Position sensors

• US 20060208725A1
• Filed: 02/21/2006
• Published: 09/21/2006
• Est. Priority Date: 08/20/2003
• Status: Active Grant

• Current Assignee: University Of Cape Town
• Original Assignee: University Of Cape Town
• Inventors: Tapson, Jonathan Craig
• Granted Patent: US 7,321,229 B2
• Time in Patent Office: Days
• US Class Current: 324/207.170
• CPC Class Codes: G01D 5/2291 Linear or rotary variable differential transformers (LVDTs/RVDTs) having a single primary coil and two secondary coils

Abstract

A position sensor comprising a primary winding (26) for generating a magnetic flux, a first secondary winding (24.1) the number of turns of which increases in one direction, a second secondary winding (24.2) the number of turns of which increases in the opposite direction to that of the first secondary winding. Both secondary windings (24.1, 24.2) are subjected to the magnetic flux generated by the primary winding (26) whereby voltages are induced in the secondary windings. The sensor further comprises an element movable with respect to the secondary windings. The element is of a magnetic or conductive material and distorts, in its vicinity, the magnetic flux generated by the primary winding (26). By providing third and fourth secondary windings at right angles to the first and secondary windings it is possible to detect position in two dimensions.

Claims

1. A position sensor comprising:

a primary winding configured to generate a magnetic flux;

a first secondary winding comprising a number of turns which increases in one direction;

a second secondary winding comprising a number of turns which increases in an opposite direction to that of said first secondary winding;

said first secondary winding and said second secondary winding being subjected to a magnetic flux generated by said primary winding wherein voltages are induced in said first secondary winding and said second secondary winding; and

,

and an element movable with respect to said first secondary winding and said second secondary winding, wherein said element comprises a magnetic or conductive material and distorting, in its vicinity, said magnetic flux generated by said primary winding.

2. The position sensor of claim 1 wherein said first secondary winding and said second secondary winding comprises a plurality of side-by-side sections, each intermediate section having more turns than a section to one side thereof and less turns than a section on another side thereof, one end section having less turns than an intermediate section next to said one end section and an other end section having more turns than said intermediate section next to said other end section.

3. The position sensor of claim 2 wherein those portions of said first secondary winding and said second secondary winding which are transverse to said one direction and said opposite direction are skew to said one direction and said opposite direction.

4. The position sensor of claim 1, wherein outputs from said first secondary winding and said second secondary winding are connected to a circuit comprising a differential amplifier and a demodulator configured to provide a direct current output.

5. The position sensor of claim 2, wherein outputs from said first secondary winding and said second secondary winding are connected to a circuit comprising a differential amplifier and a demodulator configured to provide a direct current output.

6. The position sensor of claim 3, wherein outputs from said first secondary winding and said second secondary winding are connected to a circuit comprising a differential amplifier and a demodulator configured to provide a direct current output.

7. A position sensor comprising:

a primary winding configured to generate a magnetic flux;

a first secondary winding comprising a number of turns which increases in one direction;

a second secondary winding comprising a number of turns of which increases in the opposite direction to that of said first secondary winding;

said first secondary winding and said second secondary winding being subjected to magnetic flux generated by said primary winding wherein voltages are induced in said first secondary winding and said second secondary winding;

a third secondary winding comprising a number of turns of which increases in a direction transverse to said one direction;

a fourth secondary winding comprising a number of turns of which increases in the opposite direction to that of said third secondary winding;

said third secondary winding and said fourth secondary winding being subjected to the magnetic flux generated by said primary winding wherein voltages are induced in said first secondary winding and said second secondary winding; and

,

an element movable with respect to said first secondary winding and said second secondary winding, wherein said element comprises a magnetic or conductive material and distorting, in its vicinity, said magnetic flux generated by said primary winding.

8. The position sensor of claim 7, wherein said first, second, third and fourth secondary winding comprises a plurality of side-by-side sections, each intermediate section having more turns than a section to one side thereof and less turns than a section on the other side thereof, one end section having less turns than an intermediate section next to said one end section and an other end section having more turns than an intermediate section next to said other end section.

9. The position sensor of claim 8, wherein those portions of said first, second, third and fourth secondary windings which are transverse to said one direction and said opposite direction are skew to said one direction and said opposite direction.

10. The position sensor of claim 7, wherein outputs from said first, second, third and fourth secondary winding are connected to a circuit comprising a differential amplifier and a demodulator configured to provide a direct current output.

11. The position sensor claim 8, wherein outputs from said first, second, third and fourth secondary windings are connected to a circuit comprising a differential amplifier and a demodulator configured to provide a direct current output.

12. The position sensor of claim 9, wherein outputs from said first, second, third and fourth secondary windings are connected to a circuit comprising a differential amplifier and a demodulator thereby to provide a direct current output.