An electronic device may be provided with an electronic compass. The electronic compass may include magnetic sensors. The magnetic sensors may include thin-film magnetic sensor elements such as giant magnetoresistance sensor elements. Magnetic flux concentrators may be used to guide magnetic fields through the sensor elements. To reduce offset in the electronic compass, the magnetic flux concentrators may be demagnetized by applying a current to a coil in the housing. The coil may be formed from loops of metal traces within a printed circuit or other loops of conductive paths. Magnetic flux concentrators may have ring shapes. A ring-shaped magnetic flux concentrator may be formed from multiple thin stacked layers of soft magnetic material separated by non-magnetic material.

An electronic device may be provided with an electronic compass. The electronic compass may include magnetic sensors. The magnetic sensors may include thin-film magnetic sensor elements such as giant magnetoresistance sensor elements. Magnetic flux concentrators may be used to guide magnetic fields through the sensor elements. To reduce offset in the electronic compass, the magnetic flux concentrators may be demagnetized by applying a current to a coil in the housing. The coil may be formed from loops of metal traces within a printed circuit or other loops of conductive paths. Magnetic flux concentrators may have ring shapes. A ring-shaped magnetic flux concentrator may be formed from multiple thin stacked layers of soft magnetic material separated by non-magnetic material.

A report interval mode is selected from one of multiple selectable report interval modes in cases where the preferred sensor sample intervals of multiple applications are different. By using multiple selectable report interval modes some of the problems that occur when a single fixed report interval mode is used can be avoided.

In one embodiment, a process obtains a first compensated directional reading from a first directional sensor of a directionally sensitive system, and obtains a second compensated directional reading from a second directional sensor of the directionally sensitive system. The process may then determine, a difference between the first compensated directional reading and the second compensated directional reading, and declares, in response to the difference being greater than an acceptable threshold, an inaccurate directional reading. As such, the process may then prevent performance of a directionally sensitive action by the directionally sensitive system in response to an inaccurate directional reading.

A system for tracking a location of a body-worn tracking device (BWTD) includes a global navigation satellite system (GNSS) component, one or more sensors, one or more processors, and a memory device. The memory device includes instructions that, when executed by the one or more processors, cause the one or more processors to determine whether a current location of the BWTD can be determined using the GNSS component. The instructions also cause the one or more processors to determine, based in part on the activity of the wearer of the BWTD and based on a determination that the current location of the BWTD cannot be determined using the GNSS component, whether to perform an action. The instructions also cause the one or more processors to perform the action in response to a determination to perform the action.

A system for tracking a location of a body-worn tracking device (BWTD) includes a global navigation satellite system (GNSS) component, one or more sensors, one or more processors, and a memory device. The memory device includes instructions that, when executed by the one or more processors, cause the one or more processors to determine whether a current location of the BWTD can be determined using the GNSS component. The instructions also cause the one or more processors to determine, based in part on the activity of the wearer of the BWTD and based on a determination that the current location of the BWTD cannot be determined using the GNSS component, whether to perform an action. The instructions also cause the one or more processors to perform the action in response to a determination to perform the action.

An autonomous magnetic observatory is provided that includes a scalar magnetometer for measuring the modulus of the local magnetic field vector F; an angular magnetometer for measuring the vertical direction, the direction of geographic North, and the direction of the local magnetic field vector F; a variometer for measuring three variations in the local magnetic field vector F; a clock; and a controller. In which observatory, the controller is configured to control and manage the orientation of sensors, to acquire the measurements of the variometer, of the scalar magnetometer, of the angular magnetometer and of the variometer, and to process the acquired measurements in order to obtain automatically, the local magnetic field vector F and the errors in the measurements associated with each instrument.

An autonomous magnetic observatory is provided that includes a scalar magnetometer for measuring the modulus of the local magnetic field vector F; an angular magnetometer for measuring the vertical direction, the direction of geographic North, and the direction of the local magnetic field vector F; a variometer for measuring three variations in the local magnetic field vector F; a clock; and a controller. In which observatory, the controller is configured to control and manage the orientation of sensors, to acquire the measurements of the variometer, of the scalar magnetometer, of the angular magnetometer and of the variometer, and to process the acquired measurements in order to obtain automatically, the local magnetic field vector F and the errors in the measurements associated with each instrument.

A mouth guard senses impact forces and determines if the forces exceed an impact threshold. If so, the mouth guard notifies the user of the risk for injury by haptic feedback, vibratory feedback, and/or audible feedback. The mouth guard system may also remotely communicate the status of risk and the potential injury. The mouth guard uses a local memory device to store impact thresholds based on personal biometric information obtained from the user and compares the sensed forces relative to those threshold values. The mouth guard and its electrical components on the printed circuit board are custom manufactured for the user such that the mouth guard provides a comfortable and reliable fit, while ensuring exceptional performance.

A mouth guard senses impact forces and determines if the forces exceed an impact threshold. If so, the mouth guard notifies the user of the risk for injury by haptic feedback, vibratory feedback, and/or audible feedback. The mouth guard system may also remotely communicate the status of risk and the potential injury. The mouth guard uses a local memory device to store impact thresholds based on personal biometric information obtained from the user and compares the sensed forces relative to those threshold values. The mouth guard and its electrical components on the printed circuit board are custom manufactured for the user such that the mouth guard provides a comfortable and reliable fit, while ensuring exceptional performance.