22. The sensor array in claim 20, wherein sensor elements in at least one of the half-bridges are placed in close proximity to minimize an effect of a temperature difference across the one half-bridge.

23. A magnetoresistive sensor array to detect relative motion between said sensor array and a magnetic source magnetized at a pitch λ

said magnetic source providing a magnetic pattern of alternating north and south magnetic poles, said sensor array comprising;

at least first and second pairs of magnetoresistive sensor elements, said first pair of magnetoresistive elements electrically connected to form a first quarter-bridge circuit comprising at least a first sensor element and a second sensor element positioned to magnetically complement one another such that whenever the first sensor element senses a north magnetic pole of said pattern the second sensor element senses a south magnetic pole of said pattern, said second pair of magnetoresistive elements electrically connected to form a second quarter-bridge circuit electrically connected to said first quarter-bridge circuit to form a first half-bridge circuit, said second pair of magnetoresistive elements comprising at least a third sensor element and a fourth sensor element positioned to magnetically complement one another such that whenever the third sensor element senses a north magnetic pole of said pattern the fourth sensor element senses a south magnetic pole of said pattern, a plurality of additional magnetoresistive elements electrically connected to form a plurality of additional half-bridge circuits, wherein, in use, said first half-bridge circuit and said additional half-bridge circuits, in combination, produce substantially periodic signals phase shifted with respect to one another to facilitate production of responsive frequency multiplied outputs in quadrature,

wherein at least the said first, second, third and fourth magnetoresistive sensor elements are positioned in the magnetoresistive sensor array to minimize the effect of differences in temperature between magnetoresistive sensor elements in the first and second pairs.

24. The magnetoresistive sensor array in claim 23, wherein the first and second magnetoresistive sensor elements are separated in the magnetoresistive sensor array by substantially 1.5λ

or less.

25. The magnetoresistive sensor array in claim 23,

wherein the first and second magnetoresistive elements are spaced apart by (2n− 1)λ

where n is a positive integer.

26. The magnetoresistive sensor array in claim 23, wherein magnetoresistive sensor elements in at least the first quarter-bridge are placed in close proximity to one another so as to minimize the effect of a temperature difference across said first quarter-bridge.

27. A sensor array as in claim 23 further including a frequency multiplier coupled to said elements for multiplying the output frequency of said array.

28. A sensor array as in claim 27 wherein said frequency multiplier mutliplies said output frequency while maintaining said output in quadrature.

30. The method in claim 26, further comprising:

placing sensor elements in each half-bridge in close proximity to minimize an effect of a temperature difference across each half-bridge.

29. A method of configuring a plurality of magnetoresistive elements in a frequency doubling magnetoresistive sensor that moves relative to a series of alternating north and south magnetic poles on a single track where adjacent north and south poles are separated by pitch λ

, comprising the steps of;

providing a first group of magnetoresistive elements and a second group of magnetoresistive elements with successive magnetoresistive elements in each group being separated by (n+½

)λ

, where n=0, ±

1, ±

3, ±

5, . . . ;

connecting ones of the magnetoresistive elements from the first group to corresponding magnetoresistive elements from the second group to form corresponding half-bridges, each half-bridge having a first magnetoresistive element from the first group and a second magnetoresistive element from the second group;

generating at a node in each half-bridge located between the first and second magnetoresistive element an output signal;

separating the first magnetoresistive sensor of a first half-bridge from the first magnetoresistive sensor of a second half-bridge by (n+⅜

)λ

;

separating the first magnetoresistive sensor of a third half-bridge from the first magnetoresistive sensor of the second half-bridge by (n+⅜

)λ and

from the first magnetoresistive sensor of the first half-bridge by (n+(2)*⅜

)λ

;

separating the first magnetoresistive sensor of a fourth half-bridge from the first magnetoresistive sensor of the third half-bridge by (n+⅜

)λ

, from the first magnetoresistive sensor of the second half-bridge by (n+(2)*⅜

)λ

, and from the magnetoresistive sensor of the first half-bridge by (n+(3)*⅜

)λ

;

separating the second magnetoresistive sensor element of each half-bridge from the corresponding first magnetoresistive sensor element by (n+½

)λ

; and

connecting complementary magnetoresistive sensor elements to the first and second magnetoresistive sensor elements of one or more of the half-bridges to form first and second complementary magnetoresistive pairs in each of the one or more half-bridges, the magnetoresistive sensor elements in each pair being separated by (2n+1)λ

,

wherein electrical connection of complementary magnetoresistive elements compensates for asymmetries in magnetic field detected by each magnetoresistive element that cause output signal jitter.

31. A magnetoresistive sensor for detecting the changing magnetic fields generated by relative motion between said sensor and a magnetic source incrementally magnetized with alternating north and south poles separated by the substantially uniform pitch λ

, said sensor comprising;

a magnetoresistive element array including plural pairs of magnetoresistive elements, wherein at least a first pair of said magnetoresistive elements are separated substantially by a spacing of nλ

, where n is an odd integer;

electrical conductors electrically connecting the plural pairs of magnetoresistive elements within the array to form a plurality of half-bridge circuits, each half-bridge circuit including plural quarter-bridge circuits, wherein said first pair of magnetoresistive elements are electrically connected together within the same quarter-bridge circuit;

wherein, in use, said plurality of half-bridge circuits produce plural substantially periodic signals phase shifted such that at least one of said plural periodic signals is not at 90°

, 180°

or 270°

electrical with respect to all the other plural periodic signals.

32. The magnetoresistive sensor of claim 31 wherein, in use, said first pair of magnetoresistive elements are electrically connected in series.

33. The magnetoresistive sensor of claim 31 wherein, in use, said first pair of magnetoresistive elements are electrically connected in parallel.

34. The magnetoresistive sensor of claim 31 wherein, in use, said plurality of half-bridge circuits are electrically connected to provide at least a pair of substantially periodic output signals in quadrature.

35. The magnetoresistive sensor of claim 31 wherein, in use, said plurality of half-bridge circuits are electrically connected to provide substantially periodic output signals having a predetermined phase relationship such that when said substantially periodic output signals are electronically combined, frequency multiplied further output signals in quadrature are produced.

36. The magnetoresistive sensor of claim 31 wherein said periodic signals are substantially sinusoidal.

37. The magnetoresistive sensor of claim 31 wherein said magnetoresistive elements are disposed on a common substrate.

38. The magnetoresistive sensor of claim 31 wherein said magnetoresistive elements are disposed on a common support structure.

39. The magnetoresistive sensor of claim 31 wherein, in use, any two of said periodic signals are phase shifted by substantially 45°

.

40. A magnetoresistive sensor for detecting the changing magnetic fields generated by relative motion between said sensor and a magnetic source incrementally magnetized with alternating north and south magnetic poles spaced apart by a pitch λ

, said sensor comprising;

a magnetoresistive element array including plural pairs of magnetoresistive elements disposed on a support structure and electrically connected so as to compensate for the asymmetric response of the magnetoresistive elements in said plural pairs to said north and south magnetic poles, wherein each pair of said magnetoresistive elements is separated substantially by a spacing of nλ

, where n is an odd integer; and

wherein

said array has sufficient pairs of magnetoresistive elements disposed and electrically connected so as to substantially compensate for differences in the spacing between magnetic poles on said magnetic source,

said sensor further comprising electrical conductors electrically connecting each pair of said magnetoresistive elements to form a plurality of quarter-bridge circuits, and further electrical conductors further electrically connecting at least some of said plural quarter-bridge circuits to form a plurality of half-bridge circuits producing a corresponding plurality of substantially periodic signals phase shifted such that at least one of said plural signals is not at 90°

, 180°

or 270°

electrical with respect to all other ones of the plural signals.

41. The magnetoresistive sensor of claim 40 wherein, in use, at least one of said plural pairs of magnetoresistive elements is electrically connected in series.

42. The magnetoresistive sensor of claim 40 wherein, in use, at least one of said plural pairs of magnetoresistive elements is electrically connected in parallel.

43. The magnetoresistive sensor of claim 40 wherein, in use, said sensor provides at least a pair of substantially periodic output signals in quadrature.

44. The magnetoresistive sensor of claim 43 wherein said periodic signals are substantially sinusoidal.

45. The magnetoresistive sensor of claim 40 wherein, in use, said sensor provides substantially periodic output signals having a predetermined phase relationship such that when said substantially periodic output signals are electronically conditioned and combined, further frequency multiplied output signals in quadrature are produced.

46. The magnetoresistive sensor of claim 45 wherein said periodic signals are substantially sinusoidal.

47. The magnetoresistive sensor of claim 45 wherein, in use, any two of said periodic signals are phase shifted by substantially 45°

.

48. The magnetoresistive sensor of claim 40 wherein said magnetoresistive elements are disposed on a common substrate.

49. The magnetoresistive sensor of claim 40 wherein said magnetoresistive elements are disposed on a common support structure.

50. A sensor array as in claim 40 further including a frequency multiplier coupled to said elements for multiplying the output frequency of said array.

51. A sensor array as in claim 50 wherein said frequency multiplier multiplies said output frequency while maintaining said output in quadrature.

53. The encoder of claim 51 wherein said magnetic source is adapted to be mounted to a shaft for rotation therewith and includes a substantially round periphery having said alternating north and south poles magnetized thereon;

and

said magnetoresistive sensor is electrically connected to electronic circuitry capable of providing at least a pair of output signals in quadrature and proportional to the rotational velocity of said shaft.

52. An encoder for monitoring the relative motion between a magnetoresistive sensor and a magnetic source incrementally magnetized with alternating north and south magnetic poles separater by a substantially uniform pitch λ

, said encoder including a support structure that supports said sensor and provides for magnetic coupling of said sensor with said magnetic source while permitting relative motion between said sensor and said magnetic source, said sensor comprising;

an array of magnetoresistive elements including plural pairs of magnetoresistive elements, wherein at least a first pair of said magnetoresistive elements are separated substantially by a spacing of nλ

, where n is an odd integer; and

electrical conductors electrically connecting the plural pairs of magnetoresistive elements to form a plurality of half-bridge circuits producing a corresponding plurality of substantially periodic signals phase shifted such that at least one of said plural signals is not at 90°

, 180°

, or 270°

electrical with respect to all other ones of the plural signals, each half-bridge circuit further comprising a plurality of quarter-bridge circuits wherein said electrical conductors electrically connect said first pair of magnetoresistive elements within the same quarter-bridge circuit to thereby compensate for differences in the response characteristic of said magnetoresistive elements to said north and south magnetic poles.

54. A process for manufacturing a magnetoresistive sensor for detecting changing magnetic fields generated by relative motion between said sensor and a magnetic source that is incrementally magnetized with alternating north and south poles separated by the substantially uniform pitch λ

, said process comprising;

disposing an array of magnetoresistive elements onto a substrate, including the step of spacing at least a pair of said magnetoresistive elements substantially by a spacing of nλ

, where n is an odd integer; and

electrically connecting the magnetoresistive elements within the array to form plural half-bridge circuits each comprising plural quarter-bridge circuits, said plural half-bridge circuits, in use, producing plural substantially periodic signals that are phase shifted such that at least one of said plural periodic signals is not at 90°

, 180°

or 270°

electrical with respect to all other of said plural periodic signals, said electrically connecting step including the step of connecting said pair of magnetoresistive elements within the same one of said plural quarter bridge circuits.

55. The process of claim 54 wherein said electrically connecting step includes connecting said pair of magnetoresistive elements in series.

56. The process of claim 54 wherein said electrically connecting step includes connecting said pair of magnetoresistive elements in parallel.