Magnetic position measuring device using Hall elements as sensors and method for its operation

• US 5,747,995 A
• Filed: 09/18/1996
• Issued: 05/05/1998
• Est. Priority Date: 09/30/1995
• Status: Expired due to Fees

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Spies, Alfons
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US08/715,648
• Time in Patent Office: 594 Days
• Field of Search: 324/173, 324/174, 324/207.12, 324/207.2, 324/207.21, 324/207.22, 324/207.24, 324/251, 310/12, 318/135
• 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
• CPC Class Codes: G01D 5/24428 Error prevention
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: G01R 33/075 Hall devices configured for spinning current measurements

Abstract

In a magnetic position measuring device for determining the relative position of two objects which can be moved with respect to each other, a magnetic graduation is scanned by at least two Hall elements for the generation of position-dependent output signals. The Hall elements respectively have at least one supply voltage and one measuring voltage connector. Furthermore, at least one switching unit is provided, which periodically interchanges the supply voltage and the measuring voltage connectors of each Hall element with each other. The periodic interchange of the supply voltage and measuring voltage connectors of the various Hall elements with each other is furthermore synchronized by means of at least one synchronization unit.

Claims

1. A magnetic position measuring device for determining the relative position of two objects which are movable with respect to each other, wherein a magnetic graduation is scanned by at least two Hall elements, each of the Hall elements generates, position-dependent, periodic output signal when the graduation is scanned by the two Hall elements, wherein the Hall elements each have at least one supply voltage and one measuring voltage connector, the device comprising:

at least one switching unit which periodically interchanges the supply voltage and measuring voltage connectors of each Hall element with each other; and

at least one synchronization unit which passes synchronization signals to the switching unit so that the periodic interchange of the supply voltage and the measuring voltage of one of said Hall elements is performed synchronously with respect to the other of said Hall elements so that said position-dependent periodic output signals have a phase shift of 90°

with respect to each other.

2. The magnetic position measuring device according to claim 1, wherein several Hall elements are provided, whose supply voltage and measuring voltage connectors are connected with each other in groups, and that a common switching unit is provided for each group.

3. The magnetic position measuring device according to claim 1, wherein the Hall elements used respectively have n supply voltage and measuring voltage connectors alternately disposed cyclically around the center of the Hall sensor, which are arranged at angular distances of 360°

/n from each other.

4. The magnetic position measuring device according to claim 1, wherein a magnetic graduation with a fixed graduation period (T) is provided, and at least two Hall elements are disposed, offset from each other by the distance of a quarter graduation period of the magnetic graduation, so that the resulting electrical output signals of the at least two Hall elements have a phase shift of 90°

from each other.

5. The magnetic position measuring device according to claim 1, wherein an interpolating unit for generating counting pulses is disposed downstream of the Hall elements.

6. The magnetic position measuring device according to claim 1, further comprising an oscillator unit assigned to the synchronization unit, which provides a periodic clock signal which determines the switching frequency.

7. The magnetic position measuring device according to claim 1, wherein the Hall elements employed, together with the switching and synchronization unit are arranged on a single chip in an integrated construction.

8. A method for operating a magnetic position measuring device for determining the relative position of two objects which are movable with respect to each other, the method comprising the steps of:

providing a magnetic graduation;

providing at least two Hall elements, each Hall element having a supply and measuring voltage;

scanning the magnetic graduation with the at least two Hall elements and generating a periodic position-dependent output signal with each of the two Hall elements;

providing a switching unit for periodically interchanging the supply and measuring voltages of each Hall sensor; and

providing a synchronization unit that passes synchronization signals to the switching unit so that the periodic interchange of the supply voltage and the measuring voltage of one of said Hall elements is performed synchronously with respect to the other of said Hall elements so that said position-dependent periodic output signals have a phase shift of 90°

with respect to each other.

9. The method according to claim 8, further comprising the step of supplying output signals of the Hall elements to an interpolating unit for generating counting pulses.

10. The method according to claim 8, wherein the supply and measuring voltages of the Hall elements are connected through in the same direction.

11. The method according to claim 8, wherein the supply and measuring voltages of the Hall elements are connected through in opposite directions.

12. A magnetic position measuring device for determining the relative position of two objects which are movable with respect to each other, wherein a magnetic graduation is scanned by at least two Hall elements for generating position-dependent output signals, wherein the Hall elements each have at least one supply voltage and one measuring voltage connector, the device comprising:

at least one switching unit which periodically interchanges the supply voltage and measuring voltage connectors of each Hall element with each other;

at least one synchronization unit which synchronizes the periodic interchange of the supply voltage and measuring voltage connectors of the different Hall elements with each other; and

an oscillator unit assigned to the synchronization unit which provides a periodic clock signal which determines the switching frequency.