Showing papers on "Capacitive sensing published in 1997"

Touch and pressure sensing method and apparatus

Abstract: The present invention provides a touch pad which can detect a simply stylus using a change capacitance. The touch pad is made flexible, so that the stylus pressure compresses an insulating layer between a conductive reference layer and matrix of conductive traces. The compression causes a change in capacitance due to either the two capacitive conductive surfaces being closer to each other, or a variation of the dielectric value of the insulating layer due to the replacement of air in air gaps by the material of the insulating layer.

Electrically active resonant structures for wireless monitoring and control

Abstract: A planar electromagnetic resonator utilizes an electromagnetically active material located between the capacitive or inductive elements of the resonator. A microscopic electrical property of this material is altered by an external condition, and that alteration, in turn, affects the behavior of the resonator in a consistent and predictable manner.

Equivalent circuit representation of electromechanical transducers: II. Distributed-parameter systems

Abstract: Distributed-parameter electromechanical transducers are examined theoretically with special regard to their dynamic electromechanical behaviour and equivalent circuits used to represent them. The circuits are developed starting from basic electromechanical transduction principles and the electrical and mechanical equations of equilibrium. Within the limits of the assumptions on boundary conditions, the theory presented is exact with no restrictions other than linearity. The link with lumped-parameter transducers, that were the subject of a previous publication will be indicated. Elementary electrostatic, electromagnetic, electrodynamic and piezoelectric transducers are used to illustrate the basic theory. Exemplary devices include a capacitive force (displacement) sensor, several types of a mechanical resonator, electromechanical filters, a piezoelectric thickness monitor and a piezoelectric acceleration sensor.

Capacitive filter feedthrough for implantable medical device

Abstract: A capacitive filter feedthrough assembly and method of making the same are disclosed for shielding an implantable medical device such as pacemaker or defibrillator from electromagnetic interference or noise A ferrule is adapted for mounting onto a conductive device housing by welding, soldering, brazing or gluing, and supports a terminal pin for feedthrough passage to a housing interior A capacitive filter is mounted at the inboard side of a device housing, with capacitive filter electrode plate sets coupled respectively to the housing and the terminal pin by an electrically conductive combination of solder and brazing In one embodiment of the invention, multiple capacitive filters are provided in an array within a common base structure, where each capacitive filter is associated with a respective terminal pin

Self-verifying temperature sensor

Abstract: A self-verifying temperature sensor and method for measuring and verifying the true thermodynamic temperature of a system. The sensor is constructed of various combinations of the following temperature-dependent elements: thermoelements, resistive elements, capacitive elements and other inductive elements. In the preferred embodiment, the sensor is constructed of resistive element connected between four thermoelement wires. A fifth thermoelement wire is connected to the resistive element. The sensor produces a data signature from various voltage, resistance, inductance, and capacitance measurements. Measurement electronics collect and condition the data signature. A computer analyzes the data signature and provides the system operator with a verified sensor temperature, thus, allowing the system operator to recognize and account for drift or decalibration of the sensor. The self-verifying temperature sensor can also be recalibrated in situ, thereby eliminating the necessity of sensor removal to verify recalibration.

Capacitive sensitive switch method and system

Abstract: A touch sensor switch that responds to touching, or even to the proximity of an object, is disclosed. The switch includes a number of capacitance elements, or touch pads, that produce an effective capacitance dependent upon the physical proximity of the object. A microcontroller under control of a program stored in a read-only memory causes its I/O port to set a transient voltage on each capacitance element as a logic level. Each transient voltage is at variance with the capacitive element's preferred voltage level. The program then reads the I/O port, and hence the logic levels of the capacitance elements, as the capacitive elements revert to their preferred voltage levels, and calculates the proximity of the object, or touching, from relationships among recorded signals. The circuit may also be embodied in an application specific integrated circuit.

A 3-axis force balanced accelerometer using a single proof-mass

Abstract: This paper presents a new method for wideband force balancing a proof-mass in multiple axes simultaneously. Capacitive position sense and force feedback are accomplished using the same air-gap capacitors through time multiplexing. Proof of concept is experimentally demonstrated with a single-mass monolithic surface micromachined 3-axis accelerometer.

Infrared imager using room temperature capacitance sensor

Abstract: An infrared imager includes an array of capacitance sensors that operate at room temperature. Each infrared capacitance sensor includes a deflectable first plate which expands due to absorbed thermal radiation relative to a non-deflectable second plate. In one embodiment each infrared capacitance sensor is composed of a bi-material strip which changes the position of one plate of a sensing capacitor in response to temperature changes due to absorbed incident thermal radiation. The bi-material strip is composed of two materials with a large difference in thermal expansion coefficients.

Electrostatic discharge protection of a capacitive type fingerprint sensing array

Abstract: A planar fingerprint pattern detecting array includes a large number of individual skin-distance sensing cells that are arranged in a row/column configuration. Each sensing cell includes an amplifier having an ungrounded input mode and an ungrounded output node. Output-to-input negative feedback that is sensitive to the fingerprint pattern is provided for each amplifier by way of (1) a first capacitor plate that is placed vertically under the upper surface of a dielectric layer and is connected to the ungrounded amplifier input node, (2) a second capacitor plate that is placed vertically under the upper surface of the dielectric layer in close horizontal spatial relation to the first capacitor plate and is connected to the ungrounded output node, and (3) an ungrounded fingertip whose fingerprint pattern is to be detected, which ungrounded fingertip is placed on the upper surface of the dielectric layer in close vertical spatial relation with the first and second capacitor plates. Electrostatic discharge protection relative to electrostatic potential that may be carried by the ungrounded fingertip is provided by placing a number of grounded metal paths within the dielectric layer to spatially surround each of the first and second capacitor plates, this being done in a manner that does not disturb the ungrounded state of the fingertip.

Printed circuit board (PCB) including channeled capacitive plane structure

Abstract: Electrical potentials and very high frequency (VHF) currents in a circuit board are controlled by patterning the power plane of a multiple layered, capacitive plane printed circuit board in selected geometric patterns. The selected geometric patterns, both simple and complex, control voltages and currents by channeling the capacitance capacity for usage directed to a particular integrated circuit or circuits, isolated to a particular integrated circuit or circuits, or shared between integrated circuits. Accordingly, the capacitive planes including the geometrically patterned power plane are channeled capacitive planes (CCP) that are formed on multiple layers of a single printed circuit board to support flexible, three-dimensional control of VHF electrical currents.

The microfabrication of capacitive ultrasonic transducers

Abstract: The successful fabrication of surface micromachined ultrasonic transducers is reported. In a key step of the microfabrication, amorphous silicon is used as a sacrificial layer to form sealed nitride cavities. The process is fully CMOS compatible and allows for improved geometric control compared to previously reported work. Transmission experiments in both water and air are presented. A dynamic range in excess of 110 dB is observed in air at 2.3 MHz. In water, a single pair of transducers is able to operate from 2 MHz to 20 MHz. When tuned, a 3 MHz tone burst results in a received signal with better than 60 dB signal to noise ratio. The transducer behavior agrees with theoretical understanding of transducer dynamics.

Capacitive PCB with internal capacitive laminate

Abstract: An in situ method for forming a bypass capacitor element internally within a PCB including the steps of arranging one or more uncured dielectric sheets with conductive foils on opposite sides thereof and laminating the conductive foils to the dielectric sheet simultaneously as the PCB is formed by a final lamination step, the conductive foils preferably being laminated to another layer of the PCB prior to their arrangement adjacent the dielectric sheet or sheets, the dielectric foils even more preferably being initially laminated to additional dielectric sheets in order to form multiple bypass capacitive elements as a compound subassembly within the PCB A number of different dielectric materials and resins are disclosed for forming the capacitor element A dielectric component in the capacitor element preferably includes dielectric material and thermally responsive material, the thermally responsive material either forming a carrier for the dielectric material or formed as two separate sheets on opposite sides of a sheet of the dielectric material

Vehicle occupant sensing

Abstract: A capacitive sensor (5) and systems based thereon, preferably for vehicle occupant position sensing, such systems preferably comprising arrays of such sensors wherein each sensor comprises dual adjacent planar electrodes.

Coffin-Manson fatigue model of underfilled flip-chips

Abstract: The fatigue life of an underfilled flip-chip package has been evaluated using the Coffin-Manson relation and finite element modeling (FEM)-computed solder shear strain for typical flip-chip structures. In the course of this effort, numerical simulations were performed for underfill materials of varying thermo-structural properties, two chip sizes, and two solder bump heights. The results were used to examine the parametric sensitivity of the thermal strain in the solder joints and the axial, as well as shear stress in the underfill material. The predicted improvement in the number of cycles-to-failure of the underfilled flip-chip was found to agree with empirical observation. However, the maximum improvement achievable by underfilling was found to be limited by the adhesion strength of the underfill material.

Method of manufacturing a semiconductor device

Abstract: A semiconductor device has a capacitive element with excellent leak current characteristics which has a tungsten film with a roughened surface for increasing the surface of a lower electrode. A capacitive element for use in a VLSI memory circuit such as a DRAM or the like is fabricated by forming a thin, roughened tungsten film selectively on a surface of a lower electrode of polysilicon by chemical vapor-phase growth and forming a capacitive insulating film on the surface of the lower electrode of polysilicon, densifying the capacitive insulating film, and forming an upper electrode of a metal element.

Micromachined electrostatic vertical actuator

Abstract: A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

Electronics for micromachined inertial sensors

Abstract: Capacitive interface circuits for micromachined sensors are described The focus is on the position sense electronics for accelerometers and gyroscopes Special attention is given to the characteristics of the interface between the sensor and electronic circuits, and on practical and fundamental noise mechanisms that limit the achievable resolution

Integrated or intrapackage capability for testing electrical continuity between an integrated circuit and other circuitry

Abstract: An electromagnetic probe is integrated within an integrated circuit or mounted within an IC package to provide a capability for testing continuity between the integrated circuit and a substrate to which the integrated circuit is mounted. In a first embodiment, capacitive test probes are integrated within the integrated circuit, underneath bonding pads. In a second embodiment, Hall-effect devices are integrated within the integrated circuit underneath bonding pads. In a third embodiment, an inductive loop is integrated within the integrated circuit underneath bonding pads. In a fourth embodiment, an IC package assembly includes an internal capacitive test probe for electrical continuity testing. An internal shield may also be used as a capacitive test probe. In a fifth embodiment, an IC package assembly includes an inductive loop within the package for electrical continuity testing. The integrated or intrapackage test probes provide electromagnetic coupling to bonding pads or to a lead frame and to bonding wires (if present), to detect whether there is electrical continuity between an integrated circuit bonding pad or lead frame and conductors on an external substrate. The integrated or intrapackage test probes enable continuity testing for direct-bonding with no package, or for a package assembly even if the package assembly includes grounded shielding or a grounded heat sink.

Device for monitoring the presence of a person using proximity induced dielectric shift sensing

Abstract: A capacitive array (26) is housed within a polyester mat or other appropriate nonconductive substrate material (28) and interconnected with a control module (10). The control module (10) supplies to the capacitive array (26) a suitable oscillator driver current and concurrently senses capacitance value changes within the capacitive array (26) induced through dielectric shifts within the array (26) brought about by the proximity or absence thereof of the patient's body mass. The control module (10) includes a power supply (16), a driver/sensor circuit (18), a calibration/comparator logic circuit (20), a system interconnection integrity circuit (24), and an alarm generation circuit (22). It may also optionally contain a nurse call relay circuit (32) for interconnection to a facility's nurse call system (34).

Microelectromechanical scanning probe instruments for array architectures

Abstract: A compact (150 μm×150 μm), electrostatic actuator for out-of-plane (z) actuation of a probe tip has been designed, fabricated, and tested. Static deflections of ±0.7 μm out of the plane of the substrate have been achieved. The device consists of a single crystal silicon tip on a torsional cantilever with out-of-plane interdigitated electrode capacitors. This cantilever and electrode design allows a wide range of stiffnesses, actuator force, and frequency response. Significant improvements in performance (larger tip displacement and increased sense capacitance) and a higher density of devices per unit area can be obtained as the minimum feature size decreases. Applications such as information storage, molecular manipulation, and nanolithography require high density, parallel arrays for reasonable throughput. To demonstrate the suitability of this device for use in such arrays, a 12×12 array of microelectromechanical probe tips with integrated actuators and capacitive sensors for scanning probe microscopy h...

Integral capacitive sensor array

Abstract: A capacitive sensor array wherein the plurality of electrodes and the power and data lines communicating with the electrodes are formed from a single dielectric substrate. One face of the substrate is a grounded area, with the electrodes and power and data lines formed from the substrate on the opposite face. A ground connector connects the grounded areas on the two faces without a need to penetrate the substrate. The substrate is flexible, and the power and data lines are die cut from a portion of the substrate to form an integrated cable.

Moisture sensor having low sensitivity to conductance changes

Abstract: A sensing device includes a pair of sensing electrodes disposed within a medium and a circuit connected to the sensing electrodes via impedance matching networks for producing an output signal which varies in response to a capacitive change in the medium. The circuit includes a first circuit portion including the sensing electrodes and a second circuit portion including the oscillator. The first and second circuit portions are tuned to match their impedance for more accurately measuring the capacitive changes.

Microelectromechanical capacitive accelerometer and method of making same

Abstract: A high sensitivity, Z-axis capacitive microaccelerometer having stiff sense/feedback electrodes and a method of its manufacture are provided. The microaccelerometer is manufactured out of a single silicon wafer and has a silicon-wafer-thick proofmass, small and controllable damping, large capacitance variation and can be operated in a force-rebalanced control loop. The multiple stiffened electrodes have embedded therein damping holes to facilitate both force-rebalanced operation of the device and controlling of the damping factor. Using the whole silicon wafer to form the thick large proofmass and using the thin sacrificial layer to form a narrow uniform capacitor air gap over a large area provide large capacitance sensitivity. The structure of the microaccelerometer is symmetric and thus results in low cross-axis sensitivity. In one embodiment, because of its all-silicon structure, the accelerometer exhibits very low temperature sensitivity and good long term stability. The manufacturing process is simple and thus results in low cost and high yield manufacturing. In the one embodiment, the electrodes are formed by thin polysilicon deposition with embedded vertical stiffeners. The vertical stiffeners are formed by refilling vertical trenches in the proofmass and are used to make the electrodes stiff in the sense direction (i.e. Z or input axis). In a second embodiment, the electrodes are metallized and dimensioned so as to be stiff in the sense direction.

A planar capacitive precision gauge for liquid-level and leakage detection

Abstract: A new capacitive precision liquid-level gauge has been developed. The sensor consists of a low-cost planar electrode structure, a capacitance-controlled oscillator and a microcontroller. The device is able to measure absolute levels of conducting and nonconducting liquids with a 1 mm uncertainty over a 4 m range. The system has a high resolution of 0.1 mm at short measuring times of only 0.2 s. Slow level movements of 0.02 mm/h can be detected within 18 min.

Touch mode capacitive pressure sensors for industrial applications

Abstract: The principle, simulation, design, characteristics and application of touch mode capacitive pressure sensors for industrial applications, including embedded monitoring of tire pressure are presented. In touch mode operation, the diaphragm of the capacitive pressure sensor touches the substrate structure. The advantages of touch mode of operation are: near linear output, large over-range pressure and robust structure that make it capable to withstand harsh industrial field environment. When properly packaged, the device can be used to measure fluid now, force, acceleration, and displacement, etc. in industrial applications.

Capacitive level sensor and control system

Abstract: A capacitive level detection system provides a highly accurate determination of liquid level within a container. The primary sensor is an elongate capacitive probe positioned vertically within the container so that a lower portion of the probe is in liquid and an upper portion of the probe extends above the surface of the liquid. A capacitive liquid reference sensor is proximate the lower end of the probe, and a capacitive gas reference sensor is proximate the upper end of the probe. A controller is provided for driving each of the sensors with an electrical signal and reading a resultant value corresponding to the capacitance of each of the sensors. The controller is configured to enable the system to be calibrated prior to installation by placing each of the sensors in a calibration or identical medium, reading sensor values corresponding to capacitances for each of the sensors, and calculating and storing calibration values based on the sensor values. Following installation, values read from each of the sensors are mathematically combined with the stored calibration values to determine liquid level within the container. Liquid level setpoints can also be programmed into the controller by a user to control liquid level within the container.

Padless touch sensor

Abstract: The padless touch sensor is used for detecting a touch at a sensing location onto a dielectric element by a user coupled to earth. The sensor comprises a conductive plate attached under the dielectric element and in registry with the sensing location. A predetermined potential is applied on the conductive plate. Simultaneously, test pulses are produced into earth. When the user touches the dielectric element at the sensing location, a potential variation in the conductive plate is produced during a test pulse due to a capacitive circuit formed between earth, the user and the sensor. No deposition of conductive pads on the dielectric element or other special processes are required. Foreign matter or objects placed directly on top of the dielectric element will not erroneously produce a touch condition.

A universal transducer interface for capacitive and resistive sensor elements

Abstract: This paper presents a new universal transducer interface. This interface, which is read out by a microcontroller, services the following sensor elements: capacitors, platinum resistors, thermistors, resistive bridges and potentiometers. The A/D conversion is based on a first-order oscillator. A combination of classical and some new measurement techniques has been applied on a single chip to obtain high accuracy, good long-term stability and a reduction of the effects of interference and parasitic elements. The circuit has been fabricated in a 0.7 µm CMOS process. The main test results are: an accuracy of 10–15 bits and a resolution up to 16 bits while the measurement time is in the range 1–100ms. These results hold over the temperature range −20°C to 80°C. Calibration of the electronic part is not required. The number of external components has been kept to a minimum.

Capacitive input transducers for middle ear sensing

Abstract: A hearing assistance system senses sound vibrations of an auditory element in the middle ear and provides a stimulus to an auditory sensory element. The vibrations are received through the tympanic membrane, and sensed at the tympanic membrane, malleus, incus, or other auditory element. A capacitive sensor is mechanically or magnetically coupled to a vibrating auditory element, such as the malleus, and time-varying capacitance values resulting from the vibrations are detected. One embodiment allows pivotable mechanical coupling of the capacitive sensor to at least one of the auditory element and a carrier secured within the middle ear. A resulting electrical output signal is provided to the output stimulator for assisting hearing.

A robust capacitive angular speed sensor

Abstract: This paper presents a contactless capacitive angular speed sensor for automotive applications. The sensor is based on a passive rotating electrode placed between two mechanically static and electrically active electrodes. The different characteristics of the charge transfer at various sensor positions is utilized as an input for the calculation of the rotational speed. The main advantages of this low cost system are its capability to operate at high temperatures and humidity as well as its insensitivity to vibrations, dirt, dew and moisture deposited on the three sensor electrodes. The mathematical model of the sensor further enables the optimization of the sensor characteristics for specific applications. Experimental results from a prototype designed for the speed-measurement of a steering-wheel show a relative speed error of /spl plusmn/4% at a resolution better than 1/spl deg//s.