Showing papers on "Capacitive sensing published in 2007"

Pseudocapacitive Contributions to Electrochemical Energy Storage in TiO2 (Anatase) Nanoparticles

Abstract: The advantages in using nanostructured materials for electrochemical energy storage have largely focused on the benefits associated with short path lengths. In this paper, we consider another contribution, that of the capacitive effects, which become increasingly important at nanoscale dimensions. Nanocrystalline TiO2 (anatase) was studied over a dimensional regime where both capacitive and lithium intercalation processes contribute to the total stored charge. An analysis of the voltammetric sweep data was used to distinguish between the amount of charge stored by these two processes. At particle sizes below 10 nm, capacitive contributions became increasingly important, leading to greater amounts of total stored charge (gravimetrically normalized) with decreasing TiO2 particle size. The area normalized capacitance was determined to be well above 100 μF/cm2, confirming that the capacitive contribution was pseudocapacitive in nature. Moreover, reducing the particle size to the nanoscale regime led to faster...

Multipoint touch surface controller

Abstract: A multipoint touch surface controller is disclosed herein. The controller includes an integrated circuit including output circuitry for driving a capacitive multi-touch sensor and input circuitry for reading the sensor. Also disclosed herein are various noise rejection and dynamic range enhancement techniques that permit the controller to be used with various sensors in various conditions without reconfiguring hardware.

Double-sided touch-sensitive panel with shield and drive combined layer

Abstract: A multi-touch capacitive touch sensor panel can be created using a substrate with column and row traces formed on either side of the substrate. To shield the column (sense) traces from the effects of capacitive coupling from a modulated Vcom layer in an adjacent liquid crystal display (LCD) or any source of capacitive coupling, the row traces can be widened to shield the column traces, and the row traces can be placed closer to the LCD. In particular, the rows can be widened so that there is spacing of about 30 microns between adjacent row traces. In this manner, the row traces can serve the dual functions of driving the touch sensor panel, and also the function of shielding the more sensitive column (sense) traces from the effects of capacitive coupling.

Mutual capacitance touch sensing device

Abstract: A mutual capacitive touch sensing device is disclosed. The touch sensing device includes a mutual capacitive sensing controller having a plurality of distinct drive lines and a plurality of distinct sense lines; a source for driving a current or voltage separately though each drive line; and a mutual capacitance sensing circuit that monitors the capacitance at the sensing lines. The touch sensing device also includes a plurality of independent and spatially distinct mutual capacitive sensing nodes set up in a non two dimensional array. Each node includes a drive electrode that is spatially separated from a sense electrode. The drive electrode is coupled to one of the drive lines and the sense electrode is coupled to one of the sense lines. Each node is set up with a different combination of drive and sense line coupled thereto.

Design and Operation of a MEMS-Based Material Testing System for Nanomechanical Characterization

Abstract: In situ mechanical characterization of nanostructures, such as carbon nanotubes and metallic nanowires, in scanning and transmission electron microscopes is essential for the understanding of material behavior at the nanoscale. This paper describes the design, fabrication, and operation of a novel microelectromechanical-systems (MEMS)-based material testing system used for in situ tensile testing of nanostructures. The device consists of an actuator and a load sensor with a specimen in between. Two types of actuators, in-plane thermal and comb drive actuators, are used to pull the specimens in displacement control and force control modes, respectively. The load sensor works based on differential capacitive sensing, from which the sensor displacement is recorded. By determining sensor stiffness from mechanical resonance measurements, the load on the specimen is obtained. Load sensors with different stiffness were fabricated. The best resolutions were achieved with load sensors that are designed for testing nanotubes, reaching 0.05 fF in capacitance, 1 nm in displacement, and 12 nN in load. For the first time, this MEMS-based material testing scheme offers the possibility of continuous observation of the specimen deformation and fracture with subnanometer resolution, while simultaneously measuring the applied load electronically with nano-Newton resolution. The overall device performance is demonstrated by testing freestanding cofabricated polysilicon films and multiwalled carbon nanotubes.

Capacitive Sensing of Electrocardiographic Potential Through Cloth From the Dorsal Surface of the Body in a Supine Position: A Preliminary Study

Abstract: A method for obtaining electrocardiographic potential through thin cloth inserted between the measuring electrodes and the skin of a subject's dorsal surface when lying supine has been proposed. The method is based on capacitive coupling involving the electrode, the cloth, and the skin. Examination of a pilot device which employed the method revealed the following: 1) In spite of the gain attenuation in the high frequency region, the proposed method was considered useful for monitoring electrocardiogram (ECG) for nondiagnostic purpose. 2) The method was able to yield a stable ECG from a subject at rest for at least 7 h, and there was no significant adverse effect of long-term measurement on the quality of the signal obtained. 3) Electrode area was the factor that had most influence on the signal, compared with other factors such as cloth thickness and coupling pressure, but could be reduced to 10 cm2 for heart rate detection. 4) Input capacitance of the device was assumed to be the dominant factor for the gain attenuation in the high frequency region, and should be reduced with a view to diagnostic use. Although there is still room for improvement in terms of practical use, the proposed method appears promising for application to bedding as a noninvasive and awareness-free method for ECG monitoring

Liquid-level measurement system based on a remote grounded capacitive sensor

Abstract: This paper describes the design and implementation of a liquid-level measurement system based on a remote grounded capacitive sensor. The electrodes of the capacitive sensor are built with affordable materials: a rod of stainless steel and a PTFE-insulated wire. The interface circuit relies on a simple relaxation oscillator and a microcontroller. A cable with active shielding interconnects the sensor to the interface circuit. The stability of the active-shielding circuit is analysed by taking into account the parasitic components of both the interconnecting cable and the sensor. The system has been experimentally tested by measuring the level of tap water in a grounded metallic container. Over a level range of 70 cm, the system has a non-linearity error smaller than 0.35 mm and a resolution better than 0.10 mm for a measuring time of 20 ms.

A capacitive humidity sensor integrated with micro heater and ring oscillator circuit fabricated by CMOS–MEMS technique

Abstract: This study presents the fabrication of a humidity sensor with a micro heater and a ring oscillator circuit using the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and a post-process. The micro heater is utilized to provide a super-ambient working temperature to the humidity sensor, which can avoid the humidity sensor to generate the signal drift. The humidity sensor is a capacitive type sensor. The structure of the humidity sensor consists of interdigital electrodes and a sensing film. The sensing film, which is polyimide, is coated on interdigital electrodes. The humidity sensor changes in capacitance when the sensing film absorbs or desorbs water vapor. The ring oscillator circuit is employed to convert the capacitance of the humidity sensor into the oscillation frequency output. Experimental results show that the sensitivity of the humidity sensor is about 25.5 kHz/% RH at 80 °C.

Methods and systems for guarding a charge transfer capacitance sensor for proximity detection

Abstract: Methods, systems and devices are described for determining a measurable capacitance for proximity detection in a sensor having a plurality of sensing electrodes and at least one guarding electrode. A charge transfer process is executed for at least two executions. The charge transfer process includes applying a pre-determined voltage to at least one of the plurality of sensing electrodes using a first switch, applying a first guard voltage to the at least one guarding electrode using a second switch, sharing charge between the at least one of the plurality of sensing electrodes and a filter capacitance, and applying a second guard voltage different from the first guard voltage to the at least one guarding electrode. A voltage is measured on the filter capacitance for a number of measurements equal to at least one to produce at least one result to determine the measurable capacitance for proximity detection.

Capacitive interface circuit for low power sensor system

Abstract: This disclosure describes a capacitive interface circuit for a low power system. The capacitive interface circuit is configured to achieve very low noise sensing of capacitance-based transducers, such as a micro-electro-mechanical system (MEMS)-based sensor, with high resolution and low power. The capacitive interface circuit uses a differential amplifier and correlated triple sampling (CTS) to substantially eliminate, or at least reduce, kT/C noise, as well as amplifier offset and flicker (1/f) noise, from the output of the amplifier. The capacitive interface circuit may further include an output stage that reduces glitching, i.e., clock transients, in the output signal by allowing transients in the amplifier output to settle. In this manner, the circuit can be used in a low power system to produce a stable, low-noise output.

Wireless flexible capacitive sensor based on ultra-flexible epoxy resin for strain measurement of automobile tires

Abstract: The measurement of strain of tires in-service is effective in improving the reliability of tires and ABS systems. Since conventional strain gages have high stiffness and require lead wires, conventional strain gages are cumbersome for the strain measurement of tires. The present study proposes a novel flexible patch-type strain sensor utilizing electric capacitance change. The sensor is made from flexible polyimide substrates and ultra-flexible epoxy resin, which makes the sensor low in stiffness and high in elongation as a whole structure. The sensor utilizes capacitance changes due to the applied strain, and wireless measurements are conducted using amplitude modulation. The sensor is applied to an automobile tire, and compression tests are performed. The effects of the temperature changes are also measured. The proposed sensor is found to successfully measure the applied strain of the tire wirelessly, and the effects of the temperature changes are minimized using a dummy sensor in a self-temperature compensation circuit.

Display device, method of driving same and electronic device mounting same

Abstract: A liquid crystal panel (2) includes scanning signal lines (31) for supplying scanning signals to gate electrodes (20) of TFTs (14), and data signal lines (32) for supplying data signals to data electrodes (24) of TFTs. The liquid crystal panel further includes auxiliary capacitive electrode pads (27 a) for use in forming auxiliary capacitance and an auxiliary capacitive lines (33) so as not to generate a capacitive bond with the scanning signal lines. The liquid crystal panel is driven at a rewriting frequency of a screen of not more than 30 Hz. As a result, the liquid crystal panel can be driven at a low consumption power while maintaining a desirable display quality of the liquid crystal panel.

Hybrid Capacitive Touch Screen Element

Abstract: A capacitive touch sensitive position sensor is provided which has a substrate defining a touch sensitive platform. First and second resistive bus-bars arranged spaced apart on the substrate. A conductive sensing area is formed between the bus bars and is constructed with first and second conductive elements connected to the first and second resistive bus-bars respectively, and spaced apart from each other by non-conducting gaps, so that currents induced in the conductive sensing area flow towards the bus-bars, but are prevented from flowing in a direction parallel to the bus-bars. This design removes pin-cushion distortion and enhances linearization of the output signals. Because the sensing region is not galvanically coupled from one bus bar to the other, the voltage gradients remain uniform and undistorted. Capacitive coupling from one side to the other does not produce a distortion component provided that the capacitance is allowed to fully charge and discharge across all locations in the sensing region.

Electronically Temperature Compensated Silicon Bulk Acoustic Resonator Reference Oscillators

Abstract: The paper describes the design and implementation of an electronically temperature compensated reference oscillator based on capacitive silicon micromechanical resonators. The design of a 5.5-MHz silicon bulk acoustic resonator has been optimized to offer high quality factor (> 100 000) while maintaining tunability in excess of 3000 ppm for fine-tuning and temperature compensation. Oscillations are sustained with a CMOS amplifier. When interfaced with the temperature compensating bias circuit, the oscillator exhibits a frequency drift of 39 ppm over 100degC as compared to an uncompensated frequency drift of 2830 ppm over the same range. The sustaining amplifier and compensation circuitry were fabricated in a 2P3M 0.6-mum CMOS process.

Sub-Micro-Gravity In-Plane Accelerometers With Reduced Capacitive Gaps and Extra Seismic Mass

Abstract: This paper presents a robust fabrication technique for manufacturing ultrasensitive micromechanical capacitive accelerometers in thick silicon-on-insulator substrates. The inertial mass of the sensor is significantly increased by keeping the full thickness of the handle layer attached to the top layer proof mass. High-aspect-ratio capacitive sense gaps are fabricated by depositing a layer of polysilicon on the sidewalls of low aspect- ratio trenches etched in silicon. Using this method, requirements on trench etching are relaxed, whereas the performance is preserved through the gap reduction technique. Therefore, this process flow can potentially enable accelerometers with capacitive gap aspect-ratio values of greater than 40:1, not easily realizable using conventional dry etching equipment. Also, no wet-etching step is involved in this process which in turn facilitates the fabrication of very sensitive motion sensors that utilize very compliant mechanical structures. Sub-micro-gravity in-plane accelerometers are fabricated and tested with measured sensitivity of 35 pF/g, bias instability of 8 mug, and footprint of <0.5 cm2.

Capacitive sensing and absolute position mapping in displacement type pointing devices

Abstract: A displaceable member moves in an operational zone over a sense system that includes a spatial arrangement of sense electrodes and at least one drive electrode. A conductive coupling element of the displaceable member capacitively couples signals from the at least one drive electrode to ones of the sense electrodes underlying the conductive coupling element. A measurement system generates measurement signals indicating amounts of overlap between the conductive coupling element and ones of the sense electrodes. A processing system produces from the measurement signals an output signal with information conveying motion measures corresponding to absolute positions of the conductive coupling element in the operational zone. At least one regional sense electrode may include discrete electrically conducting sensing elements distributed across a respective region of the operational zone. The drive electrode may include discrete electrically conducting sensing elements interspersed among the sensing elements of the at least one regional sense electrode.

Ultra-Low-Power Interface Chip for Autonomous Capacitive Sensor Systems

Abstract: Traditionally, most of the sensor interfaces must be tailored towards a specific application. This approach results in a high recurrent design cost and time to market. On the other hand, generic sensor interface design reduces the costs and offers a handy solution for multisensor applications. This paper presents a generic sensor interface chip (GSIC), which can read out a broad range of capacitive sensors. It contains capacitance-to-voltage converters, a switched-capacitor amplifier, an analog-to-digital converter, oscillators, clock generation circuits and a reference circuit. The system combines a very low-power design with a smart energy management, which adapts the current consumption according to the accuracy and speed requirements of the application. The GSIC is used in a pressure and an acceleration monitoring system. The pressure monitoring system achieves a current drain of 2.3 muA for a 10-Hz sample frequency and an 8-bit accuracy. In the acceleration monitoring system, we measured a current of 3.3 muA for a sample frequency of 10 Hz and an accuracy of 9 bits

Capacitive sensing apparatus designs

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.

Mobile Noncontact Monitoring of Heart and Lung Activity

Abstract: This paper describes two methods for noncontact monitoring of heart and lung activity, namely magnetic bioimpedance monitoring and capacitive electrocardiogram (ECG) recording. In principle, both methods bear the potential for mobile application in a personal healthcare scenario. To illustrate their performance, prototypes for both methods have been developed and first results are presented. Finally, the fundamental drawbacks and limitations of these methods are discussed, including a detailed stability analysis of the capacitively coupled ldquoright legrdquo in capacitive ECG measurements with mismatching electrode capacities and the development of an adaptive noise canceller for magnetic bioimpedance monitoring based on a nonlinear signal coupling model.

Contactless EMG sensors embroidered onto textile

Abstract: To obtain maximum unobtrusiveness with sensors for monitoring health parameters on the human body, two technical solutions are combined. First we propose contactless sensors for capacitive electromyography measurements. Secondly, the sensors are integrated into textile, so complete fusion with a wearable garment is enabled. We are presenting the first successful measurements with such sensors.

Electromagnetic effects in high-frequency capacitive discharges used for plasma processing

Abstract: In plasma processing, capacitive discharges have classically been operated in the electrostatic regime, for which the excitation wavelength λ is much greater than the electrode radius, and the plasma skin depth δ is much greater than the electrode spacing. However, contemporary reactors are larger and excited at higher frequencies which leads to strong electromagnetic effects. This paper gives a review of the work that has recently been carried out to carefully model and diagnose these effects, which cause major uniformity problems in plasma processing for microelectronics and flat panel displays industries.

Low-Impedance VHF and UHF Capacitive Silicon Bulk Acoustic Wave Resonators—Part I: Concept and Fabrication

Abstract: This paper presents high-performance high-frequency single-crystal silicon (SCS) capacitive resonators. Long and thick bulk-micromachined resonating block structures, which are referred to as ldquosilicon bulk acoustic wave resonatorrdquo (SiBAR), are fabricated using the high-aspect-ratio poly and single crystalline siliconrdquo (HARPSS) fabrication process on silicon-on-insulator (SOI) substrates. Such resonators operate in their horizontal width extensional modes with quality factors in the range of 10000-100000. With their comparatively large electrode area and deep-submicrometer capacitive transduction gaps, such resonators have demonstrated comparatively low impedances for capacitive resonators that are well within the desired range for high-frequency electronic applications. Sub-kilo-Ohm total electrical resistances and extracted motional resistance as low as 200 are demonstrated for the fundamental width extensional modes of SiBARs in the very-high-frequency range. Resonant frequencies up to 1.55 GHz are demonstrated for the higher resonance modes of the capacitive SiBARs with comparatively low impedances. Part I of this paper presents the basic operation concepts and fabrication methodology for the HARPSS-on-SOI SiBARs. Extensive resonator measurement data, including temperature characteristics, are presented in Part II of this paper, and different frequency tuning approaches for temperature compensation of such resonators are discussed and investigated.

Single chip interdigitated electrode capacitive chemical sensor arrays

Abstract: In this paper the design considerations, fabrication and first evaluation results of a capacitive type single chip chemical sensor array based on interdigitated electrode structure is presented. The electrode arrays have been fabricated with conventional semiconductor processes. The final structure consists of four interdigital capacitive sensors each one coated with a different polymer sensitive film by using only successive lithographic steps. The array sensors have good response to controlled concentrations of volatile organic compounds (∼35fF, ∼7fF, ∼12fF for the PHEMA covered sensor when exposed to 100 ppm of water, methanol and ethanol vapors and ∼2.5fF, in the case of 100 ppm of toluene vapors for the PDMS covered sensor).

Phase-varying metamaterial for compact steerable directive antenna

Abstract: The design of a locally phase-varying one-dimensional metamaterial working near 10 GHz is reported. It is made from a capacitive and an inductive grid. The phase-varying behaviour is obtained with a regular incrementation of the spacing between each unit cell of the capacitive grid in one direction. This composite metamaterial is then used as a partially reflecting surface in a resonant Fabry-Peacuterot type cavity together with a patch antenna to constitute a compact steerable directive printed antenna. A plusmn20deg deflection of the antenna beam is obtained

Printed capacitive sensor

Abstract: The invention relates to a flexible, resilient capacitive sensor suitable for large-scale manufacturing. The sensor comprises a dielectric, an electrically conductive detector and trace layer on the first side of the dielectric layer comprising a detector and trace, an electrically conductive reference layer on a second side of the dielectric layer, and a capacitance meter electrically connected to the trace and to the conductive reference layer to detect changes in capacitance upon interaction with detector. The sensor is shielded to reduce the effects of outside interference.

Capacitive sensing apparatus that uses a combined guard and sensing electrode

Abstract: A capacitive sensing apparatus includes capacitive sensor electrodes, and a combined guard and sensing electrode that is disposed proximate to the capacitive sensor electrodes. The combined guard and sensing electrode has at least a first operating mode and a second operating mode. In the first operating mode, the combined guard and sensing electrode can detect an object at a distance that is greater than the distance at which the object can be sensed by the capacitive sensor electrodes. In the second operating mode, the combined guard and sensing electrode can electrically guard the capacitive sensor electrodes.

Reducing sleep current in a capacitance sensing system

Abstract: An apparatus and method of measuring a collective capacitance on a group of capacitive sense elements from at least one of rows or columns of a capacitance sense array when in a first mode, and individually measuring capacitances on each of the rows and columns when in a second mode.

Capacitive micromachined ultrasonic transducers for chemical detection in nitrogen

Abstract: The authors present the prototype of a chemical sensor using a capacitive micromachined ultrasonic transducer array. Each element in the array consists of a large number of resonating membranes connected in parallel. A five-channel oscillator circuit operates at the resonant frequency around 6MHz in this prototype. The surface of the elements in the array is coated by polymers such as polyallylamine hydrochloride, polyethylene glycol, and polyvinyl alcohol to detect different chemicals. By measuring shift in oscillation frequencies due to the mass-loading effect, analytes, e.g., water and isopropanol, with concentrations around 20ppbv (parts per 109 by volume) range can be detected.

Modified inverted-f antenna for wireless communication

Abstract: An embodiment of the present invention is a modified inverted-F antenna for wireless communication. The antenna circuit includes a dielectric substrate having a first surface, a radiating stub on the first surface of the dielectric substrate, and a first ground plate on the first surface of the dielectric substrate to couple to ground. The first ground plate includes one or more grounded capacitive stubs spaced apart from the radiating stub. The one or more grounded capacitive stubs tune performance parameters for the antenna circuit.

Passive cooling of a micromechanical oscillator with a resonant electric circuit.

Abstract: We cool the fundamental mode of a miniature cantilever by capacitively coupling it to a driven rf resonant circuit. Cooling results from the rf capacitive force, which is phase shifted relative to the cantilever motion. We demonstrate the technique by cooling a 7 kHz cantilever from room temperature to 45 K, obtaining reasonable agreement with a model for the cooling, damping, and frequency shift. Extending the method to higher frequencies in a cryogenic system could enable ground state cooling and may prove simpler than related optical experiments in a low temperature apparatus.