Magnetometer employing hard axis thin film inductor

• US 4,182,987 A
• Filed: 08/28/1978
• Issued: 01/08/1980
• Est. Priority Date: 09/21/1977
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Moeller, Charles R.
• Primary Examiner(s): Wolff, John H.
• Application Number:
  US05/937,283
• Time in Patent Office: 498 Days
• Field of Search: 360/110-113, 360/125, 324/249
• US Class Current: 324/249
• CPC Class Codes: G01R 33/02 Measuring direction or magnitude of magnetic fields or magnetic flux G01R33/20 takes precedence
• CPC Class Codes: G11B 5/33 Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing onlySingle head using magnetic domains for scanning G11B5/4946; multiple head for scanning G11B5/4907 and subgroups ; general details therefor G11B5/133 - G11B5/255

Abstract

A flux-sensitive magnetic head employs, at its back part, a structure having a thin single domain magnetic film coated thereon. A coil wraps around the coated structure, and a direct current is passed through the coil, thereby to apply a hard axis magnetic bias to the film. Signal flux appearing at the head front gap asserts a magnetic force along the hard axis of the film. Contrary to what would be expected, the signal flux causes the inductance of the coil to vary. Such inductance variation may be conveniently detected by (1) connecting the variable inductor into a tank circuit, (2) applying a high frequency ac ripple to the "hard axis" dc bias, and (3) measuring the "hard axis" detuning experienced by the tank circuit.

Claims

1. Apparatus for producing an electrical signal corresponding to a magnetic signal field comprising:

(a) structural means having an essentially single domain magnetic film formed thereon;

(b) a wire wrapped around the film bearing structural means to form a coil around said means, the wire wrapping being such that the longitudinal axis of the coil is substantially orthogonal to the easy axis of the film and in the direction of the film hard axis;

(c) means for applying a magnetic bias substantially in the direction of the coil longitudinal axis;

(d) means for applying an alternating excitation magnetic field substantially in the direction of the longitudinal axis of said coil;

(e) means for applying said magnetic signal field substantially in the direction of said coil longitudinal axis; and

(f) means responsive to inductance variations in said coil for converting said inductance variations into an electrical signal.