A loading device, a monitoring system, and a method thereof can measure stiffness of a structural member (SM) and monitor progress or property thereof over time. The loading device includes two types of displacement sensors, one type being an antenna. As the SM, which is in a magnetic or electromagnetic field and electromagnetically coupled to the antenna without contact, undergoes displacement under known loads, characteristics of the electromagnetic field coupling between the antenna and the SM change over time due to the displacement of the SM. The shift in the characteristics of the electromagnetic field coupling between the antenna and the SM can be used to determine the displacement of the SM. Based on the changes in the displacement over time, diagnosis of the SM being monitored over an evaluation period can be made. The loading device includes at least one movable frame to apply a preload to the SM.

Methods and apparatus for detecting a magnetic field include a semiconductor substrate, a coil configured to provide a changing magnetic field in response to a changing current in the coil; and a magnetic field sensing element supported by the substrate. The coil receives the changing current and, in response, generates a changing magnetic field. The magnetic field sensing element detects the presence of a magnetic target by detecting changes to the magnetic field caused by the target and comparing them to an expected value.

A stroke sensor system includes a conductor, a coil which moves relative to the conductor and is fitted to one end side of the conductor; and a ferromagnetic body which is arranged on an end position side of the coil. A position of an end portion on one end side of the conductor in a state where a fitting ratio between the conductor and the coil is maximized is defined as the end position. The ferromagnetic body is located on an opposite side to the conductor with the coil interposed therebetween.

A magnetic field sensor has a plurality of magnetic field sensing elements and operates as a motion detector for sensing a rotation or other movement of a target object.

An angular position sensor for sensing the angular position of a rotor rotating on an axis relative to a stator, including a ferromagnetic target, of substantially ovoid cross section, rotating together with one from among the rotor or the stator, and a sensitive element including a first set of coils that are angularly evenly distributed, rotating together with the other from among the rotor or the stator, the coils being axially arranged in line with the target in order to be able to measure a distance from the target so as to deduce therefrom an angular position of the rotor relative to the stator.

A method for determining a voice coil position of a voice coil includes providing a magnetic circuit having a magnetic gap and suspending the voice coil in the magnetic gap, applying a driving signal to the voice coil to produce an electromotive force, providing inductive sensors mechanically coupled to the voice coil, measuring inductive sensor signals based on outputs from the inductive sensors, processing the measured inductive sensor signals by determining at least one inductive sensor signal ratio, and determining a representation of the voice coil position based on the at least one inductive sensor signal ratio. A voice coil system, which can be incorporated in a loudspeaker, is configured to carry out the method.

A shaft monitoring system includes a rotatable shaft having a target element coupled thereto that rotates along with the shaft. A proximity sensor is located adjacent to the target element. The proximity sensor measures an inductance of the target element based on one or both of a volume of the target element and a distance between the target element and the proximity sensor, and generates a proximity sensor output signal based on the measured inductance. A signal processing system determines at least one of a position of the shaft, a rotational speed of the shaft, and a rotational direction of the shaft based on the proximity sensor output signal.

An electronic sensor includes a signal generator configured to output excitation signals and a variable differential transformer connected to the signal generator to receive excitation signals. Embodiments of the variable differential transformer may include a primary coil, a first secondary coil connected to the signal generator, a second secondary coil connected to the signal generator, and a core disposed at least partially in a magnetic field generated via the first secondary coil and the second secondary coil and the first excitation signal and the second excitation signal. A phase of an output signal of the primary coil may correspond to a position of the core.

A force sensor including: a first part including a detection coil; a second part positioned opposite the first part and including: a ferromagnetic plate translationally movable relative to the first part to move towards the first part when a force is transferred to the sensor and to reduce reluctance of a magnetic circuit formed by the first and second parts in series with a variable gap; and an electronic detection circuit configured to generate a signal dependent on the reluctance of the magnetic circuit. The ferromagnetic plate is formed by an amorphous metal alloy.

The present disclosure provides position detector for an electric machine. The detector uses one or more proximity sensors, such as eddy current sensors, to detect features on the rotor of an electric machine. The detectable feature may be a spiral groove, which has a unique position at any given point around the circumference of the rotor. As the rotor is typically steel, the proximity sensors produce different output values depending on the degree to which they are aligned with the groove. As such, given that the groove has a unique position at any given location, the output of the proximity sensors is also unique for any given position. This enables the position of the rotor with respect to the sensors to be determined.