Showing papers on "Capacitive sensing published in 1975"

On the theory of self-resonant grids

Abstract: An approximate theory is developed to predict the frequency response of a self-resonant grid. The grid is comprised of capacitive and inductive elements and exhibits a band-stop resonance. The analysis is based upon the derivation, from physical considerations, of an equivalent circuit representation of the grid structure. Predicted results compare well with measured data.

Inductor-capacitor hybrid

Abstract: A 4-terminal component whose characteristics are determined by both inductive and capacitive mechanisms is analysed. Equations and normalised curves are presented which describe the input/output relationships for various load impedances. Experimental verification is reported, and the internal working of the device is described. Attention is drawn to properties and applications of the hybrid.

Level detector using oscillator circuit with two capacitive probes

Abstract: This invention relates to a device for detecting a fall of level of flowable material in a closed container by emitting an oscillation. It is electronic in nature and the circuit has an amplifier with a feed-back terminal that is connected to a feed-back network. The feed-back network in turn includes two vertically spaced apart identical probe condensers each having an open dielectric space and each being in different feed-back paths of the feed-back network. The feed-back network is activated as the level of the flowable material drops, whereby the difference in the dielectric material of the condensers provides a change in input current to the amplifier. The circuit is responsive to a positive change in input current to cause the amplifier to commence oscillation on dropping of the level past the condensers to signal the drop of the level of the flowable material. The device is stable in design, low in cost and easy and reliable to use. In particular it requires no adjustment with variations of flowable material.

Nondestructive Measurement of Complex Permittivity for Dielectric Slabs (Short Papers)

Abstract: A method has been developed for the precise nondestructive measurement of the dielectric constant and losses of slab-like samples such as microstrip substrates, for instance Basically, the test setup consists of an open-ended rectangular waveguide, the flange of which is placed in contact with one side of the dielectric material, the other one being backed by a metal plate The waveguide can be either simply cut at its end, or terminated by an inductive or capacitive iris The reflection characteristics or the resonance parameters are related to the real and imaginary parts of the permittivity by means of computer-generated charts or an optimization program

Capacitive voltage converter employing CMOS switches

Abstract: A CMOS circuit for approximately tripling battery voltage particularly adaptable for use with liquid crystal displays such as used in watches. P-wells of the CMOS circuit are coupled to active circuit nodes rather than to battery potentials. In the presently preferred embodiment a hybrid circuit with external capacitors is used to increase overall efficiency.

Differential capacitive position encoder

Abstract: Circuits and structures are arranged to serve as encoders, emitters, or switches by capacitive coupling.

Dual channel dynamic line isolation monitor

Abstract: A line isolation monitor for indicating the maximum hazard current in an ungrounded power distribution system with conductor lines having leakage impedances. A signal proportional to the maximum voltage to ground of any of the conductor lines in the system is determined and used as a reference voltage for the monitor. Separate circuits each responsive to the reference voltage generate respectively a capacitive component signal and a resistive component signal which are combined and applied as a measurement signal across the system leakage impedances in parallel. The impedance voltage response to the measurement current is separated from the line voltage signal, phase shifted and compared to the reference voltage signal to produce a difference signal which is used to control the magnitude of both the capacitive component signal and the resistive component signal. The magnitude of the combined capacitive component signal and the resistive component signal represents the maximum hazard current.

Capacitive humidity transducer

Abstract: A capacitive humidity transducer wherein an electrically non-conductive base carries at least a pair of electrically conductive coatings which are spaced from each other. A dielectric film which is active with respect to water absorption is also carried by the base and covers at least portions of the coatings, the dielectric film having a dielectric constant the value of which varies as a function of the extent to which water has been absorbed by the dielectric film. An outer electrically conductive, water-permeable layer is carried by the dielectric film with this film being situated at least in part between the coatings and the layer while the latter because of its water permeability permits moisture in the atmosphere to reach the dielectric film. The dielectric film maintains the outer layer permanently out of contact with at least one of the coatings, so that it is possible to measure between these coatings a capacitance which will be indicative of atmospheric humidity.

Method and a device for capacitive level measurement

Abstract: Capacitive level measurement apparatus comprising two sets of interdigitated capacitive elements arranged along the vertical direction for immersion in a liquid or the like, and a switch arrangement with external connections which provide sequential measurement of the electrical capacity between successive pairs of adjacent capacitive elements, from which information the level of the liquid is determined. Preferably the switches are inside an assembly of the capacitive elements, and special means are preferably used to effect the desired sequential switch actuation.

Controlled capacitive filter for active loads

Abstract: A single phase controlled capacitive filter with a smaller, more efficiently used filter capacitor than conventional capacitive filters is connected between rectifier terminals and supplies voltage to an active load producing dc output voltage. The charge and discharge intervals of the filter capacitor are controlled by gate controlled thyristors or other devices such that discharge occurs when the instantaneous rectified line voltage falls below the dc output voltage. The filter capacitor during discharge is placed in series with the load or can remain in parallel with the load in a simpler arrangement.

Noise suppression filter

Abstract: A two line power filter for digital equipment or the like comprising a pair of toroidal cores on both of which both wires are wound, on one in flux adding relationship and on the other in flux opposing or cancelling relationship in reference to the primary power supply, together with capacitive shunts between the wires and from the wires to ground to filter out both common mode and differential mode noise.

Transducer array having low cross-coupling

Abstract: An array of circular, acoustic projecting and receiving transducers is deibed, including a stainless steel baffle plate in which the transducers are mounted, each comprising a stainless steel cup containing a disc-shaped piezoelectric element set in low impedance material and covered by a water impedance matching window. Capacitive and inductive tuning means is provided between each receiving transducer and its associated electronics.

Electrical component for providing integrated inductive-capacitive networks

Abstract: An integrated electrical component is provided which functions as an inductive-capacitive network, and which may be used, for example, to form a filter, transformer, or the like. The component includes distributed capacitance and inductance with external connections to permit a variety of distributed element configurations, which results in the elimination of spurious electromagnetic radiation from the component and in the packaging of a multiple-pole filter in an extremely compact configuration, so as to provide a variety of filter networks, or the like, each of high quality factor (Q). The component comprises one or more sheets of dielectric material formed, for example, of a ceramic, and having one or more conductive sheets positioned on each dielectric sheet. The resulting assembly is turned into a spiral configuration, as will be described, to form the component, and the resulting assembly is then cured.

Nonvolatile semiconductor memory

Abstract: A nonvolatile random access memory array comprising variable threshold insulated gate field effect transistor devices is described Each memory element is comprised of a variable threshold field effect gate region located adjacent to a single sensing diffusion which is used to sense change in electrical potential of the sensing diffusion as the effective capacitance of the diffusion is coupled into a depletion region under the gate electrode during a READ cycle Information is written into the memory by selectively applying a field in excess of a critical magnitude across the variable threshold dielectric to cause the device to assume a high or low threshold state To read information out of the memory, an inversion region extending from the sensing diffusion under the gate region is used to effectively switch, or reconfigure, the equivalent electrical circuit of the device to alter the capacitive loading presented by the device to the sensing diffusion depending upon whether the device is in a high or low threshold condition Various gate structures for improving the sensitivity of the memory are disclosed along with a single or multiple pulse sensing scheme which increases sensed voltage and reduces fatigue problems usually associated with conventional variable threshold semiconductor devices

Twin-capacitive shaft angle encoder with analog output signal

Abstract: A precision capacitive shaft encoder providing a d-c signal corresponding to the angular position of a shaft Two variable capacitances are coupled in tandem by a rotatable shaft Each capacitor has a capacitance that varies linearly with a change in the angular position of the shaft, and the sum of the two capacitances is always constant for any angular position of the shaft Each capacitance is alternately coupled to a reference d-c voltage and a discharge circuit The capacitances are electrically coupled in series and the charge periodically acquired at the junction of the capacitances is a function of the position of the shaft An error-compensating voltage is imposed on the junction when the capacitances are coupled to the reference voltages, and the junction is coupled to sample-and-hold apparatus provided with a error-correcting circuit

Capacitor memory cell

Abstract: A dynamic capacitive memory cell having a storage node formed at the common junction of a fixed access capacitor and two MOS voltage variable capacitors. Data represented in the form of stored charge is written into the storage node through the fixed access capacitor under control of one of the MOS voltage variable capacitors and read out of the memory cell by a sensing device connected between the other voltage variable capacitor and ground. In another memory cell, one of the MOS voltage variable capacitors is replaced by an MOS transistor for preventing excess charge accumulation at the storage node.

Motor driven magnetically coupled variable capacitor

Abstract: A motor driven magnetically coupled variable capacitor including a follower magnet arranged internally of the capacitor and fixedly coupled to a rotatable shaft, a follower magnet drive magnetically coupled to the follower magnet for rotating the follower magnet and therefore the rotatalbe shaft, a plurality of stationary capacitive elements fixedly mounted at one end of the capacitor, and a plurality of movable capacitive elements mechanically coupled to the rotatable shaft for axial movement therealong in response to rotation of the rotatable shaft by the follower magnet. The movable capacitive elements coacting with the stationary capacitive elements to vary the capacitance of the capacitor in response to activation of the follower magnet drive.

Trielectrode capacitive pressure transducer

Abstract: A capacitive transducer and circuit especially suited for making measurements in a high-temperature environment. The transducer includes two capacitive electrodes and a shield electrode. As the temperature of the transducer rises, the resistance of the insulation between the capacitive electrode decreases and a resistive current attempts to interfere with the capacitive current between the capacitive electrodes. The shield electrode and the circuit coupled thereto reduces the resistive current in the transducer. A bridge-type circuit coupled to the transducer ignores the resistive current and measures only the capacitive current flowing between the capacitive electrodes.

Stylus for capacitive videodisc

Abstract: An alumina body having a conductive coating with a smooth surface, is made up of a conductive layer and a cementing layer sandwiched between the conductive layer and the surface of the alumina. The thus coated alumina body can advantageously be used e.g. for a pickup stylus for a video disc playback system of the capacitance variation type.

Compensated voltage divider

Abstract: A voltage divider comprising a coaxial array of spaced parallel, capacitive plates connected to one another by respective resistive elements disposed between the plates.

Compensated probe for capacitive level measurement

Abstract: A capacitive probe for measuring fluid level has two electrodes, each of which forms a capacitor with a supporting conductive body. The first electrode is a vertical band which will yield a capacitive value dependent upon the dielectric constant, conductivity, as well as level of the fluid. The bulk of the second electrode is arranged at the lower end of the supporting body totally immersed in the liquid, and will yield a capacitance based on the dielectric constant and conductivity of the liquid, but substantially not the level of the liquid. A value indicating the liquid level independent of dielectric constant and conductivity may be obtained from the two capacitive values of the electrodes.

Time-effect changes in the dielectric properties of Mo03 under the influence of a DC voltage superimposed on the AC measuring voltage

Abstract: The conductivity of polycrystalline specimens of Mo03, measured using AC voltage, changes very considerably under the influence of superimposed d.c. voltage: this change is time-dependent. In some circumstances the change in conductivity is sudden and as great as several orders of magnitude, so that the impedance of the specimen of Mo03 changes its character from capacitive to almost pure resistive. This can be regarded as corresponding to some kind of switching process in the material, caused probably by carrier injection from electrode to material under the influence of space charge built up by carrier drift in the applied d.c. field.

Suspension measuring device for concentration of solids - has capacitive sensor whose permittivity depends on concentration of particles

Abstract: An a.c. voltage is applied to the sensor capacitance, and a meter displays a value corresponding to the permittivity change. The a.c. voltage is applied to the sensor capacitance in series with a resistor whose resistance is low in comparison with the capacitance reactance and the voltage drop across the resistor is displayed. The other end of the resistor is earthed, and the a.c. voltage source has an internal resistance which is low in comparison with the reactance of a capacitance unit. The capacitance leads are in the form of separate coaxial cables.

Level measurement and control

Abstract: Method and arrangement for measuring and controlling the level of a fluid in a container. The conductivity of the fluid is measured by means of a detector and a high-frequency voltage supply. The detector operates on a capacitive or on an inductive basis. Means for eliminating the effect of the size of the container and of the transfer functions of the detector and, in the control arrangement, the pump.

Instrument for sensing level of granular materials

Abstract: A cylindrical housing contains both a circuit board and a pair of capacitive sensing electrodes. The pair of electrodes are adjacent the inside wall near an end that is to be wholly or partly covered with granular material in a container. Since an electric field is relatively concentrated about the electrodes, compared with the divergent field about the type having a single protruding electrode and depending on external ground planes, the circuits of the instrument show presence of material repeatedly quite close to a predetermined level. The unitary construction affords protection and permits the capacitive sensing electrodes to be mounted on the circuit board over a printed circuit tab.

High tension ignition test system - has two capacitors in series to form capacitive tension divider

Abstract: The test equipment consists of a metal cover to surround a small length of the cable to be tested so as to form a capacitor. A second capacitor is connected inside the switch box to the metal cover on one side and by a screened lead to the earth. The two capacitors form a potential divider whose tap off point is permanently fixed to the test apparatus. The switch box is provided with a screen whose ends are sprung over the cable and provide a set gap to screen interferences. The screen has a coated protective layer. The second capacitor has a capacitance 1 to 5 X 103 greater than that of the first capacitor.

Capacitive HF proximity switch - has HF oscillator and capacitive sensor whose capacitance to earth changes when object approaches

Abstract: The object to be detected is non-metallic, and the sensor capacitance change is evaluated to determine the distance of the object. An amplitude stabilised oscillator is connected to an h.f. transformer with two symmetrical output windings; one terminal is connected to the sensor or to a reference sensor, and the other to a capacitance current or voltage converter, whose outputs are connected to a difference forming stage. The two output windings have tappings forming the other terminals, and the other winding ends are earthed through neutralising capacitors; capacitances to earth of the reference sensor and of the test sensor are approx. equal.

Local oscillation circuit for tuner having reduced inter-channel deviation in AFC sensitivity

Abstract: A local oscillation circuit for a tuner having a reduced inter-channel deviation in AFC sensitivity. The local oscillation circuit comprises a resonance circuit capable of varying a tuning frequency by means of a variable capacitive element additionally provided with a variable capacitive diode which is applied with a control voltage in dependence upon variation in the frequency detected from the output signal of the tuner, thereby to effect an automatic frequency control. A single variable capacitive diode is coupled to the variable capacitive element of the resonance circuit in a parallel and a series connections.