Single core triaxial flux-gate magnetometer

• US 5,270,648 A
• Filed: 08/10/1990
• Issued: 12/14/1993
• Est. Priority Date: 08/10/1990
• Status: Expired due to Fees

• Current Assignee: Watson Industries, Inc.
• Original Assignee: Watson Industries, Inc.
• Inventors: Watson, William S.
• Primary Examiner(s): Strecker, Gerard R.
• Assistant Examiner(s): EDMONDS, WARREN
• Application Number:
  US07/565,794
• Time in Patent Office: 1,222 Days
• Field of Search: 324/247, 324/244, 324/253, 324/249, 324/258, 324/254, 324/255, 324/260, 324/262, 336/221, 336/233, 336/184, 336/213
• US Class Current: 324/253
• CPC Class Codes: G01R 33/0206 Three-component magnetometers
• CPC Class Codes: G01R 33/045 in single-, or multi-aperture elements

Abstract

A single core triaxial flux-gate magnetometer including a tall-toroidal core having a radial excitation winding, two orthogonal sets of axial or circumferential output windings, and an equatorial output winding oriented orthogonal to both axial output windings. The core is fabricated from a strip of magnetic tape material wrapped to form a toroid having a height approximately equal to its diameter. Each end of the strip is uniformly tapered along the top and bottom edges such that the tapered segments extend around an integer multiple of complete revolutions of the wrapping, the length of each tapered segment thereby being equal to the inner or outer circumference of the toroid or an integer multiple thereof. Leakage of the induced magnetic field at any point along the edge of the tapered segment will be generally proportional to the height of the tapered segment between its edges at that point, and will extend with equal magnitude in opposite directions from the strip parallel to the planar surface of the toroid and perpendicular to the edges. The tapered segments are oriented and aligned relative to one another in the wrapped toroid such that the induced magnetic field leakage is generally symmetrical and balanced across any diameter of the core.

Claims

1. A single core triaxial flux-gate magnetometer for measuring three generally orthogonal vector components of a superimposed ambient magnetic field, said single core triaxial flux-gate magnetometer comprising:

a core, said core being fabricated from a strip of a high permeability magnetic material and defining a geometric shape having an inner circumference, an outer circumference, and a radial axis, said strip including a center portion having a pair of opposing ends and at least one longitudinal edge, a first tapered segment extending from and connected to a first end of said pair of opposing ends of said strip, said first tapered segment having at least one first tapered edge extending from a first junction between said longitudinal edge and said tapered edge of said first tapered segment to a first endpoint, said first tapered segment having a first length being generally equal to a first integer multiple of said inner circumference of the core, and a second tapered segment extending from and connected to a second end of the pair of opposing ends of said strip, said second tapered segment having at least one second tapered edge extending from a second junction between said longitudinal edge and said tapered edge of said second tapered segment to a second endpoint, said second tapered segment having a second length being generally equal to a second integer multiple of said outer circumference of the core, said first junction being generally aligned with said second endpoint in a first vertical plane intersecting said radial axis, and said second junction being generally aligned with said first endpoint in a second vertical plane intersecting said radial axis;

an excitation winding produced by winding a first wire around said core, said excitation winding being wound axially and radially about said core;

an equitorial sensing coil formed by winding a second wire around said core, said equatorial sensing coil being wound equatorially about said core and about said radial axis;

a first axial sensing coil formed by winding a third wire around said core, said first axial sensing coil being wound axially and circumferentially about said outer circumference of said core and at least partially perpendicular to said radial axis; and

a second axial sensing coil formed by winding a fourth wire around said core, said second axial sensing coil being wound axially and circumferentially about said outer circumference of said core and at least partially perpendicular to both said equatorial sensing coil and said first axial sensing coil,

whereby an induced magnetic field leaking from a first point along the first tapered edge and from a second point along the second tapered edge within a common vertical plane intersecting both the radial axis of the core and said first point will be generally uniform and symmetrical about the core, and further whereby the equatorial sensing coil, the first axial sensing coil, and the second axial sensing col are capable of being used to measure the three generally orthogonal vector components of the superimposed ambient magnetic field.

2. The single core triaxial flux-gate magnetometer of claim 1 wherein the equatorial sensing coil, the first axial sensing coil, and the second axial sensing coil are wound on the core in an order, said order being the equatorial sensing coil followed by the first axial sensing coil followed by the second axial sensing coil.

3. The single core triaxial flux-gate magnetometer of claim 1 wherein the strip is wrapped to form a plurality of generally concentric spiraling layers.

4. The single core triaxial flux-gate magnetometer of claim 3 wherein the number of the plurality of generally concentric spiraling layers is on the order o ten.

5. The single core triaxial flux-gate magnetometer of claim 3 wherein the number of the plurality of generally concentric spiraling layers is between five and twenty five.

6. The single core triaxial flux-gate magnetometer of claim 1 wherein the geometric shape is a tall toroid, said tall toroid having a height and a diameter, said diameter being generally equal to said height within a range of approximately twenty five percent of said height.

7. The single core triaxial flux-gate magnetometer of claim 1 wherein the geometric shape is a tall toroid, said tall toroid having a height and a diameter, said height being generally equal to said diameter within a range of approximately twenty five percent of said diameter.

8. The single core triaxial flux-gate magnetometer of claim 1 wherein the geometric shape is a tall toroid, said tall toroid having a height, said height being generally less than or approximately equal to 1/2 inch.

9. The single core triaxial flux-gate magnetometer of claim 1 wherein the geometric shape is a tall toroid, said single core triaxial flux-gate magnetometer having an overall height of generally less than or approximately equal to 1/2 inch.

10. The single core triaxial flux-gate magnetometer of claim 1 wherein the geometric shape is a tall toroid, said single core triaxial flux-gate magnetometer having an overall height of generally less than or approximately equal to 1/4 inch.

11. The single core triaxial flux-gate magnetometer of claim 1 wherein the equatorial sensing coil has a number of turns about the core, said number of turns being approximately 200.

12. The single core triaxial flux-gate magnetometer of claim 1 wherein the first axial sensing coil has a first number of turns about the core and the second axial sensing coil has a second number of turns about the core, said first number of turns being approximately 200 and said second number of turns being approximately 200.

13. The single core triaxial flux-gate magnetometer of claim 1 wherein the excitation winding has a number of turns about the core, said number of turns being approximately 100.

14. The single core triaxial flux-gate magnetometer of claim 1 wherein the equatorial sensing coil has a number of turns about the core, said number of turns being approximately 1000.

15. The single core triaxial flux-gate magnetometer of claim 1 wherein the first axial sensing coil has a first number of turns about the core and the second axial sensing coil has a second number of turns about the core, said first number of turns being approximately 1000 and said second number of turns being approximately 1000.

16. The single core triaxial flux-gate magnetometer of claim 1 wherein the excitation winding has a number of turns about the core, said number of turns being approximately 200.

17. The single core triaxial flux-gate magnetometer of claim 1 wherein the equatorial sensing coil has a number of turns about the core less than 2000, the first axial sensing coil and the second axial coil each have a number of turns about the core less than 2000, and the excitation winding has a number of turns about the core less than 500.

18. The single core triaxial flux-gate magnetometer of claim 1 wherein the first integer multiple and the second integer multiple are equal to one.

19. A single core triaxial flux-gate magnetometer for measuring three generally orthogonal vector components of a superimposed ambient magnetic field, said single core triaxial flux-gate magnetometer comprising:

a core, said core being fabricated rom a strip of high permeability magnetic tape material and defining a geometric shape having an inner circumference, an outer circumference, and a radial axis, said strip including a center portion having a pair of opposing ends and at least one longitudinal edge, a first tapered segment extending from and connected to a first end of said pair of opposing ends of the strip, said first tapered segment having at least one first tapered edge extending from a first junction between said longitudinal edge and said tapered edge of said first tapered segment to a first endpoint, said first tapered segment having a first length measured as the minimum distance between said first endpoint and a first line intersecting said first junction perpendicular to said longitudinal edge, said first length being generally equal to a first integer multiple of the inner circumference, and a second tapered segment extending from and connected to a second end of the pair of opposing ends of the strip, said second tapered segment having at least one second tapered edge extending from a second junction between the longitudinal edge and said tapered edge of said second tapered segment to a second endpoint, said second tapered segment having a second length measured as the minimum distance between said second endpoint and a second line intersecting said second junction perpendicular to the longitudinal edge, said second length being generally equal to a second integer multiple of the outer circumference;

an excitation winding formed by winding a first wire around the core, said excitation winding being wound axially and radially about the core, the equatorial sensing coil, the first axial sensing coil, and the second axial sensing coil each being wound over said excitation winding

an equatorial sensing coil wound formed by winding a second wire around said core, said equatorial sensing coil being wound equatorially about said core and about said radial axis;

a first axial sensing coil formed by winding a third wire around said core, said first axial sensing coil being would axially and circumferentially about said outer circumference of said core and at least partially perpendicular to said radial axis and said; and

a second axial sensing coil formed by winding a fourth wire around said ore, said second axial sensing coil being would axially and circumferentially about said outer circumference of said core and at least partially perpendicular to both said equatorial sensing coil and said first axial sensing coil,

whereby an induced magnetic field leaking from a first point along the first tapered edge and from a second point along the second tapered edge within a common vertical plane intersecting both the radial axis of the core and said first point will be generally uniform and symmetrical about the core, and further whereby the equatorial sensing coil, the first axial sensing coil, and the second axial sensing coil a capable of being used to measure the three generally orthogonal vector components of the superimposed ambient magnetic field.

20. The single core triaxial flux-gate magnetometer of claim 19 wherein the first integer multiple and the second integer multiple are equal to one.