Showing papers on "Capacitive sensing published in 1983"

Radio frequency field coil for NMR

Abstract: An NMR radio-frequency coil is made up of a plurality of conductive segments evenly spaced about the peripheries and interconnecting a pair of conductive end-cap elements. Each conductive segment includes at least one reactive element which may include a variable capacitive or inductive element.

Capacitive pressure transducer

Abstract: The flexible membrane for sensing a differential pressure in a cylindrical sensor is made from a tube with heavy end rings that gradually taper down to form a flexible membrane such that stresses from membrane flexions are distributed throughout the end rings to prevent the stresses from being transmitted to the joints between the tube and its supporting structure thereby reducing hysteresis and creep deformation effects; temperature and stray capacitance effects are minimized by using the capacitive sensor in a tank circuit having an inductor integral to the transducer structure, the tank circuit oscillating at its resonant frequency for use in indicating the differential pressure.

Circuit arrangement for keeping the temperature-dependent sensitivity of a differential-pressure measurement apparatus constant

Abstract: The differential-pressure measurement apparatus consists of a capacitive differential-pressure sensor 1 having two measurement capacitors C1 and C2 whose capacitance values vary with the differential pressure acting on the membranes 2 and 3, of two integrating elements 9 and 10 which are fed back via the measurement capacitors C1 and C2, and which convert their capacitance values into measurement signals, and of a computing element 12 which calculates the differential pressure from the measurement signals. In order that the sensitivity of the differential-pressure measurement apparatus can be kept free of defects and constant in a simple manner, the integrating elements 9 and 10 are supplied from a controllable oscillator 11, and a temperature-dependent control voltage is obtained from the measurement signals via a computing circuit 13, which control voltage, after comparison with a constant reference voltage which can be entered via the connection 15, provides follow-up control of the oscillator 11 in such a manner that the control voltage equates to the reference voltage.

Touch control arrangement for data entry

Abstract: A touch control arrangement which employs a touch panel comprising a plurality of touch keys and a network of electrically connected capacitive elements; an oscillator which incorporates the network of capacitive elements in its timing circuit; and a microprocessor coupled to the output of the oscillator and operative to control various appliance operating components as determined by the frequency of the oscillator output signal. The keys of the touch panel are operatively coupled to the network of capacitive elements such that actuation of a key or pad by the user changes the equivalent capacitance of the timing circuit causing the oscillator a generate a control signal at the frequency associated with the actuated key.

Capacitive circuit board testing system and method using a conductive pliant elastomeric reference plane

Abstract: A capacitance measuring circuit board test system (10, 10') for measuring the electrical continuity and integrity of line segments (14) on a circuit board (12) including: a test stand support (20); a conductive pliant circuit board backside reference plane (19, 29, 34) carried by the support (20); means for pressing the circuit board (12) into intimate mutually coextensive face-to-face contact with the conductive pliant material (29) defining the reference plane (19, 29, 34) with the interface therebetween being devoid of air gaps; and, a capacitance measuring device (16, 40) having sensory terminals (5, 18 and 44, 45) respectively coupled to a relatively movable test probe (11, 46) and to the backside reference plane (19, 29, 34) for measuring the capacitance of the circuit board line segments (14) between n test points and the backside reference plane (19, 29, 34). The systems disclosed include methods and apparatus suitable for use with a wide variety of circuit boards (12) including single- or double-sided circuit boards, single- or multi-layer circuit boards, and circuit boards with and/or without internal ground and/or power planes; and, with a wide variety of different types of capacitance measuring devices including, for example, three point capacitance meters (16) and four point capacitance meters (40), in the latter of which current is driven through the circuit board (12) and test system (10') from a high-potential drive terminal (41) to a low-potential drive terminal (42) associated with the meter (40) while the voltage levels at the high- and low-potential sensory terminals (44, 45) are measured with the voltage drop therebetween being indicative of line segment capacitance.

Capacitive device for the measurement of displacements

Abstract: The device comprises a scale (1) and a slide (2) which are provided with electrodes arranged to form two pairs of capacitances for the measurement of the displacement of the slide on the scale (CA1 -CA2, CB1 -CB2). These measurement capacitances are connected to an electronic feed and processing circuit (3) in which they are connected in a bridge (4A, 4B) with switched reference capacitances of MOS type. In this circuit, the outputs of these bridges are connected via comparators (5A, 5B) to a processor (6) of CMOS type adapted to produce a terminal digital measurement signal by counting the periods of the signal of the measurement capacitances and by numerical interpolation within each of these periods. This interpolation is effected by balancing the capacitive bridges by means of a digital algorithm.

Multiple range capacitive pressure transducer

Abstract: A multirange, variable capacitance pressure transducer provided by bonding a diaphragm plate (18) that is conductive between a pair of insulating plates (10,16). The diaphragm plate has a plurality of cavities provided on each side so that diaphragm deflection areas of different sizes are defined. The surfaces of the pair of plates in the cavities are covered by a conductive coating (24,26,28,30) so that the coatings form capacitors with the deflection areas. A fluid communication path is provided to each cavity so that the pressure difference to be measured is placed across the deflection area. Electrical connection is made to selective combinations of said capacitors to provide pressure transducers for a number of ranges in one unit.

High-frequency circuit comprising an integrated capacitor

Abstract: A high-frequency circuit (11) having at least a semiconductor circuit element (12) which is arranged on a first surface (13) of an insulating substrate (14). At least one (19a, 19b) of the output terminals (17, 18a, 18b, 19a, 19b) of the semiconductor circuit element (12) is electrically coupled to a ground plane (16) through a capacitive element (20) and metallized holes (21, 22). According to the invention, the circuit element (12) is secured a plate (24) of a dielectric material provided with conductive elements (27, 28a, 28b, 29a, 29b) to which the output terminals are soldered. The conductive elements to which the terminals (19a, 19b) are secured are conductively connected to a metallic layer (30a, 30b) constituting a first plate of the capacitive element (20). A conductive layer (31) formed between the plate (24) and the substrate (14) constitutes a second plate of the capacitive element.

Electrocutaneous Stimulation with High Voltage Capacitive Discharges

Abstract: This paper presents research on the sensory and electrical properties of human subjects in response to electrical stimuli from highvoltage capacitive discharges. Threshold data for single monophasic transient stimuli are analyzed. The psychophysical measurements are related to a neuroelectric model with parameters that depend on some of the basic properties of excitable membranes.

Thermometry in high magnetic fields at low temperatures

Abstract: We have investigated the behavior of carbon resistor and capacitive thermometers from 4.2 to below 0.1 K and to 19 T. We observe, in agreement with previous work at higher temperatures, a nonmonotonic magnetoresistance in a standard carbon resistor for thermometry below 1.0 K. We provide the reader with an expression for the magnetoresistance which may be used, with proper precalibration for a particular sensor, to determine the temperature from a reading of the resistance and the magnetic field. In addition, we discuss epoxy mixing chambers for dilution refrigerators and discuss results which indicate that certain materials can be magnetized and demagnetized at low temperatures. Finally, we report measurements on two types of capacitive temperature sensors which also exhibit magnetoeffects.

Capacitive pressure sensor

Abstract: A capacitive sensor for use in the measurement of pressure or pressure changes of a fluid medium which sensor maintains the capacitor electrodes in a substantially parallel relationship. Maintenance of this parallel relationship provides a substantially linear capacitive output over a given range without further electronic buffering or calibration. The capacitive signal may be enhanced or amplified by use of multiple parallel plates which are movable simultaneously with deflection of the flexible diaphragm.

A capacitive method and apparatus for checking connections of a printed circuit board

Abstract: A first conductive plate (C1) connected to an a.c. voltage source (V1) is placed adjacent and spaced from a terminal (A2) of a printed circuit board. A conductive track between this terminal (A2) and another terminal (C4) is then energised, a signal being obtained by voltmeter (V) as a result of such energisation and capacitive coupling between the terminal (C4) and the voltmeter (V). In this way, the connections of a printed circuit board can be checked using capacitive coupling and without reliance on an ohmic connection.

Method and arrangement for measuring the contamination of a capacitive dew-point sensor

Abstract: A dew-point measuring instrument has a capacitive dew-point sensor 1 which is cooled by a cooling device 17 to the dew-point temperature measured by a temperature sensor 8. A phase measuring circuit 14 measures the phase angle of the impedance of the capacitive dew-point sensor 1. The measured phase angle is used as a gauge for the contamination of the dew-point sensor 1.

A water-level sensor using a capacitance to frequency converter

Abstract: A capacitive water-level sensor using PTFE-insulated wire and a capacitance to frequency converter is described. Construction is simple, yet overall linearity is 0.1%. Temperature drift of the sensor is -0.05%K-1 and that of the converter is <0.01%K-1. Long-term stability of the sensor appears excellent. The converter draws only 150 mu A from a 5 V supply and is insensitive to supply voltage variations.

Method and apparatus for determining dielectric constant

Abstract: An improved method and apparatus for determining the dielectric constant of materials which flow using capacitive techniques, having an electrode device with at least two output terminals and three or more electrodes spaced at fixed distances from one another. At least two of the electrodes are connected through a switch so that first and second capacitances appear at the output terminals of the electrode device depending upon the position of the switch. The output terminals of the electrode device being connected to an oscillator which produces an output signal indicative of the frequency of the oscillator's oscillation which is proportional to the capacitance at the terminals of the electrode device. The output signal of the oscillator is connected to a bi-directional counter or microprocessor which is used to calculate a value proportional to the change in capacitance of the electrode device when the switch is closed and to thereby determine the dielectric constant of a material being tested.

Capacitive level gauge

Abstract: A device for measuring capacitively the level of a fluid in a tank or container, comprising two means (2, 3, 4, 5, 6; 9) which are placed in the fluid at a determined distance from one another and being adapted for capacitive measurements, the first means consisting of a plurality of individual sections (2, 3, 4, 5, 6), each section having a determined size and further comprising means for measuring the values of the section-capacitances and means for deriving information concerning the level in the tank from the measured capacitance-values. A screen (8) is placed between the said first means and the said second means.

Capacitive digital to analog converter which can be trimmed up and down

Abstract: A capacitive digital to analog converter which can be trimmed to obtain precise capacitor matching is provided. The trimming method may be utilized with a weighted capacitive D/A converter having a scaling capacitor and an ordered plurality of capacitors for developing an analog output signal as a function of a digital input code. A compensation portion is coupled to at least a predetermined one of the capacitors for selectively changing the effective capacitive value of the predetermined capacitor.

Capacitive humidity sensor and method for the manufacture of same

Abstract: The present invention is concerned with a capacitive humidity sensor and a method for the manu-facture of same. The sensor comprises a substrate, first and second bottom electrodes arranged close to each other on the substrate, and an active layer, which fills the area between the first and the second bottom electrodes on the substrate and extends to above the top face of the second electrode. According to the invention, the sensor further comprises a plurality of conductive, beam-shaped structures placed side-by-side, connected to the first electrode, and having an upwardly widening cross-section, the structures limit-ing portions of the active layer between themselves from two sides such that a narrow slot is provided between the top faces of the structures. Owing to its construction, the sensor of the invention is not sensitive to touching.

Capacitive position transducers

Abstract: A method for measuring angular (Fig. 1) or linear position by means of a capacitive or electrostatic device where the positional information is conveyed by the relative phase of the output signal of the measuring device to that of a system of associated energizing supplies. The capacitance between an array of energized electrodes H on a stationary element E, and a sense array D on a movable element B is maintained substantially constant. By this means, and by the utilization of energizing sources that apply signals of small electrical phase difference to adjacent electrodes on the stationary element, a close approximation to a linear measurement characteristic is achieved.

Narrow bandwidth microstrip filter

Abstract: An interdigital microstrip transmission line filter (100) includes three electrically conductive strips (104, 106 and 108) each coupled to grounded portions (110 and 120) on one end and coupled to respective capacitive loading pads (112, 116 and 114) on the other end. Input and output pads (130 and 140) may be coupled to signals from other circuitry located off or on the same substrate (150). Grounded portion (110) extends between capacitive loading pads (112 and 114) for minimizing undesired coupling between non-adjacent strips (104 and 108). As a result, the unique microstrip filter (100) has a frequency response that is substantially devoid of passband transmission zeros.

Plasma jet ignition system

Abstract: An ignition system for an internal combustion engine having a capacitive plasma jet plug including a capacitor in parallel with the series combination of an auxiliary gap and a plasma cavity. The auxiliary gap increases the required breakdown voltage before the plasma cavity generates a spark and obtains supplemental energy from the energy stored in the capacitor.

Flatness measuring apparatus

Abstract: An elongated carriage has a first capacitive probe disposed from its top surface opposite to an object surface, and a second capacitive probe disposed from its bottom surface opposite to a level reference surface. An arm is orthogonally disposed from the elongated carriage member to provide lateral support. The carriage is moveably supported at opposite ends of the elongated member and at the distal end of the arm by three rolling members which roll in corresponding grooves of supporting members as the carriage is moved in lateral increments with respect to the stationary object and reference surfaces. The first capacitive probe and the object surface comprise a first capacitor, and the second capacitive probe and the reference surface comprise a second capacitor. As the carriage moves laterally, the first probe is moved across the object surface while the second probe is moved across the reference surface. The capacitance of each probe is translated into a distance measurement. The distance values derived from the first capacitor are utilized with the distance values derived from the second capacitor to generate numerical information describing the flatness of the object surface. The apparatus self-corrects for any translational deviations of the carriage.

Clock pulse generating circuit

Abstract: A clock pulse generating circuit comprises a plurality of circuit blocks connected in series successively to form a multistage configuration, each of alternate ones of which at the odd stages is composed of a first switching element being supplied with a first timing signal, first capacitive element coupled in series with the first switching element and an a NOR gate circuit to which a voltage obtained at the connecting point between the first switching element and the first capacitive element and the first timing signal are supplied, and each of another alternate ones of which at the even stages is composed of a second switching element supplied with a second timing signal, a second capacitive element coupled in series with the second switching element and an inverter to which a voltage obtained at the connecting point between the second switching element and the second capacitive element. The first one of the circuit blocks is supplied with a starting signal and the alternate circuit blocks at the odd stages are used for delivering output pulses therefrom.

Surface acoustic‐wave device for measuring high voltages

Abstract: A surface acoustic‐wave (SAW) device for measuring high voltages is described. The device consists of two SAW oscillators fabricated on a 128° rotated Y‐cut LiNbO3 substrate. The voltage to be measured is applied to one of the oscillators while the other oscillator acts as the reference oscillator for temperature compensation purposes. The frequency of the perturbed oscillator varies linearly with the applied voltage. An oscillator fabricated on a 0.5‐mm‐thick substrate can withstand greater than 9 kV of voltage giving a fractional frequency deviation greater than 1630 parts per million. Attractive features of this technique include: (1) direct measurement of high voltages without the need for resistive or capacitive voltage dividers, (2) very high input resistance, (3) direct conversion of voltage to frequency, and (4) resolution better than 0.01% of full scale. This paper will discuss the basic operation and present experimental data on the performance of the device. A technique for obtaining improved t...

High‐resolution third‐sound resonator

Abstract: A third‐sound helium film resonator using a capacitive thickness detector suitable for high‐resolution studies of third sound in 4He and 3He–4He mixtures is described. The sensitivity to changes in the helium film thickness is observed to be ≂0.1 pm.

Decoupling capacitor and method of manufacture thereof

Abstract: A decoupling capacitor and method of manufacture thereof are presented wherein the decoupling capacitor is formed in a two step molding process. The decoupling capacitor is a hermetically sealed capacitive unit consisting of a ceramic capacitor, active leads bonded to the capacitor and dummy pins for auto-insertion into printed circuit boards.

Electric field strength indicator

Abstract: An electric field strength indicator for use with high voltage conductors comprises a capacitive probe mounted within a tubular shield having an insulating spacer at one end for locating the unit with respect to a conductor under test The probe is electrically coupled to a signalling circuit and is movable axially within the shield to a position at which a threshold response is obtained Such position, which denotes the conductor voltage, is read on a scale provided Because of the shield the device is directional, the probe being shielded from neighboring conductors