Showing papers on "Capacitive sensing published in 2010"

Capacitive position sensor

Abstract: A capacitive position sensor has a two-layer electrode structure. Drive electrodes extending in a first direction on a first plane on one side of a substrate. Sense electrodes extend in a second direction on a second plane on the other side of the substrate so that the sense electrodes cross the drive electrodes at a plurality of intersections which collectively form a position sensing array. The sense electrodes are provided with branches extending in the first direction part of the way towards each adjacent sense electrode so that end portions of the branches of adjacent sense electrodes co-extend with each other in the first direction separated by a distance sufficiently small that capacitive coupling to the drive electrode adjacent to the co-extending portion is reduced. Providing sense electrode branches allow a sensor to be made which has a greater extent in the first direction for a given number of sense channels, since the co-extending portions provide an interpolating effect. The number of sense electrode branches per drive electrode can be increased which allows a sensor to be made which has ever greater extent in the first direction without having to increase the number of sense channels.

Facile Coating of Manganese Oxide on Tin Oxide Nanowires with High-Performance Capacitive Behavior

Abstract: In this paper, a very simple solution-based method is employed to coat amorphous MnO2 onto crystalline SnO2 nanowires grown on stainless steel substrate, which utilizes the better electronic conductivity of SnO2 nanowires as the supporting backbone to deposit MnO2 for supercapacitor electrodes. Cyclic voltammetry (CV) and galvanostatic charge/discharge methods have been carried out to study the capacitive properties of the SnO2/MnO2 composites. A specific capacitance (based on MnO2) as high as 637 F g−1 is obtained at a scan rate of 2 mV s−1 (800 F g−1 at a current density of 1 A g−1) in 1 M Na2SO4 aqueous solution. The energy density and power density measured at 50 A g−1 are 35.4 W h kg−1 and 25 kW kg−1, respectively, demonstrating the good rate capability. In addition, the SnO2/MnO2 composite electrode shows excellent long-term cyclic stability (less than 1.2% decrease of the specific capacitance is observed after 2000 CV cycles). The temperature-dependent capacitive behavior is also discussed. Such hi...

Wireless energy transfer using repeater resonators

Abstract: Described herein are improved configurations for a device for wireless power transfer that includes a conductor forming at least one loop of a high-Q resonator, a capacitive part electrically coupled to the conductor, and a power and control circuit electrically coupled to the conductor, the power and control circuit providing two or more modes of operation and the power and control circuit selecting how the high-Q resonator receives and generates an oscillating magnetic field.

Nonlinear dynamics of capacitive charging and desalination by porous electrodes

Abstract: The rapid and efficient exchange of ions between porous electrodes and aqueous solutions is important in many applications, such as electrical energy storage by supercapacitors, water desalination and purification by capacitive deionization, and capacitive extraction of renewable energy from a salinity difference. Here, we present a unified mean-field theory for capacitive charging and desalination by ideally polarizable porous electrodes (without Faradaic reactions or specific adsorption of ions) valid in the limit of thin double layers (compared to typical pore dimensions). We illustrate the theory for the case of a dilute, symmetric, binary electrolyte using the Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae are available for salt adsorption and capacitive charging of the diffuse part of the double layer. We solve the full GCS mean-field theory numerically for realistic parameters in capacitive deionization, and we derive reduced models for two limiting regimes with different time scales: (i) in the "supercapacitor regime" of small voltages and/or early times, the porous electrode acts like a transmission line, governed by a linear diffusion equation for the electrostatic potential, scaled to the RC time of a single pore, and (ii) in the "desalination regime" of large voltages and long times, the porous electrode slowly absorbs counterions, governed by coupled, nonlinear diffusion equations for the pore-averaged potential and salt concentration.

Touch and hover sensing

Abstract: Improved capacitive touch and hover sensing with a sensor array is provided. An AC ground shield positioned behind the sensor array and stimulated with signals of the same waveform as the signals driving the sensor array may concentrate the electric field extending from the sensor array and enhance hover sensing capability. The hover position and/or height of an object that is nearby, but not directly above, a touch surface of the sensor array, e.g., in the border area at the end of a touch screen, may be determined using capacitive measurements of sensors near the end of the sensor array by fitting the measurements to a model. Other improvements relate to the joint operation of touch and hover sensing, such as determining when and how to perform touch sensing, hover sensing, both touch and hover sensing, or neither.

Projected-Capacitive Touch Technology

Abstract: in a seismic change in the touch-screen business. Projected capacitive (pro-cap), the touch technology used in the iPhone touch screen, has become the first choice for many small-to-medium (<10-in.) touch-equipped products now in development. The technology is not just Apple-trendy but incorporates some of the best characteristics of competing touch technologies. The three most important advantages of pro-cap technology are as follows:

Capacitive touch screen stylus

Abstract: In some embodiments, a stylus for providing input to a capacitive touch screen, having a tip including or consisting of conductive felt, which provides a deformable conductive surface for contacting the touch screen. The tip is produced by felting base fibers (which are typically non-conductive) with conductive fibers. In other embodiments, a capacitive touch stylus having at least a first mode of operation and a second mode of operation, and including at least one conductive tip and switched circuitry (preferably, passive circuitry) including at least one switch biased in a default state indicative of the first mode of operation but switchable into a second state indicative of the second mode of operation in response to movement of the tip (typically, in response to exertion of not less than a threshold force on the tip). In some embodiments, a stylus having a conductive tip (e.g., a conductive, felted tip) and including switched circuitry (preferably, passive circuitry) having a first state which couples a capacitance to the tip, where the capacitance is sufficient to allow a capacitive touch screen device to recognize (as a touch) simple contact of the tip on the screen of the touch screen device, and a second state which decouples the capacitance from the tip, thereby preventing the touch screen device from recognizing (as a touch) simple contact of the tip on the screen.

Capacitive sensor device

Abstract: A capacitive sensor device comprises a first sensor electrode, a second sensor electrode, and a processing system coupled to the first sensor electrode and the second sensor electrode. The processing system is configured to acquire a first capacitive measurement by emitting and receiving a first electrical signal with the first sensor electrode. The processing system is configured to acquire a second capacitive measurement by emitting and receiving a second electrical signal, wherein one of the first and second sensor electrodes performs the emitting and the other of the first and second sensor electrodes performs the receiving, and wherein the first and second capacitive measurements are non-degenerate. The processing system is configured to determine positional information using the first and second capacitive measurements.

Photoconductively loaded plasmonic nanoantenna as building block for ultracompact optical switches.

Abstract: We propose and explore theoretically a new concept of ultrafast optical switches based on nonlinear plasmonic nanoantennas. The antenna nanoswitch operates on the transition from the capacitive to conductive coupling regimes between two closely spaced metal nanorods. By filling the antenna gap with amorphous silicon, progressive antenna-gap loading is achieved due to variations in the free-carrier density in the semiconductor. Strong modification of the antenna response is observed both in the far-field response and in the local near-field intensity. The large modulation depth, low switching threshold, and potentially ultrafast time response of antenna switches holds promise for applications ranging from integrated nanophotonic circuits to quantum information devices.

Planar capacitive sensors – designs and applications

Abstract: Purpose – The purpose of this paper is to present the sensing mechanism, design issues, performance evaluation and applications for planar capacitive sensors. In the context of characterisation and imaging of a dielectric material under test (MUT), a systematic study of sensor modelling, features and design issues is needed. In addition, the influencing factors on sensitivity distribution, and the effect of conductivity on sensor performance need to be further studied for planar capacitive sensors.Design/methodology/approach – While analytical methods can provide accurate solutions to sensors of simple geometries, numerical modelling is preferred to obtain sensor response to different design parameters and properties of MUT, and to derive the sensitivity distributions of various electrode designs. Several important parameters have been used to evaluate the response of the sensors in different sensing modes. The designs of different planar capacitive sensor arrays are presented and experimentally evaluated...

Wireless Readout of Passive LC Sensors

Abstract: This paper reports simple yet precise equations for automated wireless measurement of the resonance frequency, Q-factor, and coupling coefficient of inductively coupled passive resonant LC circuits. This allows remote sensing of all physical and chemical quantities that can be measured with capacitance transducers. Formerly reported front-end circuit concepts for wireless sensor readout, i.e., phase dip measurement and the dip meter, are subsequently discussed. It is shown that, due to fundamental system limitations, the formerly reported circuit concepts are not applicable if the distance between the sensor and the readout electronic circuit becomes too small, resulting in large coupling coefficients. Therefore, we present an improved concept for an analog front-end circuit of the readout system that overcomes these limitations and hence allows wireless sensor readout under a wider range of operating distances.

A robust, low-cost and low-noise artificial skin for human-friendly robots

Abstract: As robots and humans move towards sharing the same environment, the need for safety in robotic systems is of growing importance. Towards this goal of human-friendly robotics, a robust, low-cost, low-noise capacitive force sensing array is presented with application as a whole body artificial skin covering. This highly scalable design provides excellent noise immunity, low-hysteresis, and has the potential to be made flexible and formable. Noise immunity is accomplished through the use of shielding and local sensor processing. A small and low-cost multivibrator circuit is replicated locally at each taxel, minimizing stray capacitance and noise coupling. Each circuit has a digital pulse train output, which allows robust signal transmission in noisy electrical environments. Wire count is minimized through serial or row-column addressing schemes, and the use of an open-drain output on each taxel allows hundreds of sensors to require only a single output wire. With a small set of interface wires, large arrays can be scanned hundreds of times per second and dynamic response remains flat over a broad frequency range. Sensor performance is evaluated on a bench-top version of a 4×4 taxel array in quasi-static and dynamic cases.

Active capacitive sensing: exploring a new wearable sensing modality for activity recognition

Abstract: The paper describes the concept, implementation, and evaluation of a new on-body capacitive sensing approach to derive activity related information. Using conductive textile based electrodes that are easy to integrate in garments, we measure changes in capacitance inside the human body. Such changes are related to motions and shape changes of muscle, skin, and other tissue, which can in turn be related to a broad range of activities and physiological parameters. We describe the physical principle, the analog hardware needed to acquire and pre-process the signal, and example signals from different body locations and actions. We perform quantitative evaluations of the recognition accuracy, focused on the specific example of collar-integrated electrodes and actions, such as chewing, swallowing, speaking, sighing (taking a deep breath), as well as different head motions and positions.

A Polymer-Based Capacitive Sensing Array for Normal and Shear Force Measurement

Abstract: In this work, we present the development of a polymer-based capacitive sensing array. The proposed device is capable of measuring normal and shear forces, and can be easily realized by using micromachining techniques and flexible printed circuit board (FPCB) technologies. The sensing array consists of a polydimethlysiloxane (PDMS) structure and a FPCB. Each shear sensing element comprises four capacitive sensing cells arranged in a 2 × 2 array, and each capacitive sensing cell has two sensing electrodes and a common floating electrode. The sensing electrodes as well as the metal interconnect for signal scanning are implemented on the FPCB, while the floating electrodes are patterned on the PDMS structure. This design can effectively reduce the complexity of the capacitive structures, and thus makes the device highly manufacturable. The characteristics of the devices with different dimensions were measured and discussed. A scanning circuit was also designed and implemented. The measured maximum sensitivity is 1.67%/mN. The minimum resolvable force is 26 mN measured by the scanning circuit. The capacitance distributions induced by normal and shear forces were also successfully captured by the sensing array.

Electrical oscillations induced by the metal-insulator transition in VO2

Abstract: We systematically investigate the characteristics of an electrical oscillation observed in two-terminal vanadium dioxide (VO2) devices. These oscillations are observed at room temperature in a simple electrical circuit without inductive components. The circuit is composed only of a dc voltage source, the VO2 device, and a standard resistor connected in series with the device. We explain why the observed oscillations are a result of the percolative metal-to-insulator transition (MIT) of VO2 and the coexistence of the metal and insulating phases. Specifically, oscillations are attributed to the construction and destruction of capacitive regions composed of regions of the semiconducting phase, (as dielectric material) and metallic phase electron carriers, induced by the MIT (as capacitor electrodes). Since the coexistence of these phases—and thus the capacitive regions—is destroyed by elevated temperature, the MIT oscillation is not explained in terms of significant heat input but rather in terms of a voltag...

Projected capacitive touch sensing

Abstract: Methods, systems, and apparatus relate to touch sensors that are configured to measure input applied to the sensor from a user. Some implementations involve the measurement of changes in capacitance between pairs of adjacent patterned electrodes to detect input at a touch sensor.

A capacitive sensor system for the analysis of two-phase flows of oil and conductive water

Abstract: A sensor system for the study of oil–water flow in pipes is proposed. The purpose is to estimate the area fraction occupied by each fluid in a given section of the pipe, taking advantage of the difference in dielectric permittivity between the fluids. The estimation is done by capacitance measurements between electrodes flush-mounted on the external surface of a nonconductive section of the pipe. A key contribution of the present work is to propose a solution to the problem of capacitive sensing in presence of conductive water which introduces parasitic coupling to stray elements outside the measurement section of the pipe. To this purpose it is proposed a novel sensor configuration that employs guard electrodes, coupled to a tailored electronic interface to drive the guard electrodes and amplify the measurement signal at 2 MHz. The sensor system has been designed, manufactured and tested in an experimental plant where flows of oil–tap water have been generated. The results obtained from the developed sensor system for different fluid fractions have been compared with those obtained by the Quick Closing Valve (QCV) technique adopted as a reference. Differences between the two methods below 3% have been found in the estimations of the normalized oil-area fraction.

Detector and detection method for a capacitive touchpad to identify a real touch point

Abstract: A two-step detection for a capacitive touchpad to identify a real touch point first detects the self capacitances from multiple capacitance sensor traces of the capacitive touchpad to identify any touch point on the capacitive touchpad and then, if multiple touch points are detected, further detects the mutual capacitance at one of the detected touch points to identify whether it is a real touch point

Capacitive sensor, device and method

Abstract: Exemplary capacitive sensors may be capable of determining presence and location of a touch and capable of determining a fingerprint pattern.

Vibration Detection Using Optical Fiber Sensors

Abstract: Condition monitoring of heavy electromechanical equipment is commonly accomplished in the industry using vibration analysis. Several techniques, mainly based on capacitive and piezoelectric accelerometers, have been applied for predictive maintenance. However, the negative influence of the electromagnetic interference (EMI) can be a real problem when electrical signals are used to detect and transmit physical parameters in noisy environments such as electric power generator plants with high levels of EMI. Optical fiber sensors are increasingly used because of the nonelectrical nature of signals. In this paper, the most frequently used vibration optical fiber sensors will be reviewed, classifying them by the sensing techniques and measurement principles. The main techniques, intensity modulation, fiber bragg gratings and Fabry-Perot Interferometry, will be reviewed here.

Method of manufacturing capacitive insulating film for capacitor

Abstract: According to the invention, a Ti film is formed on a substrate and is annealed at the temperatures of 350° C.-400° C. under oxidative environment, so that a TiO 2 film having a rutile crystal structure is formed. Since the TiO 2 film having a rutile crystal structure has a high dielectric constant, it is useful for a capacitive insulating film for a capacitor.

Insulating electrodes: a review on biopotential front ends for dielectric skin-electrode interfaces.

Abstract: Insulating electrodes, also known as capacitive electrodes, allow acquiring biopotentials without galvanic contact with the body. They operate with displacement currents instead of real charge currents, and the electrolytic electrode-skin interface is replaced by a dielectric film. The use of insulating electrodes is not the end of electrode interface problems but the beginning of new ones: coupling capacitances are of the order of pF calling for ultra-high input impedance amplifiers and careful biasing, guarding and shielding techniques. In this work, the general requirements of front ends for capacitive electrodes are presented and the different contributions to the overall noise are discussed and estimated. This analysis yields that noise bounds depend on features of the available devices as current and voltage noise, but the final noise level also depends on parasitic capacitances, requiring a careful shield and printed circuit design. When the dielectric layer is placed on the skin, the present-day amplifiers allow achieving noise levels similar to those provided by wet electrodes. Furthermore, capacitive electrode technology allows acquiring high quality ECG signals through thin clothes. A prototype front end for capacitive electrodes was built and tested. ECG signals were acquired with these electrodes in direct contact with the skin and also through cotton clothes 350 µm thick. They were compared with simultaneously acquired signals by means of wet electrodes and no significant differences were observed between both output signals.

Capacitive touch screen with a mesh electrode

Abstract: An improved touch screen provides enhanced electrical performance and optical quality. The electrodes on the touch screen are made of a mesh of conductors to reduce the overall electrode resistance thereby increasing the electrical performance without sacrificing optical quality. The mesh electrodes comprise a mesh pattern of conductive material with each conductor comprising the mesh having a very small width such that the conductors are essentially invisible to the user of the touch screen.

Substrate Noise Coupling in Mixed-Signal ASICs

Abstract: The purpose of Substrate Noise Coupling in Mixed-Signal ASICs is to provide an overview of very recent research results in the field of substrate noise analysis and reduction techniques. Much of the reported work has been established as part of the Mixed-Signal Initiative of the European Union. It is a representative sampling of the current state of the art in this area. All the different aspects of the substrate noise coupling problem are covered. Some chapters describe techniques to model and reduce the digital switching noise injected in the substrate. Other chapters describe methods to analyse the propagation of the noise from the source (the digital circuitry) to the reception point (the embedded analog circuitry) through the substrate considered as a resistive/capacitive mesh. Finally, the remaining chapters describe techniques to model and especially to reduce the impact of substrate noise on the analog side. This is illustrated with several practical design examples and measurement results.

Solid-state memcapacitive system with negative and diverging capacitance

Abstract: We suggest a possible realization of a solid-state memory capacitive (memcapacitive) system. Our approach relies on the slow polarization rate of a medium between plates of a regular capacitor. To achieve this goal, we consider a multilayer structure embedded in a capacitor. The multilayer structure is formed by metallic layers separated by an insulator so that nonlinear electronic transport (tunneling) between the layers can occur. The suggested memcapacitor shows hysteretic charge-voltage and capacitance-voltage curves, and both negative and diverging capacitance within certain ranges of the field. This proposal can be easily realized experimentally and indicates the possibility of information storage in memcapacitive systems.

A Combined Inductive–Capacitive Proximity Sensor for Seat Occupancy Detection

Abstract: This paper presents a simple and efficient seat occupancy detector. A seat occupancy detector is an integral part of the airbag safety system and, in its simplest form, provides the (occupied or vacant) status of the seat to the airbag control unit. Although the occupancy sensing methods based on a capacitive principle are efficient, they typically require electrodes to be placed in the surface layer of the sitting and backrest areas of the seat. The proposed sensor uses a simple electrode structure, and it is placed below the seat foam in the sitting area of the seat. These features promise a less-expensive sensor as it can be easily manufactured and installed in a seat. The new sensor combines inductive and capacitive proximity sensing principles. The sensor detects the presence of an occupant exploiting the shielding effect of the electric field while its inductive proximity feature senses the presence of conductive objects (e.g., laptop) that may be placed in the seat and helps to achieve reliable occupancy sensing. The measurement system uses a signal conditioning unit based on a carrier frequency principle. A prototype sensing system has been built, and its application as a seat occupancy sensing system in a vehicle has been verified. The developed system successfully senses human proximity and distinguishes it from other conductive objects.

A highly area-efficient controller for capacitive touch screen panel systems

Abstract: In this paper, a highly area-efficient controller for capacitive touch screen panels (TSPs) is proposed. The proposed controller uses a 10-bit successive approximation register analog-to-digital converter (SAR ADC) with an adder to compensate for the capacitance variation in the TSP and for the offset voltage variation in the charge amplifier of the sensing circuit. By using the proposed compensation method, the area of the controller can be reduced by 90.3% of the area of the conventional controllers. The measurement results showed that the signal-to-noise ratio (SNR) of the controller increases from 12.5 to 21.3 dB after compensation. Also, its spatial jitter decreases from ±1.5 to ±0.46 mm, which is 7% of the sensor pitch of 8 mm.

Optical capacitive thumb control with pressure sensor

Abstract: A small sensor surface designed to control a smart phone or Mobile Internet Device (MID). The sensor surface may be mounted on the side of the proposed device in a position where a user's thumb or finger naturally falls when holding the device in his/her hand. The sensor surface is simultaneously convex and concave, providing both visual and physical cues for the use of the sensor surface. The sensor may include capacitive sensing, optical sensing and pressure sensing capabilities to interpret thumb gestures into device control.

Dioxythiophene-Based Polymer Electrodes for Supercapacitor Modules

Abstract: We report on the electrochemical and capacitive behaviors of poly(2,2-dimethyl-3,4-propylene-dioxythipohene) (PProDOT-Me2) films as polymeric electrodes in Type I electrochemical supercapacitors. The supercapacitor device displays robust capacitive charging/discharging behaviors with specific capacitance of 55 F/g, based on 60 μg of PProDOT-Me2 per electrode, that retains over 85% of its storage capacity after 32 000 redox cycles at 78% depth of discharge. Moreover, an appreciable average energy density of 6 Wh/kg has been calculated for the device, along with well-behaved and rapid capacitive responses to 1.0 V between 5 to 500 mV s−1. Tandem electrochemical supercapacitors were assembled in series, in parallel, and in combinations of the two to widen the operating voltage window and to increase the capacitive currents. Four supercapacitors coupled in series exhibited a 4.0 V charging/discharging window, whereas assembly in parallel displayed a 4-fold increase in capacitance. Combinations of both serial ...