A displacement sensor includes: a detectable portion: including a first coil; and being disposed on a movable member that is displaceable in response to an operation; and a signal generator: including a second coil that opposes the first coil; and being configured to generate a detection signal based on a relative position between the first coil and the second coil. A first distance from a first end of the first coil to a second end of the first coil in a first direction differs from a second distance from a third end of the first coil to a fourth end of the first coil in a second direction perpendicular to the first direction when the first coil is viewed in plan view.

One inductive sensor is configured to maintain a fixed frequency in a resonant circuit. One apparatus includes an inductance-to-digital converter (LDC). The LDC includes a digital filter to measure an inductance change of a sensor and convert the inductance change to a digital value. The LDC further includes a digital control loop to maintain a fixed frequency in the sensor. The sensor forms an oscillator in the digital control loop. An output of the digital control loop is representative of the inductance change of the sensor.

Apparatus and methods of automatically trimming a PCB-based LC circuit. The apparatus may comprise an interface to a printed circuit board (PCB). The PCB may include a PCB inductor and a PCB capacitor to form an LC circuit. The LC circuit may have an LC circuit frequency. The apparatus may comprise a variable capacitor communicatively coupled to the interface and configured to adjust an effective capacitance of the LC circuit.

Apparatus and methods of automatically trimming a PCB-based LC circuit. The apparatus may comprise an interface to a printed circuit board (PCB). The PCB may include a PCB inductor and a PCB capacitor to form an LC circuit. The LC circuit may have an LC circuit frequency. The apparatus may comprise a variable capacitor communicatively coupled to the interface and configured to adjust an effective capacitance of the LC circuit.

An inductive sensor device for detecting a reciprocating movement of an object includes an oscillator circuit and a processing unit. The oscillator circuit has a sensing coil configured for inducing eddy currents in the object. The processing unit is configured to count a plurality of oscillations of the oscillator circuit detected in a plurality of sampling periods, compare the oscillations with a predetermined mean value of oscillations, and determine both a speed and a position of the object based on a comparison of the oscillations with the predetermined mean value of oscillations.

One inductive sensor is configured to maintain a fixed frequency in a resonant circuit. One apparatus includes an inductance-to-digital converter (LDC). The LDC includes a digital filter to measure an inductance change of a sensor and convert the inductance change to a digital value. The LDC further includes a digital control loop to maintain a fixed frequency in the sensor. The sensor forms an oscillator in the digital control loop. An output of the digital control loop is representative of the inductance change of the sensor.

An apparatus includes a first resonant circuit including a first coil mounted to a movable member; a second resonant circuit including a second coil facing the first coil and generating a magnetic field upon supply of an electric current and outputs a detection signal of a voltage level depending on a relative position of the second coil to a position of the first coil; and a first equivalent circuit equivalent to the second resonant circuit in a case where a distance between the first and second coils is infinite and a second equivalent circuit equivalent to the second resonant circuit in a case where the distance is zero. A processor corrects the detection signal based on an output signal output from the first equivalent circuit and an output signal output from the second equivalent circuit, and calculates, based on the corrected detection signal, a displacement amount of the movable member.

A detection system detects a position of each of a plurality of movable members that are displaceable by a playing operation. The detection system includes a controller configured to generate a first signal with a signal that level discontinuously changes over time, a Pi filter configured to convert the first signal to a second signal with a signal level that continuously changes over time, and a signal processor configured to generate, using the second signal, an output signal that depends on a position of each of the plurality of movable members.

A rotation-detecting apparatus includes the following: a rotor coil provided on a rotor; detection coils provided on stators; a control circuit that detects the relative rotational angle between the rotor and the stators by processing detection signals induced in the detection coils as a result of the rotor coil being excited by an excitation signal; and a communicating means for performing data communication with an external device. The control circuit in the rotation-detecting apparatus has functionality whereby a switch signal that turns on and off at preset rotational angles is outputted on the basis of the aforementioned detection signals. Also, the control circuit is designed such that the set rotational angles for the aforementioned switch signal can be changed by the external device via the abovementioned communicating means.

A system may include a resistive-inductive-capacitive sensor, a measurement circuit communicatively coupled to the resistive-inductive-capacitive sensor and configured to at a plurality of periodic intervals, measure phase information associated with the resistive-inductive-capacitive sensor and based on the phase information, determine a displacement of a mechanical member relative to the resistive-inductive-capacitive sensor. The system may also include a driver configured to drive the resistive-inductive-capacitive sensor at a driving frequency and a driving amplitude, wherein at least one of the driving frequency and the driving amplitude varies among the plurality of periodic intervals.