Abstract: Disclosed is a monitoring system and method for detecting the presence or absence of material at a location. The apparatus may generally be constructed to include a sensing unit, including an antenna probe for positioning at the location wherein material is to be detected, and a control unit for responding to signals from the sensing unit indicating the presence of material at the antenna probe. The control unit may include an indicator to inform an operator of the presence or absence of material at the antenna probe, and also an output which enables peripheral equipment to operate only under selected conditions at the antenna probe. The sensing signal from the sensing unit is dc, with fluctuations indicating the presence of material at the antenna probe.

Abstract: A dielectric compensated level indicator control system including a microprocessor that controls the height and therefore the amount of a substance, such as fluid or granular solid, to be contained in a closed or open tank or vessel. The system has a measurement probe whose capacitance is a function of the level of substance in the tank and a reference probe whose capacitance is a function only of the dielectric constant of the substance. The appropriate zero capacitance is subtracted from each probe capacitance and a ratio between the resulting difference capacitances is determined. This ratio is independent of the dielectric constant of the substance and represents the percent fullness of the tank. When substances with different dielectric constants are placed in the vessel no span recalibration of the probe is required. A single transmitter is used to transmit along a single transmission channel a single signal which represents the capacitance of both probes.

Abstract: A liquid level height within a tank is measured by means of an elongated multi-segment capacitance probe that includes a column of capacitors extending through a liquid level interface. Each capacitor of the probe is sequentially measured in response to microprocessor controlled instructions as part of a measuring unit located at the tank. Up to sixteen measuring units may be interconnected in a field and individually connected to a microcomputer system at a central station. The microcomputer system addresses each of the measuring units and sends a select signal to the microprocessor controller of the measuring unit to sequentially measure each capacitor of the probe. By identifying the capacitor at the liquid level interface, the height of liquid within a tank is computed by the microcomputer system. From this height measurement and stored tank data, the volume of liquid within a tank is calculated.

Abstract: The output of a capacitance fuel sensor is supplied to two switches that are controlled by a switching control unit. The two switches are opened and closed in synchronism and antiphase with one another, and in quadrature with the drive voltage applied to the sensor. The output of one switch is supplied to the input of a first integrating current-to-voltage amplifier which in turn supplies a signal representative of fuel quantity to a fuel indicator. The output of the other switch is supplied to another integrating current-to-voltage amplifier which in turn supplies a signal representative of the quantity of contaminants to a contaminant indicator.

Abstract: A sensor for capacitively measuring the level of material in a container where the sensor extends through an opening in the container and is connected to measuring circuitry. The sensor includes an electrically conductive, tubular member aligned with the opening. An elongated electrically conductive member is in electrical contact with the circuitry and projects through the container opening and the tubular member such that a space is established between the elongated conductive member and the tubular member so that they are electrically insulated from one another. The space is sealed to prevent entry of moisture therein.

Abstract: A hollow probe which is adapted to respond to the degree to which a pipe is filled with fluid includes the use of a tubular conductive probe measuring electrode and a pair of tubular conductive guard electrodes axially displaced from the probe electrode. The tubular electrodes are hollow and are adapted to form a fluid conducting portion of the fluid-carrying pipe. The probe electrode and guard electrodes are separated by solid insulation. The guard electrodes are separated from sections of the pipe on either side of the hollow probe by solid insulation. The guard electrodes are exposed to the contents of the pipe and, by driving the guard electrodes at substantially the same potential as the probe electrode, the adverse effects of a coating of fluid adhering to the probe are substantially eliminated.

Abstract: In a device for the electric measurement of the level of a liquid in a container, particularly in the gasoline tank of a vehicle, a support developed as protective tube of a conductor foil is fastened for swinging against the force of a spring (14 and 21) to the top of the container. In order to be able to arrange the support even in containers in which the point of attachment of the support is lower than the highest level to be detected, the support is subdivided into three approximately rigid sections, (2, 3, 5) each two sections (3, 5) being articulated in the manner of a toggle joint to each other and being under spring action. In this way the outermost section (3) is swung, substantially independently of the inside height of the container, on the one end towards the bottom (4) and on the other end towards the top (1) of the container.

Abstract: A device for electrically measuring the level of a liquid in a container has a protective tube (1) in which a conductive foil (5) is arranged untwisted. The protective tube (1) is made of two tube sections (2, 3) which are connected to each other by a joint (4). The joint (4) has a well-defined direction of bend as a result of reinforcing ribs (14, 15). This direction is such that the protective tube (1) can be bent only transverse to the plane of the conductive foil (5). The joint (4) is furthermore so developed that the tube sections (2, 3) are urged into a position in which they are aligned with respect to each other. In this way the device can be installed in a container in such a manner that the lower tube section (3), while forming an obtuse angle with the upper tube section (2), has its bottom end resting against a container bottom (16).

Abstract: A device for the electric measurement of the level of a liquid within a container has a protective tube (1) within which a conductive foil (2) is helically arranged. The conductive foil (2) is wound with such a pitch that sufficient space remains between its longitudinal edges (3, 3') to provide a helically extending flexible protective-tube region (16, 16') within the protective tube (1). This protective-tube region has inwardly and outwardly directed U-shaped tube sections (17, 18, 19). As a result of this development the protective tube (1) bends exclusively in those regions which are located between the longitudinal edges (3) of the conductive foil (2).

Abstract: An AC signal source having constant frequency-amplitude product is also easily realizable in hybrid microcircuit form. A square wave oscillator output is rectified and clamped to a feedback control voltage. The resulting controlled amplitude square wave is low-pass filtered to produce a sinusoidal output signal which is typically amplified and applied to a variable-impedance load. The sinusoidal signal is also applied to a similar but simulated load of fixed impedance value and the current flowing through the simulated load is summed with a temperature-compensated reference current producing an error current which is then integrated to produce the feedback control voltage which controls the amplitude of the sinusoidal signal so as to maintain a constant frequency amplitude product.

Abstract: A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a function of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a predetermined level of material for indicating material level as a function of a difference between capacitance at the probe and the reference signal. In the preferred embodiments of the invention disclosed, an automatic calibration circuit adjusts the resonance characteristics of the parallel resonant circuit of the reference signal indicative of a predetermined reference material level.

Abstract: An improved sectionalized capacitive level gauge is provided. A screen member having appropriate openings therein is positioned between a set of sectionalized first members and a second member of a capacitive level gauge.

Abstract: The capacitive sensor has a tubular plastic housing (10) which is closed at the front end and which consists of a tubular body (11) and a cup-shaped cap (12). In the cap (12) a pot-shaped sensor electrode (13) and a tubular guard electrode (14) are disposed. The tubular body (11) contains an electronic circuit (20) and a tubular shield electrode (15). The tubular electrodes (14, 15) are impact-resistant metal tubes, preferably of steel, and the pot-shaped sensor electrode (13) is an impact-resistant metal member, likewise preferably of steel. Between the electrodes (13, 14, 15) elastically deformable spacer members (16, 17) are inserted. For assembling the sensor the sensor electrode (13) and the guard electrode (14) with the spacer (16) disposed therebetween are arranged in the cap, and the shield electrode (15) is introduced from the front into the body (11) up to a stop (24) disposed in the body (11).

Abstract: A capacitance probe and method of probe manufacture for material level sensing systems and like applications. The probe includes a probe rod, a tubular guard coaxially surrounding the rod intermediate the rod ends, and insulation material formed as an integral piece in an injection molding operation surrounding the rod between the rod and guard and also surrounding and radially overlapping axially spaced ends of the tubular guard. One end of the rod and a portion of the guard intermediate its ends are exposed through the insulation material. The molded assembly is captured within a nipple or the like for mounting to a material vessel such that the exposed surfaces of the rod and guard are disposed internally of the vessel for capacitance coupling to material therewithin.

Abstract: A microwave probe for measuring the amount of soot or water in engine crankcase oil and/or detecting the level of oil comprises a coaxial cable having a tip including five substantially parallel wires shorted together at one end and connected at the other end to the coaxial cable, one of the wires being connected to the center wire of the coaxial cable and the other four wires being connected to the sheath of the coaxial cable. The size and geometry of the wires is selected so that the impedance of the tip when immersed in oil substantially matches the impedance of the coaxial cable.

Abstract: A fuel gaging system of the type wherein the capacitance of a probe (20) within the fuel tank is used as an indication of fuel quantity via an assumed density/dielectric constant relationship (10) of the fuel. System accuracy is improved by directly measuring fuel density and dielectric constant. These values are compared with the assumed values in a processor (68) which generates an appropriate gaging correction signal in response to a discrepancy.

Abstract: A fuel gauge includes a stationary capacitor located within a fuel tank in such a manner as to be partially immersed in the fuel so that the capacitance of the capacitor varies with the level of fuel. A measuring device determines the capacitance of the capacitor to measure the level of the fuel or the amount of fuel remaining within the tank.

Abstract: A level control apparatus is disclosed for controlling a liquid level between a maximum and a minimum. An elastic circuit generates a reference pulse which receives the pulse and triggers the generation of first and second reference pulses. The first reference pulse has a width which corresponds to the function of the maximum level of liquid and the second reference pulse has a width which corresponds to the function of the minimum of liquid. A capacitance probe supplies an output to a level sensing means which generates an output control pulse which varies in time with respect to the liquid level.

Abstract: A method and apparatus for calibrating a liquid level measurement system of the type having capacitive sensors, by simulating the electrical effects of sensors in an empty condition and their interconnecting cables, at a time when the sensors are full or partially filled. By a sequential balancing technique, using a conventional bridge circuit, a precision, highly stable variable impedance device is adjusted to individually simulate the effects of each sensor and cable combination with the sensor in an empty condition. The settings of the variable impedance device are recorded, and at a later time when the sensors are no longer empty, these settings are reproduced, so as to recreate the electrical effects of each sensor cable combination one at a time. The individual effects are separately transferred into a network having a plurality of variable impedance channels, until each channel simulates the effects of a corresponding sensor and cable.

Abstract: A method and apparatus for pre-calibrating capacitive-type fuel quantity probes is proposed in which a voltage divider excitation source is connected to the low impedence electrode of the probe and is used to trim the apparent capacitance down to within a small tolerance of .+-.0.1% of the precise design value for the probe.

Abstract: A fuel-gauging system has a capacitive probe mounted in a fuel tank and supplied with an alternating voltage V.sub.s from a drive unit. The output of the probe is rectified by a diode mounted in the tank, prior to supply to a measuring unit. The voltage V.sub.D across the diode varies with temperature and is measured periodically by reducing the input voltage V.sub.s by a known factor X. The voltage V.sub.D is calculated by the measuring unit from the two output currents I.sub.1 and I.sub.2 produced respectively at the two different voltages V.sub.s and V.sub.s /X. The capacitance and hence the depth of fluid is calculated using the known voltage V.sub.D across the diode. The drive unit has a transformer that is used to reduce the voltage periodically by switching between different tappings of its secondary windings.

Abstract: An electric liquid level detector of the condenser type comprises an electrode assembly including a pair of electrodes to be submerged into the oil within a liquid container, an electric circuit assembly provided with an electric detecting circuit for generating an output signal indicative of the level of remaining oil in dependence upon an electro-static capacity between the electrodes, and a flexible tubular guide member of conductive material fixed at its one end to the electrode assembly and at its other end to the electric circuit assembly. The guide member is provided therein with an elongated partition plate of conductive material grounded together with the guide member, and the electrodes are connected to the detecting circuit by means of a pair of insulated electric wires extending through a pair of elongated spaces subdivided by the partition plate in the guide member.

Abstract: A liquid quantity sensor has at least one pair of electrode plates which are vertically disposed in a vessel, e.g. an automotive fuel tank, in a spaced and parallel arrangement so as to form a capacitor. To enhance accuracy and uniformity of the distance between the two electrode plates, a plurality of annular, synthetic resin insulating spacers having a thickness that corresponds with the aforementioned distance are interposed between the two electrode plates in such an arrangement that the distance between adjacent pairs of spacers is between 50 mm and 80 mm. The two electrode plates are fastened to each other at each location where one of the spacers is present by tightening a fastening means such as a rivet inserted through holes formed in the two electrode plates such that each spacer is subjected to a compressive load between 40 and 100 kgf.

Abstract: A reference capacitor is coupled in parallel with a capacitor of which the size thereof is variable and an oscillator is used to alternately charge and discharge both capacitors between first and second voltage levels. The absolute magnitude of the current flowing through the reference capacitor, which varies in proportion to the size of the variable capacitor, is detected which is indicative of the variations in size of the variable capacitor. If the variable capacitor is disposed in the fuel tank of a vehicle, water in the fuel will cause the effective capacitance value of the capacitor to increase which reduces the absolute magnitude of the current that is detected. The absolute magnitude of the detected current can be utilized to indicate excessive water levels in the fuel.

Abstract: A level sensor for sensing the level of viscous, electrically conducting materials in a tank includes a variable capacitor, the capacitance of which varies in response to changing material level height in the tank. The variable capacitance is connected through a charging resistor to a comparator to form an astable multivibrator which develops an output signal having a period dependent partly upon the capacitance of the variable capacitor. The charging resistor has a resistance which is small with respect to the resistance of the material so that build up or coating of material on the variable capacitor has little or no effect on the measurements. The frequency of the output signal from the multivibrator is divided to derive a signal of relatively low frequency which may be coupled to a remote location by a two wire conductor.

Abstract: Liquid level measuring capacitors, each having two vertically disposed generally polygonal plates, are made by preparing a provisional assembly including a first electrode plate having plural holes and a baffleplate shape. A second electrode plate opposite to the first electrode has plural holes corresponding to the first electrode plate holes. A one-piece dielectric spacer network inserted between the plates includes plural annular spacers arranged correspondingly to the holes of the plates. The spacer has zigzag connecting bars to breakably connect a number of the spacers to one another by relatively weak joints with a generally arc-like part of the outer periphery of each spacer. A fastener is inserted in the center hole of each spacer through aligned holes of plates. Each fastener is fixed to the plates. The end portions of the connecting bars are pulled to break and separate spacers.

Abstract: A probe for the measurement of the level of conductive materials within a conductive vessel is disclosed which is particularly suitable for the measurement of the level of conductive granular materials such as coal or other minerals or plastics or vegetable matter which are conductive. In a preferred embodiment the probe comprises a conductive steel core covered with a layer of insulating plastic and covered further with a layer of a semi-conductive material which preferably comprises a plastic which has been partially filled with a conductive material such as carbon black. Other embodiments wherein the probe may comprise a conductive plate covered by insulation further covered by a similar semi-conductive layer are also disclosed. Reference is made to prior art disclosures of circuitry and theory which enable the use of the probe of the invention.

Abstract: A capacitive transducer which comprises a pair of joined-together thin-film capacitors and a fluid-impervious container. The container may be filled with a standard solution of known composition. One of the two thin-film capacitors is immersed in the standard solution inside the container while the other is situated outside the container. The entire transducer may be immersed in a sample, and the capacitance of the outside capacitor, which is dependent on the dielectric constant of the sample, may be compared with that of the inside capacitor after the standard solution has reached thermal equilibrium with the sample.

Abstract: A filling element, used for dispensing non-carbonated or carbonated liquids having a high, a low, or no electrolytic conductivity includes a signal emitter embodied in the form of a cylindrical capacitor having an inner and an outer cylindrical electrode. The filling element is usable for single or multi-chamber counterpressure filling machines having a lower valve housing which is provided with a pressurized gas chamber, and having a filling tube which is held by a contact pin for a filling height signal emitter, which contact pin is longitudinally movable in the valve housing. The signal emitter is essentially formed in that the liquid conveying part of the filling tube is insulated relative to the valve housing, and is embodied as an inner cylindrical electrode which is in contact with the contact pin.

Abstract: An apparatus for detecting the presence of granular material at a predetermined location in conduit adapted to contain the flow of granular material and in containers adapted to store granular material, wherein the upper portion of a sensing terminal is embedded in a protective housing. The protective housing has a material deflecting surface formed thereon and the lower portion of the sensing terminal protrudes from the protective housing opposite the material deflecting surface. The sensing terminal is adapted to exhibit a change in at least one of its electrical characteristics when the lower portion is in communication with granular material. Means are provided for mounting the protective housing and sensing terminal in a predetermined orientation relative to the container or conduit wall so that the flow of granular material is substantially diverted away from the lower portion of the sensing terminal.

Abstract: A capacitance probe and method of probe manufacture for material level sensing systems and like applications. The probe includes a probe rod, a tubular guard coaxially surrounding the rod intermediate the rod ends, and insulation material formed as an integral piece in an injection molding operation surrounding the rod between the rod and guard and also surrounding and radially overlapping axially spaced ends of the tubular guard. One end of the rod and a portion of the guard intermediate its ends are exposed through the insulation material. The molded assembly is captured within a nipple or the like for mounting to a material vessel such that the exposed surfaces of the rod and guard are disposed internally of the vessel for capacitance coupling to material therewithin.

Abstract: A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a function of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a predetermined level of material for indicating material level as a function of a difference between capacitance at the probe and the reference signal. In the preferred embodiments of the invention disclosed, an automatic calibration circuit adjusts the resonance characteristics of the parallel resonant circuit of the reference signal indicative of a predetermined reference material level.

Abstract: A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a function of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a predetermined level of material for indicating material level as a function of a difference between capacitance at the probe and the reference signal. In the preferred embodiments of the invention disclosed, an automatic calibration circuit adjusts the resonance characteristics of the parallel resonant circuit of the reference signal indicative of a predetermined reference material level.

Abstract: A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a function of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a predetermined level of material for indicating material level as a function of a difference between capacitance at the probe and the reference signal. In the preferred embodiments of the invention disclosed, an automatic calibration circuit adjusts the resonance characteristics of the parallel resonant circuit of the reference signal indicative of a predetermined reference material level.

Abstract: In a capacitance type liquid level measurement gauge having an oscillation circuit including a frequency generator, a capacitance and a resistance which is connected in series with the capacitance, the capacitance including a pair of electrode plates submergible in a liquid to be measured, there is provided a further condenser which is connected in series with the capacitance.

Abstract: A multiplexed circuit for selecting one of a plurality of vertically spaced resistance temperature devices (RTDs) in a fluid storage tank. An electronic multiplexer is used to select a particular one of a plurality of vertically spaced RTDs to be connected to circuitry for reading the output value of same. The device is used in connection with an intelligent field interface device (FID) at the tank. The FID contains a table storing values for expected ranges of output values from the RTDs. When a value actually read is out of range, the FID causes the multiplexer to select another RTD for reading. The arrangement also allows reading of temperatures at various levels within the tank, irrespective of the actual fluid level.

Abstract: Apparatus for measuring the amount of fuel in a tank comprises a capacitive probe whose capacitance is a function of the fuel level in the tank, an electronic circuit including a monostable multivibrator to which the probe is connected as a timing capacitor and a trigger source for repetitively triggering the monostable multivibrator to provide a series of output signals whose duty cycle is a function of probe capacitance, and a display responsive to the pulses or a signal derived from them to indicate the amount of fuel in the tank.

Abstract: A failure sensing accumulator device and to a system embodying the same. The accumulator and system are characterized in that various failure situations are sensed by a capacitive sensor apparatus which is capable of detecting failures at an early stage and localizing the damage to the system resulting from such failed accumulator.

Abstract: An improved system for generating a signal representative of the level of a material having a dielectric constant within a vessel is disclosed. The system features use of a first probe for generating a signal indicative of the dielectric constant of the material which is divided into a signal varying with the level of the material whereby a compensated level signal irrespective of the actual dielectric constant is measured. In a preferred embodiment, a single integrator is used to perform the division operation whereby inaccuracies due to component variation including long-term drift are eliminated. The instrument is disclosed as functioning in a two-wire instrument system having low power requirements, permitting use of conventional signal limits.

Abstract: Apparatus for the dispensing of very small amounts of liquid includes a measuring vessel which can be filled with an amount of liquid, and to whose outlet there is connected an ejector of a partial quantity. A sensor responds to the liquid level in the measuring vessel, to control a filling system which receives therefrom a signal for the filling of the measuring vessel when the minimum permissible lower liquid level is reached and a signal for the ending of the filling process when the maximum permissible upper liquid level is reached. The sensor is a capacitor which extends at least over the entire range of the variable liquid level in the measuring vessel and whose dielectric is the liquid situated in the measuring vessel. A capacitance meter is provided for measuring the capacitance of the capacitor.

Abstract: A robust electronic liquid level gauge apparatus, particularly suitable for use with boiler drum water column, comprises simple probe sensors in the water column, differential amplifier sensors, detectors responsive only to the simultaneous presence of a minimum level signal and a certain frequency, and logic circuits continuously processing outputs from four detectors: its associated probe detector, the one below, and the two above.

Abstract: A pump located within the fuel tank discharges fuel into a chamber containing a plurality of reference electrodes which determine the dielectric constant of the fuel. The output of a set of measuring electrodes is calibrated using the dielectric constant determined using the reference electrodes. The fluctuations in the capacitance developed by the reference electrodes due to momentary contact with water droplets or the like can be used to indicate an excess of the water or the like in the fuel.

Abstract: A fuel-gauging system has a capacitive probe comprising an outer tubular electrode and a coaxial inner electrode. The outer electrode is supplied with an alternating signal from an oscillator, the inner electrode being connected to a detector unit via a resistor. The resistor is mounted between the electrodes about midway along the length of the probe, the resistor having a value that is selected to give a substantially linear output of the probe and is at least 0.1 of the reactance of the probe, preferably being about 0.3595 of the reactance. The resistor may be connected to a phase-sensitive circuit that is controlled by a phase-shift circuit which receives the input signals to the probe and shifts their phase by 90.degree., so as to produce an output that is in phase with the probe output. In this case the value of the resistor is preferably 0.2178 of the probe reactance.

Abstract: An apparatus for determining a capacitance includes a capacitor, an oscillator, and a detector. The capacitor is partially immersed in liquid containing gasoline and alcohol in such a manner that the liquid may enter the capacitor, whereby the capacitance of the capacitor varies with the level of the liquid. The oscillator is connected to the capacitor and generates a oscillatory signal which depends on the capacitance of the capacitor and the frequency of which is set higher than a reference value dependent on the alcohol concentration in the liquid. The detector is connected to the oscillator and measures the capacitance of the capacitor according to the oscillatory signal of the oscillator to determine the level of the liquid.

Abstract: Disclosed herein is a capacitance sensor which comprises a pulse generating circuit; a plurality of variable delay circuits, each including as a component thereof a variable capacitance transducer and adapted to delay a pulse from the pulse generating circuit by a time lag corresponding to a capacitance value of the transducer and then output the thus-delayed pulse; and a phase discriminating circuit adapted to discriminate a phase difference of the pulses output respectively from the plurality of variable delay circuits and then output measured information. This capacitance sensor can be used to measure various parameters. The capacitance sensor is particularly effective as a liquid level detection sensor for liquid containing bottles used to dispense intravenous substances in drop-wise fashion.

Abstract: A device for the capacitive measurement of liquid levels, particularly in an automobile tank has a measurement sensor with measurement electrodes arranged concentric to each other forming a measurement capacitor, the space between the measurement electrodes communicating at a variable height with the liquid to be measured, and a channel within an inner of the measurement electrodes through which the liquid is drawn up. Compensation electrodes form a compensation capacitor in a suction path of the liquid with a constant level of the liquid by which the influence of different dielectric constants of the liquid on the result of a measurement is compensatable in an evaluation circuit to which the measurement capacitor and the compensation capacitor are connected. A sump vessel has a bottom disposed lower than an upper opening of the channel within the inner measurement electrode. The compensation electrodes are arranged in the sump vessel.

Abstract: A capacitive fluid-gauging probe has a tubular electrode that is secured at its upper end to the wall of a reservoir by an integral mount moulded from a frangible plastics material. The mount has a collar that is fitted to the probe and from which extend radially three pairs of struts. The struts are joined at their outer ends with respective pillars that extend parallel to the probe. The pillars are joined with a plate that is secured to the wall of the reservoir above the probe. Domed plugs are inserted in both ends of the electrode to protect the wall of the reservoir which may be of flexible material. Preferably the ends of the probe are spaced from the reservoir walls. In operation, excessive force on the probe causes the struts to break, thereby allowing the probe to be displaced within the reservoir.

Abstract: A liquid gaging system comprising a plurality of sensors, each sensor providing a liquid measurement signal relating to a liquid depth at a particular location in a tank. The invention also comprises apparatus for selectively monitoring individual sensors one at a time. The apparatus for selectively monitoring is connected to the sensors.

Abstract: Disclosed is a capacitance level measuring device comprised of a container whose level is to be measured and a probe inserted into and spaced from the container. The capacitance between the probe and container varies in relation to the level in the container. A capacitance measuring circuit determines the capacitance between the probe and container and thus indicates the level in the container. The integrity of the probe is verified by constructing the probe so as to include it in a series circuit, as well as the capacitance measuring circuit, and a lack of continuity in the probe is indicative of questionable probe integrity. The question as to the probe's integrity would indicate a questionable level indication from the capacitance measuring circuit. Various probe constructions are also disclosed.

Abstract: A liquid quantity sensor of the capacitor type having at least one pair of electrode plates which are disposed in a liquid container, e.g. an automobile fuel tank, in a spaced and parallel arrangement so as to form a capacitor. Concerning the capacitor electrode plates of an angled shape and to resolve the difficulty in realizing a uniformly constant distance between the two electrode plates in the bent region, one of the two electrode plates is made up of two major flat portions and a minor junction portion which keeps the two flat portions spaced from each other and at an angle in conformance with the bending angle of the other electrode plate, and the two electrode plates are assembled such that the gap between the two flat portions of the split electrode plate is located right opposite the bent region of the other electrode plate.