Showing papers on "Capacitive sensing published in 1970"

The Measurement of Atmospheric Fluxes near the Surface: A Generalized Approach

Abstract: A covariance computer capable of accepting analog signals representing any two atmospheric variables is described. The instrument computes the covariance in a frequency band governed at high frequencies by the sensor response times and at low frequencies by capacitive filters. With vertical wind velocity as one input, the instrument has been successfully used for measurement of Reynolds stress, sensible heat flux, and the sum of sensible and latent heats. Given suitable sensors, direct measurement of other fluxes, such as those of CO2 and water vapor, should be possible. The instrument is small and portable. Power consumption is ∼2 W.

Epitaxial method for the fabrication of a distributed semiconductor power supply containing a decoupling capacitor

Abstract: A monolithic semiconductor structure and method of making same and in which structure supply voltages are distributed through adjacent P and N type layers to surface regions of the structure. These voltages are available for integrated circuits and other devices which are constructed in the surface regions of the structure. Good capacitive decoupling is provided between the P and N layers used to distribute voltages and a relatively high capacitive reactance at the surface region prevents AC short circuits at high frequencies.

Surge protection apparatus with improved circuit for reliable sparkover

Abstract: Surge protection apparatus such as a lightning arrester is provided with a plurality of serially connected, power-handling spark gaps with a network of voltage-grading capacitors connected thereacross. A control spark gap is connected across one of the power-handing spark gaps and has a controlled and reliable sparkover characteristic. In circuit with the control spark gap are inductive and capacitive circuit elements to assure sparkover of the entire series string of power-handling spark gaps quickly upon sparkover of the control spark gap while avoiding damage to the control spark gap from excessive current flow.

Apparatus for measuring small changes in condition-sensitive capacitance transducers

Abstract: A humidity-sensitive capacitance sensor or transducer is connected in one leg of a modified Maxwell commutated DC bridge with the other legs formed of resistors. The sensor continually senses the humidity condition and establishes a proportional output signal of the bridge in accordance with changes in capacitance over a small range on a suitable galvanometer. A crystal-controlled oscillator actuates a pair of transistors to alternately connect the condition-sensitive capacitance transducer in a discharging circuit and in a charging circuit in the bridge network. The capacitance transducer alternately charges and discharges with a null output at a given condition and a proportionate output in response to any deviation of the condition sensed by the capacitance sensor. A span adjustment and a charge reservoir capacitor are employed to facilitate the operation.

Digital transducer system

Abstract: A digital measuring transducer system is disclosed wherein a pair of oscillators are employed in combination with a mixer to produce an output from the mixer having a pulse repetition frequency equal to the difference in pulse repetition frequencies between the two oscillators and representative of a sensed condition. At least one of the oscillators employs a resonant circuit in the feedback path and a pressure-variable capacitive sensor is connected into the resonant circuit to vary the output frequency of the associated oscillator to produce a difference in frequencies between the two oscillators and a resultant output from the mixer indicative of the pressure condition adjacent the sensor. The second oscillator may be a reference oscillator providing a predetermined reference output frequency or the second oscillator may have a pressure-variable capacitive sensor associated therewith such that the pulse or digital output from the mixer is representative of differential pressure.

Capacitive distance measuring

Abstract: The measuring device comprises a feeling electrode disposed above a conductive working piece surface the distance of which is to be measured. An oscillator is controlled by a series tank circuit that comprises a series connected feeling electrode and an inductance and, in addition, a separating condenser having substantially greater capacity than that of the measuring capacitor formed by the feeling electrode and the working piece surface. A first selective amplifier is tuned to amplify only the measuring frequency that results during the normal measuring conditions. A second selective amplifier is connected to the output of the oscillator parallel to the first amplifier, and it is tuned to amplify the low frequency that will be generated if the measuring capacitor is short-circuited.

Vehicle with manually operated steering system

Abstract: A vehicle has a manually operated steering system controlled by a steering handle, there being mounted on the steering handle an operating element which, in the event of a sudden disability of the driver, effects operation of a shutting-down system on the vehicle The operating element comprises an electrical conductor mounted on the steering handle and functioning as a capacitive transmitter which constitutes the active capacitance in a capacitive bridge circuit for detecting a change in the effective capacitance of the capacitive transmitter, according to whether or not a driver's hand is on the steering handle The bridge circuit operates a relay which switches off the vehicle circuits and also controls an hydraulic ram assembly which acts on a brake when the relay is operated

Capacitive cryogenic thermometer

Abstract: A capacitive device suitable for use in cryogenic temperature measuring. The dielectric material used in the capacitor is made from a composition in which strontium titanate, SrTiO3, has been controllably crystallized in a glass matrix. A capacitive device having this type of dielectric material is particularly useful in measuring cryogenic temperatures in that the dielectric constant of such a dielectric material decreases smoothly with decreasing temperature, varies linearly with temperature over a suitable portion of the range thereof, and possesses a large sensitivity in the cryogenic temperature range.

Moisture measurement of grain

Abstract: Apparatus for the measurement of moisture in grain and other material. It weighs the sample as added, to ensure a constant sample weight; it dumps the sample in a predictable manner into a capacitive cell; it effects a capacitive measurement and compensates for the temperature of the specimen. The measurement of capacitance provides a measure of the moisture content. In order to compensate for variations in the volume of a weighed sample, arising from grain size, the capacitive cell is cylindrical in form and extends vertically, but lower parts of its metal walls are cut away to provide a lesser capacitance per unit height over the lower parts of the cell compared with upper parts of the cell.

The Influence of Surface Roughness on the Capacitive Measurement of Film Thickness in Elastohydrodynamic Contacts

Abstract: Measurements of oil film thickness according to the capacitive method as carried out on a disc machine with discs having a surface roughness of 10 μin c.l.a. showed marked deviations from the theoretical values predicted by Dowson and Higginson (1)†, especially in the region of small film thickness, i.e. smaller than 0–6 μm (23·6 [μin).In this paper the authors show that surface roughness is the cause of this discrepancy.

Electric timing circuits

Abstract: An electric timing circuit to prevent the battery of a test instrument from being discharged if the instrument is left switched on when not in use. An amplifier and a capacitive element connected across the input circuit of the amplifier so that when the battery is connected across the capacitive element, the capacitive element charges up to effect closure of a current path through the circuit, and when the battery is disconnected from across the capacitive element, the capacitive element discharges thereby breaking the current path through the circuit after an interval determined by the rate of fall of the voltage across the capacitive element.

Chord law companding pulse code modulation coders and decoders

Abstract: Capacitive voltage division and capacitive charge redistribution techniques are used in a pulse coding arrangement which selects a segment of the signal range in which an analog sample occurs. The charge on a series divider is periodically compared with the analog sample, and stored charge is subsequently redistributed in accordance with the comparison results. The invention produces a chord law characteristic, and is suitable for operation with PCM coders or decoders.

Capacitive keying module and system

Abstract: A modular key for an electrical keyboard employs a capacitive voltage divider circuit with stator and armature capacitive elements forming a pair of capacitors in ganged relation. Downward motion of one capacitor element when a key is manually depressed produces a corresponding change in the output of the divider sufficient to overcome the threshold of a transistor detector circuit. An inverted output data pulse is supplied, free of disturbing transients, at the input of associated digital processing equipment.

A thin-film capacitive bolometer.

Abstract: A thin-film capacitive bolometer is described, which depends on a temperature sensitivity derived from electron trapping effects in thin amorphous dielectric films containing an ionic space charge. The theory of this process is summarized and shown to be in good agreement with results obtained from anodized Nb2O5 capacitors. The capacitive elements can be formed on thin-film supporting structures to achieve large thermal detectivities D*. An analysis given for an optimized detector indicates that it is possible to reach the theoretical maximum D* at room temperature. Experimental detectors are described which were fabricated from anodized Nb2O5 and evaporated Al2O–TiO2 capacitors. Their performance at room temperature indicates responsivities of at least 2 mV/μW, effective time constants of about 0.05 sec, and D*’s in excess of 109.

Circuit arrangements for operating electric discharge lamps

Abstract: A starting circuit arrangement for an electric discharge lamp has a capacitive ballast connected in series with the lamp terminals and the A.C. supply terminals. A charging circuit, which includes one or more diodes, charges the capacitive ballast to twice (or more than twice) the peak voltage of the supply so that three times (or more than three times) the supply voltage is available to start the lamp. In one embodiment the capacitive ballast is divided into two equal parts, each connected to one lamp terminal and each charged to twice the peak voltage of the supply by an associated diode charging circuit, so that five times the peak voltage of the supply is available across the lamp terminals.

Solid state microwave oscillator with ceramic capacitance temperature compensating element

Abstract: An enclosed Gunn effect diode is disposed within a microwave resonant cavity. A capacitive element of dielectric ceramic such as titanium oxide having a negative temperature coefficient of capacitance is attached to the insulating portion of the enclosure for the diode. Alternatively the enclosure for the diode may be partly or entirely formed of such a dielectric ceramic.

Capacitive moisture measurement

Abstract: This application discloses apparatus for the measurement of moisture in grain and other materials. It weighs the sample as added, to ensure a constant sample weight; it dumps the sample in a predictable manner into a capacitive cell; it effects a capacitive measurement and compensates for the temperature of the specimen. The measurement of capacitance provides a measure of the moisture content.

Crosstalk minimization in multi-wire networks

Abstract: The crosstalk in a two-wire network is minimized by cancelling the crosstalk signal at every crosspoint. This is achieved by providing each crosspoint of a two-wire network with a pair of capacitive elements each having substantially the same capacitance as that of a non-actuated switch used for the crosspoint. These elements are connected at the pair of intersections of the horizontal and vertical conductors of the crosspoint other than those at which the switches are connected.

Variable capacitive apparatus

Abstract: A variable capacitance apparatus particularly adapted for use with a manually-operated keyboard and having two parallel, conductive plates with a dielectric therebetween. Depression of a key moves one conductive plate farther from the other conductive plate so as to reduce the capacitive coupling between the conductive plates, in order to determine whether the key has been depressed.

Capacitive diode controlled oscillator frequency shift keying circuit

Abstract: A crystal oscillator is shifted between two different discrete frequencies by means of two different voltages being applied to a variable capacitance diode coupled in shunt relation with the crystal. The circuit providing one of the two different voltages having a given value is permanently connected to the diode to provide the lower frequency shift. The other of the two different voltages having a value greater than the given value is provided by a transistor stage under control of a binary signal. The binary signal controls the conduction and nonconduction of the transistor stage to selectively connect and disconnect the other of the two different voltages to the diode. This other higher voltage, and, therefore, the higher frequency shift, is provided only when the transistor stage is nonconductive, which occurs when the condition of the binary signal is low, and overcomes the voltage providing the lower frequency shift.

Electrical inductive/capacitive component

Abstract: A component for providing both inductive and capacitive properties is formed by at least two interleaved spiral coils insulated from each other and each provided with a respective terminal, one of which is an input and the other an output terminal. The component has inductive and capacitive properties, or purely capacitive properties, according to the spacing between the terminals, if any, measured along the spirals.

Capacitive pick-up means for an electrical tachometer

Abstract: Herein described is an electrical tachometer which is responsive to electrical signals applied to selected spark plug wire of an automobile. The contact comprises a capacitive coupling contact which is wrapped around the exterior insulation of the spark plug wire. A clamp-on arrangement of the capacitive coupling contact includes a pair of contactor clips which are secured to the outer wire and held by an outer shield to shield, the signals picked up by the capacitive connections from outside noise environment. Electronic circuitry is responsive to the signals received by the capacity contactors and includes a signal shaping network to provide the necessary signal-to-noise discrimination. The relatively noise-free signal is then converted to a D.C. signal which is then applied to a meter.

Two-terminal reactive hybrid microcircuit having capacitive diode termination

Abstract: A phase shifter, detector and/or modulator for superhighfrequency waves includes a two-terminal reactance network whose inductive branches consist of short linear conductors, measuring a small fraction of the free-space wavelength of an oscillation to be controlled, and whose capacitive branch or branches are lumped condensers; the network is terminated in a diode, with or without a large-capacitance series condenser, which can be selectively blocked or unblocked by the application of a suitable biasing potential to vary its impedance between a very high and a very low value. The components of the network are mounted on a conductive block received in a cutout of a two-conductor or three-conductor line strip.

Vacuum capacitor with solid dielectric

Abstract: A unique combination of vacuum component techniques to a solid dielectric capacitor. The vacuum-type enclosure includes at least one generally cylindrical body shell member of insulating material and one or more metallic cylindrical sections attached thereto. A control shaft operating through a vacuum-type bellows moves an internal cylindrical member encased in an insulating material sleeve of polytetrafluoroethylene to provide variable capacitive engagement within at least one of the outer metallic shell members. The bearing arrangements common in vacuum variable capacitors are eliminated, because the fluorocarbon insulating dielectric material preserves the spacing and coaxial relationship of the inner and outer shells and provides a sliding surface of very low friction. Advantage is taken of the desirable dielectric strength of the fluorocarbon dielectric material without the destructive effects of corona in air. An alternative planar element embodiment of the invention using disc plates and a spring disc variable plate is also shown. In that embodiment the dielectric is also a planar element.

Co-axial tuning capacitor devices

Abstract: A tunable capacitor for use in precision frequency tunable circuits having a tunable slug for movement within a dielectric tube with a capacitive outer surface, wherein protrusions such as dimples are distributed on the surface of the slug in order to maintain a constant and evenly distributed air dielectric between the slug and the tube.

Shielded bushing construction

Abstract: This disclosure relates to a capacitive core bushing which is adapted to be connected to a grounded, dielectric fluid filled, tank housing high voltage electrical apparatus. The bushing comprises a through conductor, a capacitive core surrounding the conductor and a housing around the core comprising upper and lower insulating shells. A conductive electrostatic field control electrode is provided, the potential of which is intermediate the line voltage and ground, located in the lower portion of the bushing, adjacent the point at which the through conductor emerges from the lower insulating shell. The field control electrode is preferably formed as a conductive ring and maintained at a selected intermediate potential by a connection to an equipotential surface of the capacitive bushing core. The field control electrode is embedded in a bushing cap of highdielectric strength material through which the central conductor emerges at the lower end of the bushing. In a modified form a second electrostatic field control electrode is embedded in the bushing cap between the point of emergence of the through conductor and the first field control electrode and is electrically connected to a point at line potential.

Relative carbon content meter for smoke filters

Abstract: An apparatus to measure the relative quantity of carbon present in a smoke filter comprising a parallel plate capacitor between whose parallel plates are disposed rods of filter material. The parallel plate capacitor is attached to a capacitance measuring device which is calibrated to measure a capacitive change of the system comprising said parallel plates and said rods and to indicate when the carbon content of said rods deviates from a predetermined standard. An embodiment of the invention is disclosed which comprises an improved device for measuring the capacitance of said capacitive system by utilizing a linear approximation in the dependency of collector current with small variations in capacitance added to the base circuit in a tuned collector, tuned base transistor oscillator wherein said dependency is measured in a ''''Wheatstone'''' bridge circuit.

Coupled inductance impedance measuring circuit with increased sensitivity and frequency independence

Abstract: An impedance measuring circuit having two closely coupled inductances conducting alternating electric excitation from a grounded source through measuring and balancing impedance branches respectively to ground Peak detection circuitry referenced to ground in the impedance measuring circuit gives an indication of the difference in the voltage across the measuring and balancing impedances Where measuring and balancing impedances are capacitive reactances and at source frequencies above resonance of the inductance-capacitance circuit, substantial frequency independence is achieved

High-frequency impedance of a practical metal surface and the effect of a thin coating of dielectric over it

Abstract: It has always been assumed that the surface of metals used in hf cables and waveguides is sufficiently uniform to present an impedance, which is jointly resistive and inductive The evidence of computations made here and of recent experimental observations incidates that many such surfaces may well be capacitive and that, in these circumstances, a thin dielectric coating can reduce the resistive component of the impedance