Magnetic field sensors

• US 6,580,271 B2
• Filed: 12/11/2000
• Issued: 06/17/2003
• Est. Priority Date: 07/20/1999
• Status: Expired due to Fees

• Current Assignee: Spinix Corporation
• Original Assignee: Spinix Corporation
• Inventors: Li, Yi-Qun, Xiang, Xiao-Dong
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US09/734,813
• Publication Number:
  US 20010028245A1
• Time in Patent Office: 918 Days
• Field of Search: 324/207.13, 324/207.24, 324/207.25, 324/260, 324/262, 324/244, 324/209, 737/79, 738/626.9, 333/61, 333/55.R, 333/62, 333/56, 335/3, 335/215, 365/157, 310/311, 310/321, 310/323.06, 310/364
• US Class Current: 324/260
• CPC Class Codes: G01R 33/02 Measuring direction or magnitude of magnetic fields or magnetic flux G01R33/20 takes precedence
• CPC Class Codes: G01R 33/18 Measuring magnetostrictive properties

Abstract

Methods and systems for estimating a value of a static or time varying magnetic field that is present. In a first embodiment, a layer of a magnetostrictive (MNS) material and a layer of a piezoresistive (PZR) material are combined and exposed to the unknown magnetic field, and a current source and charge-carrying line are connected between two spaced apart locations in the PZR layer. A meter measures a voltage difference or current between the two locations and estimates the value of the magnetic field. In a second embodiment, a layer of a magnetostrictive (MNS) material and a layer of a piezoelectric (PZT) material are combined and exposed to a combination of the unknown magnetic field and a selected time varying magnetic field. A meter measures a voltage change, current change or other electrical variable between two spaced apart locations at two or more selected times and estimates the value of the unknown magnetic field. The layers of MNS, PZR and/or PZT material may be planar or may be selected annular sectors or cylindrical sectors.

Claims

1. A method for estimating the value of a magnetic field, the method comprising:

providing a layer of a selected magnetostrictive (MNS) material, contiguous to a layer of a selected piezoresistive (PZR) material across an MNS-PZR interface;

providing a current in a charge-carrying line between selected spaced apart first and second locations on the PZR layer;

exposing at least a portion of the MNS layer to a magnetic field, and allowing a change in electrical resistance to develop in the PZR layer in response to exposure of the MNS layer to the magnetic field;

measuring a change in a selected electrical field variable e(t) developed between third and fourth locations adjacent to the first and second locations, respectively, in response to exposure of the MNS layer to the magnetic field; and

estimating the magnetic field value that corresponds to at least one value of the change in the variable e(t).

2. The method of claim 1, further comprising choosing said magnetic field to have a substantially constant value.

3. The method of claim 1, further comprising:

allowing said value of said magnetic field to vary with time;

measuring a first value e1 and a second value e2 of said electrical field variable value e(t) at first and second spaced apart selected times, respectively; and

estimating an average value of said magnetic field using a linear combination of the measured values e1 and e2.

4. The method of claim 1, further comprising choosing said electrical field variable e(t) from the group of variables consisting of voltage change and current change.

5. The method of claim 1, further comprising choosing said MNS material from the group of materials consisting of:

terfenol-D, Fe_aCo<sub>1−

a</sub> (0≦

a≦

1), Fe, Co, Ni, Fe_bNi<sub>1−

b</sub> (0≦

b≦

1), (Tb_cDy<sub>1−

c</sub>)Fe₂ (0≦

c≦

1)TbFe₂, Fe_0.8B_0.2, and Fe_0.4Ni_0.4B_0.2;

ceramics of Fe₃O₄, Fe₂NiO₄, and Fe₂CoO₄; and

metallic glasses of FeSiB and (FeNi) SiB.

6. The method of claim 1, further comprising choosing said PZR material to comprise a selected semiconductor material doped with at least one dopant drawn from the group of dopants consisting of B, Al, Ga, In, P, As and Sb.

7. The method of claim 1, further comprising choosing said first and second locations on said PZR layer so that said current within said PZR layer is oriented substantially parallel to said interface.

8. The method of claim 1, further comprising choosing said first and second locations on said PZR layer so that said current within said PZR layer is oriented substantially perpendicular to said interface.

9. The method of claim 1, further comprising providing at least one of said PZR layer and said MNS layer as at least one of a planar layer and a selected sector of an annulus.

19. The method of claim 1, further comprising:

providing a second layer of said MNS material, contiguous to said layer of PZR material across a second MNS-PZR interface and positioned so that said PZR layer lies between said first MNS layer and the second MNS layer;

exposing at least a portion of the second MNS layer to said magnetic field, and allowing a resulting change in electrical resistance to develop in said PZR layer in response to exposure of the second MNS layer to said magnetic field;

measuring a further change in said selected electrical field variable e(t) developed between said third and fourth locations, in response to exposure of the second MNS layer to said magnetic field; and

estimating a magnetic field value that corresponds to at least one value of the resulting change in said variable e(t).

10. A system for estimating the value of a magnetic field, the system comprising:

a layer of a selected magnetostrictive (MNS) material contiguous to a selected piezoresistive (PZR) material, where the MNS layer, when exposed to a magnetic field, provides a change in electrical resistance in the PZR layer;

a charge-carrying line, electrically connected between selected spaced apart first and second locations on the PZR layer, the line having a current source;

a meter that measures a selected electrical measurement variable value e(t) developed between locations adjacent to the first and second locations, in response to exposure of the MNS layer to the magnetic field, and estimates the magnetic field value based on the value of the variable e(t) for at least one measurement time.

11. The method of claim 10, wherein said magnetic field has a substantially constant value.

12. The system of claim 10, wherein said magnetic field is allowed to vary with time and said meter:

measures a first value e1 and a second value e2 of said electrical field variable value e(t) at first and second selected times; and

estimates an average value of said magnetic field value using a linear combination of the measured values e1 and e2.

13. The system of claim 10, wherein said electeical field variable e(t) is drawn from the group of variables consisting of voltage change and current change.

14. The method of claim 10, wherein said MNS material is drawn from the group of materials consisting of:

terfenol-D, Fe_aCo<sub>1−

a</sub> (0≦

a≦

1), Fe, Co, Ni, Fe_bNi<sub>1−

b</sub> (0≦

b≦

1), (Tb_cDy<sub>1−

c</sub>)Fe₂ (0≦

c≦

1),TbFe₂, Fe_0.8B_0.2, and Fe_0.4Ni_0.4B_0.2;

ceramics of Fe₃O₄, Fe₂NiO₄, and Fe₂CoO₄; and

metallic glasses of FeSiB and (FeNi)SiB.

15. The system of claim 10, wherein said PZR material comprises a selected semiconductor material doped with at least one dopant drawn from the group of dopants consisting of B, Al, Ga, In, P, As and Sb.

16. The system of claim 10, wherein said first and second locations on said PZR layer are chosen so that said current within said PZR layer is oriented substantially parallel to said interface.

17. The system of claim 10, wherein said first and second locations on said PZR layer are chosen so that said current within said PZR layer is oriented substantially perpendicular to said interface.

18. The system of claim 10, wherein at least one of said PZR layer and said MNS layer is provided as at least one of a planar layer and a selected sector of an annular layer.

20. The system of claim 10, further comprising:

a second layer of said MNS material, contiguous to said layer of PZR material across a second MNS-PZR interface and positioned so that said PZR layer lies between said first MNS layer and the second MNS layer, wherein the second MNS layer, when exposed to said magnetic field, provides a second change in electrical resistance in said PZR layer;

wherein said meter measures a further change in said selected electrical field variable e(t) developed between said third and fourth locations, in response to exposure of the second MNS layer to said magnetic field and estimates a magnetic field value that corresponds to at least one value of the resulting change in said variable e(t).