Position sensor

A position sensor comprising:

• an electromagnetic field modifying member;
• an excitation winding which, when energised, is operable for generating an electromagnetic field;
• a sensor winding electromagnetically coupled to said excitation winding, for sensing electromagnetic fields;
• and
• a compensation winding electromagnetically coupled to said excitation winding;
• wherein said field modifying member and said windings are relatively moveable along a measurement direction and are arranged (i) so that the electromagnetic coupling between said excitation winding and said sensor winding varies as a function of the relative position of said field modifying member and said windings;
• and (ii) so that a signal obtained from said compensation winding can be used to provide compensation for variations in the signal output from said sensor winding which are not caused by said relative position.

A position sensor comprising:

• an electromagnetic field modifying member;
• an excitation winding electromagnetically coupled to said field modifying member, for generating an electromagnetic field;
• a sensor winding electromagnetically coupled to said field modifying member, for sensing electromagnetic fields;
• and
• drive means for applying an excitation signal to said excitation winding;
• wherein said field modifying member and said windings are relatively moveable along a measurement direction between a first position and a second position and wherein said drive means is arranged to apply an excitation signal having a frequency that minimises a change in the signal induced in the sensor winding between the first and second positions for different operating conditions.

A position sensor comprising:

• an electromagnetic field modifying member;
• a winding electromagnetically coupled to said field modifying member, for generating an electromagnetic field;
• and
• drive means for applying an excitation signal to said winding;
• wherein said field modifying member and said winding are relatively moveable along a measurement direction between a first position and a second position and wherein said drive means is arranged to apply an excitation signal having a frequency that minimises a change in coupling between eddy currents generated in the field modifying member and the winding between the first and second positions for different operating conditions.

A position sensor comprising:

• an electromagnetic field modifying member;
• a first winding electromagnetically coupled to said electromagnetic field modifying member;
• and
• a second winding electromagnetically coupled to said electromagnetic field modifying member;
• wherein said field modifying member and said windings are relatively movable along a measurement direction between first and second positions and are arranged (i) so that the electromagnetic coupling between the first winding and the field modifying member varies as a function of the relative position of said field modifying member and said windings between said first and second positions;
• and (ii) so that the electromagnetic coupling between said second winding and said field modifying member does not vary with said relative position between said first and second positions, whereby a signal obtained from said second winding can be used to provide compensation for variations in a signal output from said first winding which are not caused by said relative position.

A linear position sensor comprising:

• an elongate electromagnetic field modifying member;
• an elongate excitation winding which, when energised, is operable for generating an electromagnetic field;
• and
• an elongate sensor winding electromagnetically coupled to said excitation winding, for sensing electromagnetic fields;
• wherein said elongate member and said windings are relatively moveable along a measurement direction and are arranged so that their longitudinal axes are substantially aligned along said measurement direction, whereby the electromagnetic coupling between said excitation winding and said sensor winding varies as a function of the relative position of said elongate member and said windings.

A position sensor comprising:

• an excitation winding which, when energised, is operable for generating an electromagnetic field;
• a first sensor winding electromagnetically coupled to said excitation winding, for sensing electromagnetic fields;
• a second sensor winding electromagnetically coupled to said excitation winding, for sensing electromagnetic fields;
• a compensation winding electromagnetically coupled to said excitation winding;
• an elongate electromagnetic field modifying member electromagnetically coupled to said excitation winding for modifying the electromagnetic field generated by said excitation winding;
• wherein said field modifying member and said windings are relatively moveable along the measurement direction so that the electromagnetic coupling between said excitation and said first and second sensor windings varies as a function of the relative position of said field modifying member and said windings;
• and
• means for performing a ratiometric calculation of the signals induced in said first and second sensor windings to determine the position of said field modifying member relative to said windings.

A position sensor comprising:

• an excitation winding having a loop portion which, when energised, is operable for generating an electromagnetic field;
• a sensor winding having a loop portion which partially overlaps the loop portion of said excitation winding;
• an electromagnetic field modifying member for modifying the electromagnetic field generated by said excitation winding;
• wherein said field modifying member and said windings are relatively movable along a measurement direction between first and second positions and are arranged so that when said excitation winding generates an electromagnetic field:
• (i) said electromagnetic field modifying member modifies the electromagnetic field;
• and (ii) said sensor winding senses the modified electromagnetic field to output a signal which varies with the relative position of said field modifying member and said windings between said first and second positions.