Abstract: A system including a method and means for trimming capacitive-type remotely-located fuel probes that eliminates the previously-used variable trim capacitor and substitutes a rugged, inexpensive, standard-value signature resistor connected between the AC input and ground to provide "calibration offset" data needed by the fuel measurement electronics to make a determination of actual probe capacitance. The system may be applied to any such probe having a blocking capacitor in series with the probe capacitor, which blocking capacitor insures accurate measurement of the signature resistor when the leakage resistance is significant. When applied to DC or AC FHC probes, the C.sub.fhc capacitor is replaced with a non-critical DC-blocking capacitor, that is typically at least 100 times greater in capacitance value than the C.sub.

Abstract: An apparatus and method is provided for detecting the level, composition, and temperature of a liquid fuel stored in a tank on a vehicle, as well as the tank pressure, and for transmitting this data via a multiplex bus to a central vehicle computer. The apparatus for collecting liquid fuel level data comprises first capacitive sensing means located within the fuel tank for storing a charge proportional to a full liquid level, second capacitive sensing means located within the tank for storing an instant liquid level charge proportional to the instant liquid level in the tank, and first processing means in communication with the multiplex bus and first and second capacitive sensing means for comparing the full liquid level charge to the instant liquid level charge to determine an absolute liquid level value and for outputting a corresponding fuel level data signal to the multiplex bus.

Abstract: A digital liquid level sensing apparatus and method for detecting variations in the dielectric of a substance being sensed. The apparatus includes a capacitive element array which is disposed in a fluid to be measured and which includes a plurality of individual (i.e., segmented) input plates positioned along an axis of measurement of the fluid to be detected. The array also includes a common output plate having a length sufficient to span the entire accumulated length of the input plates. A controller sequentially applies DC excitation pulses to the input plates which cause a series of output currents to be coupled onto the output plate. The output currents are input to a current-to-voltage amplifier which generates a series of corresponding analog output voltages. The analog output voltages are then input to a peak voltage detector circuit to generate a series of peak voltage signals representative of the magnitudes of the analog output voltages.

Abstract: An apparatus for collecting liquid level data for any composition of fuel contained in a vehicle fuel tank and for transmitting this data via a multiplex bus to a central vehicle computer. A first capacitor stores a charge proportional to the level of a full fuel tank. A second capacitor stores a charge proportional to the instant level of the fuel in the tank. A micro-controller in communication with the first and second capacitors and with the multiplex bus for controlling the discharge of the capacitors, The micro-controller determines the absolute level of the fuel and transmits the data to the multiplex bus.

Abstract: A level detector includes a level detecting capacitor, an oscillating circuit, and an amplifying circuit. The level detecting capacitor includes a pair of continuously extended electrodes separated by a predetermined distance and disposed at a predetermined position in a container adapted for accommodating a dielectric fluid having levels which are to be detected therein. The oscillating circuit is adapted to apply an alternating voltage of a constant frequency to the level detecting capacitor by way of an impedance element adapted to provide signal voltages. The amplifying circuit is adapted to amplify voltage drops at the impedance element so as to output a signal corresponding to the level of the dielectric fluid. Thus, the level detector can output signal voltages of high linearity and dependant on the fluid level variations using a simple circuit arrangement.

Abstract: A fuel gauging system for use in determining the level of fuel in a tank. The system incorporates a resonant circuit for measuring the resonant frequency of at least one probe immersed in the fuel located in the tank. From measurements of variations of the frequency of resonance, the level of liquid in the tank is determined, and the fuel quantity is then calculated and displayed.

Abstract: A gauging apparatus for fluid containers such as fuel tanks includes a capacitance disposed in the container that changes value based on the volume of fluid in the container; a first antenna disposed below an outer surface of the container and coupled to the capacitance; a second antenna magnetically coupled with the first antenna across a coreless gap; and a gauging circuit coupled to the second antenna and comprising an oscillator for applying an excitation signal at a number of different frequencies to the second antenna, and a signal processing circuit that detects current in the second antenna caused by the excitation signal and by current in the first antenna related to the capacitance value.

Abstract: A system for the detection of knots and voids in wood or lumber employs opposed arrays of capacitor plates. The presence of knots and/or voids is detected based on changes in the dielectrical response produced in the electrical fields defined by the opposed capacitor plate arrays. A software system delineates specific knot and void defects determined. Wood or lumber strength can further be estimated by comparing a sensed dielectric value in a clear portion of the lumber or wood with an established dielectric response value for wood of known density. Employing an appropriate correlation factor the relative wood density, coupled with knot/void location and size, permits an estimate of over all wood strength.

Abstract: A volume sensing device for determining the volume of liquid present in a standard plastic disposable pipette during a pipetting operation, which operation can be an aspiration or dispensing of liquid. The device comprises a cylinder made of hard synthetic material into which a disposable pipette is lowered at a predetermined velocity. The pipette which is being lowered into the cylinder holds an amount of liquid the volume of which the volume sensing device approximately determines. A pair of metal rings are coaxially mounted near the top end of the plastic cylinder. The pair of metal rings are preferably mounted in mating machined recesses of the plastic cylinder. This pair of metal rings is separated from each other by a small gap which forms the dielectric material of a capacitative circuit when the upper ring is connected to one portion of this circuit and the lower ring is connected to an other portion of the capacitative circuit.

Abstract: A time varying excitation current (413) is provided to one side of a capacitive sensor (417), and two signal paths (420,430) are provided between the other side of the capacitive sensor (417) and signal conditioning circuitry (412), each signal path differing from the other according to its polarity. The signal paths conduct monopolar signals from the capacitive sensor the magnitude of which are directly related to the capacitance of the sensor, and bi-polar signals the magnitude of which are directly related to the stray capacitance in the signal lines. The combined monopolar and bi-polar signal currents on each signal line are converted into voltage signals (422,433), and the voltage signals are thereafter differenced (460) to provide a null bi-polar output while providing a constant monopolar voltage level the magnitude of which is directly related to the probe capacitor current.

Abstract: A highly accurate system to measure the level of material in a vessel. A probe is provided in the vessel. The vessel and the probe are at different potentials so as to create a capacitance therebetween. The air and materials in the vessel act as dielectrics. As the material level varies, so does the capacitance. This capacitance is subjected to a charge-discharge-charge cycle yielding integrated net neutral charge. The duration of the cycle is compared to a reference time to determine capacitance, which is proportional to the level of material in the vessel.

Abstract: A threshold calibration method and apparatus calibrates a reference voltage representing a selected threshold and compares the reference voltage with a measurement voltage representing a variable parameter to indicate the condition of the variable parameter. The reference voltage is set by causing the variable parameter to assume a predetermined high value and adjusting a first potentiometer to provide a first calibration voltage equal to the measurement voltage representing the high value. The variable parameter is then caused to assume a predetermined low value and a second potentiometer is adjusted to provide a second calibration voltage equal to the measurement voltage representing the low value. The first and second calibration voltages are then combined using passive resistive components to provide a reference voltage representing the selected threshold.

Abstract: A fluid sensing pipette includes an outer conductive tube forming a first electrode and an inner conductive tube forming a second electrode. The inner conductive tube is disposed concentrically within the outer conductive tube. To insulate the inner conductive tube from the outer conductive tube, the inner conductive tube is coated with a thin, uniform, and consistent Parylene coating. A hydrophobic polymeric tube is disposed concentrically within the inner conductive tube to prevent cross-contamination between different biological samples aspirated into the pipette. The inner and outer conductive tubes are separately coupled to a level detection circuit which permits the pipette to detect entry of the pipette into a conductive fluid. The level detection circuit determines the impedance between the first and second electrodes and produces a control signal in response to the impedance falling below a predetermined threshold.

Abstract: A continuous liquid level measuring system having a guarded capacitance probe and related drive circuit for providing accurate level measurements, even when measuring the level of ionic and highly viscous fluids. The capacitance probe has two parallel electrodes, each constructed of a half-tube section, that are separated from each other by an insulated guard wire. The probe is excited by a 1 MHz excitation signal applied across the electrodes. The current through the electrodes is a function of the capacitance between the electrodes, which is affected by the relative permitivity of the surrounding liquid. The effects of highly viscous ionic liquids that adhere to the probe are reduced by exciting the guard wire with a guard signal that is 180.degree. out of phase from the probe's excitation signal. The guard signal changes the electric field existing in the space adjacent the junctions of the two electrodes to reduce any liquid coating effects on the level measurement.

Abstract: A level switch includes an operational amplifier, provided with positive and negative feedback, and a sensor, together forming an astable multivibrator. The oscillation onset and frequency of the multivibrator depend on the surface level of controlled material. The sensor includes a dielectric body on which, starting from its fastening end, a grounded opposite electrode and a screening electrode, connected to the amplifier output, are mounted. A ring plate connected to the inverting amplifier input is incorporated coaxially in the dielectric body. The level switch need not be adjusted when the controlled material is changed, although materials may have quite different electrical properties and may stick to the sensor.

Abstract: An ultrasonic fuel-gauging system for an aircraft with three fuel tanks has probes in each tank connected to dual-lane data concentrator circuits. The digital outputs from one lane of the data concentrator circuits are supplied to respective tank circuits, the outputs of which are connected to two input/output circuits. The outputs of the other lanes of the data concentrator circuits are connected directly to one or the other of the two input/output circuits. The tank circuits and input/output circuits are processors of identical construction programmed with different software. If a tank circuit or input/output circuit should fail, its function is taken over by reconfiguration of one of the remaining processors.

Abstract: A capacitance point level switch includes a probe adapted to be disposed in a material containing vessel, the material having a capacitance value dependent upon its level in the vessel. An oscillator circuit develops a periodic signal at a select frequency. A reference network is driven by the oscillator and includes a reference capacitance for developing a periodic reference signal at the select frequency and phase displaced responsive to the reference capacitance. A probe network is driven by the oscillator and is connected to the probe to include the capacitance of the material for developing a periodic probe signal at the select frequency and phase displaced responsive to capacitance of the material. An output circuit is connected to the reference network and the probe network for developing a discrete output assuming a first or a second state according to the relative phase displacement of the periodic reference signal and the periodic probe signal.

Abstract: A method and apparatus for a liquid level sensor control circuit of a bioassay apparatus for controlling a position of a sampling probe with respect to a surface of a liquid in a container. The apparatus includes a sampling probe, an oscillator circuit coupled to the sampling probe for producing a first output signal having a constant frequency, a comparator coupled to the oscillator circuit for comparing the amplitude of the first output signal to a first reference amplitude and for producing a change signal when the amplitude of the first output signal changes with respect to the reference amplitude, and a controller responsive to the change signal for controlling the position of the sampling probe with respect to the surface of the liquid.

Abstract: A detector circuit in a moisture detector having an oscillator, a detector electrode and a common electrode for measuring the moisture content of wood and structural materials in buildings comprises a clamping diode network which couples an AC signal generated in the oscillator to a detector electrode. The clamping network clamps the AC signal to a reference voltage. The clamping network is balanced by a second clamping diode network which, together with a low pass filter, establishes the reference voltage. A low pass filter connected to the first clamping network produces an output voltage signal related to the impedance between the electrodes. To maintain the circuit's stability, the diodes in the clamping networks are thermally coupled.

Abstract: A low intrinsic capacitance probe system for measuring capacitance to detect the liquid fill level of a pressure vessel that incorporates a high pressure center rod retention system and an explosionproof flame path seal into its mounting gland. The system reduces or eliminates the cold flow of PTFE within the probe and eliminates the need for periodic retorquing.

Abstract: A main sensor electrode part 3 and a reference sensor electrode part 4 are deposited in patterns over the surface of a support member 10. A lead-out part 4b of the reference sensor electrode part 4 is extended through an unplated passage 11 of the main sensor electrode part 3 to the upper edge of the support member 10 to form there a terminal part 4a. A portion of the main sensor electrode part 3 is also extended to the upper edge of the support member 10 to form there a terminal part 3a. The support member 10 is deposited all over its surface with an insulating film 12 covering the both sensor electrode parts 3 and 4.

Abstract: An apparatus for detecting the level of material in a container. The apparatus comprises a power source and a first electrode, positioned adjacent the container, electrically connected to the power source. The apparatus further comprises a second electrode. The second electrode is spaced from the first electrode and positioned adjacent the container. The apparatus further comprises an electrical amplifier which is electrically connected to the second electrode. The amplifier amplifies a current induced in the second electrode and generates a voltage signal. The amplifier is adapted to maintain the second electrode at a virtual ground to minimize environmental impedance effects. The apparatus further comprises a rectifier, electrically connected to the amplifier, for rectifying the voltage signal and a comparator, electrically connected to the rectifier, for comparing the voltage signal to a predetermined voltage signal corresponding to the container being full with material.

Abstract: A proximity detection system includes a dual mode oscillator for generating a pair of ON and OFF control signals. A sensing circuit including a capacitance device detects the presence of a conductive object, such as a liquid, to cause the oscillator to switch its modes of oscillation.

Abstract: A baffle assembly for use in an ultrasonic system for measuring the level of a contained volume of liquid by calculating the density of the liquid by determining the dielectric constant thereof. The baffle assembly is located at the lower end of a stillwell located within the volume of liquid, The assembly includes a pair of concentric sleeves formed of electrically conductive material located to surround the lower end portion of the stillwell. The sleeves are uniformly radially spaced from one another so as to function as a capacitor so that the electrical capacitance between the respective opposed surfaces of the sleeves may be determined.

Abstract: A test circuit for testing operation of a liquid level detector. The liquid level detector includes a probe that is placed at a test site. A control circuit monitors changes in capacitance of the probe due to changes in the liquid level at the test site. A test switch grounds an input to the probe which and causes the control circuit to sense an alarm condition. If the detector does not activate an alarm when the test switch is actuated, the detector is not properly functioning and repair or replacement of the level detector is needed.

Abstract: A capacitive liquid level sensor having phase detecting circuitry incorporates a capacitive sensor array, an oscillator generating an input signal, a switching circuit sequentially coupling the input signal to the input plates of the capacitive sensor, one at a time, a pair of phase lock loop circuits (PLLs) each having voltage controlled oscillators (VCOs), a second switching circuit selectively coupling the output plates of the capacitive sensor array, in sequential fashion, to the PLLs, and an exclusive OR-gate (XOR) receiving the outputs of the VCOs from each of the PLLs. The XOR generates a first logic level signal when a difference in the phase of two signals from any two adjacent output plates indicates that a phase difference is present. A second logic signal is generated if no phase difference is detected. The signals are perfectly in phase when any two adjacent output plates are either submerged in fluid or both disposed in air.

Abstract: A liquid level detecting device having an overflow reservoir, a flow restriction means and a level detecting means. The reservoir defines a cavity for collecting an electrically-conductive liquid overflowing from a container. This reservoir, which has a low level position associated therewith, includes inlet means through which the overflowing liquid enters, outlet means through which the collected liquid exits, and vent means through which built-up gases escape.Flow restriction means controls the rate at which the collected liquid exits through the reservoir's outlet means. Flow restriction means is calibrated such that the rate at which liquid exits the reservoir does not exceed the rate at which liquid overflows therein.In one embodiment, level detecting means includes a capacitive sensor switch which is fixedly secured to the reservoir to detect whether the liquid level is below the reservoir's low level position.

Abstract: Digital tilt level sensing probe system comprising a set of multiple capacitor elements in a fluid container arranged along an axis of measurement where each multiple capacitor element represents a discrete level increment in dielectric material fluid to be measured. Individual capacitors in each element are horizontally spaced to reflect a level differential upon tilting of the fluid container from its normal attitude. In the case of a probe for sensing tilting in a single plane, a one-piece body is employed to include integral capacitor elements, mounting pad, connector, custom IC pad, and circuitry molded into such body. Alternative references may be employed for comparison with each capacitor assigned a unique time slot in a switching sequence.

Abstract: An automatic atmometer includes an evaporating head that is coupled to a metering vial through a three-way valve controlled by fluid sensors disposed proximate inlet and open ends of the metering vial. The three-way valve is ordinarily in a quiescient state that connects the evaporating head to the metering vial. As water evaporates from the evaporating head water is drawn by suction out of the metering vial. When a sensor proximate the inlet of the metering vial indicates that the vial is empty the three-way valve is activated. This refills the metering vial from a fluid reservoir above the metering vial. As soon as one or more sensors proximate the open end of the metering vial indicate that the vial is full the three-way valve is returned to its quiescient condition. An output signal activates a counter or other logging device to record the number of times the metering vial has been emptied and refilled.

Abstract: A fuel heater formed form an elongated structure which defines a fuel channel passing through the length thereof and which defines in the bottom thereof a fuel intake. The unitary structure also defines a heating fluid inlet and outlet on one side of the fuel channel which communicate with one another on that one side of the fuel channel and fuel measurement means. The fuel measurement means is fit to a conduit formed in the elongated structure. The fuel measurement means can be a capacitive-type level sensor.

Abstract: A digital liquid level sensing apparatus for detecting variations in the dielectric of a substance being sensed. The apparatus includes a capacitive element array including a plurality of individual (i.e., segmented) input plates positioned along an axis of measurement of a fluid to be detected. The array also includes a common output plate having a length sufficient to span the entire accumulated length of the input plates. A controller sequentially applies DC excitation pulses to the input plates which cause a series of output currents to be coupled onto the output plate. The output currents are input to a current-to-voltage amplifier which generates a series of corresponding analog output voltages. The analog output voltages are then input to a peak voltage detector circuit to generate a series of peak voltage signals representative of the magnitudes of the analog output voltages.

Abstract: The assembly comprises an electrically insulated linear array of a plurality of active plates working in conjunction with common return plate means to provide a line of capacitors. The electrically insulated active plate array and common return plate means extend through a column of multi-phase fluid. A discrete oscillator circuit is positioned adjacent to and is permanently connected to each active plate for charging and discharging it. Means are provided for sequentially enabling the oscillator circuits to produce signals which are each indicative of the dielectric constant of the thin horizontal slice of fluid extending between the active plate and the return plate means. The signals are collected by a microprocessor which analyzes them to provide a dielectric constant profile of the fluid column. Interfaces of phases can be located from the profile and the composition of the fluid phases can be determined.

Abstract: An improved capacitance level probe is shown which can be positioned within the return vapor passage of a coaxial vapor recovery refueling system for detecting changes in liquid level within an underground fuel storage tank. The level probe has an outer conductor, a spaced inner conductor, a closed upper end and a lower end with an end opening which allows liquid to enter and leave the interior of the probe as liquid level changes within the underground tank being monitored. A tubular impact vent is located at the upper end of the outer conductor and collects tank vapors from the return vapor passage in order to conduct such vapor pressure to the open interior of the outer conductor above the level of liquid within the outer conductor. This action prevents sudden pressure drops within the outer conductor as the level of fuel changes within the underground storage tank, thereby eliminating inaccuracies in the sensed capacitance of the unit.

Abstract: A device is proposed for the electrically insulated attachment of a metal probe electrode in the opening of a housing, preferably a measuring probe for measuring the filling status in the opening of a probe head housing. The device has a metal rod electrode and a metal guard electrode at which two sealing cones are arranged which are spatially separated from each other which, with the inclusion of insulating layers, electrically insulate and close off in a pressure-sealed manner the rod electrode with respect to the guard electrode and both with respect to the housing in the opening of which they are attached. Both electrodes are connected with an electronic circuit in an electrically insulated manner.

Abstract: An arrangement senses a liquid level by monitoring the peak capacitance formed between a probe and the liquid as the probe approaches or departs from the liquid. In an automated system, a computer controls the position of a pipette probe for aspirating or dispensing liquid in the vessel. The charge developed via the capacitance on the probe is coupled to a capacitive sensor circuit which provides a peak detector with an amplified signal representing the peak capacitance between the probe and the liquid. This amplified signal is detected by a peak-capacitance discrimination circuit, the output of which is monitored by the computer for determining the precise position of the probe with respect to the liquid surface level. Other aspects of the present invention include a negative-static elimination circuit coupled to the output of a detector latch and a positive-static elimination circuit coupled to the input of the detector latch.

Abstract: A system and method for detecting leaks in a storage tank that includes a stored tank liquid and an immiscible test liquid, and there is an interface formed between the tank liquid and the test liquid. The system includes a transducer and electronic device. The transducer further includes a measuring cell and a standard cell. The level of the interface within the standard cell does not change when the level of the interface changes. The level of the interface within the measuring cell changes according to the level of test liquid in the storage tank. The signal generated by the cells are processed by the electronic device to indicate whether there is leakage in the storage tank.

Abstract: Apparatus for measuring the volume of an electrically conductive liquid held in a confined area includes a tank constructed of electrically conductive, fiber-reinforced composite material having an inside surface and an outside surface. An electrically insulative liner is disposed in the tank against the inside surface thereof to receive and hold the liquid. A voltage source supplies an electrical charge to the tank walls, with ground potential being supplied to the liquid, to thereby develop a capacitance between the tank walls and the liquid. The capacitance varies with variation in the volume of liquid and thus by measuring the capacitance, a measure can be made of the volume of liquid in the tank.

Abstract: A level measuring probe in which all potential leakage paths are closed by concentrically shrinking the outmost diametrical surface of the probe by some mechanical means such as a crimper or rotary swager to provide sufficient force to substantially uniformly deform the ground, guard, and active elements and insulators around the circumference of the probe such that multiple seals are created. A circumferential notch is preferably provided in the active probe element at the point of the crimping or swaging to provide "blowout protection" whereby the active probe electrode is held in place when used in a high pressure vessel. A pressure seal between the electrodes and insulation material is also maintained by using an elastomeric insulator which returns to its original shape after heating or a thin electrode which "gives" a little when the insulator expands radially during heating. The arrangement of the invention thus eliminates the need for costly machined parts and bushings to provide pressure seals.

Abstract: A water drop sensor comprises a pair of electrodes disposed in association with a portion of a surface of a vehicle window within a wipe pattern and having edges defining an extended insulating gap between the electrodes. The electrodes define a gap which varies in width over the range of diameters of drops to be sensed. The result is that the sensor shows more sensitivity to larger drops than to smaller drops as compared with a similar sensor having a constant gap width. The variation in gap width may be continuous or stepwise over the total range of drop diameters.

Abstract: A proximity detection system includes a dual mode oscillator for generating a pair of ON and OFF control signals. A sensing circuit including a capacitance device detects the presence of a conductive object, such as a liquid, to cause the oscillator to switch its modes of oscillation.

Abstract: An apparatus is provided which includes a reaction cartridge having a plurality of reaction wells having different reagents disposed thereon, at least one well adapted to receive a sample, a well containing particles adapted to bind to the sample and which have the capability of being separated from cells which are not bound to the separation particles and at least one fluorophore adapted to bind to a specific type of cell in the sample, and a wash area adapted for washing a probe. An image forming device is provided to detect images which indicate whether specific reactions have occurred in each of the reaction wells. The apparatus also includes a mechanism for dispensing and aspirating liquids including a mechanism for detecting liquid levels. The device further includes logic for analyzing the information received from the image detection apparatus and processing the information to generate a visual indication of the results of the assays being performed.

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 device is disclosed to measure the level of material within containers, in particular containers in which free-flowing materials having different dielectric constants, for example water and oil, are collected. The device includes a sensor, which is arranged electrically nonconductively fashion on an outer side of the container and forms part of an electric capacitor, and an electrically conducting complementary plate, which is arranged on the inside of container opposite the sensor and spaced therefrom, which, forms another part of an electric capacitor.

Abstract: A filling element for filling machines is provided and includes a liquid flow valve, which comprises a valve body that can be moved back and forth in a filling element axis between a position that closes the liquid flow valve off and a position that opens this valve. Also provided is an electrical probe for determining filling heights of liquid material in containers. The probe includes a first probe element that projects beyond the underside of the filling element and has an electrode, and a second probe element that at least partially surrounds at least part of the first probe element. The lower end of the second probe element is spaced further from the underside of the filling element than is the first probe element.

Abstract: A probe assembly and method is disclosed which includes a plurality of sensors for respectively mreasuring predetermined attributes of a fluid. The probe assembly comprises a first sensor for measuring the quantity of the fluid. The first sensor includes a capacitive reference cell and a capacitive product measurement cell, each of the cells being characterized by respective associated capacitances. In particular, the capacitance associated with the capacitive product measurement cell varies in accordance with the quantity of the fluid so that the quantity of the fluid is indicated by the quantitative relationship between the magnitude of the capacitance associated with the capacitive reference cell and the magnitude of the capacitance associated with the capacitive product measurement cell.

Abstract: An electric measuring arrangement having at least one measuring sensor and an evaluation circuit which makes possible a continuous measurement of not only the level of a conductive liquid in a container but, also, enables evaluation of as much other physical data relating to the liquid as possible, such as its inclination, the position of a movable body in the liquid, linear or rotational acceleration, and speed. Each measuring sensor is designed as a stray field sensor with two measuring electrodes that are at a specific lateral distance from one another, and the container, together with the liquid placed in it, form a part of the measuring arrangement.

Abstract: A capacitive liquid level sensor utilizes capacitive principles to sense the level of a liquid contained within a receptacle. As a liquid rises and falls in the container, the dielectric effect of the liquid changes the effective capacitance of a sensing capacitor which is detected by electronic circuitry coupled to the sensor. One plate of the sensor capacitor is a probe disposed within a receptacle while a grounded conductive portion of the receptacle is a second plate of the capacitor. The liquid within the receptacle acts as a dielectric between the plates.

Abstract: A capacitive sensor includes a plurality of individual condenser elements, each of which consist of a first, preferably circular, electrode and a second, preferably surrounding ring-shaped, electrode, which are mounted on one side of a nonconducting support. A common conductor is connected to each of the first electrodes of condenser elements. A signal can be detected separately from each of the condenser elements via conductors connected separately to the individual second electrodes. To increase the sensitivity and to avoid interference, the remote side of the support opposite to the one side is provided with a third additional electrode, which is at ground potential and also acts as a shield for interfering couplings. The sensor is used for measurement of the fuel film thickness in the intake of an internal combustion engine.

Abstract: A capacitive level gauge for placement in a container (12) determines the level of substance (14) in the container (12). The gauge (10) includes a measurement capacitor (C1) for measuring level and a reference capacitor (C2) for determining dielectric constant of the substance (14). A controller (34) is responsive to the capacitors (C1, C2) for producing a level signal which simultaneously indicated the level and dielectric constant of the material. The level signal includes a frequency which is representative of dielectric constant and a pulse width representative of level. The gauge (10) supports a first pair of parallel conductive members (26, 28) to establish the measurement capacitor (C1) and a second pair of parallel conductive members (28, 32) spaced along the gauge and below the measurement capacitor (C1) to establish the reference capacitor (C2).

Abstract: Digital level sensing probe system including digital probe constructed of two (2) concentric cylinders, forming a set of discrete, cylindrical capacitors that use the substance whose level is to be measured as a dielectric material. The set of capacitors is arranged along the axis of measurement where each capacitor represents a discrete level increment. Each capacitor is assigned a unique time slot in a switching sequence. The first level capacitor is used as a reference to which all other capacitors are sequentially compared. In the switching sequence, an AC signal is applied across each capacitor and compared with the inverted signal which is applied across the first level capacitor. A logic "1" results when the substance is present and a logic "0" when the substance is absent. The logic is decoded and converted to display the appropriate quantity of substance measured.