Abstract: A device for measuring magnetic fields comprises an assembly of at least two magnetic field sensors each of which comprises a number of magnetoresistive sensor elements situated in one plane and which have the same privileged directions of magnetization, said sensor elements being connected to a power supply circuit and to a signal processing circuit. The privileged directions of magnetization of the sensor elements of different magnetic field sensors are different. The assembly of magnetic field sensors is arranged within a magnetization coil made of a number of turns of an electric conductor extending around a central axis so as to generate an auxiliary magnetic field extending parallel to the central axis.

Abstract: An apparatus for measuring a weak magnetic field in a background D.C. magnetic field such as the earth's magnetic field or the like includes a magnetic pickup portion that is supported by a support mechanism which does not impede minute movement in the x- and y-axis direction. A pair of A.C. linear gradient magnetic fields whose directions of gradients are parallel to the x-axis and y-axis, respectively, are used for obtaining reference signals for sensing the position of the pickup portion. The frequencies of the A.C. linear gradient magnetic fields are set to be sufficiently higher than the frequency of the weak magnetic field that is to be measured. The A.C. linear gradient magnetic fields are provided by A.C. current flowing in two pairs of linear conductors which are perpendicular to each other.

Abstract: A tri-axial fluxgate magnetometer and housing therefor that includes elements which facilitate a small sized, relatively low cost magnetometer assembly without sacrificing accuracy and reliability. The assembly includes a unitary sensor substrate capable of orthogonally positioning each of the three fluxgate axes and their respective coils and sensors. The assembly positions the unitary substrate on a circuit board that contains the appropriate harmonic amplifiers, phase detectors, and integrators for signals from each of the three fluxgate axes. A second circuit board positioned parallel to, but apart from, the first, incorporates an appropriate frequency oscillator, frequency divider, and, if necessary, an appropriate voltage regulator. The circuit boards, positioned in parallel as described, are mounted to an end plate that incorporates a signal/control connector and which positions and holds the components of the magnetometer assembly in a generally rectangular configuration.

Abstract: A circuit for resolving a magnetic field, including a first channel including a first magnetic field sensor, a first amplifier coupled to and receiving an output from said first magnetic field sensor, and a first three band detector coupled to and receiving an output from said first amplifier. The first three band detector provides a first two bit output. A second channel includes a second magnetic field sensor, a second amplifier coupled to and receiving an output from said second magnetic field sensor, and a second three band detector coupled to and receiving an output from said second amplifier. The second three band detector provides a second two bit output. The first and second magnetic field sensors are arranged orthogonally to one another such that said first and second two bit outputs resolve the magnetic field into eight bearings.

Abstract: Miniature magnetometer apparatus for use with external equipment in determining a position and orientation of a device located within a magnetic field includes an elongated flexible circuit for connection to external equipment, a substrate at the device with a portion of the flexible circuit secured thereto, and a planar sensor mounted on the flexible circuit at the substrate and connected to the flexible circuit.

Abstract: The invention relates to a method of determining the spatial field distribution and/or the spatial position of a useful field source, producing said field distribution, by means of a multichannel field measuring device which comprises a plurality of spatially distributed sensors which produce measured values which contain on the one hand useful measured values stemming from the useful field source and on the other hand noise measured values stemming from at least one noise field source, correction values being formed and superposed on the measured values so that compensated measured values are obtained which are compared with similarly compensated, mathematically derived reference values which are produced by a fictitious reference field source by means of the field sensors, the reference field source being determined for which the pattern of compensated reference values corresponds best to the pattern of compensated measured values.

Abstract: An improved magnetic field gradiometer having major and minor correction circuits is disclosed. The major correction circuits cancel the main components of an applied magnetic field, such as the earth's uniform field, and the minor correction circuits correct for smaller, but still significant effects, such as assembly imperfections and unavoidable cross-talk between the elements of the gradiometer. Also disclosed is a method for processing the gradient data from the gradiometer to enable the positions of magnetic objects to be located in space.

Abstract: The device comprises a target signal transmitter to induce an electromagnetic signal in the hidden object, a position reference transmitter to transmit a signal for positioning purposes, a sensor unit to detect changes in the magnetic flux of the hidden object due to the induced electromagnetic signal and the positioning signal from the position reference transmitter, and a central unit to process and display a map of the hidden object. The initial processing of the data results in a gray-scale representation of the object, but additional data processing may be performed.

Abstract: A protective circuit controls electronic equipment in the presence of a high level electro-magnetic field. The protective circuit includes a field sensor arrangement which provides output signals that are indicative of magnetic field strength components that are aligned along desired spatial axes. A vector converter circuit is connected to the field sensors and provides an output having a magnitude that is indicative of the vector sum of the electro-magnetic field strength components. A first indicator is responsive to an output from the vector converter reaching a first threshold to manifest a caution signal that the magnetic field strength has reached a cautionary level. A second indicator is responsive to an output from the vector converter reaching a second threshold that is higher than the first threshold, to disable the electronic equipment. Further circuitry is provided to re-enable the electronic equipment if it is moved outside of the area where the magnetic field exceeds the first threshold.

Abstract: The device disclosed is for measuring a Specific Absorption Rate (SAR) in a human body exposed to electromagnetic fields radiating from an antenna, and is constituted by a phantom (a model of the human body) and a probe structure. The phantom has equivalent electric constant of permittivity and permeability as those of a human body. The probe structure has a combination of first and second loop probes orthogonal to each other, and is arranged such that the second loop probe receives only a magnetic field that has been reflected from a surface of the phantom. Thus, the magnetic field radiating from the antenna and the magnetic field reflected from a surface of the phantom are distinguished from each other. The reflected magnetic field is corrected and the SAR can be accurately measured.

Abstract: An apparatus and method for detecting anomalies in ferrous pipe structures is presented. A sensor having one or more sensor shoe members is placed in the interior of a ferrous pipe structure to be inspected. Each sensor shoe member has one or more magnetic field generating apparatus, with a three-axis fluxgate magnetometer for detecting magnetic fields in the region of the ferrous pipe structure adjacent to which the sensor shoe member is placed. Any magnetic fields in the pipe structure, whether imposed externally, or remnant, which are detected, are sensed and resolved into components in three mutually orthogonal directions for enhanced accuracy.

Abstract: A device and method for reading three-dimensional information involves generating a variable magnetic field in a Cartesian coordinate system and coaxially placing first and second magnetometric sensors made up of three bi-orthogonal receiver induction coils each such that a point on the device, hereinafter referred to as a peak point, is superposed on a point having unknown coordinates. The unknown coordinates are identified based on a generalized information signal E.sub..SIGMA. =e.sub.1.sup.2 +e.sub.2.sup.3 +e.sub.3.sup.2, where e.sub.1 (i=1, 2, 3) is the amplitude of signals induced in the three bi-orthogonal receiver induction coils in each of the magnetometric sensors.

Abstract: A triaxial magnetic heading sensing apparatus includes nulling coils and netoresistive sensors having inputs and outputs. The nulling coils are arranged in parallel relation to three orthogonal planes intersecting at a common center point. The sensors are disposed along orthogonal axes in parallel relation to the orthogonal planes and in close proximity to the center point. Each sensor has a bridge configuration balanced in the absence of an applied external magnetic field and unbalanced in the presence one. Also, a signal generator is connected to the inputs of the sensors for exciting the sensors with a bipolar voltage waveform exhibiting alternating positive and negative voltage polarities punctuated by "off" states of zero volts.

Abstract: A magnetic inspection probe for use in the planar measurement of magnetic properties in two or more defined directions. The inspection probe includes a cup-shaped outer body, a centrally disposed central core, a field generating power coil, a flux coil for measuring magnetic induction and a plurality of field detection elements disposed in various known orientations. In use, the inspection probe of the present invention permits the detection and measurement of anisotropy of material characteristics in at least two directions across the plane of measurement.

Abstract: At least five planar gradiometers on at least three non-parallel surfaces are used to determine five, linearly independent components of a gradient tensor of a magnetic field.

Abstract: A reduced power consumption fluxmeter is provided which is capable of measuring the effect of continued exposure to an incident magnetic field. An incident magnetic field is measured on a sampled basis by a magnetic detecting element and integrated throughout the entire duration of continued exposure. A measurement time interval between successive measurements is calculated in accordance with the variation in magnitude between successive measurements. In one embodiment, the incident field is measured in three dimensions such that the fluxmeter is not sensitive to the direction of the incident field or the orientation of the fluxmeter. An analog-to-digital converting circuit is provided for converting detected values to digital values and the successive integrations are approximated by multiplying a calculated magnetic flux strength vector by the measuring time period. The integrated values are successively added and stored in a register. The integrated value is displayed by a display element.

Abstract: A biomagnetometer comprises an array of biomagnetic sensors, the array comprising a first plurality of magnetic field pickup coils, and a second plurality of detectors, each of which receives a pickup coil output from a pickup coil. There is a third plurality of signal processors, each of which receives an output from a detector, the third plurality of signal processors being fewer in number than the first plurality of pickup coils. The biomagnetometer further includes a selector that selects a subset of pickup coils, equal in number to the third plurality of signal processors, from the first plurality of pickup coils for signal processing by the signal processors. This biomagnetometer permits the placement of a very large array of relatively inexpensive pickup coils adjacent to a subject, and then processing information from subsets of that large array selected to optimize the gathering of data, while maintaining the cost of the signal processing electronics at a more economical level.

Abstract: A portable electromagnetic field exposure dosimeter includes a triaxial fite-loaded coil sensor, a group of amplifiers and bandpass filters, a data control board, and a computer. The triaxial sensor receives electromagnetic radiation along three orthogonal axes for measurement which is channelled through a group of amplifiers and then bandpass filtered into three frequency signal ranges. One frequency range corresponds to exposure at 60 Hz and two of its harmonics. The second frequency range corresponds to high frequency pulsed energy. The third frequency range reflects body motion of a tested individual. The data control board converts such filtered signals into digital code and controls the flow of the converted data to random access memory and to the computer. The computer performs a Fast Fourier Transform on the converted data from the 60 Hz frequency range and then stores or displays the analyzed data as a function of frequency and time.

Abstract: An apparatus for determining the direction of a magnetic field is provided with a plurality of magnetically sensitive components arranged with their sensing axes equally spaced around a circular configuration. Each magnetically sensitive component is capable of providing a binary signal representing the resolution of the direction of a magnetic field along one of the two possible directions aligned with its sensing axis. The binary signals from each of the plurality of magnetically sensitive components is arranged to provide a grey code output that can be used to directly determine the direction that the apparatus is pointing toward. The compass points that can be resolved is related to the number of magnetically sensitive components by a ratio of two to one. For example, the use of four magnetically sensitive components permits the resolution of eight compass directions.

Abstract: A detector for detecting an oriented physical variable includes, in a casing, an acceleration chip-shaped sensor and a board bearing electronic components. The sensor is mounted on a first surface of an insulating part that includes a second surface fastened to the casing, and a third surface that extends parallel with the plane of the board. Conductive paths extend from the first surface, where they are connected to the sensor, and overlap the third surface, where they are connected to contacts of the board. The sensor can be oriented in a desired direction, with respect to the plane of the board. The various electric connections can be formed by ultrasonic bonding.

Abstract: A triaxial AC magnetic field analyzer/dosimeter instrument measures the field strength of three mutually orthogonal AC magnetic field components at a plurality of different frequencies in a frequency range of interest and stores corresponding data which may be processed to indicate the field strength at each of the frequencies and/or the sum of the field strengths over the frequency range of interest. The instrument is computer controlled and comprises three measurement channels corresponding to respective magnetic field components, each channel including a sensor coil, a clock controlled, switched capacitor, bandpass filter, and a TRMS detector. The passband of each filter is swept across the desired frequency range by a varying frequency clock.

Abstract: A portable magnetic field analyzer for sensing ion specific resonant magnetic fields. The analyzer has a magnetometer which measures the magnetic field produced by both ac and dc sources along an axis and determines the dc field plus the fundamental and various harmonic frequencies. A microcontroller uses this information to calculate various cyclotron resonance frequencies and then compares the calculations to stored data relating to cyclotron resonance frequencies of certain biologically important ions such as calcium, potassium and magnesium. A display notifies the user when resonance conditions (within a set tolerance) exist.

Abstract: A passive velocity measuring system which includes first and second biaxial fluxgate magnetometers separated by a known distance and oriented precisely with respect to one another and with respect to the path of travel of a ferrous vehicle whose velocity is to be determined. An indication of the velocity of the vehicle is obtained from the ratio of the time derivative of the magnitude of the vehicle's magnetic induction to the negative of the spatial derivative of this same quantity.

Abstract: A single core triaxial flux-gate magnetometer including a tall-toroidal core having a radial excitation winding, two orthogonal sets of axial or circumferential output windings, and an equatorial output winding oriented orthogonal to both axial output windings. The core is fabricated from a strip of magnetic tape material wrapped to form a toroid having a height ranging from approximately equal to its diameter to one and one half times its diameter. Each end of the strip is uniformly tapered along the top and bottom edges such that the tapered segments extend around an integer multiple of complete revolutions of the wrapping, the length of each tapered segment thereby being equal to the inner or outer circumference of the toroid or an integer multiple thereof.

Abstract: A portable underwater mount for magnetic and electric field sensors. The mount has a gimbal-like structure comprising a ball member having a mounting flange for coupling to the magnetometer. The ball member is cast from polyurethane with Teflon powder suspended therein, providing a substantially frictionless surface. The ball member is disposed over a support platform having a spherical contour so that the weighted sensor positions itself to true vertical. A collar having a lock terminating in the support platform rests over the ball member so that once the sensor is oriented to magnetic north, the lock is engaged to secure the sensor in true vertical and magnetic north positions.

Abstract: A portable magnetic field analyzer for sensing ion specific resonant magnetic fields. The analyzer has a magnetometer which measures the magnetic field produced by both ac and dc sources along an axis and determines the dc field plus the fundamental and various harmonic frequencies. A microcontroller uses this information to calculate various cyclotron resonance frequencies and then compares the calculations to stored data relating to cyclotron resonance frequencies of certain biologically important ions such as calcium, potassium and magnesium. A display notifies the user when resonance conditions (within a set tolerance) exist.

Abstract: For the determination of all linearly independent components of an Nth order gradient tensor of a magnetic field, at least 3+2N planar gradiometers of the Nth order are arranged on at least 3 non-parallel and non-orthogonal surfaces. As a result, three-dimensional coil structures are not necessary.

Abstract: An electromagnetically complete field vector field probe has a set of three dipoles extending along three mutually perpendicular axes, and three loops situated in mutually orthogonal planes defined by different pairs of said axes. The dipoles and loops are all disposed about a common center. Each dipole has a central element and two end elements, separated by gaps. Each loop has four conducting elements each extending from a point adjacent to one of the three axes to a point adjacent to another of the three axes. The conducting elements of each loop are separated from one another by gaps at the axes, so that each gap of each loop is substantially coincident with a gap of another loop and with a gap of a dipole. Coaxial lines extending through the central conducting elements of the dipoles are connected directly to the ends of the loop elements and need not extend through parts of the loop elements themselves.

Abstract: An electronic compass (10) having at least two sense windings (11, 12) is mounted in a vehicle. The outputs (x(h), y(h)) of the windings are measured for a number of compass directions (headings). From this data an error difference angle (.phi.), from a nominal angle, which actually exists between the output windings is calculated. Preferably a look-up table (21, 39) is created relating actual compass heading (h) to measured sense winding outputs by utilizing the calculated error difference angle (.phi.). This table is then utilized for calculating actual compass heading based on actual measured sense winding outputs. The calculated error angle (.phi.) can also be used to calibrate the compass without creating a look-up table. The calibrated compass compensates for misalignment of the sense windings and provides a more accurate electronic compass without requiring creating a calibration table by orienting the compass in a very large number of exactly known directions.

Abstract: A single core triaxial flux-gate magnetometer including a tall-toroidal core having a radial excitation winding, two orthogonal sets of axial or circumferential output windings, and an equatorial output winding oriented orthogonal to both axial output windings. The core is fabricated from a strip of magnetic tape material wrapped to form a toroid having a height approximately equal to its diameter. Each end of the strip is uniformly tapered along the top and bottom edges such that the tapered segments extend around an integer multiple of complete revolutions of the wrapping, the length of each tapered segment thereby being equal to the inner or outer circumference of the toroid or an integer multiple thereof.

Abstract: 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.

Abstract: A Hall effect device with appropriate electronic circuits can sense a very weak magnetic field and it is thus useful to be used as a compass. It can also be configured as two or more directional indicators as desired.

Abstract: A method and system for compensating maneuver induced components in the magnetic field sensed by an airborne magnetic detector. The magnetic fields sensed during a series of selected aircraft maneuvers are processed to yield signals representative of the magnetic properties of the aircraft. Subsequently, these signals are combined with signals representative of the aircraft attitude to provide a compensation signal. This compensation signal may be applied directly to the output of the magnetic detector or may be used to drive a set of compensation coils.

Abstract: The radiator and the sensor each comprise three pairs of Helmholtz coils which are disposed along three orthogonal axes respectively. The coils are wound in pairs of grooves which have different depths and are recessed in a cubic support. The radiator and sensor are particularly useful for helmet-type viewfinders.

Abstract: The system comprises a radiator, a sensor (21) fixed to the moving object, a circuit for processing the signals from the sensor in order to determine their amplitudes and a computation processor with a base of processing algorithms. The system also has a multiplexer (24) for sequentially multiplexing on one channel the detector signals from the sensor (21), a device (25) for sampling the signal coming from the multiplexer (24), of amplitude A and pulsation .omega., multipliers (30, 31) for multiplying the samples from the sampling device (25) respectively by reference signals .omega.t and cos .omega.t and accumulates (33, 35, 34, 36) for accumulating the two sums of the products of the multiplications for a period at least equal to a period ##EQU1## before supplying them to the computation processor (22), which extracts from them the amplitude A.The systrem can be applied well to a helmet aiming device.

Abstract: An electronic compass for use in a vehicle includes compensation for attaining a high degree of accuracy without operator intervention or the need to drive the vehicle in a deliberate circular path. An automatic method for accurately determining maximum and minimum voltage values from a flux gate sensor having orthogonal sensing windings is provided that operates continuously to adjust for required changes in both the offset and gain compensation factors. The flux gate sensor is further mounted within the vehicle such that the axis of one of the sensing windings is positioned approximately 45.degree. with respect to the vehicle's longitudinal direction. The angled mounting of the sense winding axis results in strong sensing signals when travelling on most roads. The electronic compass further provides visual representation on the outer peripheral segments of an alphanumeric display to prompt the operator to drive in a circle during a manual compensation mode.

Abstract: Two groups of magnetic field transducers shielded from electric fields and at a known distance from each other are contained in a portable instrument. Each group consists of 3 magnetic field transducers each sensitive to the magnetic field at a single point but according to three orthogonal orientations. Rapid reading of the magnetic field values measured by all 6 coils allows evaluation of the current in a straight electrical conductor relatively near to the apparatus on the basis of the direction and amplitude of the magnetic field vectors measured at the position of each group of 3 coils. Assuming that the conductor under scrutiny is the dominant magnetic influence in the area, the determination of both current and distance of the conductor is exact within a wide range of distances between apparatus and conductor and within a large number of orientations of the apparatus with respect to the conductor because of internal computational compensations performed by a microprocessor.

Abstract: A magnetometer is prepared by depositing three thin-film SQUID magnetic field detectors upon a substrate. Two of the detectors incorporate stripline SQUID detectors deposited at right angles to each other, to measure the orthogonal components of a magnetic field that lie in the plane of the substrate. The third detector uses a planar loop SQUID detector that measures the component of the magnetic field that is perpendicular to the substrate. The stripline SQUID detectors have thin-film base and counter electrodes separated by an insulating layer which is at least about 1 micrometer thick, and a pair of Josephson junctions extending between the electrodes through the insulating layer.

Abstract: An alignment process is applied to each sensor of an array of three axis magnetic sensors to electronically align the three axes of each sensor after the array has been deployed. The alignment process compensates for each sensor not being aligned perfectly with the earth's N-S, E-W and vertical magnetic field components. A field registration process is applied to each sensor of the array that uses a dipole moment detection and localization process and the alignment process combined with a known calibrated dipole source to define the shape of the array. The present invention improves the performance of the array of sensors in detecting magnetic anomalies by digitally compensating for sensor-to-sensor nonalignment and magnetic interferers within interfering range. The alignment process electronically aligns the three axes of each of the sensors to gain maximum performance from the sensor array.

Abstract: An apparatus detects a magnetic tag implanted in an organism as detector is moved past the organism by detecting a magnetic field difference between two positions. Prior to examination of a specimen under test, the outputs of a plurality of loops detecting magnetic fields are balanced in a uniform magnetic field. As a consequence, when one of the coils is exposed to a different magnetic field than the other of the coils this difference is detected and an alarm is sounded to indicate that the magnetic tag has been detected.

Abstract: 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.

Abstract: An apparatus is provided for measuring a very weak magnetic field generated by a human body, etc. External magnetic noise components coming from other magnetic sources and existing around an object whose magnetic field is to be measured are detected by compensation coils of the apparatus. The compensation coils are oriented in multiple dimensional directions. The detected noise components are weighted and added to each other to correctly find the noise components. Thereafter, the noise components mixed in the objective very weak magnetic field are removed, thereby correctly measuring the very weak magnetic field.

Abstract: 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.

Abstract: A magnetometer and method for measuring magnetic field strength particularly adapted for use in an electronic flux gate compass. A core of magnetic material in the shape of a toroid is coupled to a drive coil and to two sense coils oriented along orthogonal axes. A current limited, current source coupled to the drive coil periodically saturates the core, drives the core out of saturation at an intermediate current level, and saturates the core again. Each sense coil is coupled to a sense circuit which measures the current in the sense coil induced by the periodically changing flux density in the coil resulting from an external magnetic field coupled to the sense coil, produces a dc feedback signal to cancel out the external magnetic field, and provides the dc signal as an output representative of the external magnetic field strength along the axis of the sense coil. The dc signal is produced by synchronously detecting the amplified ac current in the sense coil.

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 thin film dc SQUID and its driving electronic circuitry configured with very high symmetry. The SQUID loop is formed with four holes at the respective ends of crossed slits. Each of these holes forms a single turn secondary for symmetrically arranged pairs of modulation coils and signal coils. The geometrical placement of the modulation coil transformers with respect to the signal coil transformers results in a device which nominally has no mutual inductance between the two groups of coils when the SQUID is biased for normal operation. The external driving circuit is configured to preserve the highly balanced nature of the chip and forces equal magnitudes of current to flow in all four of the bias leads.

Abstract: In an electronic compass having a plurality of sensors (1, 2, 3), each reacting to a component of the earth field (Hy), it is desired to prevent errors based on variations in the signal amplification and to improve the accuracy of measurement. In accordance with the invention, three identical sensors (1, 2, 3) are disposed at an angle of 120.degree.. The compass may be used, in particular, for the navigation of vehicles.

Abstract: 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.

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 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.