Abstract: A process for measuring the thickness of an insulating material. The process includes providing a device used to measure capacitance, and electrically connecting the capacitance measuring device to a heat sink and an electrical, heat-generating component. The thickness of the insulating material is determined by measuring the capacitance of the insulating material according to the formula; B=?r?oA/C, where B is the thickness of the insulating material, C is the capacitance, A is the area of the heat generating component, ?o is the permittivity of free space and ?r is the relative dielectric constant of the insulating material.

Abstract: A displacement measuring apparatus 100 which measures a displacement of an object to be measured 1 comprises a ranging sensor 5 configured to detect a first origin position based on a distance to a base 2, a ranging sensor 6 configured to detect a second origin position based on a distance to the object to be measured 1, a stage 4 mounting the ranging sensors 5 and 6 and configured to move in a ranging direction of the ranging sensors 5 and 6, and a controller 7 configured to measure a displacement of the object to be measured 1 with respect to the base 2 using the first and second origin positions detected while moving the ranging sensors 5 and 6.

Abstract: A drive-by-wire non-contact capacitive throttle control apparatus and method of forming the same. A capacitive position sensor is provided, which includes a stationary electrode and a rotatable electrode. The rotatable electrode can be attached to a throttle lever such that the rotatable electrode rotates as the throttle lever rotates. The capacitance between the rotatable electrode and the stationary electrode varies with the position of the throttle lever. The position of the throttle lever can be measured by measuring the capacitance between the electrodes and a signal can be generated based on the sensed position. The signal can be electrically transmitted to an ECU (Electronic Control Unit) utilizing one or more electrical wires. The signal can be sent in the form of a varying voltage, which in turn controls the throttle of a vehicle.

Abstract: A fingerprint sensing module includes a sensor substrate having a sensing side and a circuit side, an image sensor including conductive traces on the circuit side of the sensor substrate, and a sensor circuit including at least one integrated circuit mounted on the circuit side of the sensor substrate and electrically connected to the image sensor. The sensor substrate may be a flexible substrate. The module may include a velocity sensor on the sensor substrate or on a separate substrate. The module may further include a rigid substrate, and the sensor substrate may be affixed to the rigid substrate.

Abstract: A capacitive switch of an electric/electronic device is provided. The capacitive switch includes a plurality of contacts which are disposed at a front of a control panel; a plurality of capacitive sensors which are disposed at a rear of the control panel, respectively face the contacts, and detect capacitance variations caused by static electricity that affects the contacts; and a plurality of void removal elements which are respectively disposed between the capacitive sensors and the contacts, remove a plurality of voids between the capacitive sensors and the contacts, and are formed of an elastic material so as to be able to compensate for various sized voids. Therefore, it is possible to easily remove various sized voids between the contacts and the capacitive sensors using the void removal elements, to prevent malfunction of the capacitive sensors due to the existence of voids, and to provide various shapes of control panels and various shapes of printed circuit boards.

Abstract: A passage detection apparatus is configured to detect the change in the properties (propagation state of sound wave, dielectric constant, etc.) of a specific space, which changes according to the passage of an object in the specific space and the size of the object. The passage detection apparatus includes a pair of detection units and configured to transmit and receive signals to and from an external device. The specific space is formed by the space between the detection unit and the detection unit. The detection unit is supported by a first substrate. The detection unit is supported by a second substrate that is parallel to the first substrate, and arranged at the position corresponding to the detection unit supported by the first substrate.

Abstract: Disclosed is an apparatus for sensing a force, comprising an actuator having a conductive deformable surface, a substrate having a first conductive trace and a second conductive trace, a housing coupled to the actuator and to the substrate, holding the actuator in proximity to the substrate, and a circuit for measuring a capacitance value.

Abstract: A system for measuring clearance between a first object and a second object is provided. The system includes a sensor configuration to generate a first signal representative of a first sensed parameter and a second signal representative of a second sensed parameter. The system also includes a clearance measurement unit configured to process the first and second signals based upon a ratiometric technique to calculate clearance between the first and second objects.

Abstract: A capacitive sensing circuit which has a uniformly resistive sense plate, a charge transfer measurement circuit connected to one side of the sense plate and a dummy load which is only connected to another side of the sense plate during some measurement cycles.

Abstract: A capacitive transducer a first part containing a first set of capacitor plates and a second part relatively movable in a plane to the first part. The second part contains a second set of capacitor plates. Both sets of capacitor plates are built on a substrate, wherein the capacitor plates form a plurality of capacitors. The second part is relatively movable in all six degrees of freedom. One set of the plurality of capacitors measures displacements in a plane and a second set of the plurality capacitors measures displacements perpendicular to the plane.

Abstract: A method for determining a distance between a first piece and a second piece includes measuring, at the first or second piece, an AC signal, and determining the distance based on the measured AC signal. A system for determining a distance between a first piece and a second piece includes a measuring device adapted to measure, at one or both of the first and second piece, an AC signal, and a signal processing device adapted to determine the distance based on the measured AC signal. The AC signal includes a DC offset.

Abstract: A method of creating an improved sensitivity capacitive fingerprint sensor involves forming vias from a first side of a sensor chip having an array of capacitive sensors, making the vias electrically conductive, and attaching a cover plate over the first side of the sensor chip spaced from the sensor chip by a distance of less than 25 ?m. An improved sensitivity capacitive fingerprint sensor has a capacitive sensor array including multiple sensor cells and electrically conductive, through-chip vias extending from connection points for sensor cell circuitry to a back side of the capacitive sensor array, a chip including active detection circuitry and electrical connection points, the electrical connection points being respectively connected to corresponding ones of the sensor cell circuitry connection points, and a cover plate, disposed above the sensor cells at a spacing of less than 25 ?m.

Abstract: Circuits and methods to read out capacitive sensors for distance measurement used by a position control system having a high accuracy and low noise have been disclosed. The ratio or difference of the capacitances of two sensor capacitors is used to determine the distance of an object from a target position. A sense amplifier is using auto-zero methods to achieve a long term stability. A sample-and-hold circuit using double correlated sampling methods minimizes noise. Low cost capacitors can be used with the sample-and-hold circuit because not the absolute value of capacitances but only the ratio of capacitances are relevant. A high resolution is ensured also by significant over-sampling of the control loop.

Abstract: The invention relates to a capacitive angle encoder for detecting a rotational position of a rotatable object relative to a stationary object as well as a withdrawable feeder for circuit board component insertion machines, said withdrawable feeder being equipped with an angle encoder according to the invention. The angle encoder comprises a stator that supports first and second transmitting electrodes and first and second receiving electrodes, and a rotor which supports an incremental coupling electrode and an absolute value-coupling electrode. The incremental coupling electrode is designed such that the first electrostatic field is modulated by a change in capacitance in response to a change in the rotational position of the rotor, while the absolute value-coupling electrode is designed such that the second electrostatic field is modulated by a change in capacitance in response to an absolute rotational position of the rotor.

Abstract: An apparatus for determining a clearance between rotor blade tips of rotor blades mounted on a rotor and a stator lining mounted on a stator casing. The stator lining is movable radially relative to the stator casing. The stator lining comprises an abradable material. At least one probe is arranged to measure the clearance between blade tips and stator lining. A first portion of the at least one probe is arranged within the stator lining and a tip of the first portion of the at least one probe is arranged flush with the surface of the abradable material. The tip of the first portion of the at least one probe comprises an abradable material. A second portion of the at least one probe is secured to the stator casing. A wire-less and connector-less coupling transmits a measurement signal from the first portion to the second portion of the at least one probe to allow radial movement of the stator lining relative to the stator casing.

Abstract: An inspecting apparatus is provided for inspecting electrical characteristics of an object (W) to be inspected, such as a semiconductor wafer. The inspecting apparatus is provided with a placing table (11) for supporting the object, a lift mechanism (12) for bringing up and down the placing table, and a driving apparatus (24) for driving the lift mechanism. The apparatus is also provided with a probe (13A) which makes contact with the object on the placing table brought up by the lift mechanism driven by the driving apparatus, and a load sensor (21), including a compression-type piezoelectric element, for detecting a contact load between the object and the probe as an oscillation waveform.

Abstract: A capacitive fingerprint sensor comprises a first transistor, a second transistor, a fingerprint capacitor and a third transistor. The fingerprint capacitor has a capacitance that is either a valley capacitance CFV or a ridge capacitance CFR, wherein CFV is smaller than CFR. The first transistor is configured to precharge the fingerprint capacitor. The second transistor is configured to discharge the fingerprint capacitor toward a bias voltage VB. The third transistor is configured to output the voltage of the fingerprint capacitor after discharge.

Abstract: An adjustable sensor strip assembly for use with a digital readout includes a plurality of sensor strip segments and a plurality of readout tracks for supporting the sensor strip segments. The readout tracks are fastened together with a wedge assembly. An alignment gauge is used to align the adjoining sensor strip segments so that precise measurements are achieved.

Abstract: In accordance with the invention, a surface capacitive sensor is mechanically coupled to a conventional macrostructure actuator to measure the displacement of the actuator along a measurement axis with high accuracy.

Abstract: A semiconductor die includes proximity connectors proximate to a surface of the semiconductor die. This semiconductor die is configured to communicate signals with another semiconductor die via proximity communication through one or more of the proximity connectors. In particular, the proximity connectors include a first group of proximity connectors that is configured to facilitate determining a first separation between the semiconductor die and the other semiconductor die by comparing coupling capacitances between the semiconductor die and the other semiconductor die. Note that the first group of proximity connectors includes a first proximity connector and a second proximity connector, and the second proximity connector at least partially encloses an in-plane outer edge of the first proximity connector.

Abstract: Embodiments of the invention relate to nanoscale measurement of displacement. In one embodiment, a measurement apparatus includes a first plurality of nanoparticles coupled to a first substrate electrically coupled to a second plurality of nanoparticles coupled to a second substrate with a guide or guides disposed between the first substrate and the second substrate that allow for the substrates to move relative to each other.

Abstract: A capacitive vehicle sensor includes a sensing electrode configured to generate an electric field, a shield electrode configured to reduce the electromagnetic influence of electric fields generated by objects outside of the electric field, a circuit coupled to the sensing electrode and shield electrode that allows a plurality of impedances to be coupled between the sensing electrode and the shield electrode, and a control system. The control system configures the impedances between the sensing electrode and the shield electrode, is configured to measure current to the sensing electrode in each configuration, and is configured to calculate a measure related to the impedance from the sensing electrode to ground.

Abstract: A capacitive fingerprint sensor comprises a fingerprint capacitor, a reference capacitor, a first transistor, a second transistor, a third transistor and a fourth transistor. The fingerprint capacitor CF has a capacitance that is either a valley capacitance CFV or a ridge capacitance CFR. The reference capacitor CS has a capacitance CS, and CFV<CS<CFR. The first transistor is configured to precharge the reference capacitor. The second transistor is configured to precharge the fingerprint capacitor. The third transistor is configured to redistribute the charges of the reference capacitor and fingerprint capacitor. The fourth transistor is configured to output the voltage of the reference capacitor after redistribution.

Abstract: A nanoscale motion apparatus comprises a fixed base, a movable platform, and means for moving the movable platform connected between the fixed base and the movable platform. A sensing device comprises a holder, at least two nanosensors, and a measurement plate. The holder is mounted on the fixed base. The nanosensors are configured on the holder. The measurement plate is mounted on the movable platform. The measurement plate can be sensed by the nanosensors so as to measure the corresponding variation between the fixed base and the movable platform.

Abstract: Methods for determining the position of multiple objects concurrently disposed within a capacitive sensing region are described. In one embodiment, indicia are received from a first plurality of capacitive sensor electrodes oriented along a first axis. Indicia are received from a second plurality of capacitive sensor electrodes oriented along a second axis, wherein the second axis is oriented non-parallel to the first axis. Indicia are received from a third plurality of capacitive sensor electrodes oriented along a third axis, wherein the third axis is oriented non-parallel to the first axis and the second axis. Then, the indicia received from the first plurality of capacitive sensor electrodes, the indicia received from the second plurality of capacitive sensor electrodes, and the indicia received from the third plurality of capacitive sensor electrodes is used to determine the positions of the multiple objects concurrently disposed within the capacitive sensing region.

Abstract: A system for measuring clearance between a stationary object and a movable object is provided. The system includes at least one sensor configured to be disposed on the stationary object and configured to measure an operating parameter corresponding to the movable object and a controller coupled to the at least one sensor, wherein the controller is configured to control an operating mode of the sensor based upon the measured operating parameter.

Abstract: A supported probe device that has a probe tip and probe body, the probe body having a sample facing surface and an opposing surface. The probe tip and a first electrode are on the sample facing surface. A second electrode is present on the probe body opposing surface. A third electrode is spaced from the second electrode, so that the second electrode is between the third electrode and the probe body. A first DC voltage source is electrically coupled to the first electrode, as is a first sensing circuit. A second DC voltage source is electrically coupled to the second electrode, and an AC voltage source electrically coupled to the third electrode. The probe body may be cantilevered.

Abstract: A capacitive sensor assembly for detecting relative movement or position between objects, such as liquid level in a tank or reservoir, movement of one machine component with respect to another, and so on, includes one or more antenna probes connected to an integrated chip normally associated with touch-screen displays. Each antenna probe operates independently and may be formed as insulated conductive wires or conductive traces between layers of a stiff or flexible substrate, such as a PCB, with the substrate material serving as the insulating layers. Each antenna probe has a different length representing different measurement positions or locations between the objects being measured to provide dynamic calibration of the measurement under changing environmental conditions.

Abstract: A switched capacitance detection circuit is responsive to changes in the fringing capacitance of a capacitive proximity sensor having at least one capacitive sensor element. In cases where the sensor has a single sensor element, the switching frequency of the detection circuit is controlled to maintain measurement accuracy in the presence of sensor moisture while minimizing power consumption and electromagnetic radiation. In cases where the sensor has multiple sensor elements, the capacitance values for each sensor element are differenced, absolute-valued and summed to form an output in which common-mode effects due to sensor moisture, temperature and sensor aging are canceled out.

Abstract: A capacitive sensor core with flexible hinge is disclosed. The capacitive sensor core comprises a main grid plate (3), an auxiliary grid plate (4), and a mechanical structure transferring the measuring quantity to the displacement between the main grid plate (3) and the auxiliary grid plate (4), the mechanical structure includes a stationary means and a moving means, the auxiliary grid plate(4) and the main grid plate (3) are fixed to the driven portion of the moving means and the corresponding position of the stationary means respectively, the stationary means and the moving means are connected through a flexible hinge; the flexible hinge consists of at least two supporting spring leafs (7), one end of each of the supporting spring leaf s(7) is connected to the stationary means, the other end is connected to the moving means; the plane of each of the supporting spring leaf s (7) is perpendicular to the planes of the main and auxiliary grid plates(3, 4).

Abstract: A clearance sensing system is disclosed. The system includes a probe separated from a test object by a variable distance d. The system also includes an alternating current (AC) source for supplying a current through the probe, wherein the AC source and the probe are configured to generate a controlled plasma channel between a tip of the probe and the test object. The system further includes a processing unit configured to determine the variable distance d based on a voltage difference between the tip of the probe and the test object.

Abstract: A position sensor has an external moving element couplable to a moving part whose angular or linear position is sought to be sensed. A sealed enclosure is engaged with the moving element such that the moving element moves relative to the enclosure, and capacitive elements are in the enclosure. An internal moving element inside the enclosure is magnetically coupled to the external moving element for movement with the external element, with the internal moving element moving between the capacitive elements thereby change the capacitance between the capacitive elements as the external moving element moves.

Abstract: A paper dispenser having a proximity detector for dispensation of paper therefrom. The dispenser includes a housing having an inner chamber adapted to support a roll of paper. The housing also has a dispensing aperture. A motor is adapted to dispense paper from the roll through the dispensing aperture. The dispenser also includes a proximity detection circuit, which comprises an antenna, an oscillator circuit to charge the antenna, an operational amplifier operated as a unity gain follower which receives an antenna signal from the antenna, a detector circuit which detects changes in the antenna signal, and a comparator which actuates the motor in response to changes in the antenna signal.

Abstract: A proximity detector employs a capacitive sensor, having: at least one detection antenna including numerous capacitive proximity sensors which each include a measuring electrode, the antenna being positioned close to an object or body; electronic elements for exciting the electrodes and processing the distance measurement signals originating from the capacitive sensors; and digital elements of controlling the electronic elements and of calculating the distances between the electrodes and the body or object using the processed measurement signals. The detection antenna also contains a single guard for all of the measuring electrodes. Moreover, the electronic elements have, for each detection antenna, a floating or floating excitation capacitive bridge which co-operates with polling elements in order sequentially to measure the respective capacitances between each electrode and the object or body to be measured.

Abstract: An apparatus includes a first capacitive sensor connected to a first supply voltage, a second capacitive sensor connected to a second supply voltage, a sensing circuit for producing a sense voltage in response to current flowing in the first and second capacitive sensors, a first mixer for combining the sense voltage with a first reference voltage to produce a first signal representative of in-plane displacement between electrodes of the first and second capacitive sensors, and a second mixer for combining the sense voltage with a second reference voltage to produce a second signal representative of out-of-plane displacement between the electrodes of the first and second capacitive sensors.

Abstract: Cylindrical capacitance force sensing device/method is disclosed. In one embodiment, an apparatus includes a capacitor having two parallel conductive surfaces, a cylindrical housing with a cover plate to encompass the capacitor, and a sensor in the cylindrical housing to generate a measurement based on a change in a distance between the two conductive surfaces when the cover plate is deflected by a load applied on the cover plate. In another embodiment, a method may include applying a load on top of a housing which encompasses a capacitive sensor having two parallel conductive surfaces to produce a deflection of a cover plate of the housing, automatically generating a measurement from the capacitive sensor when a distance between the two parallel conductive surfaces is charged due to the deflection of the cover plate, and decreasing an error in the measurement via stabilizing to a mounting surface.

Abstract: An operating element, in particular for a motor vehicle component, includes an actuating element that is movably supported in a carrier element and acts, in particular, on a switch element. To detect an approach of a user to the operating element, but at the same time to prevent a misdetection by a movable component, an electrically conductive sensor element of a capacitive proximity sensor and at least one shielding element are arranged in an interior space of the actuating element, the sensor element and the shielding element being connected to a printed circuit board in an electrically conducting fashion.

Abstract: An electric field object sensing system uses a charge pumping circuit to provide a voltage over a capacitor that varies dependent upon the capacitive coupling between a transmitter electrode and a receiver electrode. The output of the charge pump is preferably fed to a high impedance read-out means, such as an analog-digital converter (ADC). The system is preferably implemented in CMOS and integrated in control circuits of electronic products.

Abstract: A signal processing portion obtains the reciprocal of a composite impedance of gap static capacitance and a plasma impedance, obtains composite static capacitance which is the sum of the gap static capacitance and a static capacitance component included in the plasma impedance from an imaginary part of the reciprocal, and obtains a resistance component included in the plasma impedance from a real part of the reciprocal. A gap detection device obtains the static capacitance component by using a model representing the characteristics of the reciprocal of the plasma impedance and the resistance component and obtains the gap static capacitance by subtracting the static capacitance component from the composite static capacitance. The gap detection device obtains a gap from the obtained gap static capacitance. Thus provided is a technique to detect a gap between a nozzle of a laser beam machine for outputting a laser beam and an object to be machined with high accuracy.

Abstract: A capacitive sensor to detect toner volume levels in a toner container within an image forming device includes opposed electrodes disposed within the interior of the toner container. The opposed electrodes form a capacitor characterized by an inherent capacitance that varies in response to an amount of toner that exists between the opposed electrodes. A corresponding sensor circuit is electrically coupled to the opposed electrodes and adapted to sense an instantaneous capacitance of the capacitor to determine the amount of toner that exists between the opposed electrodes. The opposed electrodes may have different shapes and configurations, including for example, plates disposed within the toner container or the interior walls of the container itself. The sensor circuit is configured to apply an alternating current signal to the opposed electrodes and sense an output voltage that is indicative of an instantaneous capacitance of the capacitor corresponding to toner volume within the container.

Abstract: A capacitive proximity sensor comprising an emitter electrode (104) capacitively coupled to receive an electrode (102). A first active guard electrode (110), driven by the output of a unity gain amplifier (108), is provided in respect of the receive electrode (102), to shield parts thereof not facing a potential obstacle (122), and a grounded shield (126) is provided in respect of the emitter electrode (104) to shield parts thereof not facing a potential obstacle (122). A second active guard electrode (103) is provided between the emitter and receiver electrodes (104, 102), just behind the cover (106), which is also driven by the output of the amplifier (108). The second active guard electrode (103) acts to block shortened electric field lines (124) between the emitter and receiver electrodes (104, 102), thereby improving accuracy and reliability of the sensor.

Abstract: One type of capacitive sensing apparatus has a sensing element that includes a first portion and a second portion adjacent opposite edges of a sensing region. Signals from the first and second portions are combined. Another type of apparatus includes: a first sensing element including first and second portions; a second sensing element including third and fourth portions; and a third sensing element including fifth and sixth portions. The first, third and fifth portions form a first pattern, and the second, fourth and sixth portions form a second pattern. The patterns are bilaterally symmetrical about a median of a sensing region. In another type of apparatus, an electrical conductor coupled to a first sensing element passes through a gap in a second sensing element. An electrical conductor coupled to the second sensing element is dimensioned such that a capacitive coupling to the second sensing element is compensated for the gap.

Abstract: A method of manufacturing actuators includes the step of measuring an absolute value of a coercive voltage of an active layer. The method further includes the step of sorting the actuators based at least on the coercive voltage.

Abstract: The invention describes a sensor system (3) for measuring the thickness of flat material (2), which (1) [sic] is moved relative to the sensor system (3), said sensor system having a first sensor device (14) for measuring the thickness of the flat material (2) as well as means for generating an air cushion (23), which means are disposed in such a way that there results an air cushion (23) between that at least one side (16) [sic: (15)] of the sensor device (15) [sic: 14)] that faces the flat material (2) and the flat material (2) during operation. In the region of the air cushion (23), the first sensor device (14) comprises surface sections comprising porous material and/or material that is provided with micro-holes.

Abstract: An apparatus for determining a clearance between rotor blade tips of rotor blades mounted on a rotor and a stator lining mounted on a stator casing. The stator lining is movable radially relative to the stator casing. The stator lining comprises an abradable material. At least one probe is arranged to measure the clearance between blade tips and stator lining. A first portion of the at least one probe is arranged within the stator lining and a tip of the first portion of the at least one probe is arranged flush with the surface of the abradable material. The tip of the first portion of the at least one probe comprises an abradable material. A second portion of the at least one probe is secured to the stator casing. A wire-less and connector-less coupling transmits a measurement signal from the first portion to the second portion of the at least one probe to allow radial movement of the stator lining relative to the stator casing.

Abstract: An apparatus includes a first capacitive sensor connected to a first supply voltage, a second capacitive sensor connected to a second supply voltage, a sensing circuit for producing a sense voltage in response to current flowing in the first and second capacitive sensors, a first mixer for combining the sense voltage with a first reference voltage to produce a first signal representative of in-plane displacement between electrodes of the first and second capacitive sensors, and a second mixer for combining the sense voltage with a second reference voltage to produce a second signal representative of out-of-plane displacement between the electrodes of the first and second capacitive sensors.

Abstract: An immersion lithographic apparatus is disclosed that includes a detector to measure a distance between a substrate support structure and/or a substrate and a fluid handling system and/or to detect when an item is present between the fluid handling system and a top surface of the substrate and/or substrate support structure. The detector may use information of an electrical property of the fluid provided by the fluid handling system to measure the distance. The detector may measure variation in resistance and/or in capacitance between an electrode of the fluid handling system and an electrode of the substrate and/or substrate support structure.

Abstract: The present invention relates to a medication delivery device for expelling set doses of medicament, the medication delivery device comprising a position determining assembly for detecting absolute positions of a rotatably mounted member arranged within the device, the position determining assembly comprising a plurality of transmitter electrodes arranged on a first exterior surface part of the rotatably mounted member, a plurality of receiver electrodes arranged on a second exterior surface part of the rotatably mounted member. A number of transmitter electrodes form pairs of interconnected electrodes with a number of receiver electrodes. A reading assembly fixedly arranged relative to for example the housing of the medication delivery device is also provided.

Abstract: A method of operating a passenger screening kiosk system to perform at least one verify a passenger's identity, detect the presence of an explosive material, and detect the presence of a metallic material includes initiating a prompt to be issued by the passenger screening kiosk system to prompt the passenger to enter the passenger screening kiosk system, prompting the passenger to enter the passenger screening kiosk system, and determining whether the passenger is within the passenger screening kiosk system.

Abstract: A sensing device having a sensing surface for placing against a wall for detecting objects behind a wall lining has first and second sensors, each sensor including at least first and second capacitor plates and associated resistors forming RC circuits having time constants dependent on the adjacent wall material. Detection circuits connected to the RC circuits provide first and second voltage signals having amplitudes dependent on capacitance changes. A processor effects a comparison of the first and second voltage signals, and compares them to establish the magnitude of the voltage difference between the voltage signals, indicating a detected object center position when the difference signal is less than a predetermined value.