An inductive sensor is proposed which comprises at least one resonant circuit, an evaluation device which in a measuring phase evaluates oscillations of the at least one resonant circuit for generating sensor signals, an energy storage device, and a transfer device which in a relaxation phase of the at least one resonant circuit stores oscillation energy of the at least one resonant circuit in the energy storage device.

A proximity sensor and a method of changing a detection distance are provided to suppress changes in a consumption current of an oscillation circuit. The proximity sensor includes an oscillation circuit having an oscillation amplitude that changes with a feedback current, a comparing part comparing the oscillation amplitude with a threshold, a detecting part detecting a target object based on a comparison result of the comparing part, a voltage value signal generating part generating a voltage value signal based on the feedback current and the detection distance, a threshold setting part setting an analog signal converted from the voltage value signal as the threshold, a current value signal generating part generating a current value signal based on the detection distance and the voltage value signal, and a current value setting part setting an analog signal converted from the current value signal as a current value of the feedback current.

An inductive sensor, particularly for a proximity sensor, includes a resonance circuit including a sensing coil and an amplifier comprising a first gain stage and a second gain stage each coupled via respective adjusting elements with the resonance circuit to inject energy for maintaining an oscillation of the resonance circuit. The first gain stage provides a substantially linear amplification and the second gain stage provides a comparator characteristics.

The present invention relates to an oscillating sensor for a measurement device comprising: an oscillator comprising a resonance circuit for providing an oscillation signal; a gain stage configured to feed back to the resonance circuit to inject energy for excitation of the resonance circuit to maintain oscillation; at least one calibration element to adjust the open loop gain of the oscillator; a calibration unit to provide a modulated calibration control signal to selectively adjust an electrical measure of the at least one calibration element based on at least one predetermined duty cycle,
wherein the modulated calibration control signal has an irregularly time-varying cycle frequency.

The invention relates to an oscillating sensor for a measurement device comprising: an oscillator comprising: a resonance circuit for providing an oscillation signal; a gain stage configured to provide a feed-back to the resonance circuit to inject energy for excitation of the oscillator to maintain oscillation; at least one calibration element to adjust the open loop gain of the oscillator; a calibration unit to provide a modulated calibration control signal to selectively adjust an electrical measure of the at least one calibration element based on at least one predetermined duty cycle, wherein the calibration unit is further configured to provide the modulated calibration control signal with at least one cycle frequency which depends on the oscillation frequency.

An oscillating sensor device, particularly for a proximity sensor, for sensing a dynamic change of attenuation caused by a measurable physical effect includes an oscillator including a resonance circuit and an amplifier fed back to the resonance circuit and configured to maintain oscillation of the oscillator, and a control unit configured to control the open loop gain of the oscillator. The amplifier comprises a non-linear gain characteristics defining an operating point at a preset amplitude of oscillation. The control unit is configured to control the open loop gain of the oscillator so that the operating point is set to a preset amplitude of the oscillation.

A resonant inductive sensing system includes an active resonator target that balances losses in the target resonator. The resonant sensor includes a sensor resonator LC circuit and a resonant target including a target resonator Lt/Ct circuit characterized by a loss factor Rts and a target quality factor Qt. The sensor resonator LC circuit and the target resonator Lt/Ct circuit are configured for operation as coupled resonators. The resonant sensor includes a sensor circuit configured to drive the resonant sensor, such that the sensor resonator LC circuit projects a magnetic sensing field based on a sensor quality factor Q, and an active negative resistance circuit Ra coupled to the target resonator Lt/Ct circuit, and configured to substantially cancel the loss factor Rts, such that target quality factor Qt is substantially Qt=([Lt/Ct]/Rts)(RaRts/[RaRtsLt/Ct]).

A proximity sensor or switch having a sensing coil, an oscillator connected to the coil, a comparator connected to the oscillator, a reference voltage module connected to the comparator, and an output driver connected to the comparator. The voltage module may incorporate a resistor having an end connected to a high side of a power source, and a digital potentiometer having a first end connected to another end of the resistor and to the comparator, and having a second end connected to a ground side of the power source. The digital potentiometer may have a resistance that is varied with a signal. A variation of the resistance for the digital potentiometer may result in a change of a voltage from the reference voltage module which further changes a switching distance of the proximity switch to a predetermined value.

The invention relates to an oscillator comprising a resonant circuit having at least one inductor and one capacitor and having a feedback amplifier, wherein there is at least one trimming resistor in a feedback circuit of the amplifier. The oscillator is characterized in that there is an electronic switching device for alternately connecting and disconnecting the trimming resistor, in that a trimming circuit is formed by the trimming resistor and the electronic switching device, in that there is a drive device for driving the electronic switching device, in that the electronic switching device, together with the drive device, is designed to alternately connect and disconnect the trimming resistor in a switching sequence, and in that an average time value of the electrical resistor of the trimming circuit, which is active in an oscillator mode, is defined by the switching sequence.

Front-end circuits that combine inductive and capacitive sensing are described. In one embodiment, an apparatus includes a plurality of inductive elements, an inductive measurement circuit, and a frequency divider circuit. The inductive measurement circuit is to output a first signal with a first frequency. The first signal is associated with an inductance change of one of the inductive elements. A feedback circuit can maintain the sinusoidal operation of the first signal. The frequency divider circuit can generate a second signal with a second frequency that is lower than the first frequency.