Abstract: The present technology concerns a method and an arrangement for the detection of a coil in an electronic circuit, which is operated with a direct voltage lying within a prescribed voltage range, and in which the coil together with a condenser forms an electrical oscillating circuit.

Abstract: There is described an inductive sensor for sensing a parameter such as position. The inductive sensor includes: receive aerial which is electro-magnetically coupled to a magnetic field generator via a resonant circuit with the electromagnetic coupling varying in dependence upon the sensed parameter so that a sense signal induced in the receive aerial is representative of the sensed parameter. The magnetic field generator generates a magnetic field including a first magnetic field component at a first frequency which is operable to induce resonance in the resonant circuit and a second magnetic field component at a second frequency which is not operable to induce resonance in the resonant circuit.

Abstract: A microwave integrated circuit chip having microwave transmission line coupled to an input of a microwave circuitry: The microwave transmission line comprises: a substrate; a strip conductor disposed on a first surface of the substrate, such strip conductor having an input signal pad at one end thereof, and a ground plane disposed on a second, opposite surface of the substrate. The microwave circuitry has capacitive input impedance. The chip includes a via passing from the first surface of the substrate, through the substrate, to the ground plane. A test probe ground pad is disposed on the first surface of the substrate and spaced from a portion of the via disposed on the first surface of the substrate.

Abstract: A method of making a resonant frequency tag which resonates at a predetermined frequency. The method involves providing a first conductive pattern having an inductive element and a first land and a second conductive pattern having a second land and a third land which are joined together by a link. The second conductive pattern is overlaid the first conductive pattern such that the second land is positioned over the first land. The third land is in electrical communication with the inductive element of the first conductive pattern. The formed resonant frequency tag is energized to determine if the tag resonates at the predetermined frequency. If the tag resonates properly, the third land is electrically coupled to the inductive element. If it does not, the second conductive pattern is adjusted so that overlapping portions of the first and second lands are changed, altering the capacitance to adjust the resonant tag frequency.

Abstract: A method of making a resonant frequency tag having a predetermined frequency comprises forming a first conductive pattern comprising an inductive element and a first land having a first end connected to an inductive element end, and a second end spaced a predetermined distance from the first end; separately forming a second conductive pattern comprising a second land having a predetermined width and a link element; placing the second conductive pattern proximate the first conductive pattern at a first location wherein the second land overlies a portion of the first land with a dielectric therebetween establishing capacitive element plates having a first capacitance along with the inductive element forming a resonant circuit; measuring the resonant circuit frequency and comparing the measured and predetermined frequencies moving the second land along of the first land length to match the resonant frequency; and securing the second conductive pattern to the first conductive pattern.

Abstract: Certain characteristics of Diesel engine lubrication oil are determined. A sensor formed as a capacitor is immersed in the oil. An inductor is in series with the sensor, and a high frequency voltage with a varying frequency is applied to the resonance circuit formed by the inductor and capacitor. Resonance is sensed, and the resonant frequency and/or the resonant current are used to determine the soot content and/or the dielectric constant of the oil. The electronics temperature can be used to compensate for temperature variations in the resonant frequency and the electronics temperature and the oil temperature can be used to compensate for temperature variations in the resonant current. The compensated values are preferably used in the determination of soot content and the dielectric constant.

Abstract: A high-frequency oscillation proximity sensor with an improved detection sensitivity uses, as a detection coil 11, a two-thread coil formed of substantively two coil conductors joined together at their first ends to form a joint connection end and twisted together, one of the two coil conductors being used as a resonance circuit coil L1 and the other as a copper resistance compensation coil L2, and comprises a drive circuit 12 for supplying a drive current to the joint connection end of the two-thread coil to thereby drive the detection coil to oscillate, a buffer 13 for taking out an oscillating output voltage generated at the joint connection end of the two-thread coil, and a phase shift circuit 15 for turning the phase of the oscillating output voltage taken out by the buffer by a predetermined angle and feeding it back to the copper resistance compensation coil to thereby negate the copper resistance of the two-thread coil.

Abstract: A Langmuir probe for measuring characteristics of a plasma driven by radio frequency (RF) power comprises an elongated conductor 10 having an exposed tip 1 for insertion into an RF plasma and an outer end 3 for connection to external measuring circuitry. In order to reduce distortion over a range of RF frequencies, the probe includes an RF voltage divider 11, 12, 13, 14 in series between the tip and outer end of the conductor.

Abstract: Inner individual electrodes are formed at intervals on a piezoelectric ceramic layer so as to correspond in a one-to-one relationship with ink channels, and an inner common electrode are formed on another piezoelectric ceramic layer. The required number of piezoelectric ceramic layers with inner individual electrodes and with an inner common electrode are laminated alternately. An outer common electrode is connected to the inner common electrodes, and outer individual electrodes are connected to the respective inner individual electrodes. The capacitance between the outer common electrode and each of the outer individual electrodes is measured. A polarization electric field adjusted based on the measured value is applied between the common electrode and each of the outer individual electrodes to perform polarization.

Abstract: A process for determining the position of an influencing element, using an inductive position sensor, several coils, a capacitor, an amplifier element, at least one changeover switch and an evaluation unit, a selected one of the coils and the capacitor forming a tuned circuit and the tuned circuit and the amplifier element forming an oscillator. Each coil is connected in succession to the capacitor and its impedance measured by the evaluation unit as a function of the position of the influencing element relative to the coil and that coil which is able to determine the location of the influencing element is determined. In further operation, only the impedance of the determined coil or of the tuned circuit formed therewith is measured and used to determine the position of the influencing element, and if the impedance of determined coil changes beyond a threshold amount, the impedance of at least one other coil or tuned circuit is measured.

Abstract: A position and electromagnetic field sensor is provided. The sensor relies upon an oscillator such as a Robinson marginal oscillator to generate an rf or microwave electromagnetic field. As an inhomogeneously shaped object, such as a metallic toothed wheel, for example, moves through the resultant field, the field experiences a change in electric or magnetic susceptibility. This in turn causes energy losses in the oscillator the magnitude of which can be output as a d.c. signal related thereto. To detect non-moving objects which nevertheless generate an electromagnetic field or have attached to them a source thereof, the sensor also includes a giant or colossal magnetoresistive structure located adjacent the oscillator coil, the structure having an imaginary magnetic susceptibility which is strongly dependent upon the magnitude and direction of the field generated by or at the object to be sensed.

Abstract: A testing device is operative to sense or monitor a radiated field emitted by an igniter for heating equipment such as an oil burner and to indicate the detection corresponding to a normal operating state of the igniter.

Abstract: A method of making a resonant frequency tag which resonates at a predetermined frequency. The method involves providing a first conductive pattern having an inductive element and a first land and a second conductive pattern having a second land and a third land which are joined together by a link. The second conductive pattern is overlaid the first conductive pattern such that the second land is positioned over the first land. The third land is in electrical communication with the inductive element of the first conductive pattern. The formed resonant frequency tag is energized to determine if the tag resonates at the predetermined frequency. If the tag resonates properly, the third land is electrically coupled to the inductive element. If it does not, the second conductive pattern is adjusted so that overlapping portions of the first and second lands are changed, altering the capacitance to adjust the resonant tag frequency.

Abstract: An electronic circuit for detecting a change with respect to a quiescent condition, which includes an oscillation circuit including a first and a second oscillator circuit, each oscillator circuit includes an oscillator input terminal and an oscillator output terminal on which an oscillation signal is present. The oscillator input of the first oscillator circuit is coupled with the oscillator output of the second oscillator circuit, and the oscillator input of the second oscillator circuit is coupled with the output of the first oscillator circuit. A detection circuit includes a first and a second detection circuit, each circuit further includes a detection input terminal and a detection output terminal on which a detection signal is present, while the detection circuit is arranged for detecting a change between the oscillation signals of the two oscillator circuits as a result of an external influence.

Abstract: An inductive path sensor for determining the position of the influencing element (2) is described, with several coils (4) arranged in succession, with one capacitor (5), with an amplifier element (6), with at least one changeover switch (7) and with an evaluation unit (8), one coil (4) at a time and a capacitor (5) forming an oscillating circuit, and one oscillating circuit and the amplifier element (6) forming an oscillator (9), the individual coils (4) being chosen in succession by the changeover switch or switches (7) and the evaluation unit (8) measuring the change of impedance of the coil (4) chosen by the changeover switch (7) or of the oscillating circuit chosen by the changeover switch (7) depending on the position of the influencing element (2) relative to the respective coil (4).

Abstract: A non-contact probe for determining the conductivity of coating materials is disclosed. The probe includes a free running oscillator operating at a selected frequency, a sensor made up of an LC circuit, a detector for detecting a change in the LC circuit in response to change in the sensor coil induction, and a processor for converting the detected changes in the signal to surface conductivity data. The detector may be a frequency detector that detects changes in the resonant frequency of the LC circuit or the detector may be a magnitude detector that detects changes in the signal magnitude of the LC oscillator. The sensor is the coil inductor of the LC circuit. Inductance of the sensor coil is variable depending on conductivity of the material near the sensor coil.

Abstract: A process for determining the position of an influencing element, using an inductive position sensor, several coils, a capacitor, an amplifier element, at least one changeover switch and an evaluation unit, a selected one of the coils and the capacitor forming a tuned circuit and the tuned circuit and the amplifier element forming an oscillator. Each coil is connected in succession to the capacitor and its impedance measured by the evaluation unit as a function of the position of the influencing element relative to the coil and that coil which is able to determine the location of the influencing element is determined. In further operation, only the impedance of the determined coil or of the tuned circuit formed therewith is measured and used to determine the position of the influencing element, and if the impedance of determined coil changes beyond a threshold amount, the impedance of at least one other coil or tuned circuit is measured.

Abstract: In a device for the monitoring and the prognosis of the failure probability of inductive proximity sensors (1) for the monitoring of the position of movable switch rails or rail components, in which the proximity sensor (1) has at least one coil (5) that is supplied by an oscillator (7), and the sensor current flowing by means of variable attenuation is measured and then fed to an evaluation circuit, characteristic lines (18, 22) of the sensor (1) are stored for the course of the sensor currents in dependency of the distance of the movable switch rails or rail components, i.e. the mechanical attenuation in an electric not additionally attenuated condition, and in an electric additionally attenuated condition. The measurement currents (22) corresponding to a mechanical attenuation condition (18), as well as to respective additionally electric attenuated condition are cyclic scanned.

Abstract: The invention relates to a device and method for carrying out a contactless measurement of the conductivity of a liquid situated in a flow channel, and to the use of said device and method. According to the invention, the invention provides that a toroidal coil is precisely arranged around the flow channel. Said toroidal coil is interconnected with a capacitor to an oscillating circuit. The invention also provides that the electric characteristics of this circuit are then measured according to the conductivity which is sought after.

Abstract: A position and electromagnetic field sensor is provided. The sensor relies upon an oscillator such as a Robinson marginal oscillator to generate an rf or microwave electromagnetic field. As an inhomogeneously shaped object, such as a metallic toothed wheel, for example, moves through the resultant field, the field experiences a change in electric or magnetic susceptibility. This in turn causes energy losses in the oscillator the magnitude of which can be output as a d.c. signal related thereto. To detect non-moving objects which nevertheless generate an electromagnetic field or have attached to them a source thereof, the sensor also includes a giant or colossal magnetoresistive structure located adjacent the oscillator coil, the structure having an imaginary magnetic susceptibility which is strongly dependent upon the magnitude and direction of the field generated by or at the object to be sensed.

Abstract: An electrical-technical product has a sensor (1) through which can be supplied a measured variable corresponding to a reactive resistance within a range of measurement, a matching network (2) and a surface acoustic wave (SAW) element in which the sensor is connected via the matching network (2) to a first reflector of the SAW element (3), and the first reflector (4) forms a resonator with the matching network (2) and the sensor (1). The resonator for one value of the measured variable within the range of measurement, is tuned to an acoustic surface wave on the surface wave element (3), in view of a reflection of the surface wave propagating at the first reflector (4). The resonance is determined by a maximum reflectivity of the first reflector (4).

Abstract: A system and method for determining characteristics of a proximity sensor. According to a preferred embodiment, the admittance of a proximity sensor/cable assembly is measured at two frequencies. Assumptions about sensor characteristics and cable characteristics are made, and an admittance corresponding to the assumed characteristics is derived. The assumptions are adjusted to obtain a correspondence between the measured admittance and the derived admittance. When the assumptions have been updated a specified number of times or when a desired accuracy threshold has been met, the adjusted assumptions may be used to determine one or more sensor characteristics, such as the separation between the proximity sensor and the target object.

Abstract: An apparatus and method for determining the position of magnetic tape within a magnetic tape cassette to ascertain whether the magnetic tape is in a rewound position within the cassette is provided. In a first aspect of the present invention, the magnetic tape cassette has two internal magnetic tape take-up reels. The magnetic tape stored on the tape-up reels is detected. The rewound status of the tape is determined by whether the magnetic tape is detected on only one reel or on both reels. In a second aspect of the present invention, a preselected amount of magnetic tape is detected within the magnetic tape cassette. The magnetic tape cassette is oriented and the position of the detected magnetic tape is determined relative to the orientation of the magnetic tape cassette. In a third aspect of the present invention, an electronically detectable member positioned in a known location of the cassette is detected. A preselected amount of magnetic tape within the cassette is detected.

Abstract: A road vehicle sensor provides an output signal having a magnitude which varies with time through a plurality of values as a vehicle passes the sensor. Signal processing apparatus monitors the timing of sensor signals generated from sensors in adjacent lanes of a highway and provides an indication when such sensor signals could correspond to a double count with a single vehicle being detected by both sensors. Then, the geometric mean of the amplitudes of the sensor signals from the sensors in adjacent lanes is calculated and is used to indicate a double count if the geometric mean is below a threshold value. Signal processing arrangements are also described to detect tailgating vehicles which may be simultaneously detected by a sensor, and for determining the length of slow moving or stationary traffic.

Abstract: Several sensors are provided for determining one of a number of physical roperties including pressure, temperature, chemical species, and other physical conditions. In general, the sensors feature a resonant circuit with an inductor coil which is electromagnetically coupled to a transmitting antenna. When an excitation signal is applied to the antenna, a current is induced in the sensor circuit. This current oscillates at the resonant frequency of the sensor circuit. The resonant frequency and bandwidth of the sensor circuit is determined using an impedance analyzer, a transmitting and receiving antenna system, or a chirp interrogation system. The resonant frequency may further be determined using a simple analog circuit with a transmitter. The sensors are constructed so that either the resonant frequency or bandwidth of the sensor circuit, or both, are made to depend upon the physical properties such as pressure, temperature, presence of a chemical species, or other condition of a specific environment.

Abstract: An inductive proximity sensor oscillator having a differential comparator in combination with a negative feedback network and a positive feedback network connected to the comparator. The positive feedback network determines the frequency and amplitude of the generated oscillations. An LC resonant tank circuit is connected between a non-inverting input and a fixed reference voltage, and a current limiting resistor connected between the non-inverting input and the output of the comparator. The negative feedback network provides a simple, fast and reliable start-up mechanism. It comprises a capacitor connected between the inverting input of the comparator and the circuit ground and a resistor connected between the non-inverting input and output of the comparator.

Abstract: Several sensors are provided for determining one of a number of physical properties including pressure, temperature, and other physical conditions. In general, the sensors feature a resonant circuit with an inductor coil which is electromagnetically coupled to a transmitting antenna. When an excitation signal is applied to the antenna, a current is induced in the sensor circuit. This current oscillates at the resonant frequency of the sensor circuit. The resonant frequency and bandwidth of the sensor circuit is determined using an impedance analyzer, a transmitting and receiving antenna system, or a chirp interrogation system. The resonant frequency may further be determined using a simple analog circuit with a transmitter. The sensors are constructed so that either the resonant frequency or bandwidth of the sensor circuit, or both, are made to depend upon the physical properties such as pressure, temperature, presence of a chemical species, or other condition of a specific environment.

Abstract: The change in thickness of a film on an underlying body such as a semiconductor substrate is monitored in situ by inducing a current in the film, and as the thickness of the film changes (either increase or decrease), the changes in the current are detected. With a conductive film, eddy currents are induced in the film by a generating an alternating electromagnetic field with a sensor which includes a capacitor and an inductor.

Abstract: A measuring system measures forces, deformations, and movements. The measuring system comprises at least one LC-circuit, at least one power supply for generating a voltage and a current in the LC-circuits, whereby the frequency, the amplitude, and the phase difference between the current and the voltage in a default situation are known and are furthermore a function of the variable to be measured, as well as at least one detection unit for detecting the frequency and/or the phase difference and/or the amplitude in the LC-circuit. The invention provides therewith a compact, simple and multifunctional measuring system by means of which a reading of the measured value is possible without contact with the subject.

Abstract: The period T.sub.nv of an oscillator signal is measured. A number N.sub.meas of cycles of the oscillator signal is determined based upon the measured oscillator period T.sub.nv and upon a desired minimum change in inductance .DELTA.L (sensitivity) which will result in an object being detected. The N.sub.meas cycles of the oscillator signal represent a measurement period. The length of the measurement period, defined by N.sub.meas oscillator cycles, is periodically determined. The length of the measurement period is compared to a reference value. An output, based upon the results of the comparison, is provided. Thereafter, the desired minimum change in inductance .DELTA.L (sensitivity) may be automatically adjusted by determining an average magnitude change in inductance .DELTA.L.sub.ave caused by a plurality of vehicles. The number N.sub.meas of oscillator cycles, which define the measurement period, is recalculated based upon the average magnitude change in inductance.

Abstract: An object has a plurality of parts, wherein each part of the plurality of parts can face a predetermined direction. A plurality of resonant circuits are mounted in different predetermined positions of the object, and have different resonance frequencies. A sending unit sends signals having a plurality of frequencies corresponding to the resonance frequencies of the plurality of resonant circuits. A detecting unit detects resonance signals of the plurality of resonant circuits. A plate has therein the sending unit and detecting unit. A determining unit determines a part of the object placed on the plate, the part facing the predetermined direction, using differences of detected levels of the resonance signals of the plurality of resonant circuits of the object detected by the detecting unit.

Abstract: A shaft position detection device for detecting a certain position on a shaft comprising: a movable shaft including a detection portion to be detected, a characteristic of which is different from the other portions; a position detection coil to which the movable shaft is freely inserted; an inductance detecting means for detecting changing of inductance between a case of the movable shaft being in the position detection coil and a case of the movable shaft being out of the position detection coil; in which a position of the detection portion in response to the changing of the inductance. The difference of the magnetic characteristic is defined by a cross section area of the shaft, winding a magnetic tape, forming a magnetic layer.

Abstract: In a capacitive discharge ignition system there being a first circuit detecting the voltage across the storage capacitor marking the onset of discharge of the storage capacitor, a second circuit detecting the voltage across the storage capacitor marking the substantially complete discharge of the storage capacitor, a third circuit for measuring the time between the events marked by the first and second circuits, and a fourth circuit for analyzing the measured time to determine conditions in the ignition system.

Abstract: The present invention discloses a method for obtaining frequency parameters to determine the resonator inductances of a crystal. Under this method, a plurality of frequencies are applied to a first electrode. This application is performed once while the second electrode and the common electrode are connected by a short circuit, and then again when the second electrode and the common electrode are capactively connected or open circuited. During each application of the plurality of frequencies to the crystal, the phase response for the output of the resonator circuit is monitored. Then the time response of the crystal is determined. Next, the time delay relative maxima for the time response is determined. Finally, the frequencies at which the time delay relative maxima occur are determined. These frequencies correspond to the inflection points where the change in phase goes from monotonically increasing to monotonically decreasing.

Abstract: A device for detecting attempts at fraud by connection of an electric feed line (13) to an apparatus for reading and writing on a chip card (3) essentially comprises a resonance unit (6) coupled to a contacting element (2) of the apparatus, and a measuring device (7). In the resonance unit (6) a generator (4) which is coupled to a resonator (1) by way of an impedance converter (5) generates a standing wave. The feed line (13) disturbs the properties of the resonator (1), that being detected by the measuring device (7) and evaluated.

Abstract: An electrical conductivity tester accurately measures the time-varying electrical conductivity .sigma.(t) and steady-state electrical conductivity .sigma..sub.ss, of a test material. In a first embodiment, the transmission phase of a probe circuit is monitored to determine the conductivity of a test material. In the first embodiment, an oscillator circuit generates a reference oscillator signal. A probe circuit receives the reference oscillator signal, magnetically couples to the test material, and modifies the reference oscillator signal via electromagnetic induction to derive a modified transmission phase signal. Finally, a phase detector circuit derives a transmission phase signal by combining the reference oscillator signal and the modified transmission phase signal, the transmission phase signal being directly convertible to the conductivity. In a second embodiment, an amplifier is connected to the probe circuit to form an oscillator circuit.

Abstract: A magnetometer vehicle detector for detecting various parameters of traffic on a roadway. A number of sensors, having a compact package, along with connecting cables, may be placed in road way with a small number of standard width sawcuts. Alternatively, sensors may be placed in the roadway within tubes under the external surface of the roadway. The package design of the sensor is such that the sensor can be placed in the sawcut or tube only in a certain way or ways resulting in the most sensitive axis of the sensor being most likely affected by just the traffic or vehicles desired to be detected and measured. The sensor may be a magnetoresistive device having a permalloy magnetic sensing bridge. Multiple sensors may be placed in single or multiple lanes of the roadway for noting the presence of vehicles and measuring traffic parameters such as average speeds, vehicle spacings, and types and numbers of vehicles.

Abstract: A system for sensing metallic debris in fluid flow, including an inductive probe utilizing one or more capacitors with a single turn resonant coil disposed about the flow passageway wherein a second, co-linear, multiple turn coil is provided about the passageway and loosely coupled via mutual inductance to the resonant coil such that the two windings produce a step-up transformer with increased impedance to closely match the impedance of the electrical output cable. This impedance matching reduces output signal loss permitting the sensitive components of the system to be remotely located from the usually hostile environment of the probe. Additionally, a toroid element of low loss, low reluctance material is disposed between the probe and its conductive housing to provide a guiding path for the magnetic "lines of force" of the sensing field produced by the probe, to avoid losses in the housing.

Abstract: An apparatus for sensing a target characteristic, such as relative distance between the apparatus and target, target thickness, target material, or lateral position between the apparatus and the target, includes a coil for directing an electro-magnetic field at the target. A voltage controlled oscillator energizes the coil at a resonant frequency which is functionally related to the target characteristic. The coil has an effective impedance value at resonance functionally related to the target characteristic. A frequency monitor measures the resonant frequency. An impedance monitor determines the impedance value when the drive frequency is at the resonant value. A PROM or controller determines the target characteristic in response to the measured resonant frequency and the determined impedance value. The PROM or controller provides a signal responsive to the determined target characteristic.

Abstract: A Langmuir probe system for measuring plasma internal discharge parameters in a radio frequency excited plasma processing system includes an electrically tuned resonant circuit. The electrically tuned resonant circuit includes a semiconductor variable capacitor. Specifically, an inductor and FET are connected in parallel to form a resonant circuit used to electrically tune the Langmuir probe. The tuning circuit is placed within a moveable, electrically floating, probe housing and is electrically tuned to improve tuning accuracy and to reduce detuning during operation.

Abstract: The resonance frequency and/or damping of a high-frequency oscillator which contains a variable impedance (such as a capacitor in a moisture detector for coffee or tobacco) is ascertained by generating first signals which denote the envelope curves of oscillations during intervals between successive excitations of the oscillator. Pairs of second signals denoting predetermined portions of envelope curves are transmitted to a dividing circuit, and the quotients of such pairs of second signals are indicative of the damping. Resonance frequency is ascertained by counting the number of oscillations per interval. Oscillations of the oscillator can be rectified prior to the generation of first signals.

Abstract: A microwave proximity detector includes a microwave oscillator circuit having a dielectric resonator, or having a micro strip line as an inductor thereof so as to sense a change in an oscillation frequency or output from the oscillator circuit caused by a variation in an impedance of a circuit including the dielectric resonator, or of the micro strip line, due to a loss which takes place in a leakage magnetic field from the micro strip line when an object approaches the leakage magnetic field, thereby detecting an object in the neighborhood of the switch.

Abstract: A detection apparatus for detecting a dielectric constant of fuel having an electrode disposed in a fuel passage and applied with an excitation signal, a monolayer-wound coil disposed in the vicinity of the electrode so that fuel is introduced in a space between the excitation electrode and the coil, a phase comparator which receives the signal to be applied to the excitation electrode and a signal induced in the coil to thereby compare the signals. The phase difference between both signals is detected using a low-pass filter to output the d.c. signal component of an output signal of phase comparator, a comparison integrator connected to the low-pass filter to output a controlled output signal so that the phase difference between the excitation signal and the induced signal in the coil becomes 90.degree.

Abstract: An inductive sensor is driven by a series resonant oscillator circuit to produce an oscillator signal having a frequency which is a function of inductance of the inductive sensor. An inductive load, which includes the sensor, is connected in series with a capacitive impedance. Power to the series resonant circuit formed by the inductive load and the capacitive impedance is controlled as a function of current in the series circuit as sensed by a current sensor. A detection system provides a detector output based upon the frequency of the oscillator signal.

Abstract: An apparatus for the measurement of the critical current of a superconductive sample, e.g., a clad superconductive sample, the apparatus including a conductive coil, a means for maintaining the coil in proximity to a superconductive sample, an electrical connection means for passing a low amplitude alternating current through the coil, a cooling means for maintaining the superconductive sample at a preselected temperature, a means for passing a current through the superconductive sample, and, a means for monitoring reactance of the coil, is disclosed, together with a process of measuring the critical current of a superconductive material, e.g., a clad superconductive material, by placing a superconductive material into the vicinity of the conductive coil of such an apparatus, cooling the superconductive material to a preselected temperature, passing a low amplitude alternating current through the coil, the alternating current capable of generating a magnetic field sufficient to penetrate, e.g.

Abstract: A method of controlling preselected parameters in an engine powered by a fuel mixture of first and second liquids utilizes differing dielectric constants of the first and second liquids to alter the frequency of an oscillator using a tank circuit formed by an inductor coil immersed in the fuel mixture and the distributed capacitance of the coil. The frequency of the oscillator therefore can be used to determine the percentages in the fuel mixture of the first and second liquids. The percentages, in turn, are used to control the preselected engine parameters.

Abstract: An L-C circuit (tank circuit) is located in close proximity to polymer impregnated composite material layers during the fabrication process. Applicant has determined that the resonant frequency of the tank circuit and the shape of the frequency absorption curve vary as a function of the fiber density of polymer impregnated composite material. The frequency of the input to the tank circuit is periodically swept through a range of frequencies, and the tank circuit impedance is measured to determine the resonant frequency and shape of the frequency absorption curve.

Abstract: The inductors in a switched resonant circuit are alternately connected in make before break fashion to ensure that at least one inductor is always connected to the tank circuit. This avoids switching discontinuities caused by signal propagation delay. By connecting both coils together between individual coil reading cycles, transients are absorbed.

Abstract: Method for determining qualities and/or frequencies of electrical tuned circuits. The method includes the steps of exciting the turned circuit with a switching pulse which has a short rise and fall time as compared with a period corresponding to the resonant frequency of the circuit, and evaluating the oscillation dying out after the switching impulse.

Abstract: An apparatus for measuring the electromagnetic values of a coil, in particular for measuring the position of the armature of a coil/armature magnetic system includes a capacitor connected parallel at an arbitrary location to a supply line for the coil so as to define a parallel resonant circuit containing inductance of the coil and capacitance of the capacitor. An exciting frequency is introduced into the parallel resonant circuit by a transducer which is connected to the supply line. In addition, an evaluation instrument is connected to the supply line for determining the resonant frequency of the parallel resonant circuit and thus the position of the armature of the coil/armature magnetic system.