Patent ID: 7394247
Filing Date: 2008-07-01
Classification: B82Y,G01D,G01R

Abstract:
1. A method of measuring an angle, from 0 to 360 degrees, that corresponds to a direction of a magnetic field, comprising: providing a type A magneto-resistive element having a reference layer that is magnetically pinned in a direction that is at a positive angle relative to an X direction; providing a type B magneto-resistive element having a reference layer that is magnetically pinned in a direction that is parallel to said X direction; providing a type C magneto-resistive element having a reference layer that is magnetically pinned in a direction that is at a negative angle relative to said X direction, said positive and negative angles having the same absolute value; providing first and second Wheatstone bridges energized by a common voltage source, each of said Wheatstone bridges comprising electrically parallel first and second sections; each of said sections further comprising serially connected first and second pairs of said magneto-resistive elements, there being a voltage output terminal between each of said first and second pairs; the first resistive element pair of the first section of the first Wheatstone bridge further comprising two serially connected type C elements; the second resistive element pair of the first section of the first Wheatstone bridge further comprising two serially connected type A elements; the first resistive element pair of the second section of the first Wheatstone bridge further comprising two serially connected type A elements; the second resistive element pair of the second section of the first Wheatstone bridge further comprising two serially connected type C elements; the first resistive element pair of the first section of the second Wheatstone bridge further comprising a type A element in series with a type C element; the second resistive element pair of the first section of the second Wheatstone bridge further comprising two serially connected type B elements; the first resistive element pair of the second section of the second Wheatstone bridge further comprising two serially connected type B elements; the second resistive element pair of the second section of the second Wheatstone bridge further comprising a type A element in series with a type C element; connecting said voltage output terminals from said first Wheatstone bridge to a first amplifier and connecting said voltage output terminals from said second Wheatstone bridge to a second amplifier whereby said first amplifier outputs a voltage whose magnitude is proportional to the sine of said angle and said second amplifier outputs a voltage whose magnitude is proportional to the cosine of said angle; connecting said first and second amplifier outputs to a microcontroller wherein a value for said angle is then computed from the equation arctan θ=sine θ/cos θ; and determining in which quadrant said angle belongs through comparison of the signs of said first and second amplifier outputs.