A magnetic sensor device includes a switching region defined by a switching range and a variation range, the switching range being set in a stroke direction of a magnet generating a radial magnetic field and defined by a start position and an end position for switching of the state, and the variation range being set in a direction intersecting the stroke direction and being a range of variation in the position of the magnet, and a magnetic sensor including plural first divided elements that are formed by dividing a first circular magneto-resistive element and are consecutively rotated and rearranged around the switching region such that change in a magnetoresistance value due to the magnetic field of the magnet in the switching region increases from the start position to the end position.

A magnetic sensor device includes a switching region defined by a switching range and a variation range, the switching range being set in a stroke direction of a magnet generating a radial magnetic field and defined by a start position and an end position for switching of the state, and the variation range being set in a direction intersecting the stroke direction and being a range of variation in the position of the magnet, and a magnetic sensor including plural first divided elements that are formed by dividing a first circular magneto-resistive element and are consecutively rotated and rearranged around the switching region such that change in a magnetoresistance value due to the magnetic field of the magnet in the switching region increases from the start position to the end position.

A method for measuring a magnetic field with a micro-sensor system includes applying a direct current (I.sub.Th) to a curved micro-beam to control a stiffness of the curved micro-beam; placing the micro-sensor system into an external magnetic field (B); selecting with a controller, based on an expected value of the external magnetic field (B), a given resonant frequency of the micro-beam; measuring with a resonant frequency tracking device the given resonant frequency of the micro-beam; and calculating in the controller the external magnetic field (B), based on (1) the measured resonant frequency, (2) the applied current (I.sub.Th), and (3) calibration data stored in the controller. The calibration data is indicative of a dependency between a change of the selected resonant frequency and the external magnetic field.

An electromagnetic gradiometer that includes multiple torsionally operated MEMS-based magnetic and/or electric field sensors with control electronics configured to provide magnetic and/or electric field gradient measurements. In one example a magnetic gradiometer includes a first torsionally operated MEMS magnetic sensor having a capacitive read-out configured to provide a first measurement of a received magnetic field, a second torsionally operated MEMS magnetic sensor coupled to the first torsionally operated MEMS magnetic sensor and having the capacitive read-out configured to provide a second measurement of the received magnetic field, and control electronics coupled to the first and second torsionally operated MEMS magnetic sensors and configured to determine a magnetic field gradient of the received magnetic field based the first and second measurements from the first and second torsionally operated MEMS electromagnetic sensors.

An electromagnetic gradiometer that includes multiple torsionally operated MEMS-based magnetic and/or electric field sensors with control electronics configured to provide magnetic and/or electric field gradient measurements. In one example a magnetic gradiometer includes a first torsionally operated MEMS magnetic sensor having a capacitive read-out configured to provide a first measurement of a received magnetic field, a second torsionally operated MEMS magnetic sensor coupled to the first torsionally operated MEMS magnetic sensor and having the capacitive read-out configured to provide a second measurement of the received magnetic field, and control electronics coupled to the first and second torsionally operated MEMS magnetic sensors and configured to determine a magnetic field gradient of the received magnetic field based the first and second measurements from the first and second torsionally operated MEMS electromagnetic sensors.

Sensor-based privacy-event detection for a mounted electronic device is described. In aspects, a security system includes a head assembly removably and magnetically coupled to a mounting device having a magnet. The electronic device also includes a camera module and a sensor disposed within the housing. The sensor detects a magnetic field associated with the magnet when the head assembly is coupled to the mounting device. When a user detaches the head assembly from the mounting device (e.g., to recharge the electronic device), the sensor no longer detects the magnetic field and determines the occurrence of a privacy event, which is used to deactivate the camera module to prevent unintentional recordings during the privacy event.

A gradiometer includes a at least one magnet attached to a beam. The magnet moves in response to a magnetic force. A sensing element is configured to measure movement or deflection of the beam or magnet. The gradiometer is configured to determine a gradient of a magnetic field acting on the first magnet based on movement of the magnet. The gradiometer can further measure higher order gradients.

A gradiometer includes a at least one magnet attached to a beam. The magnet moves in response to a magnetic force. A sensing element is configured to measure movement or deflection of the beam or magnet. The gradiometer is configured to determine a gradient of a magnetic field acting on the first magnet based on movement of the magnet. The gradiometer can further measure higher order gradients.

A soft magnetic sensor comprising a soft material containing randomly distributed magnetic microparticles and a magnetometer that can estimate force and localize contact over a continuous area. A reference magnetometer can be used to filter motion and ambient noise. Methods for locating contact and determining force comprise data analysis of the magnetometer output. In some embodiments, the sensor can localize an object prior to contact.

A frac dart including a pressure housing, a mechanically actuated magnetic sensor including a first magnet outside of the pressure housing, a signal generator inside the pressure housing and in operable communication with the first magnet, and an electrical counter disposed in the frac dart responsive in increments to the signal generator.