Magnetic displacement sensor including first and second flux paths wherein the first path has a fixed reluctance and a sensor disposed therein

A displacement sensor for sensing relative displacement between a valve housing and a movable valve operator comprising:

• a sensor housing for mounting to the valve housing;
• magnet means mounted to the sensor housing, the magnet means having first and second pole tips;
• a flux sensor mounted to the sensor housing to sense magnetic flux in a first flux path between the first and second pole tips, the first flux path having a fixed reluctance;
• and
• a target for mounting to the valve operator to form a second flux path between the first and second pole tips having a reluctance that varies with displacement between the valve operator and the valve housing.

A differential displacement sensor for sensing relative displacement between first and second members, comprising:

• first and second magnet means for mounting to the first member, the first and second magnets means each having first and second pole tips;
• a target for mounting to the second member;
• a first magnetic circuit having
• a first flux path between the first and second pole tips of the first magnet means and containing a first magnetic flux sensor mounted between the first and second pole tips of the first magnet means to sense magnetic flux in the first flux path, the first flux path having a fixed reluctance, and
• a second flux path between the first and second pole tips of the first magnet means and containing at least a portion of the target, the second flux path having a reluctance that varies with displacement between the first and second members;
• and
• a second magnetic circuit having
• a third flux path between the first and second pole tips of the second magnet means and containing a second magnetic flu sensor mounted between the first and second pole tips of the second magnet means to sense magnetic flux in the third flux path, the third flux path having a fixed reluctance, and
• a fourth flux path between the first and second pole tips of the second magnet means and containing at least a portion of the target, the fourth flux path having a reluctance that varies with displacement between the first and second members, the reluctance in the fourth flux path increases as the reluctance in the second flux path decreases.

A differential displacement sensor for sensing relative displacement between first and second members comprising:

• a housing for mounting to the first member;
• first and second magnet means mounted to the housing, the first and second magnet means each having first and second pole tips;
• a first flux sensor mounted to the housing to sensing magnetic flux in a first flux path between the first and second pole tips of the first magnet means, the first flux path having a fixed reluctance;
• a second flux sensor mounted to the housing to sensing magnetic flux in a second flux path between the first and second pole tips of the second magnet means, the second flux path having a fixed reluctance;
• and
• a target for mounting to the second member to form a third flux path between the first and second pole tips of the first magnet means and to form a fourth flux path between the first and second pole tips of the second magnet means, the third and fourth flux paths each having a reluctance that varies with displacement between the first and second members, the reluctance of the third flux path increasing as the reluctance in the fourth flux path decreases.

In a valve having a housing and a movable valve operator, a displacement sensor for sensing relative displacement of the valve operator with respect to the housing, the sensor comprising:

• a source of constant magnetic flux mounted to the housing;
• magnetic flux sensing means magnetically coupled to the source to sense magnetic flux in a first flux path having a reluctance independent of the displacement between the valve operator and the housing;
• and
• a target mounted to the valve operator having a target surface confronting the source, the target being magnetically coupled to the source in a second flux path having a reluctance that varies with displacement between the valve operator and the housing so that magnetic flux in the second flux path varies with displacement between the valve operator and the housing to alter the flux in the first flux path.

Magnetic flux generator and pickup apparatus for a magnetic displacement sensor that senses relative displacement between a valve housing and a movable valve operator, the displacement sensor having a target mounted to the valve operator, the apparatus comprising:

• a sensor housing for mounting to the valve housing;
• magnet means mounted to the sensor housing for generating a magnetic flux, the magnet means having first and second pole tips arranged to confront the valve operator when the sensor housing is mounted to the valve housing, the target forming a first flux path between the first and second pole tips having a reluctance that varies with displacement between the valve operator and the valve housing;
• and
• a flux sensor mounted to the sensor housing between the first and second pole tips, the sensor sensing magnetic flux in a second flux path between the first and second pole tips having a fixed reluctance.

A displacement sensor for sensing relative displacement between a valve housing and a movable valve operator comprising:

• a source of constant magnetic flux mounted to the valve housing;
• magnetic flux sensing means magnetically coupled to the source to sense magnetic flux in a first flux path having a reluctance independent of the displacement between the valve operator and the valve housing;
• and
• a target mounted to the valve operator and confronting the source, the target being magnetically coupled to the source in a second flux path having a reluctance that varies with displacement between the valve operator and the valve housing so that magnetic flux in the second flux path varies with displacement of the valve operator and the valve housing to alter the flux in the first flux path.