Apparatus for sensing two components of a magnetic field
First Claim
1. Apparatus for sensing first and second orthogonal components hx and hy of an external magnetic field h, said apparatus including a planar magnetoresistive element, said element comprising a magnetically anisotropic thin film having an easy axis of magnetization in the plane of the film, said film being provided with electrical contacts connectable to means for passing an electrical current through the film in a direction substantially parallel to said easy axis, said contacts also being connectable to detecting means for sensing a signal indicative of the resistivity of said film when said current is passed therethrough, said apparatus further including application means for selectively applying to the film a first magnetic bias field and a second magnetic bias field, said first bias field acting substantially at right angles to said easy axis in the plane of the film and said second bias field acting substantially parallel to said easy axis, and control means permitting said first and second bias fields to be applied to said element in a plurality of pre-determined relationships, said element, in use, being placed in said external magnetic field h with said component hx lying in a direction at right angles to said easy axis in the plane of the film and said component hy lying parallel to said easy axis, and said detection means sensing signals indicative of the resistivity of said film whilst said application means selectively applies said first and second bias fields in a plurality of different relationships, said relationships being chosen such that said components hx and hy may be derived from said signals.
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Accused Products
Abstract
A sensing element suitable for sensing two components hx and hy of an external magnetic field in an orthogonal co-ordinate system comprises a reverse C-shape first electrical conductor vacuum deposited onto an electrical insulating substrate. A layer of photoresist applied to a region insulates the conductor from a magnetoresistive element which has two connectors linked thereto. Further application of photoresist insulates the element from a second vacuum deposited electrical conductor. Wires locate with respective conductors where gold deposition in the vicinity of the wire ends achieves electrical continuity. A control circuit applies current, within a periodic cycle, in alternate directions through the first conductor while a current is applied in a single direction through the second conductor. In the following cycle the current direction through the second conductor is reversed. Values of the element electrical resistivity for the four combination of current (and hence magnetic field) directions allow solution of a simultaneous equation to yield hx and hy.
16 Citations
7 Claims
- 1. Apparatus for sensing first and second orthogonal components hx and hy of an external magnetic field h, said apparatus including a planar magnetoresistive element, said element comprising a magnetically anisotropic thin film having an easy axis of magnetization in the plane of the film, said film being provided with electrical contacts connectable to means for passing an electrical current through the film in a direction substantially parallel to said easy axis, said contacts also being connectable to detecting means for sensing a signal indicative of the resistivity of said film when said current is passed therethrough, said apparatus further including application means for selectively applying to the film a first magnetic bias field and a second magnetic bias field, said first bias field acting substantially at right angles to said easy axis in the plane of the film and said second bias field acting substantially parallel to said easy axis, and control means permitting said first and second bias fields to be applied to said element in a plurality of pre-determined relationships, said element, in use, being placed in said external magnetic field h with said component hx lying in a direction at right angles to said easy axis in the plane of the film and said component hy lying parallel to said easy axis, and said detection means sensing signals indicative of the resistivity of said film whilst said application means selectively applies said first and second bias fields in a plurality of different relationships, said relationships being chosen such that said components hx and hy may be derived from said signals.
Specification