Abstract: Magnetic process for determining the trajectory of a moving vehicle for finding a fixed or moving magnetic object and apparatus for performing the process.The apparatus comprises magnetometers for measuring at least p independent components of the gradient of the local magnetic field, in which p is an integer equal to the number of dimensions of the space in which the moving vehicle is displaced, a circuit for storing a scalar criterion which is a function of at least one of the components of the measured gradient, a circuit for calculating the direction (.theta., .psi.) maximizing the criterion as a function of the measured gradient and a display, for use in guiding the vehicle.

Abstract: A digital compass (20) has a sensing coil (60) wound on an elongated strip of high direct current permeability magnetic material. The sensing coil (60) is connected to a sensing circuit (56). The sensing coil and sensing circuit are responsive to the Earth's magnetic field to provide an oscillating signal at an output (28) of the sensing circuit (56) which varies in frequency with orientation of the at least one sensing coil (60) with respect to the Earth's magnetic field. A microprocessor (36) is connected to receive information inputs from the oscillating signal. The microprocessor converts the information inputs to an indication of orientation of the sensing coil with respect to the Earth's magnetic field based on the frequency of the oscillating signal. A display (52) receives the orientation indication from the microprocessor.

Abstract: A toroidal or similar body (1) of a non-magnetic, insulating material, preferably glass fibre-reinforced plastic or ceramic is provided with at least three recesses for receiving in each case a corresponding one magnetoresistive sensor. The associated measuring directions of said sensors are orthogonal to one another. For producing a magnetic auxiliary field applied to the sensors, a coil is arranged on the body. for increasing the accuracy and reliability of the measured result, the body is provided with at least one further recess for receiving a further sensor. The measuring direction of the further sensor differs from that of other sensors and forms preferably the same angle with the other measuring directions. The body can be in multipart form and is in particular made from two identical parts.The apparatus can be used in electronic compasses and for north finding devices.

Abstract: A system for measuring X and Y vector components of a composite magnetic field including static portions such as those produced by the earth's magnetic field, and time varying portions such as those produced by current flowing in a target anomaly to thereby permit determination of the distance and direction from a sensor to the anomaly is disclosed. Highly sensitive fluxgate magnetometers sense total field X and Y axis vector components of the composite magnetic field of interest and produce output signals which are fed through corresponding detector and null circuits to produce total field signals corresponding to the components being measured. These total field component signals are fed through corresponding signal conditioning circuits to equalize the time varying and static field portions of the signal components.

Abstract: A system for determining the relative orientation in three dimensions between a fixed frame of reference and an unconstrained object. Mutual coupling between three orthogonally disposed transmitting coils driven by a multifrequency source and three orthogonal receiving coils produce sets of analog voltages which are sampled; digitized and processed using a fast fourier transform device to yield directional components for determining the pitch and yaw angles about a line-of-sight axis. By using a multi-frequency source to drive the transmitting coils and by deriving coordinate component measurements to at least two discrete frequencies, errors in the results due to eddy currents in surrounding conductive structures can be compensated for.

Abstract: An apparatus and method for determining the position and orientation of a remote object in relation to an observation point comprises a transmitter for sending a magnetic field signal and a receiver for receiving and analyzing the magnetic field signal. The transmitter or the receiver is positioned at the observation point and the other is secured on the remote object. The transmitter has three coils positioned on a ferromagnetic core with their axes mutually orthogonal to each other and connected to a polyphase power to produce a magnetic field around the coils. The coils are connected and energized in pairs to produce a magnetic field rotating about the axis of the third coil. The receiver has three coils positioned on a ferromagnetic core with their axes mutually orthogonal to each other and responsive to the magnetic field produced by the tranmsitter. The receiving coils are connected in pairs to detect the phase relationship and magnitude of the signal to indicate the orientation of the remote body.

Abstract: The orientation of a moving platform with respect to a magnetic field is determined by rotating a 3-component vector magnetometer mounted on the platform about at least two axes in the magnetic field. Changes in the signals from the magnetometer are monitored, and the direction of the magnetic field relative to the platform is computed from the signal changes. It is not necessary to know the DC bias of each magnetometer channel or the component of the background magnetic field along each axis of the magnetometer.

Abstract: A direction sensor includes at least one sensor element including a ring-shaped core formed from at least one flexible wire made of zero-magnetostrictive amorphous magnetic material, two pairs of series connected coils spaced from each other at equal intervals about the core for sensing an external magnetic field, with the core being formed by threading the wires through the coils, the coils being excited by an alternating frequency f, wherein voltages of frequency f are produced across each pair of coils; and a process circuit for providing a differential voltage between the voltages of frequency f produced across each pair of coils.

Abstract: A process for automatically correcting alignment errors between the measuring magnetometers of a magnetic gradient meter, consists in adding to such a gradient meter two additional magnetometers perpendicular to each other and to the axis of the measuring magnetometers. The measurements delivered by these additional magnetometers allow, with two coefficients obtained by previous calibration, the two main errors terms to be calculated and the measured value of the gradient to be corrected accordingly, which allows the alignment error to be corrected electronically and automatically.

Abstract: A system for the detection, location and extraction of an intrauterine device ("IUD") including a magnetic IUD, a locator probe to be used intravaginally and an extractor probe to be used intrauterinally, both containing at least one Hall effect generator. The probe is inserted into the patient and an indicator means is provided to communicate the presence of the IUD, in the case of the locator, or the distance of the IUD from the probe, in the case of the extractor. After positioning the extractor next to the IUD using the indicator for guidance, grasping means in the extractor is actuated to effect temporary attachment of the IUD to the extractor which is then withdrawn from the uterus.

Abstract: A change in curvature or displacement of a section of submarine or subterranean fluid transmission pipeline is measured by traversing the pipeline with a pig having an onboard instrument package, including accelerometers and a longitudinal position measuring device comprising a magnetometer for counting the girth welds or other known magnetic anomalies along the section of pipeline to be measured. The accelerometers are mounted at the central longitudinal axis of the pig which is substantially coincident with the central longitudinal axis of the section of pipeline being measured so that the roll attitude of the pig does not influence the signals generated by the accelerometers. This arrangement precludes the requirement of mounting the accelerometers on a gyroscopic stabilized platform since the absolute position of the pig in space is not required, but primarily the change in curvature or displacement of the pipeline from a predetermined course is what is desired to be known.

Abstract: An electromagnetic communications and switching system provides for line-of-sight remote selection and actuation of a wide variety of apparatus. The system has a plurality of radiating antennas having independent components defining a reference coordinate frame. A transmitter is provided for applying electrical signals to the antennas which generate a plurality of radio frequency electromagnetic fields. The signals are multiplexed so that the electromagnetic fields are distinguishable from one another. An array of control positions is provided that is fixed with respect to the reference coordinate frame. A plurality of receiving antennas are provided which are adapted for mounting on the head of an operator. The receiving antennas are provided with independent components for detecting and measuring the components of the electromagnetic fields. A sight couples the eyes of the operator and the array of control positions.

Abstract: A magnetic field probe contains an injected coil body having a cloverleaf shape and on which two windings offset relative to one another by 90.degree. are provided. The coil body is positionally fixed in precise fashion in recesses of a bipartite housing, and are fixed therein via supporting tabs. The housing is formed of two identically fashioned half shells which are joined to one another with a friction-type lock by means of fastening elements applied in complementary fashion relative to a center plane.

Abstract: A current location updating display for indicating the current location of moving members such as an automobile while updating from time to time based on output from a magnetic azimuth sensor adapted to detect the azimuth of terrestrial magnetism. Output signals from the magnetic azimuth sensor are stored in a data memory after A/D conversion and correction, and a predetermined amount of data read out from the data memory is subject to the averaging processing. With this, plural angle information (sin .theta. and cos .theta.) signals or plural angle (.theta.) signals are averaged out including a signal corresponding to disturbance magnetism. Thus average data signals are integrated by an integrator and then sent to a display portion. Through the averaging processing an azimuthal error is restrained as small as possible, so that the current location or running path of the moving member may be indicated correctly.

Abstract: A magnetic axis is imparted to an object which effects three-dimensional rotational movement. The magnetosensitive semiconductor elements are disposed in the directions of three axes or two axes of a space determined for the object in such a manner that the elements are not in contact with the object. Any variation in direction of the magnetic axis resulting from movement of the object is detected by the magnetosensitive semiconductor elements. The detection signals from the magnetosensitive semiconductor elements are electrically processed so that the three-dimensional rotational position and movement of an object may be detected without contact and continuously.

Abstract: A solid-state heading sensor is comprised by a three-axis Hall effect magnetometer and a three-axis accelerometer. The magnetometer is comprised by a cube-like structure (10) of non-magnetic material on each of three orthogonally related faces of which is located a respective Hall effect device (11, 12, 13), for example of GaAs. The three-axis accelerometer may be comprised by a three-axis module (15) disposed in a recess in the cube-like structure, or by three separate accelerometer structures (23, 24, 25), for example planar etched silicon accelerometers, each disposed on a respective one of the orthogonally related faces adjacent the Hall effect device (20, 21, 22) thereon.

Abstract: A method and apparatus for measuring the individual strengths of two superimposed vector fields at different frequencies by sensing the three orthogonal directional components of the field, sampling these three components in rapid repetitive sequence, squaring the amplitudes of the resulting samples, filtering the squared samples to select the second harmonics of those field frequency components to be measured, amplitude-detecting the filtered signals, and detecting the square root of the amplitudes of the detected signals. Such method and system eliminates the need to provide highly accurately matched components for each separate frequency channel, as is required in previously-known systems.

Abstract: A magnetic probe for detecting the location of a magnetic anomaly. The probe includes an outer dewar jacket that defines a chamber maintained at cryogenic temperatures by a helium reservoir. Mounted on the reservoir in the chamber is a substrate which supports a plurality of pairs of gradiometer coils and a magnetometer. A plurality of SQUIDs detect the magnetic fields sensed by the magnetometer and the pairs of gradiometer coils to determine the magnetic field intensities, directions and gradients from which can be determined location, speed and direction of the anomaly. A valving network connecting the reservoir to a vent allows the probe to be operated in any orientation around its horizontal axis.

Abstract: The separation between first and second points is determined. At the first point are first, second and third mutually orthogonal coils that are excited in sequence, so that first, second and third magnetic fields are sequentially derived. At the second point are first, second and third mutually orthogonal magnetic field sensors that respond to the first, second and third magnetic fields, respectively to derive responses indicative of the magnetic fields coupled to them. The derived responses are combined in accordance with: ##EQU1## to derive the separation magnitude, where:V11, V12 and V13 are responses of the first, second and third sensors while the first coil is excited;V21, V22 and V23 are responses of the first, second and third sensors while the second coil is excited;V31, V32 and V33 are responses of the first, second and third sensors while the third coil is excited.

Abstract: A magnetic field sensor which may be rendered preferentially sensitive to magnetic field components in each of two, preferably orthogonal, directions by application of appropriate magnetic bias fields is disclosed.

Abstract: A method of well logging in petroleum exploration and apparatus for use in the method as 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 a pair of elongated U-shaped cores of laminated, high-permeability metal, with portions of each core being surrounded by a sensing coil. The coil output is fed to surface equipment for detection and analysis.

Abstract: A magnetic field measuring apparatus including a magnetic sensor having an excitation winding and orthogonal first and second output windings for generating a first and a second output signal indicative of the orthogonal components of an external magnetic field, adjusting circuits for adjusting the amplitude and frequency of the sensor output signals, circuits responsive to common timing signals whereby the outputs of the adjusting circuit are subjected to sample-and-hold operation and A/D conversion and the resulting converted outputs are counted to generate count outputs, and a first and a second display unit for simultaneously displaying the count outputs.

Abstract: An apparatus, using three gradiometers, measures the spatial variation of a agnetic field along a path of motion of the apparatus. The apparatus comprises three gradiometers oriented along the mutually orthogonal axes, x', y' and z' defined on the moving platform. The outputs of the gradiometers are the gradients of the magnetic field when the motion is considered to be in the y' direction. Three filters, each having an input connected to the output of one of the gradiometers, are constructed to have an output signal which has a relatively narrow positive peak with a relatively wide negative area on each side of the peak. The net area is approximately zero when the input to the filter is a doublet. Three squares, each having an input connected to the output of a filter, square their input signals. A summer, having three inputs connected to the outputs of the squarers, obtains the sum of the squares of the high-pass filtered components x', y' and z' of the magnetic field.

Abstract: A vehicle's heading indicating apparatus includes a direction-finding sensor having a pair of external field sensing windings wound perpendicular to each other, a sensor exciting oscillator circuit, a signal sampling timing circuit, sample-and-hold circuits, comparators, a logic circuit and an indicator circuit. The output of each of the sensor windings is divided into predetermined (N+1) signal levels such that the heading or direction of travel of a vehicle is detected and indicated in accordance with the combination of each two signal levels sensing the heading, and also large disturbance of the earth's magnetic field is sensed such that the just preceding direction of travel obtained is indicated when the earth's magnetic field is excessively low or high.

Abstract: Device for positioning a moving body in a plane indicated by the axes OX and OY by using a magnetic field. A current i, which is the sum of a current i.sub.o at frequency f.sub.o in which f.sub.o .perspectiveto.100 Hz and a current i.sub.1 at frequency f.sub.1 in which f.sub.1 .perspectiveto.10 kHz modulated by bursts of recurring pulses having a period T.sub.o with T.sub.o =1/f.sub.o flows through a conductor. The moving body carries two pairs of magnetometers supplying the components of the magnetic field h.sub.x.sup.o, h.sub.y.sup.o and h.sub.x.sup.1, h.sub.y.sup.1 with respect to axes associated with the moving body about frequencies f.sub.o and f.sub.1. A subassembly, on the basis of the values of h.sub.x.sup.o and h.sub.y.sup.o, supplies a signal U.sub.1 of frequency 2f.sub.o. A subassembly, on the basis of the signal U.sub.1, supplies two signals S.sub.1 and S.sub.2 displaced by T.sub.o /2. Another subassembly supplies signals T on the basis of the values of h.sub.x.sup.1 and h.sub.y.sup.

Abstract: A vehicle is guided along a desired path forwardly and backwardly by electromagnetically detecting deflection and attitude angle of the vehicle with respect to a guidance cable carrying an alternating current and producing a magnetic field.The deflection of the vehicle thus detected is compared with a predetermined deflection value from the guidance cable to produce an attitude angle setting signal, which is subsequently compared with the detected attitude angle to produce a steering control signal according to which the vehicle is controlled to run a desired path.

Abstract: An optical system is disclosed wherein light is transmitted through fibertic members orthogonally configured in a triaxial arrangement for measuring the magnetic field vector preset in the environment. In one preferred embodiment, a set of three fiber-optic coils positioned coaxially along respective orthogonal axes and having predetermined lengths and diameters are coupled to a source of polarized light for transmitting the light subject to Faraday rotation of its plane of polarization. In another preferred embodiment, light, not necessarily polarized. is transmitted along respective orthogonal axes through a set of three bifurcated fiber-optic cables each formed having a reference branch and a substantially equilaterally sensor branch on which a magnetostrictive material is intimately connected to produce optical path length changes related to the magnetic field component along the respective axes.

Abstract: A gradiometer for measuring magnetic field gradients. The gradiometer is formed by a number of magnetic field sensing devices. Each device has its own axis of sensitivity and produces a signal proportional to the magnetic field strength in the direction of its axis of sensitivity. The devices are mounted so that the different axes of sensitivity are at different angles to each other and so that at least some of the devices are displaced from each other along a common axis. The signals from the devices are combined so as to balance out unwanted components, particularly those due to the earth's magnetic field.

Abstract: A cable buried under a sea bottom is located by causing to flow in the cable an AC current, and measuring the magnetic flux near the cable.

Abstract: A structure is disclosed for mounting separate magnetic sensor assemblies in a magnetometer and the like with the axes of the respective assemblies disposed in mutually orthogonal planes. In a preferred form, the structure comprises three separate elongated housings of rectangular cross section for carrying three separate sensor assemblies. The housings are connected together so that two housings cross one another at right angles and are centered lengthwise with respect to one another. The third housing is connected to one of the first or second housings with its axis disposed at right angles to each and being centered lengthwise with respect to each. Also disclosed is a suspension assembly for suspending the structure in an outer casing, the suspension assembly including a gimbal arrangement whereby the structure is free to swing about a pair of mutually perpendicular gimbal axes.

Abstract: A system for, and a method of, detecting the proximity of a source of an alternating magnetic field, such as that emanating from power transmission cables, comprising a sensor coil sensitive to the magnetic field under detection, processing means to derive from the signal induced in the coil a warning signal indicative of the proximity of the magnetic field under detection, and cancelling means operable to cancel the earth's field in the region of the sensor coil. The sensor coil may be one of a pair operable to provide a signal representative of the directional heading of the magnetic field under detection, with respect to the system, which embodiment is particularly useful in helicopters for detecting the proximity of power cables.

Abstract: 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.

Abstract: Two mutually orthogonal radiating antennas each transmit electromagnetic radiation to three mutually orthogonal receiving antennas. The transmitted electromagnetic radiation carries data characterizing the phase and magnetic moment of the electromagnetic radiation. Measurement of the two transmitted signals as received by the set of three orthogonal receiving antennas produces information which, in combination with two known position or orientation parameters, is sufficient to determine in a noniterative manner the six position and orientation parameters of the receiving antennas with respect to the radiating antennas. Use of only two radiating antennas increases the speed of the system and simplifies the transmitter. Alternatively, three radiating antennas and two receiving antennas may be provided to simplify the receiver.

Abstract: An improved self-powered vehicle detector (SPVD) uses a two-axis magnetomr to sense a vehicle's magnetic signature and then telemeter vehicle presence information to a roadside receiver. The SPVD system includes digital nulling loops to cancel D.C. offset changes in the magnetometic output, a multi-tone code transmitter to transmit vehicle presence and SPVD condition signal, and an omnidirectional microstrip antenna to simplify installation and maintenance of the SPVD.

Abstract: Electrically conducting magnetic recording tape having a coating of .gamma.-Fe.sub.2 O.sub.3 particles on a polyester substrate is used as leads for probes in oven cavities and other microwave fields. The tape leads are flexible, have a high resistance per unit length, and are nearly transparent to electromagnetic waves. Electric diode-dipole probes with such leads are uniquely electric and a magnetic loop detector is uniquely magnetic.

Abstract: A compass device for underwater use and having substantially no magnetic nature or influence utilizes three Hall effect generators in an array wherein two of the generators have their principal axes of magnetic response extending normal to one another and at 45.degree. to the axis of the third generator. The array is rotatable relative to a base carrying three lights and solid state analog logic circuitry for causing the lights to be variously lighted and extinguished to indicate a need to turn left, to turn right, or being on course.

Abstract: A flux gate unit for producing an output representing the directional orientation of the unit with respect to the horizontal component of the earth's magnetic field, and in which a saturable flux gate magnetic core structure is mounted for leveling movement relative to associated flux gate coil means, in a manner enabling maintenance of the core structure substantially continuously in level condition while avoiding the necessity for leveling movement of the flux gate coils, and thereby avoiding the necessity for connection of electrical leads to a movable part.

Abstract: A three axis magnetometer is provided with a single calibration checking l lying in a plane disposed at equal angles to each of the three orthogonal axes of sensitivity. Energization of the calibration checking coil with a known current while the calibrated magnetometer is in a known condition of calibration provides sensitivity readings for each of the three axes, which readings provide a standard of comparison for checking the calibration and sensitivity of the magnetometer by similar energization of the coil when the magnetometer is disposed in a remote operational environment.