Abstract: An electromagnetic device includes a jig and multiple wires. The jig includes a center member and coil-separating blocks. The coil-separating blocks protrude from the center member and are separated from each other to provide a coil channels. Each of the wires is wrapped on the jig, around the center member, and in one of the coil channels to form one of a multiple coils. Each of the coils is configured to connect to an electromagnetic navigation system and generate respective electromagnetic fields to be emitted relative to a subject.

Abstract: A system implementing fiber optics to monitor pipeline cathodic protection systems includes a cathodic protection system coupled to a hydrocarbon pipeline and a fiber optic system connected to the cathodic protection system. The cathodic protection system passes a current through the hydrocarbon pipeline to control corrosion of the hydrocarbon pipeline. The fiber optic system measures the current flowing through the hydrocarbon pipeline over time and provides the measured current.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may include synchronic symmetrical integrator circuitry and a magnetic field measurement device comprising an excitation circuit including an excitation coil, the excitation coil being wound around an amorphous soft magnetic core having a certain temperature coefficient such that inductance of the excitation circuit will change with temperature variations of the amorphous soft magnetic core; a detection circuit including a detection coil, the detection coil being wound around the same amorphous soft magnetic core, such that inductance variation of the detection circuit with temperature of the core can be detected from the excitation coil; and a resonation control circuit coupled to the excitation circuit and to the detection circuit to adjust a resonant frequency of the detection circuit responsive to temperature variations of the core. Additional apparatus, systems, and methods are disclosed.

Abstract: Improved magnetic sensor excitation circuitry is presented for providing a periodic bidirectional excitation waveform to a fluxgate magnetic sensor excitation coil using a bridge circuit connected to the excitation coil and having lower transistors for switched selective connection to a current mirror input transistor to mirror a current provided by pulsed current source, and with integrated filtering to control pulse rise times and slew rate.

Abstract: This disclosure provides methods and apparatus, including computer-readable media, for wireless power transfer and particularly active cancellation of undesirable electric or magnetic field emissions from a wireless power transmitter. In one aspect, the disclosure provides for an apparatus including a sensor, controller, and emitter, wherein the sensor is used to sense the electric or magnetic field emissions from a transmit antenna, the controller configured to determine the undesirable components of the field, and the emitter to generate a field to destructively interfere with the undesirable components.

Abstract: A geomagnetic sensor includes: a core that constitutes a closed magnetic circuit; a pair of coils that are wound around the core in positions facing each other and are connected in series to generate magnetic flux in the same circumferential direction in the core; an excitation power supply that applies an alternating current with a superimposed direct current to the pair of coils; and a detection circuit that is connected to a connection point of the pair of coils. Unlike a conventional flux gate type geomagnetic sensor, it is not required to excite the core until the core is magnetically saturated, and it is therefore possible to reduce power consumption.

Abstract: Compact, low power fluxgate magnetic sensor readout circuits and apparatus are presented in which demodulator or rectifier circuit to modulates a sense signal from the fluxgate sense coil, and the demodulated signal is provided to an amplifier circuit with a transconductance or other amplifier and one or more feedback capacitors connected between the amplifier input and amplifier output to integrate the amplifier output current and provide a voltage output signal indicating the magnetic field sensed by the fluxgate sensor.

Abstract: A magnetic element control device of the present invention includes an excitation signal generation unit that generates an alternating signal, a feedback signal conversion unit that converts a time width between detection signals of a positive voltage and a negative voltage into voltage information, an adjustment signal generation unit that generates an offset signal that cancels an offset component which is superimposed on a data signal indicating a magnetic field intensity, and an excitation signal adjustment unit that generates an alternating current, a feedback current, and an offset current from the alternating signal, the feedback signal, and the offset signal, respectively, superimposes the feedback current and the offset current on the alternating current, and generates an excitation current which is applied to an exciting coil.

Abstract: There is provided a thin film tri-gate fluxgate for detecting a component of a magnetic field in directions of three axes, the thin film tri-gate fluxgate comprising: two first thin film fluxgates of a bar-type disposed on a plane for detecting horizontal components of the magnetic field in direction of dual axis; and a plurality of second thin film fluxgates for detecting a vertical component of the magnetic field, wherein each of the first thin film fluxgates and the plurality of the second thin film fluxgates comprises a drive coil for applying a power, a pickup coil for detecting a voltage and, a magnetic thin film, and wherein the plurality of the second thin film fluxgates are substantially perpendicular to each of the first thin film fluxgates wherein a length of the magnetic thin film of each of the plurality of the second thin film fluxgates is shorter than that of each of the two first thin film fluxgates, and wherein two end portions of each of the plurality of the second thin film fluxgates is wid

Abstract: A method, and apparatus resulting from the method, for fabricating a circuit board suitable for mounting electronic components. The method includes drilling a plurality of through-holes in a plurality of dielectric sheets, forming a conductive film on at least one side of each of the plurality of dielectric sheets, and substantially filling each of the plurality of through holes with a conductive material. The conductive material is both electricallly and thermally uninterrupted from a first face to a second face of each of the plurality of dielectric sheets. The plurality of dielectric sheets are then sequentially mounted, on atop another, to form the circuit board. The sequential mounting step is performed after the steps of drilling the plurality of through-holes, forming the conductive layer, and substantially filling the plurality of through-holes.

Abstract: A fluxgate magnetometer including a fluxgate and a digital processor. The digital processor includes an analog to digital converter for digitizing the back EMF from the fluxgate and a signal generator to generate the fluxgate driving signal. Further, a current sourcing circuit is provided to receive the fluxgate driving signal from the signal generator and transmit a current amplified driver signal to the fluxgate capable of driving the fluxgate in and out of saturation. The signal generator is a pulse width modulator used in conjunction with a voltage shaper and driver to create a triangle-shaped driving signal to excite the fluxgate. The digital processor is further configured to reverse the sign of the digital back EMF signal at a frequency corresponding to two times the frequency of the fluxgate driving signal thereby capturing only the second harmonic of the back EMF signal.

Abstract: Disclosed is a method for improving the sensitivity of a fluxgate magnetometer for which high-order harmonics are detected and utilized in determining a weak external magnetic field expressed in the core region. These harmonic signals are processed coherently so as to increase the signal-to-noise ratio, since noise can only add to the signal incoherently at these harmonic frequencies. Also disclosed is a method for improving the sensitivity of a fluxgate magnetometer for which the technique of waveform autocorrelation is used in determining a weak external magnetic field expressed in the core region. By convolving the gated signal with a waveform duplicating the signal itself, noise content is effectively suppressed, thereby increasing the resolution power of the fluxgate magnetometer.

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: A non-contact probe provides information as to relative amplitudes of harmonics of a current or voltage waveform as well as total harmonic distortion. The probe includes a non-contact sensor with an amplifier coupled thereto. Output signals from the amplifier are digitized and analyzed in a programmed processor. Output from the processor provides a display of relative harmonic amplitudes as well as an indicator of total harmonic distortion.

Abstract: A high resolution, independent position sensor is provided, having application in a magnetic tape drive and other environments in which a linear or angular position is to be monitored. Analog outputs from an inexpensive, low resolution optical encoder are processed to correct gain and offset distortions and are used as the basis for an interpolation process. If a code strip having a 127-micron grating is used, a resolution of about 0.125 microns can be achieved.

Abstract: Digital logic and a high resolution digital to analog converter are used to adequately digitize a magnetic signal that is subsequently processed by magnetic data processing algorithms. The high resolution digital to analog converter is directly incorporated in a feedback loop of a magnetometer sensor, an expensive precision analog to digital converter is replaced by a less expensive, lower power digital to analog converter. The circuit improvement provided by the present invention includes an analog low pass filter coupled to the sensor, a digital logic circuit coupled to the analog low pass filter for providing an output signal from the magnetometer and a feedback output signal, and the digital to analog converter coupled between the digital logic circuit and a feedback coil of the sensor for coupling the feedback output signal thereto.

Abstract: Digital logic comprising a high speed analog to digital converter, a high speed analog to digital converter, a digital multiplier, and an infinite impulse response filter and decimation circuit are used to digitize a magnetic signal that is subsequently processed by magnetic data processing algorithms. The high resolution digital to analog converter is directly incorporated in a feedback loop of a magnetometer sensor, and an expensive precision analog to digital converter is replaced by a less expensive, lower power digital to analog converter. The improvement provided by the present invention includes a high speed analog to digital converter coupled between the oscillator and a first input of a multiplier, and a second analog to digital converter that is coupled between the sense coil of the sensor and a second input of the multiplier. The output of the multiplier is coupled to an infinite impulse response filter and decimation circuit that produces the digital output signal from the magnetometer.

Abstract: The sensor device uses the flux-gate principle and detects and cancels a second harmonic frequency (2f.sub.o) output by a sensor coil (23). The sensor device includes a master oscillator (1) that provides a stable output that is supplied to a generator (2) which generate two signals which respectively have a basic operating frequency (f.sub.o) and a double basic operating frequency (2f.sub.o or 2fc). The basic operating frequency (f.sub.o) is amplified in a power booster (3) and is connected to drive coil (22) mounted on a core (39) in the sensor head (4) to saturate the core (39). The output signal from the sensor coil (23) of sensor head (4) is filtered in a first bandpass filter (5) to obtain the second harmonic of the sensor coil, the output signal of the first bandpass filter (5) is detected in a phase detector (6) that is also connected to receive the double (2fc) frequency. The phase detector output is connected to a second low filter (7).

Abstract: A high sensitivity magnetic field sensor comprises a high permeability magnetic circuit (10) and excitation means (L.sub.e) for periodically saturating the magnetic circuit. Two identical windings (L.sub.1, L.sub.2) are symmetrically wound around symmetrical parts (A, B) of the magnetic circuit. Identical first and second capacitors (C.sub.1, C.sub.2) are respectively connected to the terminals of the windings. The voltages on the windings determine the value of the magnetic field.

Abstract: A method of measuring an azimuth by detecting the earth's magnetism by using two perpendicular coils to detect the azimuth according to the outputs of the coils, including the steps of converting the outputs of the coils by multiplying them by a constant so as to vary in a range determined by a reference value, dividing the converted signal by the reference value, and measuring the azimuth at each coil output according to an inverse trigonometric function, with the divided result as a variable. An azimuth measuring apparatus for executing the method is also provided. Thus, the method and apparatus can accurately detect the azimuth and can further detect an error due to a disorder of the earth's magnetism or the inclination of the apparatus.

Abstract: A roll-independent magnetometer which may be used for example in a towed array magnetometer system comprises a first magnetic field sensor having iso-angular flux sensitivity about a roll axis and a second magnetic field sensor having sensitivity along the roll axis, the arrangement being such that a component of a magnetic field along the roll axis is measured by the second unidirectional sensor and the component of the field lateral to the roll axis is measured by the first sensor. Corrections may be applied for the inclination of the sensor and the angle of dip of the Earth's field. The angle of dip may be measured either in the towing vessel, in the towed body, or provided in look-up tabulated form.

Abstract: A highly accurate, predictable and stable magnetic voltage and/or current reference that is substantially impervious to potentially hazardous radiation including neutrons, single or multiple particles, ionizing doses, particle beams and the like. The magnetic reference includes a stable permanent magnet which functions as a primary magnetic reference and generates a magnetic field. A magnetic field detector, comprising a second harmonic null detector (or fluxgate), senses the magnetic field generated by the magnet. A fed back current applied to control windings of the magnetic field detector cancels the magnetic field generated by the magnet and, in so doing, produces an AC error signal. This AC error signal is processed by an electronic control amplifier which provides the current that is fed back to the magnetic field detector.

Abstract: Disclosed is an azimuth determination apparatus attached to a motor vehicle for determinating the forward direction of the vehicle. The azimuth determination apparatus includes an azimuth sensor for generating orthogonal first and second signals indicative of the forward direction of the vehicle. Two azimuth vectors are obtained on the basis of the orthogonal first and second component signals, first components of the two azimuth vectors being maximum and minimum. The determination is made in terms of the fact that the difference between second components of the two azimuth vectors is below a predetermined value. In accordance with the determination, the orthogonal first and second component signals are corrected on the basis of said two azimuth vectors so that the accurate moving direction of the motor vehicle can be obtained irrespective of the remanence of the vehicle.

Abstract: A magnetic displacement transducer system for measuring the movement of a member includes an elongated permanent magnet which is mechanically coupled to the member so that the magnet moves parallel to its axis. A magnet-position sensor assembly, which includes at least one magnetometer having an elongated ferromagnetic core with a coil wrapped around it, is positioned adjacent the magnet so that the axis of the core and coil intersects the axis of the magnet at right angles. A pair of wires carry a sinusoidal excitation current to the assembly, convey the second harmonic from the assembly, and deliver a DC biasing current to the assembly in order to null the component of the permanent magnet's field that is perpendicular to the axis of the magnet. The value of the DC biasing current is measured to obtain the displacement of the member.

Abstract: An alternating magnetic excitation field is generated in the flux concentrators (11,12) of a Hall effect device, including a Hall element (13), by passing an a.c. current through a coil (14). This alternating field serves to drive the flux concentrators into and out of saturation. In the presence of a d.c. magnetic field and when a Hall current is applied to the Hall element, a second harmonic component is generated in the output voltage of the Hall element (13); the amplitude of the second harmonic component providing a measure of the d.c. magnetic field. In an alternative arrangement (FIG. 4) the flux concentrator means is in loop form rather than in a flat configuration as in FIG. 3.

Abstract: An electrical drive dircuit for a flux-gate magnetic sensor used in a digital compass for a vehicle provides signals for application to the primary of a flux-gate sensor to assure the core is saturated at a predetermined time during each cycle of the drive signal.

Abstract: In a contact-less electronic angular-position transmitter having a turnable magnet (5), sensor coils (11, 12) arranged at right angles to each other are provided on a toroidal core (9), common to all sensor coils, of a magnetic-field detector formed in accordance with the flux-gate principle in order to determine the angular position. The angular-position transmitter is preferably arranged, together with the turnable magnets and the turnable core having the sensor coils, in a housing (1) which shields them from the terrestrial field. In the said housing, the inner space (2), within which the magnet can turn, is hermetically separated from an inner space (3) in which the toroidal core (9), together with the sensor coils and the electronic system (15-19) is arranged.

Abstract: Methods and apparatus for detecting and locating residually magnetized misplaced tools and the like are disclosed. A sensitive gradiometer having a hand-held probe provides a balanced, phase cancelling magnetic field. The presence of a weak residual mangetic field emanating from the misplaced tool upsets the balance of the generated field, and this imbalance provides an audio signal which is used to locate the tool.

Abstract: A fault location system for use with sealed, gas-insulated electrical power apparatus. The system includes a sensor for placement in close proximity to the outer surface of a housing of the apparatus and a detector for in-place reading of the sensor. The detector comprises a first fluxgate magnetometer for detecting magnetization of the sensor. A second fluxgate magnetometer is positioned adjacent and parallel to the first magnetometer to detect only the background magnetic field. An alternating current electrical signal is applied to the magnetometers. A direct current is then automatically generated wherein the direct current is a function of the even harmonics of the ac output of the second magnetometer. The direct current is used to cancel the effects of the background magnetic field detected by the second magnetometer. As such, the direct current is applied to the first magnetometer to cancel the effects of the background magnetic field therefrom.

Abstract: In a direction indicator including a direction sensor having an excitation coil wound on a core and two output coils wound thereon to cross at the right angles with each other, a direct current of given amount is supplied to the two output coils and a direct current magnetic field is produced so that the maximum values of the output signals is made equal by adjusting the gain of the output signals.

Abstract: A flux gate magnetometer system utilizes three independent flux gates for measuring the three mutually orthogonal components of the earth's magnetic field. A sensor for each flux gate includes a ring core with a toroidal winding as the drive winding and a differential winding for sensing the difference in saturation due to the earth's flux linkages in the core. The operation of the flux gate magnetometer system is stabilized by a second harmonic servo type null circuit. The output of the differential sense winding is beat with a signal twice the frequency of the drive signal and in phase with the sensor output. This demodulated signal is the error signal for an integration stage. The integration stage drives a high impedance current source which sums into the flux gate sense winding and eliminates the effect of the earth's field in the sensor. An error signal is generated only when the high impedance current source does not null the earth's flux linkages in the core.

Abstract: The drive signal applied to the drive winding of a magnetometer is provided by a voltage controlled oscillator. The average current flowing through the drive winding is monitored, and a signal representative of the average current is applied to the input of the voltage control oscillator. The sense windings of the magnetometer are connected to a servo-loop which causes a current to flow in the sense windings which produces a magnetic field cancelling the sensed components of the earth's magnetic field. The magnetometer uses a drive signal which saturates the core for only a short duration of time thereby reducing the power required by the magnetometer while ensuring complete saturation of the core.

Abstract: It is known for current meters to operate by sensing the magnetic field produced by the unknown current being measured. Such meters may include a core (200-1) of magnetic material which may be opened to receive a current carrying conductor (400-1) and which is adapted to be coupled to the magnetic fields surrounding the conductor. Winding (300-1), placed around the core, is excited at a fundamental frequency as supplied by an ac source (110). Responsive thereto, an output voltage of twice or higher even harmonics of the exciting frequency is produced. The output voltage is proportional to the magnetic flux produced by the current being measured and hence may be extended through a meter for indicating the unknown current. Such arrangements tend to be expensive. The instant current meter (100) includes an arrangement for providing a dc current (190) through the core winding to neutralize the nonsymmetry of the magnetic field created by the unknown current.

Abstract: A magnetic locator in which flux-gate sensors are mounted in longitudinal notches at the ends of a tubular support to form an assembly which is inserted into a tubular housing, the sensors being press-fitted into the notches and the tubular support being provided with spaced bushings of material which is compressed when inserted into the housing. A stiff hairpin excitation conductor extends through the sensors and through the tubular support, being preassembled with one of the sensors and being connected to a circuit chassis for positioning the sensor assembly in the housing. A simplified electrical circuit is employed which produces a beat frequency signal when a magnetic object is located and which avoids the need for a voltage to frequency converter.

Abstract: The elongated core of a magnetic field probe is constructed of a heat-resistant diamagnetic body with lengthwise openings into which are received closely fitting wires of a magnetizable material. The wires are secured to the body by a heat-resistant cement. An excitation winding wound onto the core extends substantially beyond the core wire ends and a receiver winding is slidably received on the core.