Abstract: Apparatus and associated methods relate to a measurement system that calculates a current in a conductor based on an odd-order spatial derivative function of signals representing magnetic-field strengths within a hole in the conductor. In an illustrative embodiment, the odd-order spatial derivative function may generate an output signal representing a spatial derivative of the in-hole magnetic field greater than the first-order. The three or more magnetic-field sensors may be configured to align on the hole's axis when inserted into the hole. When inserted into the hole, the sensors may be aligned on an axis perpendicular to a direction of current flow and be responsive to a magnetic-field directed perpendicular to both the direction of current flow and the aligned axis. Some embodiments may advantageously provide a precise measurement indicative an electrical current in the electrical conductor while substantially rejecting a stray magnetic field originating from an adjacent electrical conductor.

Abstract: Apparatus and associated methods relate to a measurement system that calculates a current in a conductor based on an odd-order spatial derivative function of signals representing magnetic-field strengths within a hole in the conductor. In an illustrative embodiment, the odd-order spatial derivative function may generate an output signal representing a spatial derivative of the in-hole magnetic field greater than the first-order. The three or more magnetic-field sensors may be configured to align on the hole's axis when inserted into the hole. When inserted into the hole, the sensors may be aligned on an axis perpendicular to a direction of current flow and be responsive to a magnetic-field directed perpendicular to both the direction of current flow and the aligned axis. Some embodiments may advantageously provide a precise measurement indicative an electrical current in the electrical conductor while substantially rejecting a stray magnetic field originating from an adjacent electrical conductor.

Abstract: A system for tracking motion of an object comprises at least a first magnetic source configured to generate a static magnetic field, with the magnetic source fixed in a first coordinate frame, and a plurality of magnetic sensors configured to be located on the object and to detect the static magnetic field. The magnetic sensors are located in a second coordinate frame that is movable relative to the first coordinate frame. A processor is operative to receive magnetic field data from the magnetic sensors. A memory unit coupled to the processor stores a magnetic field model or a magnetic field database defined for the first coordinate frame, and a magnetic sensor measurement model with uncertainties defined for the second coordinate frame. The processor computes and outputs an estimated position and orientation of the object based on the magnetic field data and other information stored in the memory unit.

Abstract: A solid state magnetic sensor for sensing magnetic information on a magnetic track is provided. The solid state magnetic sensor includes at least one half of a Wheatstone bridge including at least two legs, each of the at least two legs including at least a portion of a strip of magnetic material, and barber pole nonmagnetic shorting bars arranged on the portions of the strip forming the at least two legs of the at least one half of the Wheatstone bridge. An inner gap between parallel and adjacent strips of a respective at least two legs is on the order of a transition length on the magnetic track to be sensed.

Abstract: A method to measure an applied magnetic field in a plane is provided. The method includes simultaneously applying a first and second alternating drive current to a respective first and second strap overlaying a magnetoresistive sensor so the magnetoresistive sensor is subjected to a periodically rotating magnetic drive field rotating in the plane in the magnetoresistive sensor. When the applied magnetic field to be measured is superimposed on the periodically rotating magnetic drive field rotating in the plane, the method includes extracting a second harmonic component of an output voltage output from the magnetoresistive sensor. The magnitude of the magnetic field to be measured in the plane is proportional to an amplitude of the extracted second harmonic component of the output voltage. The orientation of the magnetic field to be measured in the plane is related to a phase angle of the extracted second harmonic component of the output voltage.

Abstract: A method to measure a magnetic field is provided. The method includes applying an alternating drive current to a drive strap overlaying a magnetoresistive sensor to shift an operating point of the magnetoresistive sensor to a low noise region. An alternating magnetic drive field is generated in the magnetoresistive sensor by the alternating drive current. When the magnetic field to be measured is superimposed on the alternating magnetic drive field in the magnetoresistive sensor, the method further comprises extracting a second harmonic component of an output of the magnetoresistive sensor. The magnetic field to be measured is proportional to a signed amplitude of the extracted second harmonic component.

Abstract: A solid state magnetic sensor for sensing magnetic information on a magnetic track is provided. The solid state magnetic sensor includes at least one half of a Wheatstone bridge including at least two legs, each of the at least two legs including at least a portion of a strip of magnetic material, and barber pole nonmagnetic shorting bars arranged on the portions of the strip forming the at least two legs of the at least one half of the Wheatstone bridge. An inner gap between parallel and adjacent strips of a respective at least two legs is on the order of a transition length on the magnetic track to be sensed.

Abstract: A method to measure an applied magnetic field in a plane is provided. The method includes simultaneously applying a first and second alternating drive current to a respective first and second strap overlaying a magnetoresistive sensor so the magnetoresistive sensor is subjected to a periodically rotating magnetic drive field rotating in the plane in the magnetoresistive sensor. When the applied magnetic field to be measured is superimposed on the periodically rotating magnetic drive field rotating in the plane, the method includes extracting a second harmonic component of an output voltage output from the magnetoresistive sensor. The magnitude of the magnetic field to be measured in the plane is proportional to an amplitude of the extracted second harmonic component of the output voltage. The orientation of the magnetic field to be measured in the plane is related to a phase angle of the extracted second harmonic component of the output voltage.

Abstract: A method to measure a magnetic field is provided. The method includes applying an alternating drive current to a drive strap overlaying a magnetoresistive sensor to shift an operating point of the magnetoresistive sensor to a low noise region. An alternating magnetic drive field is generated in the magnetoresistive sensor by the alternating drive current. When the magnetic field to be measured is superimposed on the alternating magnetic drive field in the magnetoresistive sensor, the method further comprises extracting a second harmonic component of an output of the magnetoresistive sensor. The magnetic field to be measured is proportional to a signed amplitude of the extracted second harmonic component.

Abstract: Systems and methods for three-axis sensor chip packages are provided. In one embodiment, a directional sensor package comprises: a base; a first sensor die mounted to the base, the first sensor die having a first active sensor circuit and a first plurality of metal pads electrically coupled to the first active sensor circuit; a second sensor die mounted to the base, the second sensor die having a second active sensor circuit located on a first surface, and a second plurality of metal pads electrically coupled to the second active sensor circuit located on a second surface. The second sensor die is positioned such that the second active sensor circuit is oriented orthogonally with respect to the first active sensor circuit region and is perpendicular to the base. The second surface is adjacent to the first surface and angled with respect to a plane of the first surface.

Abstract: An apparatus includes a write element for writing to a medium. The apparatus is configured to effectuate an electrical potential difference between a portion of the apparatus and a portion of the medium such that a current flows between the apparatus and the medium to reduce a coercivity of the medium proximate to the write element.

Abstract: An ultrasonic emitting apparatus (10) for cauterizing and ablating tissue. Ultrasonic waves are focused at an intended region of operation by an elongated waveguide (15), thus reducing damage to adjacent unintended tissue. The waveguide (15) can be inserted into structures of the body through overlying organs. The device may be used, for example, to ablate protruding portions of spinal disks.

Abstract: A tubular anatomical structure in a mammalian subject is occluded by directing ultrasonic energy from outside of the body. For example, a male subject may be sterilized by directing ultrasonic energy through the skin of the scrotum, onto the vas deferens. The focal spot of an ultrasonic transducer may be registered with the structure to be treated by means of guide members on a probe holding the transducer. The procedure is simple and can be entirely non-invasive. Apparatus for performing this and other treatments may be provided as a disposable unit, and the guide members may be arranged to hold a fold of tissue without substantially obstructing the sonic path from the transducer to the fold.

Abstract: An apparatus and method for applying sonic energy within the body of the living subject. A probe for applying sonic energy within the body of a subject comprises a probe body having a proximal and a distal end adapted for insertion into the body of a subject, a spatially-distributed sonic transducer disposed adjacent to the distal end of the probe body and a device for moving one portion of the spatially-distributed transducer relative to another portion of the transducer while the distal end of the probe is disposed within the body of the subject.

Abstract: A multi-layer piezoelectric transducer includes a first polymeric layer of piezoelectric material having spaced apart first and second surfaces and a second polymeric layer of piezoelectric material having spaced apart first and second surfaces. A first ground layer overlies the first surface of the first polymeric layer and a second ground layer overlies the first surface of the second polymeric layer. A signal layer is sandwiched between the second surfaces of the first and second polymeric layers.

Abstract: An apparatus and method for applying sonic energy within the body of the living subject. A probe for applying sonic energy within the body of a subject includes a probe body having a proximal and a distal end adapted for insertion into the body of a subject, a spatially-distributed sonic transducer disposed adjacent to the distal end of the probe body and a device for moving one portion of the spatially-distributed transducer relative to another portion of the transducer while the distal end of the probe is disposed within the body of the subject.

Abstract: A magnetic field sensor that isotropically senses an incident magnetic field. This is preferably accomplished by providing a magnetic field sensor device that has one or more circular shaped magnetoresistive sensor elements for sensing the incident magnetic field. The magnetoresistive material used is preferably isotropic, and may be a CMR material or some form of a GMR material. Because the sensor elements are circular in shape, shape anisotropy is eliminated. Thus, the resulting magnetic field sensor device provides an output that is relatively independent of the direction of the incident magnetic field in the sensor plane.

Abstract: Apparatus for mounting and making electrical connections to sensor devices for use in three axis sensing including a flexible circuit and a substrate shaped so that when a portion of the flexible tape is secured to the substrate the sensor devices can be mounted on the substrate for sensing in the desired three directions. The sensors are connected to conductors in the flexible tape by wirebonds or by other means.

Abstract: A method and apparatus for sensing a desired component of a magnetic field using an isotropic magnetoresistive material. This is preferably accomplished by providing a bias field that is parallel to the desired component of the applied magnetic field. The bias field is applied in a first direction relative to a first set of magnetoresistive sensor elements, and in an opposite direction relative to a second set of magnetoresistive sensor elements. In this configuration, the desired component of the incident magnetic field adds to the bias field incident on the first set of magnetoresistive sensor elements, and subtracts from the bias field incident on the second set of magnetoresistive sensor elements. The magnetic field sensor may then sense the desired component of the incident magnetic field by simply sensing the difference in resistance of the first set of magnetoresistive sensor elements and the second set of magnetoresistive sensor elements.

Abstract: Miniature magnetometer apparatus for use with external equipment in determining a position and orientation of a device located within a magnetic field includes an elongated flexible circuit for connection to external equipment, a substrate at the device with a portion of the flexible circuit secured thereto, and a planar sensor mounted on the flexible circuit at the substrate and connected to the flexible circuit.