Abstract: The present invention provides an apparatus and method for measuring the resistivity of a sample of cement-based material. A transformer is formed with a primary coil, a secondary formed by means of a sample of said cement-based material, means for supplying a voltage to said primary, means for measuring the voltage induced in said sample, and means for measuring the current induced in said sample. The resistance of the sample can be measured and thus the resistivity of the concrete sample can be calculated.

Abstract: A vibrating sample magnetometer controls an electromechanical drive using both ac and dc control and a position sensor. Absolute position sensing is used in a feedback loop to control both an alternating current (ac) drive and a direct current (dc) drive to the electromechanical drive. Improved performance and stability results.

Abstract: A method for improving the operational performance of a disc drive through the identification of vital product information associated with a head-disc assembly (HDA) of the disc drive. The disc drive comprises a printed wiring assembly (PWA) housing control circuitry for the disc drive. The HDA of the disc drive is operably coupled to the printed wiring assembly and includes a rotatable disc to which data are written by a controllably positionable head. A non-volatile memory device is mounted on the HDA and operably coupled to the PWA so that, when the disc drive is initialized, the PWA verifies the configuration of the HDA before proceeding with the initialization of the disc drive, thereby preventing errors and damage to the disc drive as a result of the installation of a new, replacement PWA in the disc drive, or the downloading of new, incorrect firmware to the PWA.

Abstract: The present invention relates to a method for detecting changes of magnetic response of at least one magnetic particle provided with an external layer in a carrier fluid, wherein the method comprises using a measuring method comprising measuring the characteristic rotation time of said magnetic particle with respect to said external layer, which measuring method involves measuring Brownian relaxation in said carrier fluid under the influence of an external alternating magnetic field. The method implies that upon modification of the effective volume of the particle or its interaction with the carrier fluid a hydrodynamic volume of the particle changes, which implies a change of the frequency (fmax) where an out of phase component of the magnetic susceptibility has its maximum.

Abstract: The invention relates to a device for measuring magnetic field(s). This device comprises at least one measurement acquisition pathway (221, 222, 223; 231, 232, 233) comprising a measurement current generator (24), a coil (25), a measurement resistor (26), at least one amplifier (27) and at least one antialiasing filter, delivering a measurement voltage.

Abstract: A hand held subsurface object locator has a pocket sized housing that contains circuitry and a power source for electrically detecting substratum objects hidden behind a surface. The housing is preferably less than two inches wide and at least three times as long as it is wide. The housing has a pocket clip preferably affixed to a battery compartment door at one end of the housing and the other end of the housing is tapered and includes a plurality of tapered indicators.

Abstract: This invention is a method for nondestructively determining the deterioration of determining ferromagnetic materials by quantifying the change in brittleness with aging of the materials. This invention supposes acquirement of an embrittlement coefficient b by measuring a magnetic susceptibility &khgr;b of ferromagnetic materials under a magnetic field having a specified intensity H. And the coefficient b of the ferromagnetic materials is calculated by putting the intensity H and the susceptibility &khgr;b into an equation: b=&khgr;bH2. By the coefficient b, a correlation between the coefficient b and a referenced embrittlement factor of materials like said determining materials is obtained previously. The coefficient b of the determining materials in the initial and the deteriorated states is acquired. The factor corresponding to the coefficient b is obtained from the correlation. It is possible to quantify the change by comparing the values of the factor in the initial and deteriorated states.

Abstract: A sensor for detecting defects in a component includes an electric coil fed with a varying electrical current to create a varying magnetic field penetrating at least partly into the component under test, and a defect detector including a magnetoresistor. The above components are accommodated in a protective housing having a detection face disposed near and parallel to a surface of the component under test. The coil has its axis &Dgr; perpendicular to the detection face and the magnetoresistor is in the vicinity of the detection face. The magnetoresistor is a giant magnetoresistor and is disposed so that its sensitivity axis &Dgr;1 sensitive to variations in a magnetic field is parallel to the detection face of the housing.

Abstract: A vertical probe card assembly containing a plurality of vertical probe cards is mounted within a central corridor or opening within a magnetic field generator. Each of the vertical probe cards has a multiplicity of probe needles extending downwardly therefrom for electrically contacting test pads of a device under test that is positioned below the magnetic field generator.

Abstract: The variation in properties of a ferromagnetic material with depth below the surface is assessed in a nondestructive fashion using a probe that incorporates an electromagnet. An alternating magnetic field is generated in the electromagnet and so in the object, and a magnetic sensor is arranged to sense a magnetic field due to the electromagnet. Signals from the magnetic sensor are analysed into an in-phase component and a quadrature component, and these are mapped directly into material property and lift-off components; this analysis enables accurate measurements of material property (such as stress) to be distinguished from changes in lift-off. The measurements are repeated for at least five different frequencies of the alternating magnetic field; and the measurements at different frequencies are deconvolved assuming a functional form for the variation of material property with depth, the function having no more than five unknown constants. The stress at depths for example in the range 0.5 mm to 5.

Abstract: A geometry for a pickup coil assembly that improves the balance of a hysteresis loop tracer is described. First and second balance coils are placed on either side of a pickup coil. The first and second balance coils are wired in series to form a symmetric balance coil that senses the magnetic H field on either side of the pickup coil. The voltage produced by the symmetric balance coil is subtracted from the voltage produced by the pickup coil. This geometry reduces susceptibility to external electromagnetic fields and also reduces susceptibility to changes in the uniformity of the drive field. Mechanical and thermal stability is improved by physically connecting the balance and pickup coils together. Mechanical and thermal stability is further improved by winding the coils on alumina coil forms.

Abstract: In a method and device for measuring at least one parameter of a metal bed, measuring is obtained by a magnetic field being generated from one side of the metal bed so that eddy currents are generated in the metal bed as the metal bed moves relative to the magnetic field. The metal bed and the magnetic field are made to move relative to one another. A force related to the eddy currents affects a body and the action of the force on the body is detected by a detecting device, the detected force being a function of a desired parameter of the metal bed.

Abstract: A detector for detecting magnetic field disturbances resulting from the movement of equipment 11 through a pipe 10 of magnetic material. A pair of linear ferrite magnetic elements 22A, 23A are positioned end to end and aligned with the axis of the pipe, and a Hall effect device 21A is positioned between the magnetic elements. The ferrite rods concentrate magnetic field changes due to the equipment 11 through the Hall effect device. Two pairs of elements 22A-23A and 22B-23B are spaced around the pipe, and a second set of pairs of elements 25B-27B, 26B is spaced along the pipe. The detector can be attached to an existing pipe, or mounted in an instrument package which passes through the pipe.

Abstract: The present invention relates to a head tester for testing heads having a read element and a write element. The tester comprises a substrate on which a read coil is positioned to be sensitive to the write element of the head. A write coil is also formed on the substrate and this coil is positioned such that the read element of the head to be tested is sensitive to the write coil.

Abstract: An electromagnetic induction coil includes a casing with high magnetic permeability with a magnet disposed within the casing. The magnet has a central hole. A core with high magnetic permeability is disposed within the central hole of the magnet. The core is in physical contact with the casing. A multi-loop coil of conductive wire is disposed within the central hole of the magnet encircling the core. The multi-loop coil is insulated from the magnet.

Abstract: A vibrating sample magnetometer controls an electromechanical drive using both ac and dc control and a position sensor. Absolute position sensing is used in a feedback loop to control both an alternating current (ac) drive and a direct current (dc) drive to the electromechanical drive. Improved performance and stability results.

Abstract: An eddy current inspection probe for inspecting a preselected surface. The eddy current inspection probe includes an expandable element at least partially defining an interior space which is expandable by introducing a pressurized fluid into the interior space from a collapsed position to an expanded position for contacting the preselected surface of the component for inspecting the surface. The probe also includes an eddy current array positioned over the expandable element for generating and detecting magnetic fields in the component to inspect the preselected surface.

Abstract: Disclosed are apparatus and method for measuring Hall effect related-values in a semiconductor, such as a mobility, a carrier concentration and a resistivity using a Hall effect. A sample is loaded into an IC socket or a similar target, which is fixed on the inside of a heat insulating material container capable of containing injected liquid nitrogen. The Hall effect related-values are measured using a moving member for moving a pair of permanent magnets to an outside of the heat insulating material container. The measuring equipment has a simple structure, and a measuring operation is simple. A level of an input voltage of a sample is measured depending on a constant current that is supplied by a constant current supplying unit contained in a Hall voltage measurement unit. A measurement error detection unit detects and displays a measurement error of the sample using the level of the measured input voltage.

Abstract: A method for detecting core faults includes (a) positioning a magnetic yoke near at least one tooth of the core, the magnetic yoke being wound by a winding; (b) supplying current to the winding to inject magnetic flux into the at least one tooth of the core; (c) measuring a signal resulting from the injected magnetic flux; and (d) using the measured signal to detect core faults.

Abstract: A scanning head for eddy-current testing includes a probe coil configuration disposed on a film on a film base. The film base is matched to a shape of an object to be tested. This allows quick, low-interference eddy-current testing. A method for producing a scanning head for an eddy-current test and an eddy-current test method are also provided.

Abstract: A system and method for measuring volumes and areas using electromagnetic induction techniques. A current is generated and fed into one of two coil assemblies to induce voltage into another coil assembly to provide accurate values for volume or area.

Abstract: Physical-health tuning means that may adjust and bring into harmony physical health—that in particular may improve physical health out of sorts due to electromagnetic-wave harm—are presented. The physical-health tuning means include: (A) a plurality of bar magnets whose obverse sides are N poles and whose reverse sides are S poles, running lengthwise; (B) wire that is non-magnetic yet electroconductive; and (C) a shaping support material. The wire is arranged coiling the magnet obverse faces in right-hand turns from one end to the other end of the bar magnets in the lengthwise direction. The plurality of magnets onto which the wire is wound are disposed to form a tubular hollow with the N-pole faces adjoining the S-pole faces in alternation, and the shaping support material being put on the outside of this assembly.

Abstract: A magnetic sensor for detecting magnetic fields deriving from a magnetic body to detect any magnetic body on a non-magnetic body by moving relative to the non-magnetic body in prescribed relative moving directions along the surface of the non-magnetic body includes a magnetizing magnet in which a line connecting the N and S poles thereof is a direction substantially orthogonal to, and of which one pole is arranged either in contact with or in proximity to, the surface of the non-magnetic body; and a magnetism detecting element having two magnetic detectors arranged along a magnetic field detecting direction, the magnetic field detecting direction being orthogonal to the relative moving directions in a surface parallel to the surface of the non-magnetic body, wherein the magnetic body is magnetized by the magnetizing magnet along with the movement relative to the non-magnetic body, and magnetic fields according to the quantity of the magnetized part of the magnetic body are differentially detected by the two m

Abstract: A method and apparatus are provided for distinguishing synthetic diamonds from natural diamonds by detecting the effect the synthetic diamonds have on a magnetic field. A counter can be provided for measuring counting transitions of an oscillator having an inductor in a frequency determining circuit. The inductor has a port therein for admitting a sample diamond for testing. First, the oscillations are up counted over a precise time interval with no sample present, and then a sample diamond is placed into coupled proximity with the inductor to change the frequency of the circuit by an amount related to the quantity of ferromagnetic material in the sample diamond. Thereafter, a down count is performed for the oscillations with the sample diamond in place over a second time interval equal to the first interval. The difference in the up counts and the down counts is determined and displayed in a digital readout as a measure of the degree of likelihood of the sample being synthetic.

Abstract: In accordance with the present invention, the initialization for orienting the magnetized directions of the free layers of GMR heads (mounted on the diagonally shaded surface of sliders 14) by an external magnetic field is again executed also for the opposite direction, thereby to increase the yield of the GMR heads. Further, it is determined whether the magnetized direction of the pinned layer of GMR heads can be once reversed to the opposite direction, thereby to select damaged GMR heads at an early stage. Then, by performing a reset while performing a quasi-static test for seeing the read back response of the GMR head after restoring the magnetized direction of the pinned layer to a positive rotation, a safe and efficient reset is executed. The reset can be executed not only by applying only a pulse, but also while providing an external magnetic field in the pinning direction, or only by giving a high magnetic field.

Abstract: A stud detector for detecting studs behind the surface of a wall, the stud detector having a measuring member with first and second ends and a preselected length that corresponds to a conventionally used stud configuration. A sensor is connected to the second end of the measuring member, the sensor including a magnet for detecting the presence of a stud behind a surface of a wall by detecting the presence of a metal object. The measuring member is adapted to permit identification of a surface portion of a wall behind which a stud might be located by measuring a preselected distance from a reference point.

Abstract: Disclosed are a method and an apparatus for easily, sensitively and reliably detecting the presence of a magnetic substance in a non-magnetic product, and even a minuted magnetized material such as a broken needle erroneously included in a sewn product. Magnetic sensors as a sensing unit are disposed at a prescribed position between a pair of opposed magnetic shielding members made of a soft magnetic material as a magnetic flux converging unit. A non-magnetic product including a magnetic substance is passed through between the pair of magnetic shielding members. A magnetic flux generated by the magnetic substance mingled in the product is converged to the magnetic shielding members, while shutting off a magnetic field due to external disturbance, and residual magnetization of the magnetic substance is detected by the magnetic sensors.

Abstract: 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.

Abstract: An electronic autoclave cycle passively records the number of thermal cycles to which an instrument has been subjected in a steam autoclave. When a sterilization cycle has been completed, and the instrument is next energized in use, a microprocessor is employed to read the sensor and record the occurrence of a sterilization cycle. Information as to the cumulative number of cycles through which the instrument has been subjected is stored in a non-volatile memory. This data is suitably displayed on a display panel. The sensor employed uses either the Curie temperature or a temperature near but below the Curie temperature of a ferromagnetic material by first magnetizing the material and then, later, checking its flux density to determine whether a thermal cycle has occurred. In a first embodiment, a Hall effect sensor is used to directly measure the magnetic field strength of the magnetizable material.

Abstract: A helically movable system for the detection of cracks in a pipeline, capable of moving inside this pipeline, produces a magnetic flux that passes into a portion of the pipeline. Detectors measure local magnetic fields on the inner surface of the pipeline. These measurements are provided for processing and storage. The system is driven by the fluid flowing in this pipeline. Devices for the generation of flux and the measuring are arranged within at least one cylindrical housing having wheels to make this housing follow a substantially helical path inside the pipeline.

Abstract: A compact portable transmitter includes a ferromagnetic tubular housing. A electro-magnetic coil is wrapped around an exterior surface of the housing, such that the housing serves as a transmitter core. A protective covering is positioned over the electro-magnetic coil. Batteries are positioned within the housing to supply power to the electro-magnetic coil and associated transmitting electronics.

Abstract: A nail locating device includes a seat, a coupling member and an indicating rod. The seat is adapted to be moved on a surface of a board into which a nail has been driven, and has an open upper end portion and an open lower end portion. The seat further has an intermediate portion between the upper and lower end portions and is formed with a ball socket therein. The coupling member has a ball portion hinged to the seat in the ball socket. The indicating rod is received in the seat and extends from the upper end portion, through the ball portion of the coupling member, and into the lower end portion of the seat. The indicating rod has a bottom end provided with a magnet that is adapted to be attracted to the nail such that the indicating rod pivots in the seat due to attraction of the magnet to the nail in order to indicate the location of the nail in the board.

Abstract: An apparatus for deactivating a surveillance tag comprising a first coil located in a first plane, a second coil located in a second plane, and a third coil located in a third plane such that the third plane intersects the first and second planes at an angle that is greater than zero degrees and less than ninety degrees.

Abstract: Small metallic patches embedded in a mainly non-metallic surface may be detected and mapped by placing a wire coil at the free end of a cantilever, with a fine tip made of a ferro-magnetic material located at its center. An alternating current is passed through the coil so that when it is near a metallic patch eddy currents are induced in the patch. These produce a small magnetic moment in the patch which pulls the tip towards the surface. This movement of the tip is detected by observing a light beam that is reflected off the surface of the cantilever. By plotting the output of a photodetector, sensistive to small changes in the reflected beam's position, as a function of the tip's location over the surface, a map of the metallic patches is produced.

Abstract: A method of and apparatus for torque magnetometry in which a specimen, the magnetic moment of which it is desired to determine, is disposed on a support. A temporally varying, for example sinusoidal, magnetic field is generated in the region of the specimen so that interaction between the magnetic moment of the specimen and the magnetic field causes a torque to be exerted on the specimen. Consequently, the specimen and/or the support are deflected and typically exhibit a vibratory motion. The motion of the specimen and/or support due to the torque is measured. When the magnitude and direction of the magnetic field are known, the magnetic moment of the specimen can be determined from the results of the motion measurement. The frequency of the magnetic field can be adjusted so that the specimen and/or the support resonate. The support is typically a single silicon crystal having two orthogonal modes of vibration which have different resonant frequencies.

Abstract: Banknotes printed with magnetic ink pass through a tri-color age detector 34, and then between a pair of premagnetization rollers (10,12) having opposite magnetic polarity of such strength that the magnetic signature of all banknotes is enhanced to the same level; the notes are then stacked 50 in an electromagnetic stacker 42. Such notes, having magnetic signatures of the same level, can also be recognized and/or validated by magnetic techniques also.

Abstract: A metal detector (10) which uses a metallic test sphere (5) to pass with the product through the detector head (2) at periodic intervals. The frequency generator (21) which generates the signal sent to the oscillator coil (11) is capable of operating on numerous frequencies in the 50 kHz to 2 MHz range. The product is passed through the detector head (2), with and without the sphere (5) present, for each of the operating frequencies. The detected signal from the product and the product with metal is characterized for each of the operating frequencies. In this manner the frequency which produces the highest ratio of product with metal present signal to product signal without metal present can be identified. A second version of the metal detector (40) uses a frequency synthesizer (43) which may be rapidly scanned through a range of frequencies while the product is passing through the detector head (41).

Abstract: An openable ring assembly is externally centered around and moved parallel to the centerline of a stationary pipe. As a low-frequency EM source signal is applied to the ring assembly, the time and/or frequency shifts of a detected EM signal from the source signal can be correlated to pipe wall thickness without removal of external pipe insulation and metal cladding, if present. The ring assembly may be opened or expandably segmented to allow pipe thickness detection around obstructions or larger diameter pipe. Centering is preferably accomplished by using rollers circumferentially attached to the ring assembly.

Abstract: A process is presented for the direct determination of characteristic magnetic values of thin magnetizable layers, in which an element creating a magnetic field creates the magnetization of a part surface in such a way that the thin magnetizable layer, the element creating the magnetic field, and a magnetic field sensor are located in a relative position of rest to one another. The magnetic field sensor is then positioned opposite the magnetized part surface by a relative movement of the element creating the magnetic field, the magnetic field sensor, and the thin magnetic layer. During the subsequent measurement of the magnetization of the part surface, the thin magnetic layer, the element creating the magnetic field, and the magnetic field sensor are in a relative position of rest to one another.

Abstract: A non-destructive inspection system is disclosed for testing oilfield tubulars, and particularly for testing coiled tubing. The system includes a support housing and an inspection head removably positioned within the support housing and including a thru-bore for receiving coiled tubing. A magnetizing coil is provided for saturating the tubing while passing through the inspection head.

Abstract: A combination of three factors for increasing the spatial resolution of a polar coordinates sensor. (1) a coefficient of coupling factor including a gap in the magnetic circuit path between the driving core and the pick-up core. (2) a tuned "tank-circuit" factor including a capacitor connected in shunt with the pick-up coil. (3) a driving frequency spectrum factor for modulating the frequency of the sine-cosine excitation to the driving core.

Abstract: An emitter for a system of electromagnetic tomographic measurements, as well as a process and a generator (5) adapted to produce a variable frequency current supplying a solenoid (1), constituted of turns wound about a magnetic core (3). The solenoid (1) is constituted by several windings (4a, 4b, 4c) disposed side by side with each other on the core (3), and the emitter comprises switching means (6) adapted to connect in series or in parallel and/or to disconnect the different windings (4a, 4b, 4c) with and from each other, constituting the solenoid (1), so as to control the number of active turns of the solenoid (1).

Abstract: A nondestructive inspection apparatus having a SQUID is made with compact configuration and is capable of detecting a metallic or non-metallic metal for defects, corrosion, and the like, by forming the SQUID and a magnetic field applying coil on the same substrate. The SQUID comprises two Josephson junctions, a washer coil connected to the Josephson junctions to form a superconducting loop, shunt resistors, a damping resistor, and a feedback modulation coil, all of which are formed from a superconducting thin film on a supporting substrate. A magnetic field applying coil is formed on the same supporting substrate with a superconducting thin film or a normal conducting metal thin film. The magnetic field applying coil, which generally has plural turns around the SQUID, applies a dc or ac magnetic field to a sample. The change in magnetic field caused by a defect in the sample is detected by the washer coil, and the position and size of the defect may thus be determined.

Abstract: A method and apparatus for detecting a loss in cross-sectional area of metallic reinforcing members having magnetic properties of a conductor indicating corrosion effects on the conductor. The method and apparatus comprises a tug component to provide the motive force to move a data collection component and a detector component along a length of conductor. The tug component further includes a rechargeable battery, a motor energizable by the rechargeable battery, a guide wheel and tensioner assembly. Linked to the tug is a data collection component. In turn, a detector is linked to the data collection unit. The tug, data collection unit and detector all ride along the same conductor by a series of guide wheels and tensioners. The detector further includes a magnetic source spaced apart from an electronic coil winding. In use, a conductor is interpositioned between the magnetic source and electronic coil winding.

Abstract: A test apparatus for testing a plurality of magnetic recording heads. The apparatus includes a tool which supports a bar that contains a number of individual magnetic recording heads. Alternatively, the tester may contain a tool which supports a plurality of individual sliders. The tool locates the heads within a magnetic field emanating from a coil wound magnet. The magnet has a length and permeability that provides a uniform magnetic field for each slider in the entire bar. The test apparatus includes a probe card that has a plurality of probe needles which make simultaneous contact with the bonding pads of each head. The needles are coupled to a test circuit that applies a constant current to the magnetic recording heads and measure a change in voltage as a function of a varying magnetic field. The tester can sequentially test the heads without spatially moving the bar, thereby minimizing the test cycle time of testing the heads. Alternatively, the tester may test two or more of the heads simultaneously.

Abstract: A torque magnetometer employing integrated piezoresistive levers to measure magnetization of very small anisotropic samples. A sample holding platform is cantilevered from the substrate by parallel legs on which piezoresistors have been applied. A Wheatstone bridge, which includes the piezoresistors, is completely integrated on a magnetometer substrate. Specific output connections are made to the electrical conductors of the bridge in a manner to eliminate Hall effect error signals in an alternative embodiment.

Abstract: A method of increasing the spatial resolution of polar coordinates sensor devices by phase-amplitude modulating the sine-cosine excitation signals to the hollow toroid driving core. A rotating elliptical sensing pattern is generated by digital synthesis means. Values of the elliptical sensing pattern and its complete revolution are stored in digital "look-up" tables and sequentially read at a high rate into two digital-to-analog converters to produce two "staircase" approximations of the sine-cosine waveforms. The ellipse generation has a first angular frequency and the ellipse precession has a second sub-multiple frequency.

Abstract: A method of magneto optic imaging to locate the presence of a crack around a circular drilled bolt hole wherein the circular bolt hole, because of its sharp corners, locally disturbs the magnetic field used to form the image and obscures the presence of a crack therearound. Initially, a magneto optic image is formed of the drilled circular bolt hole under test, wherein a crack near the circular hole will perturb the circularity of the hole image by driving the magnetic field away from the circumference of the circular hole to cause it to appear out of round and eccentric. A pattern recognition analysis is then applied to the image to check the image for circular shapes, wherein each circular shape image is correlated with a circle of similar diameter to check the circularity of the image, and an eccentricity of the circular image shape is indicative of a crack around the drilled circular bolt hole.

Abstract: A non-magnetic material such as cardboard or plastic is used as the packaging material for the product to be protected from counterfeiting. The packaging material is configured as a box whose parts are bonded together by use of a hot-melt adhesive. The adhesive contains magnetic particles such as barium ferrite, and small molten globules of adhesive are applied to appropriate surfaces of the box during box fabrication. The box parts are folded to form the finished box, and under the application of pressure the globules of adhesive spread out and solidify, bonding the box surfaces together. It will be noted that presence of the magnetic particles in the adhesive does not modify the box fabrication procedure in any way, and that the box material may be processed and the box's surfaces printed in the usual manner.

Abstract: An elongated hollow toroid driving core having a pick-up core formed as an integral part. A cross shaped driving core having two orthogonal sine-cosine excited flux circuits, a polar sensor is mounted where the cross arms intersect, the axis of the polar sensor being perpendicular to the driving core surface, thus disposing the winding turns of the pick-up coil coplanar to the driving flux lines. A third embodiment of a driving core device includes a hollow toroid and cross shaped driving core combination providing dual interacting rotating fields generating a sensing pattern having additive or subtractive dipoles that may be steerable.