Showing papers on "Capacitive sensing published in 1971"

Bandpass Filters for a Prescribed Insertion Loss Characteristic

Abstract: A design theory for evanescent dominant mode wave- guide filters is presented. The cutoff guide is represented by its equi- valent z-section network, the elements of which closely approximate lumped inductances. Resonators may be formed by introducing ap- propriate capacitive obstacles at suitable intervals along the guide. The filter that results is a microwave analog of lumped inductance filters with series inductance coupling, the magnitude of the series "inductance" being controlled by the separation between capacitive obstacles. The theory derives the equivalent ladder network from the low-pass prototype and is accurate up to at least 20 percent band- widths. Filters may be designed to couple into other cutoff waveguide components using the same basic principles, a propagating guide, and coaxial terminations. The filters are normally constructed in standard production waveguide and are simple and cheap to manu- facture. A considerable size and weight reduction, compared with orthodox waveguide filters, is possible at the cost of a small increase in insertion 10ss.

Capacitive pressure transducer

Abstract: Known capacitive pressure transducers comprise a wheatstone bridge connection in each branch of which there is a capacitance. Two of them are variable while the two others are arranged on a diaphragm in a casing. The chamber of the casing is subdivided by the diaphragm into a pair of compartments and each compartment is arranged for being connected to a system the pressure of which is to be measured. Such arrangement requires considerable space and is intricate to manipulate. Moreover, its output signals are of low level due to only one pair of capacitances being variable. This invention employs four variable capacitances distributed in the individual branches of a Wheatstone bridge connection for which purpose four electrodes are supported on opposite sides of the diaphragm. Further four electrodes are arranged within the casing opposite to the electrodes on the diaphragm. Thus, four variable capacitances are formed which are connected to form a wheatstone bridge connection. Deflections of the diaphragms caused by such pressure entail variations of the bridge capacitances and, thereby output voltage signals of increased strength on the bridge terminals.

Transient Response Characteristics of Capacitive Potential Devices

Abstract: Full voltage line to ground fault tests are performed on typical potential devices and the subsidence transient recorded. To show the worst case of residual voltage, faults are initiated while the primary voltage is passing through crest and zero.

Capacitive pick-off transducer

Abstract: A capacitive pick-off transducer is disclosed in which small relative movement between aligned capacitive elements is utilized to provide an electrical output signal responsive to such movement. The capacitive elements include a fixed driven element having 2n driven sectors each connected to one of two sources of input electrical signals of opposite phase, a fixed receptor element including 2n 1 active areas connected to an electrical signal output circuit, and a moveable shield element between the driven and receptor elements and including 2n 1 shielding lobes. Circuit means including a high gain amplifier with a negative feedback circuit are provided for maintaining the signal levels of the shield element and the active areas substantially lower than the absolute values (ignoring polarity) of the input signals, and preferably at or near ground.

Three-terminal capacitive apparatus for remotely responding to a condition or dielectric properties of a material

Abstract: Three-terminal capacitive apparatus are disclosed which provide information concerning a condition of a material by responding to the dielectric properties of the material. A three-terminal capacitor, which may be a cell or probe, may be used, for example, to measure the dielectric constant of a material, to determine the level of a material in a container, to determine the interface between liquid materials in a pipeline, or the proximity of a material to the probe. Each cell or probe includes a conductive driven element connected to a regulated square wave source, and a conductive receptor element connected to the input of a high gain amplifier with a capacitor in the feedback loop which maintains the receptor element at virtual ground. The output of the feedback amplifier is proportional to the feed through capacitance of the capacitive probe or cell. A synchronous demodulator, synchronized by the drive signal or a signal in phase with it, is connected to the feedback amplifier output and is used to produce a DC output signal used for display or control. The cell or probe is connected to associated electronics through shielded cables and may be remotely located from the electronics. Suitable mechanical apparatus is associated with a particular three-terminal capacitor cell or probe for mounting it in position to respond to a particular condition being monitored.

Differential methods and apparatus for measuring dielectric constant to determine a condition of a material

Abstract: Method and apparatus responsive to conditions such as the moisture content or ingredients ratio of a material are disclosed in which the dielectric constant of a standard sample of such material of a reference moisture content or ingredients ratio is compared in a three-terminal differential capacitive device including two three-terminal capacitor probes with the dielectric constant of a test sample of such material of unknown moisture content or ingredients ratio. The comparison provides an electrical output signal proportional to the differences in moisture content or ingredients ratio of the test sample and the standard sample. For example, the differential capacitive device may be mounted in a differential capacitive cell which includes a standard sample cavity in which the standard sample is placed around the electrodes or conductive elements of one threeterminal capacitive probe and a test cavity in which the test sample is placed around the electrodes or conductive elements of a second three-terminal capacitive probe. Each probe of the differential capacitive device includes a conductive driven element, a conductive receptor element connected to an amplifier and maintained at virtual ground, and suitable shielding connected to a ground terminal. The test cavity is maintained at the same temperature as the standard sample cavity and the feed through capacity of each probe is a function of the dielectric constant of the material between their electrodes.

Paired Comparison Tests of the Relative Signal Detected by Capacitive and Floating Langmuir Probes in Turbulent Plasma from 0.2 to 10 MHz

Abstract: Paired comparison tests of relative signal detected by capacitive and floating Langmuir probes in steady state turbulent plasma confined in magnetic mirror geometry

Temperature compensator for capacitive pressure transducers

Abstract: A pressure transducer of the capacitor type having a body of dielectric material has a thin film resistor deposited on the body for sensing the temperature of the body. The resistor is of a material having a suitable temperature coefficient of resistivity to provide a signal corresponding to the temperature of the body for temperature correction.

LSA relaxation oscillator principles

Abstract: Oversized n-GaAs diodes operating in the LSA mode with doping-to-frequency ratios in the 1-5×105s/cm3range are investigated in circuits that contain a short-circuited high impedance transmission line foreshortened to resonate the electronic parallel capacitance of the diode. By comparing computer simulations with experiments, such diodes are shown to operate in a nonsinusoidal LSA relaxation mode which offers good efficiency, effective space-charge control, and a fast buildup of the oscillations; details of the computer program are also given. A simple analysis is developed which defines the inductive and capacitive time constants controlling the voltage waveshape and explains the frequency tuning with bias voltage and the effective space-charge control. The analysis is shown to be suitable for oscillator design purposes.

A two-dimensional charge scanning instrument for flat insulating sheet

Abstract: The charge associated with an insulating sheet is monitored by scanning the specimen underneath a capacitive probe coupled to a detection system of very high input impedance. The charge distribution is displayed either on an XY recorder as a deflection modulation of the raster pattern, or with a cathode ray oscilloscope operating in the beam intensity modulation mode.

Capacitive displacement transducer

Abstract: A capacitive displacement transducer for measuring relative displacement between two points or objects is disclosed as including a driven element connected to a source of input electrical signals, a receptor element connected to an electrical output signal circuit means, and two shield elements mounted between the driven and receptor elements for relative movement with respect to each other. One of the shield elements mechanically responds to one of the objects and the other shield element mechanically responds to the other object and any resulting relative movement between the shield elements changes the capacitive coupling between the driven and receptor elements to provide an electrical output signal proportional to this movement and the displacement between said objects.

Variable capacitance displacement transducers

Abstract: A capacitive position transducer in which a movable element controls the ratio of the capacitances of two capacitors. The movable element is a screen which, in the preferred embodiments, moves between the plates of one of the capacitors thereby changing its capacitance. The ratio of said capacitances is used to provide an indication of the position of the screen and hence of the movable element.

Isolated power ground fault detector system

Abstract: A ground fault detector system for isolated power lines, especially those for use with operating room and intensive care monitoring equipment including an isolated test circuit arrangement for checking the operation of the system, that does not itself introduce potentially hazardous and dangerous ground faults into the isolated power lines being monitored. More specifically, the isolated power ground fault detector system of the present invention functions to alternately connect a detector circuit to the power lines at a frequency which is a submultiple of the source frequency. The detector senses both capacitive and resistive ground faults and provides an output voltage signal representative of the magnitude of the ground fault. This output voltage signal is compared to a reference voltage in a voltage comparator which activates alarms and indicators if the ground fault exceeds a preset threshold value. The system also includes a test circuit for checking the operation of the system which when actuated simultaneously switches the detector system from the isolated power lines to auxiliary power lines and introduces a simulated capacitive resistive fault into either of the auxiliary lines. By this arrangement, the system may be checked without introducing a potentially hazardous and dangerous ground fault into the isolated power line supplying the equipment.

Fet driver for capacitive loads

Abstract: A field effect transistor (FET) amplifier circuit for driving capacitive loads includes two amplifier stages, each having an input FET and a related load FET, one stage driving the load, the other stage providing capacitively coupled bootstrap drive to the load FET of the load driving stage.

Susceptance measuring system for indicating condition of a material

Abstract: A system for measuring the condition of a material using a capacitive probe which is immersed in or placed in proximity to the material whose condition is to be measured, in which the probe exhibits both susceptive and conductive components, and in which means are provided for producing an indication representative of the susceptive component and substantially independent of the conductive component.

Capacitive switching device

Abstract: A capacitive switching device including a driven element with at least one active, conductive driven sector connected to a source of alternating voltage, a receptor element with at least one active, conductive receptor sector and a conductive shield element with at least one open slot permitting capacitive coupling between said driven sector and said receptor sector when these are in alignment with said slot. The elements are aligned with respect to each other so that relative movement of the shield element with respect to the driven and receptor elements produces output electrical signals responsive to a switching pattern on the driven element, the receptor element or on both. The shield element is preferably grounded.

Permanent information store

Abstract: A permanent information storage device has a hidden conductive pattern of first areas selectively connected to a second area. Reading is by energizing capacitive couplings to the first areas and detecting for response in the second area.

Continuous monitoring of eccentricity and coaxial capacitance variables during electrical insulation extrusion

Abstract: A system for monitoring telephone cable insulation and jacket wall thickness and centering during manufacture consists of four capacitive probe segments spaced at 90* intervals with a dielectric gap separating adjacent segments. The probe is flanked by guard tubes which along with each segment are connected to a switch capable of placing any or all segments at guard potential. In various configurations ordered by the switch, capacitance measurements are made to yield indicia of coaxial capacitance, eccentricity and ovality.

Dynamoelectric machine apparatus, such as brushless exciter for a. c. generator, with flexible tape capacitive means

Abstract: A capacitor tape is applied over the shaft of a brushless exciter and is connected to provide interphase capacitance with or without an additional resistive tape connected in series with each capacitor to provide damping resistance. The voltage suppressor functions of the capacitors can also be obtained by winding a tape to provide a distributed capacitance directly in the A.C. exciter winding. A flexible capacitive tape in accordance with this invention can be variously applied in dynamoelectric machine apparatus.

Undervoltage sensing circuit

Abstract: A circuit is provided to sense the occurrence of an undervoltage on any one or more phases of an AC electrical system The phase voltages are compared with a reference level with charging of a capacitive means occurring for the duration of any undervoltage, even for part of normal phase voltage wave forms If the level to which the capacitive means is charged exceeds another reference level, an output signal is created for indicating the undervoltage condition has existed beyond a tolerable limit The nature of the circuit''s operation is inherently frequency sensitive so that occurrence of underfrequency phase voltages is also detected

Apparatus and method for direct readout of capacitively gauged dimensions

Abstract: An electronics system and method for processing the output of a dimension sensing capacitive gauge or probe having a measured capacitance between electrodes. Control of the capacitive gauge''s output through control of its excitation allows a parameter of the excitations output to be used as an indication directly proportional to a dimension, typically electrode separation, which varies inversely with the capacitance between the electrodes. An output from a second similar gauge is used to deflect a meter for a direct indication of the dimension. Alternatively a second excitation for the second gauge is provided with its output used to control the first excitation whereby the frequency ratio of the two excitations provides a direction indication of the dimension and is easily digitized. Environmentally induced changes in either gauge are balanced by proximity of the gauges and the excitation amplitude is regulated.

Capacitive coupling switch and actuator

Abstract: A variable capacitance switch element is disclosed in which varying capacitance is effected by increasing the active surface area of a capacitive coupling member in proximity to a second capacitive plate. The structure of the variable capacitive element is such that the capacitance of the device varies in nearly linear fashion with the depression of an actuator member.

Surface acoustic wave generating system

Abstract: In a surface acoustic wave generating system, a portion of a body of semiconductor material is incorporated in structure having electrical capacitance. The capacitive structure is energized to produce mechanical stress in the body of semiconductor material and thereby generate surface acoustic waves on a surface of the body of semiconductor material. In one embodiment of the invention the capacitive structure comprises one or more p-n junctions formed in the body of semiconductor material and intersecting the surface. In another embodiment the capacitive structure comprises one or more MOS capacitors disposed on the body of semiconductor material.

Effect of Source Resistance on Current‐Voltage Characteristics of Superconducting Weak Links

Abstract: The effect of finite source resistance on the computed current‐voltage characteristics of superconducting weak links is considered for both capacitive and inductive devices. Hysteresis is found to vanish for a sufficiently small‐source to shunt‐resistance ratios.

Theory of cylindrical antennas with arbitrary impedance loading

Abstract: A method of analysing cylindrical antennas with distributed impedance loading is presented. The loading is assumed to be an arbitrary but differentible function of position along the antenna. As an illustration, the most important class of such antennas in practice, the broadband cylindrical antennas with distributed resistive or capacitive loading, for which exprimental data are available, are analysed. The theoretica results are in satisfactory agreement with experiments.

Mechanically adjustable high voltage inductive reactor for series resonant testing

Abstract: Mechanically adjustable inductive reactor for series-resonant corona and dielectric testing of capacitive loads, such as, long lengths of high voltage electrical transmission cable which enable unusually long lengths of unusually high voltage cable to be tested conveniently and economically. The invention provides advantages when testing shorter lengths of cable at the usual voltage levels of 150,000 volts or 225,000 volts, but the advantages become greater at the higher voltages and longer lengths forseen in the future by the inventor. A mechanically adjustable high-voltage inductor is resonated directly in series with the cable capacitance of a long cable at high voltage. Three embodiments of mechanically adjustable, low flux-fringing, inductors are disclosed which are linear in inductance variation as a function of mechanical movement and are convenient and quiet to operate as well as being economical in amounts of steel and copper materials employed for a given electrical (kilovoltampere) rating.

Method of controlling high electric field domain in bulk semiconductor

Abstract: The invention disclosed is for a method and apparatus for controlling high electric field domain in a bulk semiconductor as well as an information processing method thereby. By means of a capacitive electrode, the high electric field domain may be either sustained or extinguished.

Process and apparatus for measuring the composition of fluid plastics

Abstract: 1. A PROCESS FOR DETERMINING THE PROPORTION OF MONOMERS IN A COPOLYMER, WHEREIN THE MONOMERS HAVE DIFFERENT DIELECTRIC CONSTANTS, SAID PROCESS COMPRISING CONTACTING A CAPACITIVE DETECTOR RESPONSIVE TO THE DIELECTRIC CONSTANT OF FLUIDS WITH A FLUID STREAM OF SAID COPOLYMER IN A ZONE OF RELATIVELY CONSTANT TEMPERATURE AND PRESSURE, MEASURING THE CAPACITANCE OF THE CAPACITIVE DETECTOR WHILE IN CONTACT WITH THE FLUID STREAM AND COMPARING THE VALUE OF THE CAPACITANCE SO MEASURED WITH A PREDETERMINED REFERENCE VALUE. D R A W I N G

Capacitive type ignition arrangement for internal combustion engines

Abstract: Energy from a storage capacitor is transferred to an ignition capacitor when a first switch is made conductive, and the spark is initiated by discharge from the ignition capacitor through the ignition transformer upon closing of a second switch. The current limiting element between the storage capacitor and the ignition capacitor is an inductance.

Fluorescent lamp idling circuit

Abstract: A circuit is described for operating a fluorescent lamp at a low power consumption idling level. The circuit provides a capacitive impedance in series between the fluorescent lamp and an AC supply. The capacitive impedance is selected to reduce the current flow through the lamp to a low idling level, yet full illumination may be quickly and reliably restored by effectively removing the capacitive impedance.