Fixed Coil Magnetometer Patents (Class 324/258)
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Patent number: 6304083Abstract: Sensors, systems and methods for measuring magnetic field strengths in both AC and DC magnetic fields by using CMR material in tunable, radio-frequency LC oscillators are disclosed.Type: GrantFiled: September 15, 1998Date of Patent: October 16, 2001Assignee: The United States of America as represented by the Secretary of the ArmyInventor: Frank Owens
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Patent number: 6255815Abstract: A device for measuring and calibrating the strength of magnetic fields is provided. The device includes a coil of wire and either conductive pads or an ammeter/voltmeter attached to the coil of wire. The coil is disposed in the interior of a housing, and a locator window is formed in the housing in a position internal to the coil. The locator window allows the user to see through the device and thus position the device properly with respect to the source of the magnetic field. Preferably, a microprocessor is provided which converts a value of voltage or current induced in the coil into a value of magnetic field strength. The microprocessor transmits the value of magnetic field strength to the display.Type: GrantFiled: August 20, 1998Date of Patent: July 3, 2001Assignee: Neotonus, Inc.Inventor: Kent R. Davey
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Patent number: 6239596Abstract: A magnetic flux measuring device includes a coil of conductive material for sensing magnetic flux and producing a voltage in the presence of a changing magnetic field. An analog to digital converter is coupled to an output of the sensing coil for sampling the voltage produced by the magnetic flux sensing coil and for converting that voltage to digital data. A digital integrating device determines the total magnetic flux sensed by the coil over an event time interval by integrating the digital data over that same time interval.Type: GrantFiled: June 9, 1997Date of Patent: May 29, 2001Inventors: Joseph J. Stupak, Jr., Todd R. Hoffman, Rian M. Callahan, Michael Stupak
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Patent number: 6218831Abstract: The present invention is a system for cyclically driving an electrical current through at least one non-linear (i.e., saturable) inductor in alternating directions so as to produce a substantially periodic current waveform, and for producing an output signal representative of the current waveform. The system includes at least one capacitive node electrically coupled between a voltage source and a system ground, for storing electrical energy provided by the voltages source. The energy stored within the system is transferred as electrical current in alternating directions through the inductor via a switching network and a controller for configuring the switching network. The controller allows current to flow in each direction until the inductor saturates.Type: GrantFiled: May 19, 1999Date of Patent: April 17, 2001Assignee: Arthur D. Little, Inc.Inventor: J. Thomas Fowler
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Patent number: 6163150Abstract: A magnetic field sensor is provided which can be easily downsized and has a capability to detect a magnetic field in the Ghz band with a high space resolution and to reduce a voltage induced by an electric field. The magnetic field sensor is composed of a first layer, a second layer and a third layer. The first layer is provided with a straight-lined conductor pattern disposed in a perpendicular manner to a mid-point of another straight-lined conductor pattern being the longest among J-shaped conductor patterns. The third layer has the same conductor pattern as the first layer. The second layer has a ladle-shaped conductor pattern disposed along the center of the width of the conductor pattern of the first layer and third layer and an L-shaped conductor pattern disposed so as to form a loop face to face with the bending section of the J-shaped conductor pattern.Type: GrantFiled: September 15, 1999Date of Patent: December 19, 2000Assignee: NEC CorporationInventors: Naoya Tamaki, Norio Masuda, Masahiro Yamaguchi, Kenichi Arai
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Patent number: 6154028Abstract: A magnetic sensor device comprising a magnetic element and a wire wound around the magnetic element. The magnetic element has a cross-sectional area of not more than 0.55 mm.sup.2 and a saturation magnetostriction constant .lambda.s whose absolute value is smaller than 1.times.10.sup.-6, with Sw/Sm being equal to or smaller than 9, provided that Sw is the cross-sectional area of the wire and Sm is the cross-sectional area of the magnetic element. Preferably, the magnetic element has an elastic limit .sigma.m greater than 1,000 MPa, and the elongation the magnetic element experiences upon application of a stress equal to the elastic limit .sigma.m is between 1.0% and 5.0%. It is also preferable that the magnetic element and the wire are covered with a resin layer to form an integral unit.Type: GrantFiled: November 16, 1998Date of Patent: November 28, 2000Assignee: Unitika Ltd.Inventors: Kenichi Bushida, Shuji Ueno, Shinji Furukawa, Isamu Ogasawara
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Patent number: 6150811Abstract: A magnetic field sensor consists of a cylinder (2) with a core of premagnetized amorphous ferromagnetic metal. The inductance of the coil (2) is controlled by earth magnetic field H.sub.E and forms part of an L.C. oscillator (1). An adjusting device is provided to smooth out fluctuations from a target value in the oscillator frequency caused by the action of the field H.sub.E on the oscillator coil (2). This is done by allowing another adjustable magnetic field to influence the inductance (2) of the oscillator (1): the adjustable magnetic field is generated by a second coil (3) in the form of a compensating coil and the current flux (1) through the second coil (3) is controlled by the adjusting device in such a way that the magnetic field generated by the second coil (3) compensates for the action of the field H.sub.Type: GrantFiled: April 18, 1998Date of Patent: November 21, 2000Assignee: Mannesmann VDO AGInventors: Thomas Grill, Helmut Bacic, Martin Gruler, Oliver Springmann
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Patent number: 6124713Abstract: A matching amplifier for an induction probe which detects low-frequency alternating magnetic fields of floating bodies propagating in water. The matching amplifier has an isolating amplifier and a frequency response-determining network, with the network being provided with a frequency pass region having a band-pass characteristic and an integrating response in the band pass for the purpose of canceling the decorrelation of the measuring values emitted by the induction probe, with the integrating response being matched to compensate for the decorrelation of the measuring signal of the induction probe generated by the differentiating effect of the induction probe.Type: GrantFiled: December 15, 1997Date of Patent: September 26, 2000Assignee: STN Atlas Elektronik GmbHInventors: Wolfgang Bornhofft, Gerhard Trenkler
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Patent number: 6084406Abstract: A magnetic field sensor element comprises an elongated core of high-magnetic permeability material having a coil of electrically-conductive wire wound around and along a central axis of the core. The sensor, due to inductance of the core which changes with application of a local magnetic field, exhibits a characteristic of delaying an electrical input as a function of the strength of a magnetic field in the direction of the axis of the core, and the delay is measured as a function of the strength of the magnetic field. Appropriate circuitry provides at least one step-function voltage input to the coil such that the resulting delay in current charge-up into the coil creates a voltage across the coil which decays to a known reference value. The time delay for the voltage decaying to the reference value varies as a monotonic function with the strength of the applied magnetic field to be measured.Type: GrantFiled: April 1, 1997Date of Patent: July 4, 2000Assignee: Precision Navigation, Inc.Inventors: John J. James, George Hsu
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Patent number: 6002253Abstract: A probe for the detection of alternating magnetic fields has a highly permeable probe core (10) and a measuring winding (11) surrounding the probe core, with the measuring winding being put together of several coils (111, 112, 113) which are connected in series. In order to produce a probe which is suitable for the detection of extremely low-frequency alternating magnetic fields from a minimum distance commonly required for the detection of floating bodies that emit such alternating fields, the probe core (10) is put together from flat strips (16) of amorphous or microcrystalline magnetizable material with insulating strips (17) disposed in-between. The coils of the measuring winding (11) are configured as self-supporting coils, preferably as self-bonding wire coils, and surround the probe core (10) with almost no clearance.Type: GrantFiled: December 15, 1997Date of Patent: December 14, 1999Assignee: STN Atlas Elektronik GmbHInventors: Wolfgang Bornhofft, Gerhard Trenkler
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Patent number: 5955954Abstract: A warning and measuring device for personal protection with a rod-shaped casing shape. The shape of the casing allows the device to be suitable 1. for measuring if held in the hand or mounted on a tripod, 2. for warning when carried on the body and 3. for leak detection in hollow conductors. This is made possible through a compact construction and a movable absorber which in an absorber package within a cap can be fitted to the casing while the cap is detachable and can be used as handle on the other end. The device can be economically manufactured and with regard to quality can be considered a high-quality measuring instrument.Type: GrantFiled: June 15, 1998Date of Patent: September 21, 1999Assignee: Wandel & Goltermann Management Holding GmbHInventor: Helmut Keller
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Patent number: 5825183Abstract: A superconducting loop is formed by two Josephson junctions connected to both ends of a washer coil which serves also as a pick-up coil. The washer coil which is a magnetic field detection portion is constituted by two coils, i.e., a coil having a radius r.sub.1 and a number of turns n.sub.1 and a coil having a radius r.sub.2 and a number of turns n.sub.2 which are in the form of concentric circular loops. The two coils are coupled in opposite directions and are designed so that effective areas n.sub.1 .pi.r.sub.1.sup.2 and n.sub.2 .pi.r.sub.2.sup.2 are equal to each other. Since a magnetic field is directly detected by the washer coil, sensitivity to a magnetic field is enhanced. This makes it possible to obtain sufficient sensitivity to a magnetic field even if the area of the magnetic field detection portion is reduced to improve spatial resolution.Type: GrantFiled: April 19, 1996Date of Patent: October 20, 1998Assignee: Seiko Instruments Inc.Inventors: Toshimitsu Morooka, Kazuo Chinone, Nobuhiro Shimizu
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Patent number: 5818226Abstract: A magnetic sensor includes an elongated magnetic core and a coil wound on the periphery of the magnetic core so as to detect a magnetic field based on the change of inductance of the coil with high sensitivity and without increasing the number of turns of the coil. The number of turns of the coil in the central part of the magnetic core is larger than that of the coil at the end parts of the magnetic core. Thus, a bias field due to a bias current supplied to the coil is efficiently applied to the magnetic core. As a result, the inductance of the coil can be set to a large value without increasing the number of turns of the coil and a high sensitivity can be obtained.Type: GrantFiled: September 27, 1996Date of Patent: October 6, 1998Assignee: Sony CorporationInventor: Manabu Aizawa
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Patent number: 5804965Abstract: A method and apparatus for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring.Type: GrantFiled: September 24, 1996Date of Patent: September 8, 1998Assignee: The United States of America as represented by the United States Department of EnergyInventor: Robert D. Woolley
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Patent number: 5789920Abstract: A sensor and process for manufacturing same having an electrical circuit arranged on a carrier which is connected to an electrical connector and a sensor element. The carrier is disposed within a housing having one opening for the connector element and another opening for the sensor element. The sensor element and a first part of the carrier with the electrical circuit are embedded in a duroplastic molding compound. A second part of the carrier with the electrical circuit and the electrical connector are enclosed by a thermoplastic molding compound. A seal is arranged adjacent an intermediate space between the duroplastic molding compound and the housing.Type: GrantFiled: April 2, 1996Date of Patent: August 4, 1998Assignee: Gebhard Balluff GmbH & Co.Inventor: Ernst Gass
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Patent number: 5777470Abstract: An H-field probe for a radiation measuring system includes pairs of symmetrical planar magnetic loops for detecting electromagnetic (EM) radiation. EM radiation induces E-field and H-field currents in the loops. The individual loops of each pair are electrically coupled such that the E-field induced currents cancel while the H-field induced currents combine. The symmetrical construction results in virtually complete discrimination of the E-field.Type: GrantFiled: March 8, 1996Date of Patent: July 7, 1998Assignee: General Microwave CorporationInventors: Zdenek (Danny) Adler, Refael Popovich
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Patent number: 5773974Abstract: Apparatus for detection of the electro-magnetic field and measurement of its strength in the near field. The apparatus includes an antenna suited to receive specified type of the electro-magnetic field; a detector to convert received signal into DC voltage, a summing device and a potentiometer to set the reference level, a DC amplifier for amplification of resulting signal. The apparatus further includes a voltage-controlled oscillator and a speaker that produces an audible tone with the pitch proportional to the field strength. The apparatus further includes a squelch circuit that blocks the sound when the field strength gets lower than the preset range. The apparatus further includes LED level bar as visual means of indicating field strength. The apparatus is constructed as a fully self-contained unit needing no additional equipment for its operation.Type: GrantFiled: April 13, 1995Date of Patent: June 30, 1998Assignee: Credence Technologies, Inc.Inventor: Vladimir Kraz
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Patent number: 5764052Abstract: A magnetic field sensor comprises a substantially planar core member having flux concentrating fins, and relatively narrow segments that interconnect the fins so that an external magnetic field becomes concentrated within the segments. A quality factor (Q) of a single coil which is wrapped around the segments is monitored to measure or detect the presence of an external magnetic field. To measure an external field, a current is passed through the coil to charge the coil with a known quantity of energy. A circuit of the sensor then measures the quantity of energy returned by the coil to measure the Q of the coil, and to thereby measure the external magnetic field. The magnetic sensor is suitable for pacemaker applications as a substitute for reed switches.Type: GrantFiled: June 16, 1995Date of Patent: June 9, 1998Assignee: Pacesetter, Inc.Inventor: Herman Lee Renger
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Patent number: 5757184Abstract: A magnetic detection apparatus is disclosed, the size and cost of which can easily be reduced and with which excellent sensitivity can be obtained. The magnetic detection apparatus according to the present invention has a magnetic sensor formed by winding a coil around a magnetic member, wherein change in a response waveform of an electric current allowed to flow in the coil of the magnetic sensor occurring when time-varying voltage is applied to the coil is detected. Since the response waveform of the electric current allowed to flow in the coil is changed in accordance with the intensity of an external magnetic field, the external magnetic field can be detected.Type: GrantFiled: September 25, 1996Date of Patent: May 26, 1998Assignee: Sony CorporationInventors: Kazuo Kurihara, Manabu Aizawa
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Patent number: 5719501Abstract: A mine simulation system includes a magnetic field disturbance sensing apparatus carried by a moving vehicle and a plurality of randomly distributed passive permanent magnetic field disturbing devices located on the ground and simulated as mines. The sensing apparatus detects a magnetic field disturbance caused by the presence of any one of the passive permanent magnetic field disturbing devices when the vehicle comes into proximity of one passive permanent magnetic field disturbing device. A method for training personnel in mine field action can use this mine simulation system by entering the training vehicle into an area where the magnetic field of the earth has been disturbed by the presence of the passive permanent magnetic field disturbance device. When the training vehicle comes into proximity of one passive permanent magnetic field disturbance device, an output voltage is generated in the sensing apparatus detectable by a personnel being trained.Type: GrantFiled: November 6, 1995Date of Patent: February 17, 1998Assignee: Israeli Aircraft Industries, Ltd.Inventors: Moshe Spektor, Gil Shalev, Boaz Kartoon
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Patent number: 5555207Abstract: An electromagnetic field frequency and image magnetic forms quantum analyzer apparatus for collecting and evaluating magnetic field waves, which includes a sensor, a tape recorder for recording the waveforms, an oscilloscope for displaying the waveforms, film and video cameras to record the locations and wave images, a cassette recorder for recording and playback for studying the waveforms and can include a computer to display and dissect the waveforms.Type: GrantFiled: May 3, 1994Date of Patent: September 10, 1996Inventor: Stanley Barker
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Patent number: 5532681Abstract: The present invention is a magnetic field warning device suitable for protecting fetal health by alerting the mother whenever she or her fetus is exposed to alternating magnetic field levels which exceed predetermined levels. The device may also be used by anyone concerned about exposure to excessive alternating magnetic fields. The device comprises a magnetic field sensor for sensing alternating magnetic fields of arbitrary orientation, a detector for obtaining the magnitude of the sensed magnetic field, a filter for reducing the possibility of false alarms, a comparator for comparing the magnitude of the sensed field to a predetermined magnitude, and an alarm mechanism. The predetermined magnitude may optionally be adjustable, and the alarm mechanism is designed to minimize unwanted coupling of vibration to the user's abdomen. The device may be made small enough to be easily clipped on a belt so as to be worn by pregnant women at the abdominal level to monitor magnetic field exposure at the abdomen.Type: GrantFiled: February 13, 1995Date of Patent: July 2, 1996Assignee: Bodysonics, Inc.Inventors: Aemil J. M. Peters, Byron J. Masterson, Robert M. Abrams
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Patent number: 5512823Abstract: A hand-held detector for determining whether the exposure to electromagnetic fields resulting from electric power lines, faulty wiring, and electrical and electronic appliances is within acceptable limits. The device includes a shielded pickup coil, a filter circuit having a transfer function which provides a distinct response in two frequency bands, a summing circuit which provides a voltage indicative of the detected levels of electromagnetic flux density in the two frequency bands, and a display circuit, to provide a visual indication of the detected energy level. The filtering circuit preferably includes a first, extremely low frequency (ELF) amplifier having an upper cutoff frequency of approximately 2 kHz, and a second, very low frequency (VLF) amplifier having a lower cutoff at approximately 6 kHz.Type: GrantFiled: December 15, 1993Date of Patent: April 30, 1996Assignee: Eakes Research, Inc.Inventor: Raymond Nepveu
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Patent number: 5512824Abstract: An H-field probe for a radiation measuring system includes pairs of symmetrical planar magnetic loops for detecting electromagnetic (EM) radiation. EM radiation induces E-field and H-field currents in the loops. The individual loops of each pair are electrically coupled such that the E-field induced currents cancel while the H-field induced currents combine. The symmetrical construction results in virtually complete discrimination of the E-field.Type: GrantFiled: June 15, 1994Date of Patent: April 30, 1996Inventors: Zdenek (Danny) Adler, Refael Popovich
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Patent number: 5469058Abstract: The present invention features an active sensor for detecting a magnetic field. The sensor includes a pickup coil wound on a semi-flexible bobbin, which in turn is mounted on a suitable core assembly. Optionally, the core/coil assembly can then be mounted on a flexible substrate. Thin strips of either standard or amorphous crystalline high-permeability alloy are laminated to form the core. Once the coil has been assembled with the core laminations, output leads from the coil are connected to conductors of a miniature coaxial cable, the sheath of which is grounded to the core laminations. An operational amplifier is connected to the coil assembly. The operational amplifier has a positive feedback path to substantially cancel the combined dissipative loss of resistance and core eddy currents of the coil assembly. The operational amplifier also has a negative feedback path to set the maximum gain of the active sensor.Type: GrantFiled: December 30, 1992Date of Patent: November 21, 1995Inventor: Curt Dunnam
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Patent number: 5434500Abstract: A device for determining a position by locating a point on one side of a barrier such as a wall from the other side of the barrier has two main parts, a magnetic field generator (sending unit) and a receiver (receiving unit) which is able to detect the magnetic field. The sending unit, which is placed on the first side of the wall at the spot to be located, creates a magnetic field at that spot. The receiving unit is composed of two pairs of detectors (four detectors total) which measure the relative strength of the magnetic field at each detector. Measurement of the relative strength of the magnetic field at each detector allows the position of the source to be determined. The strength of the field is indicated by the display of light emitting diodes. When the strength of the field is equal at all four points the receiving unit is centered directly on the opposite side of the wall from the sending unit.Type: GrantFiled: July 26, 1993Date of Patent: July 18, 1995Inventors: Bruce Hauck, Gwynn Holbrook
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Patent number: 5365170Abstract: A continuous method of measuring magnetic properties of a strip or sheet of an electrical steel comprises the steps of inducing in the strip or sheet electro magnetic forces and measuring the value of such induced electro magnetic forces by passing the strip or sheet continuously through a flux density detecting search coil. The search coil comprises along a part of its length a jet of fluid electrolyte.Type: GrantFiled: January 19, 1993Date of Patent: November 15, 1994Assignee: ORB Electrical Steels LimitedInventor: Philip Beckley
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Patent number: 5329229Abstract: Superconducting detection coils for a superconducting quantum interference device are foraged on a flexible printed wiring film having a pair of opposed edges. The flexible printed wiring film is capable of being shaped into a cylinder by bringing the opposed edges toward each other. A superconducting wiring pattern is formed on the flexible printed wiring film and has at least one substantially U-shaped wiring portion. The U-shaped wiring portion forms at least two circular wiring patterns when the printed wiring film is shaped into a cylinder by bringing the opposed edges toward each other. The superconducting wiring pattern also has a first and a second electrode portion for connecting the circular wiring patterns to at least one superconducting quantum interference device. A resistor is electrically connected between the electrode portions of the superconducting wiring pattern.Type: GrantFiled: July 15, 1992Date of Patent: July 12, 1994Assignee: Seiko Instruments Inc.Inventors: Norio Chiba, Satoru Yabe, Akikazu Odawara, Satoshi Nakayama
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Patent number: 5311130Abstract: A system for detecting the presence of a magnetic field emanating from a video display terminal (VDT) in which a current induced through a sensing element is first amplified by a high gain amplifier stage having a very broad low band frequency response curve then rectified by a precision rectifier to convert the AC signal induced through the sensing element to DC current. The DC current is used as one input to a comparator, the other input being set by means of a potentiometer to provide flexibility in setting a threshold input voltage differential representative of a harmful magnetic field radiation level. The output of the threshold comparator triggers a driver which is connected to a battery powered solenoid. The solenoid actuates an indicator flag in the presence of a magnetic field which exceeds the threshold magnetic radiation level.Type: GrantFiled: March 8, 1993Date of Patent: May 10, 1994Assignee: Rad Devices, Inc.Inventors: Richard Bill, Enrique Rodriguez
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Patent number: 5311126Abstract: Field strength of an electromagnet is monitored at a threshold with a coupling coil positioned to monitor magnetic flux in a leg of an electromagnet. In the context of magnetic particle inspection for surface flaws (e.g. cracks) in ferromagnetic materials, sensing magnetic flux in a portion of a magnetic circuit including the material being inspected provides a continuous direct indication of whether or not the magnetic field strength produced is sufficient for reliable inspection to be performed. Since the magnetic flux in the electromagnet will be reduced with increases in reluctance of the magnetic circuit, the continuous monitoring of magnetic field strength also effectively monitors correct inspection technique by the magnetic particle inspection methodology.Type: GrantFiled: September 11, 1992Date of Patent: May 10, 1994Assignee: The United States of America as represented by the Secretary of the NavyInventors: John Mittleman, Robert DeNale, Lawrence M. Brown
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Patent number: 5309097Abstract: A system for detecting the presence of a magnetic field emanating from a video display terminal (VDT) in which a current induced through a sensing element is first amplified by a high gain amplifier stage having a very broad low band frequency response curve then rectified by a precision rectifier to convert the AC signal induced through the sensing element to DC current. The DC current is used as one input to a comparator, the other input being set by means of a potentiometer to provide flexibility in setting a threshold input voltage differential representative of a harmful magnetic field radiation level. The output of the threshold comparator triggers a driver which is connected to a battery powered solenoid. The solenoid actuates an indicator flag in the presence of a magnetic field which exceeds the threshold magnetic radiation level.Type: GrantFiled: April 15, 1992Date of Patent: May 3, 1994Assignee: Enrique RodriguezInventors: Richard Bill, Enrique Rodriguez
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Patent number: 5256960Abstract: The invention discloses a magnetic field radiation monitor which comprises at least one sense coil adapted to sense magnetic flux from the electromagnetic field to be measured for both ELF and VLF type of fields. The sense coil is coupled to a detection circuit wherein an EMF generated in the sense coil will be amplified and frequency compensated in the circuit to give an extremely flat frequency response allowing accurate detection of complex magnetic fields. The circuit consists of an ELF and VLF stage, both selectively coupled to the sense coil and incorporated into the circuit by a user activated switch. The output of either the ELF or VLF stages is further processed and the output is provided to a display to indicate the magnetic field strength measured. The magnetic field radiation monitor may be calibrated to yield a true RMS measuring platform using a RMS detector circuit which will give an accurate indication of magnetic energy content for complex waveforms.Type: GrantFiled: April 9, 1991Date of Patent: October 26, 1993Inventor: Amir R. Novini
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Patent number: 5150051Abstract: A meter (10) for measuring extremely-low-frequency radiation includes a coil circuit (22) whose output is filtered by a sharp-cut-off high-pass filter (24) to pass standard house-current frequencies but suppress the frequency components that would predominate as a result of movement of the meter with respect to the earth's magnetic field. An integrator (26) compensates for the frequency response of the coil circuit (22), an RMS circuit (35) converts the signal to its root-mean-square value, and a display circuit (28) provides a display determined by the resultant signal.Type: GrantFiled: April 11, 1991Date of Patent: September 22, 1992Assignee: Memtec CorporationInventors: Michael Friedman, Owen Harrington, David Dunn
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Patent number: 5130655Abstract: A borehole magnetic sensor includes a plurality of primary detector coils, aligned along parallel axes, and connected in series with each other. A corresponding plurality of feedback coils, each associated with a respective detector coil, are arranged to cooperate with an amplifier system to provide negative feedback and null the magnetic field through the detector coils. The feedback coils are connected in parallel.Type: GrantFiled: March 20, 1991Date of Patent: July 14, 1992Assignee: Electromagnetic Instruments, Inc.Inventor: Ugo Conti
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Patent number: 5105548Abstract: Apparatus and method for determining the azimuth (heading), pitch and roll which include a magnetometer-type sensor providing signals measured in three axes relative to a reference frame, and coil elements wound around the magnetometer which selectively impose specific magnetic fields about the sensor. Three axes field components of the magnetic field are measured from the sensor with and without the selective energization of the magnetic coils and stored, from which the azimuth, pitch and roll are calculated. Furthermore, quadrant correction is applied such that a unique reading is produced for all angles through 360.degree. of azimuth, pitch or roll.Type: GrantFiled: December 28, 1990Date of Patent: April 21, 1992Assignee: DigiCourse, Inc.Inventor: John T. Fowler
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Patent number: 5038104Abstract: Pickup coils for imaging magnetometers are formed from plural turns of a conductor with varying spacing between turns selected so that the Fourier transform of the coil turns function which is the filter function of the coil, has no zeroes within the spatial frequency bandwidth of the magnetic field generated by a two or three dimensional current to be imaged. Various exemplary coil configurations are presented including a Gaussian distribution for the turns of a planar coil.Type: GrantFiled: February 5, 1990Date of Patent: August 6, 1991Assignee: Vanderbilt UniversityInventors: John P. Wikswo, Jr., Bradley J. Roth
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Patent number: 5010653Abstract: Apparatus and method for determining the azimuth (heading), pitch and roll which include a magnetometer-type sensor providing signals measured in three axes relative to a reference frame, and coil elements wound around the magnetometer which selectively impose specific magnetic fields about the sensor. Three axes field components of the magnetic field are measured from the sensor with and without the selective energization of the magnetic coils and stored, from which the azimuth, pitch and roll are calculated. Furthermore, quadrant correction is applied such that a unique reading is produced for all angles through 360.degree. of azimuth, pitch or roll.Type: GrantFiled: October 20, 1989Date of Patent: April 30, 1991Assignee: Digicourse, Inc.Inventor: John T. Fowler
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Patent number: 4994742Abstract: Magnetic field sensing circuits including wire coils and Hall effect devices are provided which produce high-gain output for a relatively low change in perceived field intensity. Series connected plural Hall effect devices are connected to the coil and include amplifier and integrator circuits interposed at selected points between Hall effect devices to modify the output signal gain and passband. The circuits may include diode and capacitance elements to modify the circuit output signal.Type: GrantFiled: September 6, 1989Date of Patent: February 19, 1991Assignee: Atlantic Richfield CompanyInventor: Frank E. Lowther
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Patent number: 4945306Abstract: Relatively minute changes in magnetic field intensity are sensed by a circuit including a wire coil connected to a Hall effect element to provide the bias current to the element. The Hall effect element is disposed in the magnetic field with the coil and the output signal of the element is proportional to the square of the intensity of the magnetic field. The circuit is included in a device for measuring magnetic anomalies such as stress or corrosion cracks in structures of magnetic material including fluid transmission pipelines.Type: GrantFiled: October 25, 1988Date of Patent: July 31, 1990Assignee: Atlantic RichfieldInventor: Frank E. Lowther
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Patent number: 4939459Abstract: A magnetic sensor is provided for use in detecting an external magnetic field, typically geomagnetism. Pulse or alternating current is applied across a wire or strip-shaped electrically conductive, magnetic body in its longitudinal direction to create an internal magnetic field in the magnetic body. A pick-up winding is wound around the magnetic body. The sensor detects an electric signal developed in the winding as a result of interaction of the internal and external magnetic fields.Type: GrantFiled: December 21, 1988Date of Patent: July 3, 1990Assignee: TDK CorporationInventors: Yoshiaki Akachi, Mutumi Kinosita
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Patent number: 4839585Abstract: A magnetic field sensor coil wherein the coil is formed into a shape comprising two generally C-shaped limbs (2, 3) one within the other, one of these limbs being covered by a magnetic screening material (4). In operation an e.m.f. is induced in each turn of the unscreened part of the coil (3) while no e.m.f. is induced in the screened part (4) and so the total e.m.f. induced is approximately equal to the e.m.f. that would be induced in a simple concentrically wound coil of the same number of turns and of the same dimensions as the unscreened portion of the coil. The coil according to the invention is especially suitable for use with a system for monitoring an electric motor where the coil may be placed adjacent the motor end plate concentrically around the motor shaft without having to uncouple the motor from its load.Type: GrantFiled: June 2, 1987Date of Patent: June 13, 1989Assignee: Bonar Bray LimitedInventor: John Bicknell
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Patent number: 4724390Abstract: The present invention relates to an apparatus for detecting magnetic and electromagnetic waves or fields through use of non-superconducting materials. The present invention relates to apparatus which are used to measure such fields in order to predict earthquakes, volcanic eruptions and other violent earth movements which generate substantial abberations in magnetic and electromagnetic fields. The present invention can be used to detect any fluctuating magnetic or electromagnetic fields regardless of their origin. The present invention incorporates the use of antennae for the electromagnetic components and coils to detect magnetic fields, in conjunction with electronic elements involving amplification, smoothing elements, frequency response networks, networks to make frequency response uniform within the band and notch filters where necessary.Type: GrantFiled: March 24, 1986Date of Patent: February 9, 1988Inventors: Elizabeth A. Rauscher, William L. Van Bise
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Patent number: 4714880Abstract: This detector comprises at least one bar of a ferromagnetic material about which are wound several turns of a conductive coaxial cable cut in its center into first and second portions, said portions being connected in such a way that the sheath or tube of the first portion is connected to the core of the second portion and the sheath or tube of the second portion is connected to the core of the first portion, each of the two free cable ends being used for measuring the output voltage of the detector.Type: GrantFiled: June 5, 1986Date of Patent: December 22, 1987Assignee: Commissariat a l'Energie AtomiquesInventor: Paul Charmet
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Patent number: 4634969Abstract: A passive safety probe for placement in a time varying magnetic field to alert personnel when the power density of high intensity electromagnetic fields reach and exceed applicable personnel safety limits. The probe senses the magnetic field present with a loop antenna. The loop antenna produces a voltage output in response to the magnetic field. The output voltage is linearized by a frequency dependent filter and rectified to provide a direct current output which is subsequently coupled to an attention getting indicating means such as a light emitting diode and/or a horn. When detected field voltage exceeds the threshold of the indicating means, a visual or audible response occurs, indicating that safe field levels have been exceeded.Type: GrantFiled: May 14, 1984Date of Patent: January 6, 1987Assignee: The United States of America as represented by the Secretary of the ArmyInventors: George R. Edlin, Robert A. Snead
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Patent number: 4605899Abstract: The sensor makes it possible to increase the performances, particularly from the sensitivity and frequency band standpoints, by means of a coaxial helical coil, matched to the connecting end to an auxiliary current measuring apparatus. At each turn, a portion of the external conductor is bared and equipped with elements for matching to the characteristic impedance in order to compensate the breaks caused in this way.Type: GrantFiled: October 11, 1983Date of Patent: August 12, 1986Assignee: Thomson CSFInventors: Gregoire Eumurian, Jean-Pol Levan
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Patent number: 4323848Abstract: A method of well logging in petroleum exploration and apparatus for use in the method is described. An improved magnetometer is disposed in a well bore to provide indications of the distribution, filimentation, and distortion of a controlled current flow within adjoining strata of interest. The current flow is excited by a distant alternating source located at the surface or at other boreholes, and perturbations in the current flow and accompanying magnetic field caused by the electrical characteristics of the adjoining strata are registered by the magnetometer.The magnetometer comprises two pairs of elongated U-shaped cores of laminated, high-permeability metal, adjacent portions of each pair being surrounded by a sensing coil. The coil outputs are fed to surface equipment for detection and analysis.Type: GrantFiled: March 17, 1980Date of Patent: April 6, 1982Assignee: Cornell Research Foundation, Inc.Inventor: Arthur F. Kuckes
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Patent number: 4305785Abstract: A sensor for detecting changes in the magnetic field of the equilibrium-field coil of a Tokamak plasma device comprises a pair of bifilar wires disposed circumferentially, one inside and one outside the equilibrium-field coil. Each is shorted at one end. The difference between the voltages detected at the other ends of the bifilar wires provides a measure of changing flux in the equilibrium-field coil. This difference can be used to detect faults in the coil in time to take action to protect the coil.Type: GrantFiled: February 26, 1980Date of Patent: December 15, 1981Assignee: The United States of America as represented by the United States Department of EnergyInventor: Walter F. Praeg
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Patent number: 4305034Abstract: A device powered by a DC source produces an output signal the frequency of which changes as a function of changes in external magnetic fields sensed by such device. A pair of non-linear amplifiers are interconnected so that the output of one amplifier is the input of the other amplifier. An inductive sensor is connected between the outputs of the amplifiers. The inductive sensor has an elongated magnetic core and a coil is wound on the core. The voltages at the outputs of the amplifiers, across the inductive sensor, switch between zero and the full voltage of the DC source.Type: GrantFiled: April 9, 1979Date of Patent: December 8, 1981Assignee: Hughes Aircraft CompanyInventors: James C. Long, Monroe J. Willner, William R. Good