Magnetic field sensors

• US 20010028245A1
• Filed: 12/11/2000
• Published: 10/11/2001
• Est. Priority Date: 07/20/1999
• Status: Active Grant

• Current Assignee: Spinix Corporation
• Original Assignee: Spinix Corporation
• Inventors: Xiang, Xiao-Dong, Li, Yi-Qun
• Granted Patent: US 6,580,271 B2
• Time in Patent Office: Days
• US Class Current: 324/312
• 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 connected across an interface to a layer of a selected piezoresistive (PZR) material;

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

exposing at least a portion of the MNS layer to a magnetic field, and allowing a strain 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 locations adjacent to the first and second locations, 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;

forming a measurement value Δ

e of said change in said electrical field variable value e(t) at a selected time; and

estimating said magnetic field value for at least one time at the selected time using the measurement value change Δ

e.

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> (1≦

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 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, a selected sector of an annular layer, and a selected sector of a cylinder.

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

providing a layer of a selected magnetostrictive (MNS) material connected across an interface to a layer of a selected piezoelectric (PZT) material;

exposing the MNS layer to a first magnetic field and to a selected time varying second magnetic field, and allowing a strain to develop in the PZT layer in response to exposure of the MNS layer to the combined first and second magnetic fields;

measuring a value of a time varying electrical field variable e(t) developed between first and second spaced apart locations on the PZT layer at two or more selected times; and

estimating the first magnetic field value that corresponds to the measured value of the variable e(t) at the two or more times.

11. The method of

claim 10

, further comprising choosing said first magnetic field to have a substantially constant value.

12. The method of

claim 10

, further comprising:

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

measuring said variable value e(t) at at least first and second selected times; and

estimating said first magnetic field value, at a time in a selected time interval including at least one of said first and second times, from said measured value e(t) for the first and second selected times.

13. The method of

claim 10

, further comprising choosing said electrical field variable e(t) from the group of variable consisting of voltage change and current change.

14. The method of

claim 10

, 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.

15. The method of

claim 10

, further comprising choosing said PZT material to comprises at least one of lead zirconate titanate, PbTi_x(Mg_1/3Nb_2/3)₁₋

xO₃ (0≦

x≦

1), polyvinylidene fluoride, aluminum nitride and quartz.

16. The method of

claim 10

, further comprising choosing said first and second locations on said PZT layer so that said variable e(t) is measured within said PZT layer substantially parallel to said interface.

17. The method of

claim 10

, further comprising choosing said first and second locations on said PZT layer so that said variable e(t) is measured within said PZT layer substantially perpendicular to said interface.

18. The method of

claim 10

, further comprising providing at least one of said PZT layer and said MNS layer as at least one of a planar layer, a selected sector of an annular layer, and a selected sector of a cylinder.

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

a layer of a selected magnetostrictive (MNS) material connected across an interface to a layer of a selected piezoresistive (PZR) material, where the MNS layer, when exposed to a magnetic field, provides a strain 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 selected 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.

20. The system of

claim 19

, wherein said magnetic field has a substantially constant value.

21. The system of

claim 19

, wherein said magnetic field is allowed to vary with time and said meter:

forms a measurement Δ

e of said electrical field variable value e(t) at a selected time; and

estimates said magnetic field value at the selected time using the measured value change Δ

e.

22. The system of

claim 19

, wherein said electrical field variable e(t) is drawn from the group of variables consisting of voltage change and current change.

23. The system of

claim 19

, 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.

24. The system of

claim 19

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

25. The system of

claim 19

, 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.

26. The system of

claim 19

, 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.

27. The system of

claim 19

, wherein at least one of said PZR layer and said MNS layer is provided as at least one of a planar layer, a selected sector of an annular layer, and a selected sector of a cylinder.

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

a layer of a selected magnetostrictive (MNS) material connected across an interface to a layer of a selected piezoelectric (PZT) material, where the MNS layer, when immersed in a first magnetic field, provides a strain in the PZT layer;

a source of a selected time varying second magnetic field;

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

a source of a selected time varying second magnetic field, to which the MNS layer is exposed;

a meter that measures a selected electrical measurement variable value e(t) developed between spaced apart first and second locations on the PZT layer, in response to exposure of the MNS layer to the combined first and second magnetic fields, and estimates the first magnetic field value based on the value of the variable e(t) measured at two or more selected times.

29. The system of

claim 28

, wherein said first magnetic field has a substantially constant value.

30. The system of

claim 28

, wherein said first magnetic field is allowed to vary with time and said meter:

measures said variable value e(t) at said two or more selected times; and

estimates said first magnetic field value, at a time in a selected time interval including at least one of said two or more selected times, from said measured value e(t) for said two or more selected times.

31. The system of

claim 28

, wherein said electrical field variable e(t) is drawn from the group of variables consisting of voltage change and current change.

32. The system of

claim 28

, wherein said MNS material is drawn from the group of materials consisting of:

tterfenol-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.

33. The system of

claim 28

, wherein said PZT material comprises at least one of lead zirconate titanate, polyvinylidene fluoride, aluminum nitride, quartz and PbTi_x(Mg_1/3Nb_2/3)_1-xO₃ (0≦

x≦

1).

34. The system of

claim 28

, wherein said first and second locations on said PZT layer are chosen so that said variable e(t) is measured within said PZT layer substantially parallel to said interface.

35. The system of

claim 28

, wherein said first and second locations on said PZT layer are chosen so that said variable e(t) is measured within said PZT layer substantially perpendicular to said interface.

36. The system of

claim 28

, wherein at least one of said PZT layer and said MNS layer is provided as at least one of a planar layer, a selected sector of an annular layer, and a selected sector of a cylinder.