Caliper tool and sensor for use in high pressure environments

1. A caliper tool for measuring a shape of a wellbore, comprising:

a tool housing defining a tool cavity;

a movable measurement component comprising:

a hub rotatably coupled to the tool housing at a pivot axis; and

an upper measurement arm extending from the hub;

a magnetically-permeable target, coupled to the hub, configured to rotate with the hub upon movement of the upper measurement arm; and

a sensor assembly disposed within the tool cavity, the sensor assembly comprising:

a primary coil inductively coupled to the target and receiving an alternating current excitation from a controller;

a secondary coil angularly spaced apart from the primary coil relative to the hub about the pivot axis, wherein the secondary coil is inductively coupled to the target and providing a secondary output signal based on the rotational position of the target relative to the tool housing; and

another secondary coil angularly spaced apart from the secondary coil relative to the hub about the pivot axis, wherein the another secondary coil is inductively coupled to the target and providing another secondary output signal based on the rotational position of the target relative to the tool housing, the secondary and another secondary output signals facilitating measurement of the shape of the wellbore.

2. The caliper tool of claim 1 , wherein the tool housing comprises a non-magnetic material.

3. The caliper tool of claim 1 , wherein the target comprises a rectangular body.

4. The caliper tool of claim 3 , wherein the rectangular body comprises a sector.

5. The caliper tool of claim 1 , wherein the target comprises a diamond or triangular shaped body.

6. The caliper tool of claim 1 , the measurement component further comprising a lower measurement arm coupled to a distal end of the upper measurement arm via a central pivot, the lower measurement arm including a lower hub disposed opposite of the central pivot, the lower hub being rotatably coupled to the tool housing at a lower pivot axis, wherein the lower hub is longitudinally spaced apart from the hub of the upper measurement arm.

7. The caliper tool of claim 1 , further comprising a magnetically-permeable extension extending through the secondary coil, wherein a proximal end of the magnetically-permeable extension is disposed proximally to the target for inductively coupling the secondary coil to the target.

8. The caliper tool of claim 7 , further comprising another magnetically-permeable extension extending through the another secondary coil, wherein a proximal end of the another magnetically-permeable extension is disposed proximally to the target for inductively coupling the another secondary coil to the target.

9. The caliper tool of claim 1 , further comprising:

a first magnetic shield disposed between the primary coil and the secondary coil; and

a second magnetic shield disposed between the primary coil and the tertiary another secondary coil.

10. A sensor, comprising:

a sensor body comprising a non-magnetic material and having an interface end proximal to a magnetically-permeable target;

a primary coil disposed within the sensor body, the primary coil configured to provide a primary output signal in response to receiving an alternating current excitation from a controller;

a secondary coil disposed within the sensor body away from the interface end of the sensor body and adjacent to the primary coil;

a magnetically-permeable extension at least partially disposed within the sensor body and extending through the secondary coil to the interface end of the sensor body for inductively coupling the secondary coil to the target, the secondary coil configured to provide a secondary output signal based on the rotational position of the target relative to the sensor body;

another secondary coil disposed within the sensor body away from the interface end of the sensor body, adjacent to the primary coil and angularly spaced apart from the secondary coil;

another magnetically-permeable extension at least partially disposed within the sensor body and extending through the another secondary coil to the interface end of the sensor body for inductively coupling the another secondary coil to the target, the another secondary coil configured to provide a secondary output signal based on the rotational position of the target relative to the sensor body.

11. The sensor of claim 10 , wherein one or both of the magnetically-permeable extension and the another magnetically-permeable extensions are cylindrical in shape.

12. The sensor of claim 11 , wherein one or both of the magnetically-permeable extension and the another magnetically-permeable extension comprise an end portion that is flat.

13. The sensor of claim 10 , wherein one or both of the magnetically-permeable extension and the another magnetically-permeable extensions are a disk.

14. The sensor of claim 10 , further comprising a magnetic shunt disposed around a distal end of the magnetically-permeable extension and the another magnetically-permeable extension.

15. The sensor of claim 10 , further comprising a tubular magnetic shield disposed around the magnetically-permeable extension and a tubular magnetic shield disposed around the another magnetically-permeable extension.

16. The sensor of claim 10 , wherein the non-magnetic material is disposed around the secondary coil, the another secondary coil, and at least a portion of the magnetically-permeable extension and the another magnetically-permeable extension to form the sensor body.

17. The method of claim 16 , wherein the non-magnetic material which is around the secondary coil, the another secondary coil, and at least a portion of the primary magnetically-permeable extension and the another magnetically-permeable extension are sintered.

18. The sensor of claim 10 , wherein at least a part of the non-magnetic material is brazed to at least a part of a large diameter flange connected to the magnetically-permeable extension or the second magnetically-permeable extension.