With Device Responsive To External Physical Condition Patents (Class 331/65)
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Patent number: 5153525Abstract: 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.Type: GrantFiled: June 17, 1991Date of Patent: October 6, 1992Assignee: Minnesota Mining and Manufacturing CompanyInventors: Earl B. Hoekman, Steven M. Hamer
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Patent number: 5148126Abstract: An improved oscillator circuit and method for measuring capacitance and small changes in capacitance is described. The circuit provides a digital output signal that has a frequency inversely proportional to the capacitance being measured, is substantially immune to stray capacitance, has low sensitivity to noise and temperature variations, is relatively simple and inexpensive to implement and provides a high precision measurement. One embodiment of the oscillator includes a capacitor to be measured, an integrator, an inverting amplifier, a comparator, a summing amplifier and a digital output circuit. A second embodiment of the oscillator further provides compensation for the non-linear response of a parallel plate capacitive transducer.Type: GrantFiled: December 13, 1991Date of Patent: September 15, 1992Assignee: Sentech CorporationInventor: Mark E. Spencer
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Patent number: 5148125Abstract: Monitoring of the average dielectric constant in an extended volume of a medium such as soil is achieved using an oscillator incorporating a transmission line to be embedded in the medium. The transmission line is connected as the feedback loop of an amplifier, for one-way propagation of an electrical signal with a delay determined largely by the dielectric properties of the medium, such as its moisture content. The oscillation frequency is indicative of the dielectric constant of the medium.Type: GrantFiled: June 21, 1991Date of Patent: September 15, 1992Assignee: Lincoln CollegeInventors: Ian M. Woodhead, Stephen J. J. Hirsch
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Patent number: 5148149Abstract: An electromagnetic intrusion sensor including a sensing element, a first phase shifter circuit for phase shifting an input or oscillation signal in accordance with a capacitance of the sensing element, a second phase shifter circuit for outputting a reference signal having a fixed delay relative to the input or oscillation signal, a phase detector circuit for providing a detector signal having a duty cycle representing the phase differential between the outputs of the first and second phase shifter circuits, and an oscillator circuit for outputting a signal having a frequency which changes according to the duty cycle of the detector signal.Type: GrantFiled: January 31, 1991Date of Patent: September 15, 1992Assignee: Allied Security Devices, Inc.Inventors: David J. Campbell, Kenneth I. DeWitt
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Patent number: 5136262Abstract: An improved oscillator circuit and method for measuring capacitance and small changes in capacitance is described. The circuit provides a digital output signal that has a frequency inversely proportional to the capacitance being measured, is substantially immune to stray capacitance, has low sensitivity to noise and temperature variations, is relatively simple and inexpensive to implement and provides a high precision measurement. One embodiment of the oscillator includes a capacitor to be measured, an integrator, a comparator, a resistive attenuator, a summing amplifier and a digital output circuit. A second embodiment of the oscillator further provides compensation for the non-linear response of a parallel plate capacitive transducer.Type: GrantFiled: December 13, 1991Date of Patent: August 4, 1992Assignee: Sentech CorporationInventor: Mark E. Spencer
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Patent number: 5134371Abstract: A magnetic detection device including at least one oscillator circuit having a magnetoresistance element which converts a change of magnetism detected into a digital signal and a comparator for comparing the digitalized oscillating frequency of the oscillator circuit with another digitalized oscillating frequency generated from another oscillating circuit by taking a ratio thereof or by detecting a phase difference between the pulse signals. Utilizing the magnetic detection device, the amount of change of magnetism can be stably detected with a high accuracy within a wide range of ambient usage temperatures.Also, a physical quantity detection device including the magnetic detection device which can detect any physical quantity with a high accuracy.Type: GrantFiled: January 18, 1990Date of Patent: July 28, 1992Assignees: Nippondenso Co., Ltd., Nippon Soken, Inc.Inventors: Takamoto Watanabe, Yoshinori Ohtsuka, Muneaki Matsumoto, Tadashi Hattori, Kouichi Hoshino, Masanori Ohsawa, Katsumi Nakamura
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Patent number: 5130672Abstract: A sensor, especially for detecting misfeeds in a stream of sheets of paper, comprises a pair of sensing plates sensing changes in the capacitance between the plates, a first oscillator providing an output signal at a frequency representative of the capacitance, a second oscillator set to a reference frequency which is the same as or close to that frequency generated by the first oscillator when no object is between the sensing plates, gating means to produce an output representative of the frequency difference between the oscillator outputs, a low-pass filter, and a microprocessor which responds to changes in the difference frequency.Type: GrantFiled: September 19, 1990Date of Patent: July 14, 1992Assignee: Watkiss Automation LimitedInventors: Michael C. Watkiss, Allan G. Coaker
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Patent number: 5124648Abstract: A magnetometer having only a single coil winding for sensing the magnetic field along a single axis. Functionally, the invention comprises an oscillator, an integrator, and a voltage-controlled current source. The oscillator uses a saturating inductor which also serves as the magnetic-field-sensing element. The inductor is driven with a positive voltage and when the current through the inductor exceeds a value which indicates that the core is saturated, the driving voltage switches to an equal-magnitude negative value. This negative drive is maintained until the current again indicates the core to be saturated, at which point the driving voltages switches back to the positive value. With no externally applied field, the inductor current averages to a zero value. An externally applied field helps the core saturate in one direction and hinders it in the other, resulting in a change in average inductor current.Type: GrantFiled: August 25, 1987Date of Patent: June 23, 1992Assignee: Analog Devices, Inc.Inventors: Spencer L. Webb, A. Paul Brokaw
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Patent number: 5119044Abstract: An inductive proximity switch with adjustable switching hysteresis includes a presence indicator having an oscillator with an oscillating circuit and oscillator amplifier, a switch amplifier connected downstream of the presence indicator, an electronic switch controllable by the presence indicator through the switch amplifer, and a demodulator assigned to the oscillator. The presence indicator has an electronic circuit with a temperature dependency compensating for a temperature dependency of the switching point of the inductive proximity switch. The temperature dependency of the switching point of the inductive proximity switch is dictated by the temperature dependency of the quality of the oscillating circuit.Type: GrantFiled: June 19, 1991Date of Patent: June 2, 1992Assignee: Siemens AktiengesellschaftInventors: Franz Hoedlmayr, Michael Lenz
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Patent number: 5097227Abstract: A microwave oscillator circuit having an antenna, wherein the effective reactive impedance of the oscillator circuit is altered by the movement of a reactive impedance changing element past the antenna to cause change of the oscillation condition of the oscillator. A change in oscillation condition is sensed and sent to a utilization device to determine speed and/or position. The utilization device can be a computer which receives a signal from a wheel speed determining system, wherefrom a signal is sent back to a braking system for the wheel to control braking thereof. This can be accomplished individually for each of the four wheels to provide an anti-locking braking system.Type: GrantFiled: October 9, 1990Date of Patent: March 17, 1992Assignee: Texas Instruments IncorporatedInventors: Han-Tzong Yuan, Hua Q. Tserng, Hung Y. Yee
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Patent number: 5091704Abstract: An oscillator for use in a fluid detection apparatus for determining the respective percentages of first and second liquids in a mixture disposed within a chamber, including an inductive element immersed in the mixture such that the mixture at least partially determines a value of distributed capacitance exhibited by the element when energized; where the inductive element is a coil acting as a resonant element in an oscillator, and where the oscillator is of the tuned input type such that the coil and its distributed capacitance define a parallel resonant tank circuit which generates an oscillating signal at a resonant frequency of the tank circuit, the resonant frequency being inversely proportional related to the distributed capacitance of the coil.Type: GrantFiled: March 12, 1991Date of Patent: February 25, 1992Assignee: Chrysler CorporationInventor: John J. C. Kopera
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Patent number: 5079523Abstract: An inductive position indicator in particular for determining an angular position of a throttle flap of an internal combustion engine comprises an oscillator circuit, reversible oscillating circuit branches, a position detecting element cooperating with the oscillating circuit branches for position-dependent change of their inherent frequencies, and an evaluating circuit which determines the position from the current inherent frequencies, the oscillator circuit having two oscillators which in one reverse position cooperate with an associated first respectively second oscillating circuit branch and in another reverse position oscillating circuit elements of the first and second oscillating circuit branches are exchanged with one another so that each oscillator cooperates with a third respectively a fourth oscillating circuit branch of another inherent frequency.Type: GrantFiled: January 29, 1991Date of Patent: January 7, 1992Assignee: Robert Bosch GmbHInventor: Josef Kleinhans
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Patent number: 5078010Abstract: A sensor for sensing the level of adhesive medium in a dispensing device, which sensor comprises; (a) a coil which is adapted to surround a dispensing device for dispensing adhesive medium at an adhesive dispensing station; (b) means for connecting the coil to the input of an oscillator; (c) detector means for detecting the frequency of the output of the coil; (d) conversion means to perform a frequency to voltage conversion on the varying frequency detected at the detector means (c); (e) analogue to digital conversion means to convert the signal from the frequency to voltage conversion means (d) into a form which can be compared with a calibration scale obtained by measuring the signals generated at the output of the coil, when the coil is surrounding a dispensing device containing at least two different known quantities of adhesive medium; and (f) display means for displaying the result of this comparison.Type: GrantFiled: August 16, 1990Date of Patent: January 7, 1992Assignee: Emhart Inc.Inventor: Graham D. Lock
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Patent number: 5077528Abstract: 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.Type: GrantFiled: May 2, 1990Date of Patent: December 31, 1991Assignee: Borg-Warner Automotive Electronic & Mechanical Systems CorporationInventor: Amnon Brosh
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Patent number: 5051921Abstract: A liquid level and composition sensor includes a first interdigitated capacitor mounted substantially vertically in a tank, and a second interdigitated capacitor mounted substantially horizontally in and near the bottom of the tank. An electronic processor is responsive to the value of capacitance of the first capacitor for producing a first voltage signal proportional to the level of the liquid in the tank and is responsive to the value of capacitance of the second capacitor for producing a second voltage signal having a voltage level corresponding to the composition or dielectric constant of the liquid. The processor also multiplies the first and second voltage signals together to produce a liquid level voltage output signal having a constant slope for voltage amplitude versus liquid level, regardless of the composition of the liquid in the tank.Type: GrantFiled: November 30, 1989Date of Patent: September 24, 1991Assignee: David Sarnoff Research Center, Inc.Inventor: Robert W. Paglione
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Patent number: 5047734Abstract: A series-feedback crystal oscillator has a crystal element in series with a buffer amplifier. The oscillator maintains a linear oscillation signal by using an amplitude control circuit to hold the oscillation signal to a certain level at which distortion, clipping, or saturation does not occur. A control signal indicative of the amplitude of the oscillation signal linearly multiplies the oscillation signal to control the amplitude of the oscillation signal. Shunt capacitance across the crystal is compensated for by connecting a compensating capacitor to the same input terminal of the buffer amplifier as is connected the crystal. A compensating signal, which is equal in amplitude but opposite in phase to the signal passing through the shunt capacitance of the crystal is fed to the input terminal of the buffer amplifier to cancel the effect of the shunt capacitance. A noninverted tracer signal is injected in the feedback loop and passes through the shunt capacitance.Type: GrantFiled: May 30, 1990Date of Patent: September 10, 1991Assignee: New SD, Inc.Inventors: Gerald R. Newell, Michael W. Nootbaar, Pradeep Bhardwaj
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Patent number: 5043679Abstract: The invention relates to a temperature-stable inductive proximity switch having a transistorized resonant circuit oscillator. The feeding into the emitter-to-collector circuit of the resonant circuit transistor T1 of a balancing current, which depends on the individually determined temperature of the resonant circuit transistor T1 and the individually determined temperature of the resonant circuit coil, ensures that the proximity switch is temperature-stable with respect to its switching distance for every adjusted basic current.Type: GrantFiled: May 14, 1990Date of Patent: August 27, 1991Assignee: Christian Lohse Beruhrungslose Schalttechnik GmbHInventors: Dieter Kriz, Peter Heer
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Patent number: 5034704Abstract: A high frequency oscillation type proximity switch, comprising: an oscillation circuit having a first resonant frequency; a tank circuit connected in a positive feedback path of the oscillation circuit and including an LC resonant circuit having a second resonant frequency slightly different from the first resonant frequency; and a comparator circuit which discriminates the amplitude of an oscillation output of the oscillating circuit at a predetermined threshold level; the comparator producing a detection output signal when a nonmagnetic metallic object is brought to a certain proximity of a coil included in the LC resonant circuit and a level of the oscillation has thereby changed by a certain amount as a result of a change in the susceptance of the coil.Type: GrantFiled: May 29, 1990Date of Patent: July 23, 1991Assignee: OMRON CorporationInventors: Hidehiro Tomioka, Masakatsu Hosoya, Kenji Ueda
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Patent number: 5034722Abstract: A capacitance sensing security system in which comparison/reference and sensing oscillator are coupled together to operate in substantial frequency synchronism, each of the oscillators includes an amplifier having input and output terminals and a feedback circuit including a capacitor connected to the input terminals, the feedback circuit connected to the sensing oscillator exhibiting a low capacitive reactance, the input terminals of the sensing oscillator being connected to one or more objects to be secured so that extraneous transient signals appearing at or on the objects do not affect the phase/frequency of the sensing oscillator, the resistive component being substantially greater than the resistance of the input terminals and is provided either by adjusting the value of the capacitive component in the feedback circuit and/or disposing a resistor in series therewith.Type: GrantFiled: January 16, 1990Date of Patent: July 23, 1991Inventor: Joshua Premack
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Patent number: 5030955Abstract: A remote control transmitter includes a function selector device (17) for outputting selection signals in dependence on a function selected by operating the device. A function is selected by tilting the function selector device which includes optically functioning tilt switches. For this purpose, a ball guide housing (50) is constructed with five ball resting places, i.e. places in which a ball (K) within each specified tilt range always adopts a stable position. At one of the ball resting places a light transmitter (D) is mounted, while at other ball resting places light receivers (P1-P3) are located. A multi-bit signal is outputted by the light receivers, with the different bit sequences corresponding to different selection signals.Type: GrantFiled: July 10, 1990Date of Patent: July 9, 1991Assignee: Nokia UnterhaltungselektronikInventors: Klaus Durst, Richard Kramer
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Patent number: 5029300Abstract: A sensor according to this invention comprises an oscillation circuit including an LC resonant circuit, wherein a detection signal is prohibited upon arrival of an external radio wave.Type: GrantFiled: June 21, 1990Date of Patent: July 2, 1991Assignee: Omrom CorporationInventors: Keisuke Ishibashi, Hidetoshi Matsumoto
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Patent number: 5029268Abstract: The circuit arrangement for self-excitation of a mechanical oscillation system to natural resonant oscillations includes an electromechanical transducer system which is arranged in the feedback circuit of an electronic amplifier circuit so that it is stimulated by the output AC voltage of the amplifier circuit to mechanical oscillations and furnishes an AC voltage with the frequency of the mechanical oscillations to the input of the amplifier circuit. The amplifier circuit has a non-linear gain characteristic which at small values of the input signal gives a greater amplification than at lower values of the input signal. As a result a reliable oscillation start is ensured even under unfavorable operating conditions while on the other hand the danger of erroneous indications of the oscillation state, for example due to external vibrations, is reduced.Type: GrantFiled: February 27, 1989Date of Patent: July 2, 1991Assignee: Endress u. Hauser GmbH u. Co.Inventor: Martin Pfandler
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Patent number: 5025227Abstract: Metal detection apparatus comprises an oscillator circuit including an inductive detection coil and a detector for rectifying the output of the oscillator circuit synchronously with the frequency of oscillation. A comparison circuit compares the rectified output of the oscillator circuit with a reference signal and generates an output signal having a value related to the amplitude of the oscillator output. A feedback circuit generates a positive feedback signal and applies it to the oscillator circuit to maintain its oscillation at a predetermined amplitude under quiescent conditions. The circuit is largely immune to electromagnetic interference and temperature sensitive effects.Type: GrantFiled: October 11, 1989Date of Patent: June 18, 1991Assignee: William YoungInventor: Richard J. Walton
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Patent number: 5019782Abstract: 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.Type: GrantFiled: March 20, 1990Date of Patent: May 28, 1991Assignee: Siemens AktiengesellschaftInventor: Eckart Schatter
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Patent number: 5014908Abstract: A control circuit (1) for use in a humidifier (H). A capacitor functioning as a humidity sensor (55) includes a sulphonated fluorocarbon material acting as the dielectric (57) of the capacitor. The material is sandwiched between sheets (59a, 59b) of a screen material which act as plates of the capacitor. An RC oscillator (53) has a variable frequency output and incorporates the capacitor. Changes in the dielectric value of the material due to sensed changes in humidity produce changes in the oscillator output frequency. A DC voltage is supplied to the oscillator. The amount of voltage impressed on the sensor at relatively high-humidity levels is controlled to prevent leakage currents caused when the material is exposed thereto. The generation of such leakage currents otherwise adversely effects sensor operation. Operation of the circuit to control operation of the humidifier is also described.Type: GrantFiled: November 27, 1989Date of Patent: May 14, 1991Assignee: Emerson Electric Co.Inventor: Karmen D. Cox
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Patent number: 5012206Abstract: An inductive proximity switch in which a quartz oscillator is connected to a sensor resonant circuit having a sensor coil which is adapted to be influenced by the approach of electrically conductive nonmagnetic nonferrous metal (NF) objects and ferromagnetic metal (FE) objects. A detecting circuit detects when the sensor resonant circuit has an impedance which is indicative of either an NF object or an FE object at a predetermined switching distance from the sensor coil, thus causing the proximity switch to exhibit the same switching distance for both NF and FE objects. The oscillator frequency and the impedance of the sensor resonant circuit at the oscillator frequency are respectively set to be equal to a critical frequency and a critical impedance value at a critical response point defined by a point where impedance-frequency characteristic curves of the sensor resonant circuit under the influence of NF objects and FE objects at the predetermined switching distance intersect.Type: GrantFiled: April 20, 1990Date of Patent: April 30, 1991Assignee: Werner Turck GmbH & Co. KGInventor: Burkhard Tigges
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Patent number: 5005409Abstract: 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).Type: GrantFiled: February 7, 1990Date of Patent: April 9, 1991Assignee: Teleflex IncorporatedInventor: Peter A. Hochstein
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Patent number: 4994738Abstract: An inductive proximity switch comprises a high-frequency oscillator, an oscillator coil and an oscillator core. An analyzing circuit detects the inclination amplitude depending on the degree of core saturation. The analyzing circuit triggers a switching process when a certain threshold value of amplitude is reached. The core consists, for example, of ferrite. A yoke-like body is assigned to the core. The use of such a soft-magnetic material for the yoke-like body, allows the construction of smaller sensors with a higher sensitivity and a more cost-advantageous production. Their permeability curve in relation with one quadrant of the coordinate system is clearaly S-shaped.Type: GrantFiled: January 17, 1989Date of Patent: February 19, 1991Inventors: Gerno Soyck, Peter Dahlheimer
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Patent number: 4988953Abstract: An amplifier includes a first integrated circuit differential amplifier, the output of the first differential amplifier being fed back to its inverting input, an input is applied to its non-inverting input and second and third differential amplifiers are provided in the positive and negative supply line by which the input signal to the first differential amplifier may be imposed on the positive and negative supplies, so that the input capacitance of the first differential amplifier is effectively zero.Type: GrantFiled: June 14, 1989Date of Patent: January 29, 1991Assignee: ABI Systems LimitedInventor: Bernard Bollons
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Patent number: 4987366Abstract: A proximity switch having a test and an evaluation circuit contains a control circuit for generating pulses, an oscillator, a periodically activated damping circuit for the oscillator and a relay circuit. The test circuit, with the damping circuit and a control circuit, generates a pulse sequence required for the active testing only so long as the proximity switch is not damped by an outside element. The evaluation circuit carries a response current only as long as the test circuit also actively tests in its faultless condition.Type: GrantFiled: September 23, 1988Date of Patent: January 22, 1991Assignee: Siemens AktiengesellschaftInventor: Manfred Hamel
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Patent number: 4987389Abstract: Three series connected inverters (38, 40, 42) are attached to a tank circuit (18) which includes an inductance (12, 14) and a capacitance (16, 17). Negative (38) biases the inverters at the midpoint between the bistable low and high logic level states. Positive feedback from the second inverter (40) to the tank circuit induces oscillation in the tank circuit. The negative feedback is decoupled at the resonant frequency and the energy delivered to the tank circuit from the positive feedback maintains a low level oscillation in the tank circuit. Negative feedback around the three inverter digital circuit prevents lockup in the event of power loss or momentary short.Type: GrantFiled: April 2, 1990Date of Patent: January 22, 1991Assignee: Borg-Warner Automotive, Inc.Inventors: Amnon Brosh, Wolf S. Landmann
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Patent number: 4977404Abstract: A remote control transmitter contains on a circuit board (3), which is rigidly connected to the transmitter housing (1) of the remote control transmitter, a positional-deviation switch configuration (17), which in the event of an angular deviation of the circuit board (3) and thus of the remote control transmitter beyond a particular trigger angle (a.sub.o) from a particular given or instantaneously determined reference operating position generates an output signal designating the direction of the positional deviation. In a signal converter (5) of the remote control transmitter, this direction-dependent output signal is converted as a control command into a transmission signal, and emitted via a transmitter element (4) of the remote control transmitter to a remotely controlled electrical appliance.Type: GrantFiled: November 28, 1989Date of Patent: December 11, 1990Assignee: Nokia UnterhaltungselektronikInventors: Klaus Durst, Gerd Reime
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Patent number: 4968953Abstract: An oscillation circuit of a proximity switch includes a parallel LC resonance circuit (L, C), an oscillation transistor (Tr6) controlled by an output voltage from the resonance circuit for switching a constant current and a feedback circuit (Tr2, Tr3) for feeding back a current flowing through the oscillation transistor to the resonance circuit. In the circuit, there is further disposed a feedback current increase circuit including a second transistor (Tr7) controlled by an output voltage from the resonance circuit and a resistor (R) connected in series to the second transistor. The resonance circuit is supplied via the feedback circuit with a feedback current obtained by adding a current flowing through the feedback current increase circuit and a current passing through the oscillation transistor, thereby developing a large change in the amplitude of the oscillation.Type: GrantFiled: November 22, 1989Date of Patent: November 6, 1990Assignee: Omron Tateisi Electronics Co.Inventors: Yoshimi Kanda, Akio Matsumoto, Yasushi Matsuoka, Tsutomu Ajioka, Hirofumi Endo, Satoshi Motouji
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Patent number: 4965532Abstract: Circuit for use in a surgical operation including a phase lock loop having a voltage controlled oscillator, and a phase comparator for comparing a phase of a voltage of a driving signal and a phase of a signal representing the vibration phase of the ultrasonic transducer to derive a phase difference therebetween which is applied to the voltage controlled oscillator as a frequency control voltage such that the driving signal is phase-locked with a resonance frequency of the ultrasonic transducer, the improvement being characterized in that during a start period, a reference signal having a frequency which is increased monotonously is applied to the phase comparator such that the frequency of the driving signal is increased until the driving signal is phase-locked with the vibration phase of the ultrasonic transducer vibrating at the resonance frequency.Type: GrantFiled: June 14, 1989Date of Patent: October 23, 1990Assignee: Olympus Optical Co., Ltd.Inventor: Tomohisa Sakurai
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Patent number: 4947689Abstract: 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).Type: GrantFiled: January 13, 1989Date of Patent: August 14, 1990Inventor: Peter A. Hochstein
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Patent number: 4949054Abstract: An oscillator including a first frequency control network having a series coupled inductance and sensor capacitor, a pair of cascaded capacitors, and an emitter follower amplifier coupled thereto. The emitter follower amplifier drives a current limiter and a feedback path, whereby the current through the emitter follower amplifier is divided between the current limiter and the feedback path in a manner establishing an oscillatory potential in the oscillator, while keeping the transistor of the emitter follower amplifier substantially out of its saturation state.Type: GrantFiled: August 24, 1988Date of Patent: August 14, 1990Assignee: Setra Systems, Inc.Inventor: Dennis K. Briefer
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Patent number: 4942372Abstract: The temperature dependency of an oscillator can be reduced by a method and circuit that uses two positive feedback paths to provide the positive feedback necessary for maintaining the oscillation of an LC-oscillating circuit. One of the two feedback paths compensates the temperature dependent influences while the other compensates temperature independent influences.Type: GrantFiled: November 17, 1988Date of Patent: July 17, 1990Inventor: Peter Heimlicher
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Patent number: 4926143Abstract: A vibrating type transducer wherein an H-shaped vibrator, formed integrally with a silicon substrate and having a hollow chamber provided therearound, is kept self oscillating at its natural resonance frequency together with an amplifier. A physical quantity, such as force, pressure, differential pressure, or the like, which is applied to the silicon substrate is detected by a change in the natural frequency arising at the vibrator corresponding to the physical quantity. The invention also includes a method for manufacturing such transducer using a semiconductor technique, including steps for keeping a vacuum internally in the hollow chamber, imparting an initial tension to the vibrator, and then operating the amplifier to have stable self oscillation.Type: GrantFiled: September 16, 1988Date of Patent: May 15, 1990Assignee: Yokogawa Electric CorporationInventors: Kinji Harada, Kyoichi Ikeda, Hideki Kuwayama, Takashi Kobayashi, Tadashi Nishikawa, Tetsuya Watanabe, Takashi Yoshida
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Patent number: 4912976Abstract: A liquid level sensing system comprising a probe and a reactive element carried by the probe. The reactive element forms a portion of a tuned circuit in a voltage-controlled oscillator. The output of the voltage-controlled oscillator is compared to a fixed frequency reference signal and a frequency/phase detector generates a signal indicative of any difference. The frequency/phase detector output is applied to the voltage-controlled oscillator to maintain the output frequency of the oscillator at the frequency of the reference signal. The output of the frequency/phase detector is also differentiated to develop a pulse when the frequency/phase detector output signal varies rapidly, indicating initial contact between the probe and the surface of a liquid held within a container.Type: GrantFiled: June 26, 1987Date of Patent: April 3, 1990Assignee: Beckman Instruments, Inc.Inventor: Donald P. Labriola, II
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Patent number: 4914388Abstract: A proximity switch assembly (10) for signaling the location of a movable member (36) at either of opposite end limits of movement relative to a stationary frame (44,46) includes a compact elongate housing (58) adapted to be mounted on the frame to extend along the path of movement of a power driven member (32), such as the piston rod of a hydraulic cylinder, which shifts the movable member between its end limits. The proximity switch is fixedly mounted in the housing and carries a switch actuating member (74) mounted for sliding movement over a relatively short distance sufficient to move two actuating targets (104,106) into an out of actuating proximity of respective air core proximity sensing coils (132,134) within the housing. Lost motion abutment structure (76,78) on the switch actuation member and power driven member (54) move into engagement with each other as a power driven member approaches each end of its stroke.Type: GrantFiled: June 30, 1988Date of Patent: April 3, 1990Assignee: Eaton CorporationInventors: Daniel J. Kalista, Earl T. Piber
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Patent number: 4879474Abstract: A contact-free operating electronic switchgear, having an oscillator capable of being externally affected, a switching amplifier with at least two operating units disposed downstream of the oscillator, an electronic switch, which can be controlled by the oscillator via the switching amplifier, and a supply circuit for the provision of the supply voltage for the oscillator and for the switching amplifier, is shown and described. In electronic switchgear operating contact-free in accordance with the invention the maximum switching frequency is considerably increased in that a control circuit is provided between the two operating units of the switching amplifier and the oscillator and that the oscillator is controlled by means of the control circuit in such a way that the oscillator also oscillates in the affected state.Type: GrantFiled: July 7, 1988Date of Patent: November 7, 1989Assignee: i f m Electronic GmbHInventor: Jean-Luc LaMarche
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Patent number: 4879512Abstract: A circuit is provided for processing a pseudo-oscillatory signal generated by an oscillating circuit including a comparator and a logic circuit. The oscillating circuit has a first terminal connected to an energy source by a first switch and a second terminal referenced alternately to a potential substantially equal to half the high potential of the power supply and to the low potential of the power supply. This alternate reference is determined by a second switch controlled synchronously with the first switch by the logic circuit.Type: GrantFiled: April 22, 1988Date of Patent: November 7, 1989Assignee: La Telemecanique ElectriqueInventors: Didier Leonard, Jean-Marie Periot, Pierre Petit
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Inductive proximity switch oscillator having same activating range for ferrous and nonferrous metals
Patent number: 4879531Abstract: An inductive proximity switch including an oscillator circuit with a frequency resonant circuit (1) determining the frequency and with an impedance member (7) determining the amplification, this impedance member containing an impedance resonant circuit with a sensor coil (9) that can be influenced by the approach of a metallic trigger. In order to provide that the proximity switch has the same activating range for ferrous and nonferrous trigger metals, the resonant frequency (f.sub.o) of the frequency resonant circuit (1) and the critical impedance value (Z.sub.o) of the impedance member (7) are tuned, according to this invention, to the coordinates (f.sub.o,Z.sub.o) of the point of intersection (P.sub.o) of the impedance/frequency characteristics (II, III), resulting for respectively identical activating range, for an NF trigger and for an FE trigger.Type: GrantFiled: April 29, 1988Date of Patent: November 7, 1989Assignee: Werner Turck GmbH & Co., KGInventors: Burkhard Tigges, Dierk Brasse -
Patent number: 4879528Abstract: A circuit for generating a driving signal for an ultrasonic vibrating element including a voltage controlled oscillator for generating an oscillation signal which is supplied to the ultrasonic vibrating element as the driving signal, a phase difference detector for detecting a phase difference between the voltage and the current of the driving signal to produce a control voltage corresponding to the detected phase difference, said control voltage being applied to a control input of the voltage controlled oscillator, a comparator for comparing the control voltage from the phase difference detector with a reference voltage to generate an output signal when the control voltage exceeds the reference voltage, and a voltage setter for responding to the output signal to reset the oscillation frequency of the voltage controlled oscillator to a predetermined frequency which is lower than the optimum resonance frequency so that the ultrasonic vibrating element is energized in the most efficient manner.Type: GrantFiled: August 30, 1988Date of Patent: November 7, 1989Assignee: Olympus Optical Co., Ltd.Inventor: Masakazu Gotanda
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Patent number: 4876892Abstract: A pressure sensor includes a variable capacitor responsive to an applied fluid pressure to predictably change capacitance value. A tuned oscillator circuit having an inductive impedance includes the variable capicitor and simulates a resonant inductive-capacitive circuit not including an inductor. The tuned circuit oscillator to provide a signal with a period which is a function of the variable capacitance value, and of the applied fluid pressure. Additional elements are provided for precise measurement of the variable signal, correction for temperature effects, correction of measurement aberrations, and production of an output signal in a preferred format.Type: GrantFiled: April 19, 1988Date of Patent: October 31, 1989Assignee: Allied-Signal Inc.Inventors: F. Gene Arabia, Zvi Shkedi, Randy L. Brandt
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Patent number: 4873494Abstract: An inductive loop presence detector, more especially a vehicle detector, including a loop oscillator having an inductive loop connected as a frequency determining element of the oscillator, which inductive loop may be buried in a roadway to sense the presence of vehicles, and sensing circuitry to detect changes in the loop oscillator frequency due to vehicle movements in the vicinity of the loop, with a filter network inserted between the output of the loop oscillator and the sensing circuitry to improve performance when cross-talk occurs due to mutual interference between a number of inductive loop detectors forming part of a total installation. The filter network can be a phase-locked loop incorporating a low pass filter to attenuate high frequency components due to cross-talk.Type: GrantFiled: March 13, 1984Date of Patent: October 10, 1989Assignee: Sarasota Automation LimitedInventor: Brian C. Jefferis
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Patent number: 4868499Abstract: An object detector uses product feedback in order to eliminate false indications of the presence of an object due to a change in operating frequency and/or transmitter coil current. The alternating current in the transmitter coil is measured with a capacitor, resistor and operational amplifier and rectified to develop a voltage which is compared with a reference voltage producing a constant voltage in the pickup coil. Additionally, combination feedback may be provided whereby nearly constant pickup coil voltage is maintained where a transmitting coil inductance change is associated with a geometrical change in the spacing between the transmitting coil and the pickup coil.Type: GrantFiled: June 23, 1988Date of Patent: September 19, 1989Assignee: Honeywell, Inc.Inventor: Charles S. Walker
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Patent number: 4868521Abstract: A method and a circuit for exciting an ultrasonic generator comprises a control loop which includes the ultrasonic generator itself and a voltage-controlled oscillator. The control loop keeps the active power consumption to a desired value, which is compared in a comparator with the instantaneous active power consumption. One output of a further rectangular oscillator is connected to the control input of the voltage-controlled oscillator. The rectangular oscillator is put into operation if in the control loop there are no control oscillations or only those which are smaller than a predetermined threshold. The output of the rectangular oscillator is connected across one diode to the control input of the voltage-controlled oscillator and across another diode to the controlled input of comparator. The additional signal is applied to the voltage-controlled oscillator, apart from the control signal of the control loop.Type: GrantFiled: August 16, 1988Date of Patent: September 19, 1989Assignee: Satronic, AGInventor: Manfred Konrad
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Patent number: 4866377Abstract: A proximity detector of the integrated electronic type which includes an oscillator, which detector detects the position of a target relative to a proximity zone limit by Eddy current changes. The detector is operated over a cycle having a first period during which its functioning is checked by alternately starting and stopping the oscillator and for a second period during which the position of the target is determined.Type: GrantFiled: April 16, 1987Date of Patent: September 12, 1989Assignee: ABB Petercem S.A.Inventor: Mihail Macovschi
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Patent number: 4859944Abstract: A magnetometer having only a single coil winding for sensing the magnetic field along a single axis. Functionally, the invention comprises an oscillator, and means for measuring the duty cycle thereof. The oscillator uses a saturating inductor which also serves as the magnetic-field-sensing element. The inductor is driven with a position voltage and when the current through the inductor exceeds a value which indicates that the core is saturated, the driving voltage switches to an equal-magnitude negative value. This negative drive is maintained until the current again indicates the core to be saturated, at which point the driving voltages switches back to the positive value. With no externally applied field, the inductor current averages to a zero value and the duty cycle of the driving voltage is fifty percent. An externally applied field helps the core saturate in one direction and hinders it in the other, resulting in a change in average inductor current and drive duty cycle.Type: GrantFiled: August 25, 1987Date of Patent: August 22, 1989Assignee: Analog Devices, Inc.Inventor: Spencer L. Webb