Abstract: Field implantable and laboratory sensors for the measurement of moisture in soil based on the increase of soil dielectric permittivity with volume fraction of water were developed. A typical sensor consists of a case containing a high-frequency (31-MHz) oscillator whose frequency determining resonance LC network is coupled to the built-in electrode via a capacitor T network. Increases in moisture cause a shift in the resonance frequency, which is detected by an external differential frequency counter or readout. The T network and electrode electronic switches reduce the undesirable influence of soil conductivity on the frequency shift. Although the sensor contains active elements, it acts as a passive transducer since power is supplied to the sensor from the readout unit through the two-conductor cable which transmits the RF.

Abstract: A method and implementing apparatus for measuring in situ the electrical capacitance and resistance of soils and determining therefrom the density and fabric thereof. The apparatus includes a self-contained probe adapted to be driven into the soil to be measured. The probe has a soil sensor element and a measuring circuit such as a capacitance and resistance bridge. The measuring circuit employs radiofrequency current to enable direct measurement at the probe of the resistance and capacitance of the soil sample and of the pore liquid. A remote indicator and control unit in communication with the probe is provided with indicators such as meters or displays which provide direct readout of measured resistance and capacitance, and which may also enable the bridge in the probe to become balanced. Alternatively, the probe may include a computer for automatically balancing the bridge and calculating critical soil properties. The apparatus can automatically register such engineering properties as density, porosity, friction angle, elastic and secant modulus, coefficient of dynamic settlement, stress ratio required to cause liquefaction, and permeability coefficient. The probe and measuring equipment can, alternatively, be manually balanced and the engineering properties and related properties can be hand calculated. The concept outlined and apparatus can be extended or modified for a wide variety of other uses also.

Abstract: Capacitance measuring device for measuring a physical quantity proportional or inversely proportional to the capacitance X of a first capacitor. A oscillating circuit includes a second capacitor having a reference capacitance X E or the first capacitor during successive reference and measuring phases under control switching network respectively. A counter counts a predetermined oscillation pulse number N E during the reference phase and a oscillation pulse number N X during the measuring phase. The duration of two phases are equal or in a predetermined ratio R by means of a counter-down-counter which counts and down-counts the same number of clock pulses at least a predetermined frequency. The change of the counting to down-counting condition is controlled by the counter when its count is equal to N E . The stopping of the counter is controlled by the counter-down-counter when its count is equal to zero at the end of the measuring phase. A displaying and computing unit computes the physical quantity in dependence on the capacitance value X=(N E X E )/(R N X ) which is not affected by the drifts of device components and interference capacitances.

Abstract: Digital circuitry for use primarly in measuring the volume of gasoline in an automobile fuel tank. A measurement capacitor is mounted in the fuel tank to have its capacitance vary with the level of gasoline in the tank and forms part of a multivibrator circuit the repetition rate of which is consequently varied in an inverse manner with the capacitance of the measurement capacitor. Pulses generated in the multivibrator are fed to a counter coupled to a resetting circuit which is triggered by an output of this counter when a predetermined number of the said pulses has been counted so that a train of resetting signals are generated separated by intervals the length of which is a measure of the capacitance of the measurement capacitor. Further pulse generating means of fixed repetition rate is gated by the resetting signals and the resultant batches of pulses supplied to a digital display device which displays a reading representative of the number of pulses in each of the said batches, so that the display number is dependent on the capacitance of the measurement capacitor and hence on the level of gasoline in the tank. The capacitor is so shaped and arranged that the capacitance thereof is determined by the fuel level is representative of the volume of fuel in the tank.

Abstract: An absolute measurement of loss angle has recently been completed at NBS. The measurement utilized a special toroidal cross capacitor in which the effects of dielectric films are greatly attenuated. The resulting unit of loss angle has an estimated uncertainty of 0.02 ?rad at an optimum frequency of 1592 Hz.

Abstract: A semiconductor tunable capacitor is described. This tunable capacitor employs a plurality of metal-insulator-semiconductor (MIS) capacitive segments and each element has a first and a second value of capacitance. The solid state capacitor employs a plurality of tuning terminals and a single capacitor terminal. Tuning signals are applied to each of the tuning terminals for switching that capacitive segment into its high or low capacitive state. The capacitor terminal is capacitively connected to each capacitive segment and is employed for summing the individual values of capacitance into a total value of capacitance. An MNOS capacitor is shown as the preferred embodiment.

Abstract: An electrical length-measuring system comprises two capacitors and electronic means for obtaining an indication voltage proportional to the displacement. The measuring capacitor, whose capacitance is varied in a linear manner by the displacement to be measured, is connected to a reference a.c. voltage, whilst the reference capacitor with the same dielectric is connected to a measuring a.c. voltage of the same frequency and opposite phase, whose amplitude can be varied by electronic means in such a way that the a.c. voltage induced on an electrode common to both capacitors becomes zero, forcing the measuring a.c. voltage to be proportional to the displacement. Preferably the capacitance change of the measuring capacitor is brought about by an earthed screen inserted between both electrodes. In the system specifically described and illustrated, the measuring capacitor comprises two coaxial cylindrical electrodes and a coaxial cylindrical screen is inserted axially between the electrodes as a function of the displacement. In the described and illustrated system also, the a.c. voltages are of a rectangular nature, making it easy to eliminate errors due to transient couplings.

Abstract: A film flaw detection system has capacitive sensing members for sensing capacitance changes in correspondence with irregular film variations. The sensing members take two forms. One form senses variation in film thickness by using the film as a dielectric between two plates of the capacitor. Changes in film thickness result in changes in the dielectric and hence in the capacitance. The other form consists of feelers which ride along the surface of the film and which move transversely to the film movement in response to flaws in the film. Each feeler forms a plate of a capacitance, and movement of the feeler changes the distance between this plate and an associated fixed plate which results in a capacitance change. The detecting circuit comprises a phase detection system for measuring phase changes in a high frequency signal. These phase changes correspond to capacitance changes caused by flaws in the film and sensed by either of the two forms of sensing means.

Abstract: An antenna tuning circuit of the type having a first variable capacitance diode connected in parallel with a coil to form a resonance circuit and a second variable capacitance diode through which the resonance circuit is connected to an antenna, in which the connection position of the first variable capacitance diode to the coil is adapted to be changed for the reduction in the image interference ratio. Reductions in the maximum capacitance and the ratio between the maximum capacitance and the minimum capacitance required for the variable capacitance diodes are also intended by the connection of a third variable capacitance diode to the antenna side of the second variable capacitance diode.

Abstract: An electrical capacitor is formed which relies on a thin dielectric layer which is metallized on both sides to provide electrode areas to provide the major part of the capacitance of the capacitor. An unmetallized margin area runs along one side of the dielectric layer along one longitudinal edge of the dielectric layer and an unmetallized margin area runs along the other side of the dielectric layer along the opposite longitudinal edge dimension of the dielectric layer. A pleated capacitor section is formed by pleating, or folding, the dielectric layer along its longitudinal dimension. This pleated capacitor segment is incorporated into an initial portion of the capacitor formed of two metal foil electrodes and a separating dielectric layer which are wound about the leads of the capacitor.

Abstract: A pressure-sensing capacitor and a method for trimming the capacitor is disclosed. The capacitor includes a pair of spaced flexible parallel quartz plates. A thin circular layer of conductive metal is formed on the opposing inner surfaces of the plates to define the electrodes of the capacitor. A glass frit sealing compound, forming a concentric ring about the conductive layers, is disposed between the plates to seal the evacuated space between the plates. The thickness of the ring is small enough so that the capacitance between the electrodes is higher by an unknown amount than the desired value of capacitance at every point in the range of variation of the value of pressure. The capacitor is trimmed by first measuring the capacitance value at zero pressure and also at a maximum pressure. The size and location of a path on one of the electrodes is computed from the measured capacitance values and the deflection characteristics of the plates. A point on the inner surface of one of the flexible plates moves a maximum perpendicular distance towards the other plate under pressure. That point defines a maximum deflection point along a deflection axis perpendicular to the inner surface at the maximum deflection point. Radiant energy in the form of a laser beam is applied to the electrode to cut through the electrode along the computed path which is closed on itself to define a disc eccentrically spaced a calculated distance from the deflection axis so that the value of capacitance at zero and the maximum pressure is substantially equal to the desired values.

Abstract: The device positions tools, workpieces and machines. It consists of a mechanical and electrical part. A shaped piece of dielectric (3) is moved by the monitored object between plates (1, 2) of a first capacitor (5) connected to a transformer (B) secondary winding (2B) whose end is connected to the end of a further secondary winding (3B). The secondary winding (3B) is connected to a second fixed capacitor (4). Both windings are balanced, and the primary winding (1B) is connected to an oscillator (A). The junction point between the two secondary windings (2B, 3B) is connected to an amplifier (C), a rectifier (D) and a digital display unit (E).

Abstract: A monitoring circuit for monitoring a plurality of signals developed by remote sensors which preferably are capacitance probe sensors. The circuit is intended for use with a motor vehicle maintenance system employing capacitance probes to detect low and safe levels of oils and coolants in a vehicle engine. The monitoring circuit includes a constant voltage source with a voltage divider in circuit therewith to develop a plurality of reference voltage signals of predetermined values which are applied to respective inputs of a plurality of voltage comparators that receive, at their other terminals, condition-responsive voltage signals generated by a condition sensing circuit. The condition sensing circuit comprises a liquid level capacitance probe which generates intermediate, high and low voltage signals indicative of safe and low, respectively, levels of sense liquid. Open or shorted leads in the sensing circuit generate zero and maximum voltages, respectively, which are also applied to comparator circuits, whose outputs activate visible indicators to register safe and unsafe liquid level, and shorted or open sensing circuits.

Abstract: A ceramic trimmer capacitor comprising a cylindrical casing, a stator and a rotor comprising a rotor casing and a dielectric assembly consisting of a disk-shaped ceramic dielectric member, a semicircular dielectric layer formed upon the upper surface of the dielectric member and having a low dielectric constant less than 20 and a coefficient of thermal expansion substantially equal to the dielectric member and a rotor electrode formed on the whole surface of the dielectric member including the semicircular dielectric layer, the dielectric assembly being inserted into the rotor casing and electrically and mechanically connected thereto; the stator and the rotor being placed in the cylindrical casing and resiliently supported. Stray capacitance is almost negligible; the variable capacitance range may be considerably improved; and the mechanical strength may be increased. The ceramic trimmer capacitor is especially adapted to be used in an electronic watch.

Abstract: The capacitance of an unknown capacitor is determined by counting the cycles of a known frequency contained within a time gate whose time duration is determined by subtracting a gate whose length is equivalent to the stray measuring capacitance from a gate whose length is determined by the capacitance of the unknown capacitor plus the unavoidable stray measuring capacitances

Abstract: The circuit has a first variable capacitance diode (C1) in parallel with a coil (L) and forming with it a resonant circuit, and a second capacitance diode (C2) connecting the coil (L) to the aerial (ANT). Its capacitance is controlled together with that of the first diode (C1). One coil (L) terminal, together with first capacitance diode (C1) terminal is earthed through a large capacitance capacitor (CE). The tuning voltage is collected from the capacitor two terminals. The resonant circuit parameters are such, that the frequency corresponding to the tuning voltage minimum coincides with a mirror frequency to be eliminated.

Abstract: A capacitive level meter has a first measurement capacitor immersed in the fluid measured, an oscillator producing an electrical output corresp. to the fluid level, and a compensation circuit for different fluid dielectric constants. It gives extremely accurate level indications yet is very economical to produce. Two compensation capacitors of equal capacitance have the medium and air as dielectric respectively. A second measurement capacitor has the same capacitance as the first measurement capacitor when it is completely surrounded by air as the dielectric. The fluid height is the ratio of the second compensation and measurement capacitances multiplied by the ratio of the differences between the measurement and compensation capacitances. The capacitances are measured by charging them and then measuring the discharge time using pulsed signals.

Abstract: When breakdowns occur between the electrodes of a capacitor the dielectric is plastically deformed or its melted by the heat generated by the discharge. Possibly an additional dielectric is provided. The capacitor body is provided on at least its lateral surfaces with a first metal layer. There is an insulating layer which melts or which is at least plastically deformed when overheated, and a second metal layer. Each metal layer is connected to a capacitor electrode, and the capacitor is provided with an internal fuse.

Abstract: A device comprising an electron tube having two electrodes between which a potential difference generated by a high voltage generator exits. A protection circuit is connected between these electrodes to protect the device against excess voltages. The protection circuit consists of a series network of a capacitor having a capacitance which is substantially higher than the parasitic capacitance beween the electrodes and a number of diodes whose forward direction extends from the electrode of highest potential to the electrode of lowest potential.

Abstract: In a relaxation oscillator having its frequency determined by the charge rate of a capacitor, a switch means is controlled through a field effect transistor to discharge the capacitor at a predetermined charge level when channel current through the FET is reduced as voltage across the capacitor approaches the voltage supply level. The charge rate of the capacitor is substantially unaffected by the FET and substantially no power is drawn to control the switch means while the capacitor is charging. The duty cycle of the output level may be readily controlled in this oscillator without substantially affecting the low power attributes thereof.

Abstract: Thick-film capacitors have been fabricated on aluminium metal plate and metallized glass plates using dielectric paste type 780 supplied by Transene Company Inc, USA and two-component silver-filled conducting paste type H20 supplied by Epo-Tech, USA. Their dependence on temperature, voltage and frequency has been studied The temperature co-efficient of capacitance showing a pronounced minimum with capacitance has been observed to decrease with rise of linear co-efficient of thermal expansion of the substrate material and shifts to a higher capacitance value. The capacitance has also been found to be independent of frequency and voltage.