Device with a magnetic position encoder

• US 20020167306A1
• Filed: 03/20/2002
• Published: 11/14/2002
• Est. Priority Date: 03/23/2001
• Status: Active Grant

• Current Assignee: Melexis Tessenderlo NV
• Original Assignee: Sentron AG (Sensinnovat BVBA)
• Inventors: Zalunardo, Ivano, Popovic, Radivoje, Schott, Christian
• Granted Patent: US 6,731,108 B2
• Time in Patent Office: Days
• US Class Current: 324/207.2
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A magnetic position encoder comprises a magnetic field source and a magnetic field sensor which are movable relative to each other along a given path. The magnetic field sensor measures two components of the magnetic field produced by the magnetic field source. From the measured components a position signal is then derived which represents the relative position of the magnetic field sensor and magnetic field source. Embodiments, of the position encoder in accordance with the invention are characterized in that the determination of the position signal includes a division of the two measured components of the magnetic field. These embodiments in accordance with the invention have the advantage that the position signal is a linear function of the position.

Claims

1. Device with a magnetic position encoder, the position encoder comprising a magnetic field source producing a magnetic field which is rotationally symmetrical in relation to an axis of symmetry and a magnetic field sensor measuring a first and a second component of the magnetic field, the first and second components lying in a plane running orthogonally to the axis of symmetry of the magnetic field source, whereby the magnetic field source and the magnetic field sensor are movable relative to each other and whereby the position encoder delivers a position signal for the relative position of the magnetic field source and the magnetic field sensor, whereby the position signal is derived from the measured first and second components of the magnetic field, and whereby the derivation includes a division of the first measured component of the magnetic field by the second measured component of the magnetic field.

2. Device according to claim 1, the position encoder comprising at least one further magnetic field sensor which, in relation to the first magnetic field sensor, is arranged in movement direction of the relative movement of the magnetic field source and the magnetic field sensor.

3. Device according to claim 1, the position encoder comprising at least one further magnetic field source which, in relation to the first magnetic field source, is arranged in movement direction of the relative movement of the magnetic field source and the magnetic field sensor.

4. Device according to claim 1, wherein the magnetic field source moves with the relative movement along a circular path and wherein the distance of the magnetic field sensor to the circular path is less than the radius of the circular path.

5. Device according to claim 1, further comprising an electronic circuit for operating the magnetic field sensor, whereby the magnetic field sensor has a first Hall element for measuring the first component of the magnetic field and a second Hall element for measuring the second component of the magnetic field and whereby the division of the measured components of the magnetic field takes place analogously in that the current flowing through the second Hall element is proportional to the Hall voltage of the first Hall element.

6. Device according to claim 4, further comprising an electronic circuit for operating the magnetic field sensor, whereby the magnetic field sensor has a first Hall element for measuring the first component of the magnetic field and a second Hall element for measuring the second component of the magnetic field and whereby the division of the measured components of the magnetic field takes place analogously in that the current flowing through the second Hall element is proportional to the Hall voltage of the first Hall element.

7. Device according to claim 2, further comprising an electronic circuit for operating the magnetic field sensors, whereby each magnetic field sensor has a first Hall element for measuring the first component of the magnetic field and a second Hall element for measuring the second component of the magnetic field and whereby the respective division of the measured components of the magnetic field takes place analogously in that the current flowing through the second Hall element is proportional to the Hall voltage of the first Hall element.

8. Device according to claim 3, further comprising an electronic circuit for operating the magnetic field sensors, whereby each magnetic field sensor has a first Hall element for measuring the first component of the magnetic field and a second Hall element for measuring the second component of the magnetic field and whereby the respective division of the measured components of the magnetic field takes place analogously in that the current flowing through the second Hall element is proportional to the Hall voltage of the first Hall element.

9. Device with a magnetic position encoder, the position encoder comprising a magnetic field source producing a magnetic field which is rotationally symmetrical in relation to an axis of symmetry and a first and a second magnetic field sensor each measuring a first and a second component of the magnetic field, the first and second components lying in a plane running orthogonally to the axis of symmetry of the magnetic field source, whereby the first and a second magnetic field sensor are separated by a fixed distance, whereby the magnetic field source and the magnetic field sensors are movable relative to each other and whereby the position encoder delivers at least one position signal for the relative position of the magnetic field source and the magnetic field sensors, whereby the formation of the position signal includes a division of the first component of the magnetic field measured by the first magnetic field sensor by the second component of the magnetic field measured by the first magnetic field sensor and a division of the first component of the magnetic field measured by the second magnetic field sensor by the second component of the magnetic field measured by the second magnetic field sensor.

10. Device according to claim 9, further comprising an electronic circuit for operation of the two magnetic field sensors, whereby the first and second magnetic field sensor each has a first Hall element for measuring the first component of the magnetic field and a second Hall element for measuring the second component of the magnetic field and whereby the division of the measured components of the magnetic field takes place analogously in that the current flowing through the respective second Hall element is proportional to the Hall voltage of the respective first Hall element.

11. Device according to claim 9, further comprising a ferromagnetic yoke for concentrating the magnetic field in the plane.

12. Device according to claim 10, further comprising a ferromagnetic yoke for concentrating the magnetic field in the plane.

13. A magnetic position encoder comprising:

a magnetic field source producing a magnetic field rotationally symmetrical in relation to an axis of symmetry;

a magnetic field sensor positioned movably relative to the magnetic field source and producing signals representative of a first and second component of the magnetic field, the first and second components lying in a plane running orthogonally to the axis of symmetry of the magnetic field whereby the signals represent the relative position of the magnetic field source and magnetic field sensor; and

an electronic signal processing circuit connected with the magnetic field sensor to receive the signals representative of the first and second components of the magnetic field and processing the signals to produce a position signal representative of the position of the source and sensor relative to one another from a division of the signal representing the first component of the magnetic field by the signal representative of the second component of the magnetic field.

14. A magnetic position encoder comprising:

a magnetic field source producing a magnetic field which is rotationally symmetric in relation an axis of symmetry;

first and second magnetic field sensors, each sensor measuring a first and a second component of the magnetic field and producing signals representative of the first and second components respectively, the first and second components lying in a plane orthogonal to the axis of symmetry of the magnetic field, the first and second magnetic field sensors being separated by a fixed distant and being jointly movable relative to the magnetic field source whereby the signals from the sensors represent the position of the source and sensors relative to one another;

electronic signal processing means receiving the signals from the first and second magnetic field sensors and processing the signals to produce a position signal representative of the position of the source relative to the sensors from a division of the first component of the magnetic field as measured by the first magnetic field sensor by the second component of the magnetic field as measured by the first magnetic field sensor, and a division of the first component of the magnetic field as measured by the second magnetic field sensor by the second component of the magnetic field as measured by the second magnetic field sensor.