Abstract: A rain sensor for the windshield of a vehicle has one or more electrically conductive layers which are arranged in a given pattern upon the outer surface of such windshield, and is constructed as a laminate of conductive and resistive layers formed by process steps of printing and sintering for construction of electrodes of the sensor. A conductive layer is formed of a mixture of electrically conductive particles and a glass frit which melts at a lower temperature than a melting temperature of the material of the window which serves as a support for the sensor. The conductive paste is applied with a heating action step, in the configuration of an electrode structure, by sintering to the window.

Abstract: Vapor-deposition polymerization films serve as vapor-sensitive dielectrics (130, 530) over surface-type capacitive electrodes (110 and 120, 510 and 520), or as protective layers (140, 142) over vapor-sensitive dielectrics (132) or flux-concentrators (150) in surface-type capacitive-electrode vapor sensors. Arrays of sensors (411-422) with different vapor-deposition polymerization films provide selectivity among different vapor species. Vapor-sensitive films (530) covering surface-type capacitive electrodes (510, 520) cointegrated with heater elements (560, 570) on thermally isolated suspended substrates (500) provide selectivity among different vapor species.

Abstract: A dewpoint/frostpoint hygrometer that uses a surface moisture-sensitive sensor as part of an RF oscillator circuit with feedback control of the sensor temperature to maintain equilibrium at the sensor surface between ambient water vapor and condensed water/ice. The invention is preferably implemented using a surface acoustic wave (SAW) device in an RF oscillator circuit configured to generate a condensation-dependent output signal, a temperature sensor to measure the temperature of the SAW device and to distinguish between condensation-dependent and temperature-dependent signals, a temperature regulating device to control the temperature of the SAW device, and a feedback control system configured to keep the condensation-dependent signal nearly constant over time in the presence of time-varying humidity, corrected for temperature.

Abstract: A liquid level sensor based on a closed field circuit comprises a ring oscillator using a symmetrical array of plate units that creates a displacement current. The displacement current varies as a function of the proximity of a liquid to the plate units. The ring oscillator circuit produces an output signal with a frequency inversely proportional to the presence of a liquid. A continuous liquid level sensing device and a two point sensing device are both proposed sensing arrangements. A second set of plates may be located inside of the probe housing relative to the sensing plate units. The second set of plates prevent any interference between the sensing plate units.

Abstract: The invention concerns rainwater sensors for windshields. In one embodiment, a first, inner, conductive film is applied to the inner surface of the windshield, and a second film, of same size and shape as the first, is applied to the outer surface. However, a narrow strip is removed from the second film, forming a gap which divides the second film into parts 1 and 2. The resulting structure forms two capacitors, namely: (1) inner film plus part 1, and (2) inner film plus part 2. The impedance of one capacitor is monitored. When rain occurs, it falls into the gap between parts 1 and 2, and acts as a resistor, bridging part 1 to part 2. This bridging adds a new impedance in parallel with the first capacitor, thereby changing the effective impedance. This change indicates the presence of rain.

Abstract: A portable grain moisture meter has a large 16 character digital display allowing an alphabetical list of grain selections to be selectably displayed in full text format and subsequently tested for moisture content with the test results also displayed on the same display. The meter also has provisions for calibrating the meter to a remotely located meter and has dual temperature transducers for achieving automatic grain temperature compensation by monitoring both the grain temperature along with the cell temperature.

Abstract: A method and apparatus for automatically detecting a lubricant type and the relative quantity of water present in a test sample of lubricating oil includes the use of an open grid capacitive sensor element that incorporates the lubricating oil as a dielectric medium. The sensor element grid is energized by a frequency variable oscillator that automatically responds to changes in the oil dielectric constant with corresponding frequency changes. As a reference, a sample of new or uncontaminated test oil is confined in wet surface contact with the energized, open grid sensor element. Oscillator frequency changes are measured and recorded, either continuously or at frequent intervals, over a standardized elapsed time interval to generate a reference characterization of the frequency-time relationship distinctive of the particular oil. The same is repeated for a sample of contaminated oil and a corresponding frequency-time relationship generated.

Abstract: A sensor system is operable for detecting the presence of water in an oil emulsion inside the lower gear unit of a marine engine, and for providing an alarm signal when the presence of water is detected within the gear unit. The sensor system includes a ring oscillator circuit and a symmetrical array of passive input probes which are disposed in the oil/water emulsion inside the oil chamber. Each of the passive input probes is electrically connected to the ring oscillator circuit wherein the probes function as fixed capacitors for measuring the electrical characteristics of the emulsion. When a voltage is applied to the oscillator circuit, the oscillator circuit generates an oscillating signal that circulates at a frequency which varies according to the dielectric-properties of the liquid emulsion. When water is introduced into the chamber, the water is emulsified with the oil thereby changing the electrical characteristics of the oil.

Abstract: A circuit for use with an ultrasonic transducer utilized to measure depths of liquids in tanks is described.

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: An impedance detector, in particular for radiosonde operation. The detector comprises a substrate (10 . . . 10E) made of an insulating material, onto which substrate the electrode and contact patterns (11, 11a, 13) necessary for the formation and connecting of the detector impedance have been applied. Between the detector impedance electrodes (11, 13), there is an active film (12), whose impedance values are a function of the physical quantity measured by means of the detector. The substrate of the detector is an oblong core filament (10; 10B; 10C; 10D; 10E) of an insulating material, onto and around which core filament said electrodes (11, 13) and said active insulating film (12) have been applied. Also, a novel process is described for the manufacture of said impedance detector.

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: An impedance detector, in particular for radiosonde operation. The detector comprises a substrate (10 . . . 10E) made of an insulating material, onto which substrate the electrode and contact patterns (11, 11a, 13) necessary for the formation and connecting of the detector impedance have been applied. Between the detector impedance electrodes (11,13), there is an active film (12), whose impedance values are a function of the physical quantity measured by means of the detector. The substrate of the detector is an oblong core filament (10;10B;10C;10D;10E) of an insulating material, onto and around which core filament both electrodes (11,13) and such active insulating film (12) have been applied. Also, a novel process is described for the manufacture of such impedance detector.

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: An electric alarm which includes a dual tone electronic chime, light emitting diode (LED) indicators, electronic circuitry, batteries, and with the exception of the AC adapter and the water sampler, all active and passive devices are housed in a small box to detect wet environments such as water that leaks from defective hot water heater tanks, flooded basements, storage spaces, room spaces below sea level, or any other spaces or tangible things not readily accessible or observable. It uses a water-activated-dielectric capacitor as a water sampler to absorb a small amount of water as the sample. And when it becomes wet or damp, the water dielectric signal controls the current required to energize the gate of the silicon control rectifier (SCR). In turn, the SCR turns "ON" a dual tone electronic chime and also turns "ON" a LED that simply glows. This action provides the audible and visual alert warning signals to indicate that the water does in fact exist.

Abstract: A portable grain moisture meter has a large 16 character digital display allowing an alphabetical list of grain selections to be selectably displayed in full text format and subsequently tested for moisture content with the test results also displayed on the same display. The meter also has provisions for calibrating the meter to a remotely located meter.

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: An improved soil moisture sensor and circuity are described which permit a more compact, simplified, and less expensive integrated unit wherein the essential circuitry of the device is sealed within the sensor head. Determinations of resistance and capacitance are made using a coaxial or other capacitor having spikes or probes which are inserted into the soil or other material.

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: In an apparatus for determining the material moisture of a medium by measuring the dielectric coefficient of the medium around a measuring probe, wherein the apparatus includes a signal generator providing to one end of the probe a pulse signal, the echo of which, when returning from the other end of the probe, is received by a receiver, and a timing device determining the time elapsed between the introduction of the pulse signal and the return of the echo, the probe consists of a body structure which has electrical signal conductors disposed on its surface.

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: An improved method and capacitance probe arrangement for determining the fluid phase fractions of fluids having differing permitivity such as those of gas, oil, and water and oil-water emulsion in a fluid stream flowing from an oil well which includes trapping the primarily liquid in a vertically disposed chamber. The liquid is held therein to permit separation of the phase fractions to the extent possible within a reasonable time. A number of measurements are taken of the capacitance at a plurality of discrete vertically spaced locations within the chamber. These capacitance measurements relate directly to the varying permittivity of the phase fractions of the various liquids contained therein which may be gas, oil, and water and a oil-water emulsion. The measurements are processed by a data processor to provide precise information on such phase fractions and emulsion interfaces. A number of embodiments of the novel probe are disclosed for determining capacitance at spaced locations within the chamber.

Abstract: A sensor for measuring the mixture ratio of liquids, particularly of fuel mixtures, comprises a measuring cell, which has a cavity with one inlet and one outlet. The liquid is directed through the cavity, whereby regions of the inner wall of the cavity are electrically conductive and, together with at least one additional electrically conductive surface, form a capacitor, which is a component of an evaluation circuit. The measuring cell is manufactured from at least two ceramic carriers, which are connected by way of at least one connection layer to form a layer arrangement. The cavity is produced between the ceramic carriers as the result of the lack of at least one connection layer in certain regions. In each case, at least one electrode is applied, in the vicinity of the cavity, to the ceramic carrier delimiting the cavity using thick-film technology.

Abstract: A capacitive moisture sensor includes insulator means; capacitance means including a sensing capacitor having a plurality of spaced capacitive sensor conductors mounted with the insulator means for exposure to the atmosphere; and first and second electrodes mounted with the insulator means remote from the spaced capacitive sensor conductors; means for applying a periodic input current across the first and second electrodes; and means for detecting a change in capacitance between the first and second electrodes indicative of moisture bridging at least two of the capacitive sensor conductors.

Abstract: A particulate moisture measurement gauge of the type using a resonant electric circuit connected to a diode detector and to an AC signal generator having a frequency near the resonant frequency of the resonant circuit and in which the resonant circuit is electrically coupled to the particulate by a capacitor having the particulate as its dielectric. A probe is formed as a transmission line having a length which is approximately an integral number of one quarter wave lengths long. One end of the transmission line is connected to the circuitry and its opposite, moisture sensing end is immersed in the particulate. Preferably the probe is a rigid, conductive tube with a central rod having a ceramic insulator sealing its moisture sensing end and the circuitry housed in its opposite end.

Abstract: A relative humidity sensor includes a printed circuit board having a central passageway therethrough and a dielectric film extending across the passageway with electrodes mounted on that portion of the film in the passageway so as to generate a capacitance which will vary directly with the amount of moisture content in the film.

Abstract: A system for monitoring the moisture content of soil uses a timing capacitor. The capacitor has several conductive elements adapted for insertion into soil to sense the hydration state capacitance of the soil. A capacitance-to-frequency converter electrically connected to the capacitor has an oscillator circuit. The frequency of the oscillator circuit has a frequency dependent upon the value of the capacitor and independent of the electrical losses in the capacitor. A data logger measures the frequency generated by the capacitance-to-frequency converter, the frequency bearing a known relationship to the dielectric constant and, hence, the water content of the soil. The conductive elements are surrounded by shields of electrical potential substantially equal to that of the timing capacitor.

Abstract: The invention relates to a measurement cell for granular or powdered products, including a fill opening in its upper portion. A cell according to the invention is remarkable in particular in that the plane of its fill opening, in the operational position, forms an acute dihedral angle with a horizontal plane in order by gravitation to limit the size of the dome formed by the product after filling. A cell according to the invention has numerous applications and may in particular be intended for measuring the moisture content of cereals, deaginous, or proteaneceous.

Abstract: Apparatus and method for determining the water content of an oil and water mixture such as is transported by pipelines and which oil and water may vary in density from time to time. A densitometer measures the density of the oil and water mixture in the pipeline and a value for the dielectric constant of the oil is obtained from the density measurement by correlating the density reading with a capacitance or dielectric constant reading from an empirically generated chart. A basal sediment and water instrument measures the dielectric constant of the same mixture. The difference between the two dielectric constants is then obtained. This result is converted directly into a water based percentage by volume of the oil-water mixture being carried by the pipeline.

Abstract: A humidity meter includes a humidity-frequency converter (2) which is essentially a pulse oscillator, the oscillation frequency of which depends upon the impedance of a humidity sensor (1), a differentiation circuit (3) and a wave-form shaping circuit (4) which essentially operate as a pulse width modulator for adjusting pulse width of an output pulse of the converter (2) for assuring a linear relationship between humidity and the output signal, and an integrator (6) for integrating the output of the pulse width modulator to provide an output signal as a DC level. A feedback path (5) is provided to apply the output signal to the pulse width modulator for assuring a linear output irrespective of the exponential characteristics of the humidity sensor. Said differentiation circuit (3) has a capacitor (31), a first variable impedance element (32) which is controlled by said feedback path , and a second variable impedance element (33) coupled in series with the first variable impedance element (32).

Abstract: A moisture sensitive device includes a polymer capacitive moisture sensitive element and a heater. The polymer capacitive moisture sensitive element is formed by sequentially stacking a lower electrode, a moisture sensitive film made of an organic polymer resin material, and an upper electrode on an insulating substrate. The heater serves to heat the moisture sensitive film to restore the original characteristics thereof.

Abstract: The present invention includes a dielectric sensor which provides at least two signals corresponding to the sensed dielectric of a petroleum stream. A temperature sensor also senses the temperature of the petroleum stream and provides a corresponding temperature signal. Crossplot data arrange the two parameters associated with the petroleum stream dielectric is stored in a memory. The memory is accessed using signals from the dielectric sensor and the temperature sensor to select data from the memory. An output circuit provides a water cut signal in accordance with the selected data.

Abstract: A capacitance monitor for monitoring the moisture content of soil is disclosed in which a capacitance sensing probe having a generally cylindrical probe body and an elongate tubular handle is inserted into an access tube to measure the capacitance of the soil and to thereby determine the moisture content of the soil. The cylindrical probe body has aluminum electrodes separated by a polypropylene dielectric spacer and two sets of circumferentially spaced apart spring biased stainless steel plungers that extend radially outwardly from the probe body to engage the side wall of the access tube and to center the probe body within the access tube. The two sets of plungers are located at opposite ends of the probe body.

Abstract: A system for the non-invasive monitoring of the hydration state of a plant comprising the elements:a timing capacitor comprising a plurality of conductive elements adapted for mounting on a plant part to sense the hydration state capacitance of the plant part;a capacitance-to-frequency converter electrically connected to the timing capacitor comprising an oscillator circuit having a frequency dependent upon the value of the timing capacitor and independent of the electrical losses in said timing capacitor;means for supplying electrical power to the capacitance-to-frequency converter;means for measuring the frequency generated by the capacitance-to-frequency converter, the frequency bearing a known relationship to the dielectric constant and, hence, the water content of the plant part; anddevices for electrically guarding the circuit generated by the elements from capacitance extraneous to the plant part comprising means for surrounding the elements with shields of electrical potential substantially equal to t

Abstract: A method for the nondestructive measurement of the moisture content of single grain kernels, seeds, nuts, or fruits which is independent of their weight, thickness, and projected area. At least two independent parameters of complex electrical impedance or admittance of a single grain kernel, seed, nut, or fruit are measured at two different frequencies and the moisture content is calculated therefrom.

Abstract: In an apparatus for determining the moisture content of a material by measuring the dielectric constant of the material by means of a measuring conductor which is disposed such that the material becomes a dielectric for the measuring conductor and wherein the time lapse between the application of an electrical signal to the measuring conductor and the return of the echo of the signal is employed as an indication of the dielectric constant and consequently the moisture content of the material, the electrical signal is a pulsed signal with a pulse duration which is greater than the time lapse between signal start and return of the echo of the signal start and an independent oscillator is provided whose cycles are counted during the opening state of a gate circuit which is open between the application of electrical signal to the measuring conductor and the return of the echo thereof, the counted cycles thereby providing an indication for the time lapsed from signal start to echo return in a simple manner with si

Abstract: Process for contactless measurement of the electrical resistance (or of the electrical conductivity) of a preferably flat material (test material) in which an alternating current is capacitively coupled into the test material with the help of two coupling electrodes. The total impedance is measured at at least three different frequencies, and from that measurement, the stray capacitance between the two coupling electrodes, the coupling capacitance between the two coupling electrodes and the test material, as well as the resistance of the test material are determined. In a preferred embodiment the process is used for controlling the windshield wipers of a motor vehicle.

Abstract: The invention is an apparatus for measuring the volume of water intrusion underwater cables without dissecting the cables. The apparatus comprises a novel arrangement of a capacitive test fixture and an electrical impedance analyzer to provide measurement of the volume of water in a cable based on cable capacitance. The capacitive test fixture measures the electrical capacitance along the cable as the cable is fed through the test fixture.

Abstract: A device, for detecting a sufficient glue coating on a first surface of a paper strip to be adhesively bonded in a cigarette machine, includes a sliding plate having a plate surface engaging a second surface of the paper strip, opposite to the first surface, and over which the paper strip runs in a first direction. A plurality of capacitive sensors, for detecting presence of moisture in the glue coating, on the first surface of the paper strip, are directed toward the second surface of the paper strip, are mounted in recesses in the sliding plate and are arranged in a row extending transversely to the first direction. A control is coupled to the sensors for evaluating signals emitted from the sensors and for emitting a fault signal for controlling the cigarette machine when the moisture sensed in the glue coating is insufficient.

Abstract: A liquid presence detector and method of using the same for a gas fluid conduit is provided by a capacitor that is placed inside the conduit and that is formed of two interwoven wire grids with one of the grids being insulated and the other grid being uninsulated. In one embodiment, the capacitor is generally planar and is oriented generally transverse a longitudinal axis of the conduit with a peripheral portion lying in a generally axial orientation along an inner surface of the conduit. A circuit is provided that measures capacitance between the two wire grids. The conduit is electrically grounded. Liquid particles entrained in the gas fluid or traveling along the conduit wall contact the capacitor and changes the capacitance thereof. In another embodiment, the capacitor is formed as a generally open cylinder positioned coaxially within the conduit.

Abstract: A ceramic bodied sensor having helical metallized electrodes for measuring the capacitance of an oil-water-gas or oil-water mixture flowing through a central bore of the sensor is disclosed. The sensor generally is a hollow cylinder with an inner ceramic layer which is very thin, a thicker outer ceramic layer which forms a strong structural unit, and a pair of isolated metallized electrodes which are generally approximately located between the inner and outer ceramic layers. The inner ceramic layer, outer ceramic layer and metallized electrodes form a dense monolithic ceramic tube. The electrode plates are preferably identical in size and shape and are isolated from one another electrically so that a condenser is formed by the separated plates. The inner ceramic layer is preferably very thin to minimize its capacitance value in comparison to the capacitance value of the water-oil-gas or oil-water mixture flowing through the central bore of the sensor.

Abstract: A contamination capacitance probe system is disclosed that capacitively mtors whether or not two or more fluids or materials that have to remain separated have been mixed or mingled and that provides first and second control signals respectively representative of the unmingled and mingled conditions. The system includes a capacitance sensor constituted by spaced-apart first and second capacitor plates of preselected size and spacing. The plate size and spacing is selected to render negligible any effect that the different materials or fluids or materials might have on the capacitance of the sensor. Circuit means are disclosed that includes a capacitance to frequency convertor, a frequency to voltage convertor, and a Schmidt trigger operative to provide the first and second control signals. The contamination capacitance probe system of the present invention is operable with any two or more fluids or materials having different dielectric constants and that are either immiscible or miscible.

Abstract: The present invention discloses an apparatus and method for continuous measurement of water volume in oil or steam which overcomes many of the shortcomings. In the present invention may shortcomings encountered in the prior art devices are overcome by placing a dielectric capacity probe inside the main pipeline, to measure the average dielectric constant (E) of the flowing mixture. This `in situ` sampling, will account for the entire cross-sectional area of the pipe or duct and its contents. The `in-situ` probe will have a high intrinsic capacitance approaching that of air, which has a dielectric constant equal to "1". The probe placed within the pipeline shall offer a minimal impedance to flow of the crude oil or steam and the oil's normal impurities and sediments. The probe will automatically self-calibrate, `in-line`, at selected time intervals and shall be fully automated for the overall routine operation.

Abstract: A device for measurement of moisture in a body of particulate material, such as a grain in a pile or in a silo, is in the form of a spear with a set of conductive plates 2 carried at one end of a shaft 1 for immersion in the body of particulate material, and a read out meter 4 and carrying handle 3 at the other end of the shaft. Normally the set of conductive plates measure capacitance of the material via a phase locked loop oscillatory circuit. The plates are disposed and shaped to facilitate entry into and removal from the body of particulate material.

Abstract: The device comprises: a high frequency alternating voltage generator the output of which is connected to a sensor probe 5 which is to be applied to a substrate to be measured, an amplifier the input of which is connected to the sensor probe, and a detector arranged to furnish a D.C. voltage signal based on the output from amplifier. The generator, the amplifier and the detector are located inside a metal envelope enclosure. An electromagnetic radiation shield is disposed inside the envelope to separate the amplifier and the detector from the high frequency generator. In operation, voltage output from the detector is indicative of the electrical impedance of the substrate as sensed at the probe. In the preferred application, the substrate is skin and the measured electrical impedance is indicative of the water content of the skin.

Abstract: A protection device for a waterbed protects the water bladder and water heater from damage due to overheating when a dangerous condition, such as an insufficient level of water within the bladder or an element of the waterbed surroundings interposed between the bladder and the water heater, arises. The protection device employs a detector in the form of two capacitance plates placed adjacent to the water bladder and connected to a circuit which is operative to prevent power from being supplied to the water heater upon detection of a dangerous condition. The capacitance of the detector plates varies with the level of the water within the bladder and with the presence of a surrounding element between the bladder and heater.

Abstract: A system for controlling the operating speed of a can machine having an input conveyor for temporarily storing cans while moving them along a path toward the machine includes a metal wire capacitance sensor. The wire may be formed in a repeating pattern and serve as an area mass sensor. The capacitance formed by the sensor wire and the can is connected in a capacitance bridge circuit which is excited by an oscillator. A detector circuit coupled to the bridge circuit generates an output signal representative of the number of cans in the conveyor. Output drive circuitry including an optical coupler for isolating the detection circuitry from the machine under control, transmits a signal for a desired control function to a remotely located variable speed drive controller for controlling either the machine to which the cans are being fed or a machine which is feeding the cans to keep the size of the can queue at a desired value.

Abstract: This invention relates to the measurement of the moisture content retained in the skin, and enables accurate diagnosis of the skin conditions by a device which can be switched in the connection of measurement electrodes to measure the moisture content either in the surface or in the depth of the keratinous layer of the skin.

Abstract: A moisture sensing device for an irrigation system. A pair of concentrically disposed cylindrical conductors are separated by a layer of beads, such that a capacitor is formed whose resistance will vary in response to the level of moisture present in the fibrous material. An electrical circuit is connected across the cylindrical conductors for measuring the variable resistance caused by the level of moisture present in the layer of beads. If the soil is dry enough to require watering, the sensor circuit will produce an output signal to the appropriate solenoid in the irrigation system to permit watering.

Abstract: A method of determining the moisture content of a material in which the material is caused to flow continually through a sensor region, the spatially averaged temperature of the material being continually determined independently of the dynamic thermal response of the material. The loss and capacitance of the sensor is also continually determined, the moisture content of the material than being determined in response to the spatially averaged temperature and the loss and capacitance determinations independently of changes in the packing density of the material as it continually flows through the sensor region.