Abstract: An axial direction groove is formed in a high permeability toroidal core taking the form of a pot core half with a mounting hole, a high cross-section ratio copper casing being tightly fit around core circumference, having poly-phase excitation windings shuttled through the mounting hole to encompass both the copper casing and the pot-core, forming an integral driving-sensing eddy current probe. A naked pot-core is wound as an integral driving-sensing probe. Poly-phase excitation of the probe is mesh-connected as a gramme-ring.

Abstract: A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing.

Abstract: Magnetoresistive sensor (1) for measuring relative displacements of construction parts (2, 3). A magnetoresistive element (4) is formed on a surface (7) of a substrate (8). A magnet system (5) generates a magnetic field (13) having a component (14) directed parallel to the substrate surface at the area of the magnetoresistive element. Upon the relative displacement of the construction parts, this field component extends at different angles &agr; to the magnetoresistive element and is so large that the magnetoresistive element is always magnetically saturated during the displacement. Upon a relative displacement of the construction parts, the magnetoresistive element describes a path (20, 21) with respect to the magnet system. The sensor is suitable for measuring rotations through angles up to 360° and for measuring large translations.

Abstract: A detector for detecting a rotational angle of a gearshift lever. The detector includes a magnet that forms a magnetic flux in a predetermined direction along its surface. A magnetic resistance sensor generates a detection signal corresponding to the direction of the magnetic flux. The detected object is connected to the magnet or the magnetic resistance sensor. The magnet and the magnetic resistance sensor are rotated relatively to each other to generate the detection signal and obtain the rotational angle of the detected object. The magnetic resistance sensor is separated from an axis of rotation of the sensor or the magnet.

Abstract: In an angle-based binary encoded crankshaft position sensing system, a target wheel is coupled to a crankshaft and a single VR sensor is juxtaposed with the target wheel for sensing the angular position of the wheel and, hence, the angular position of the crankshaft. To permit the use of a single VR sensor in conjunction with an angle-based binary encoded system, the periphery of the target wheel is formed with teeth and slots defining a binary pattern. The slots are wider than the teeth, and the depth of the slots relative to the portion of the periphery defining a nominal radius is greater than the height of the teeth relative to the nominal periphery. With this structure, the signal generated by the sensor in response to a slot advantageously is symmetric to the signal generated by the sensor in response to a tooth.

Abstract: An apparatus for detecting the displacement of a magnet is to be provided. The errors on the detected value due to the variation of temperature or that with time are hardly caused in the apparatus. The apparatus can detect the displacement in high resolution and precision. The apparatus is simple in its structure, and it can be expected that the apparatus can be manufactured in low cost. The apparatus is not limited in its application by the range of the displacement of the magnet. Further, a method for detecting the displacement of a magnet will be provided.

Abstract: A non-contact sensor for sensing a rotational position of a rotating object is provided. A ring-shaped permanent magnet magnetized in the axial direction is sandwiched between two pairs of magnetic plates from above and below. Two pairs of upper and lower protruded magnetic substance portions are provided between the upper and lower magnetic plates at opposite outer ends thereof. Magnetic sensitive devices are inserted in air gaps between the two pairs of upper and lower protruded magnetic substance portions. A magnetic flux generated from the ring-shaped permanent magnet is substantially concentrated to the protruded magnetic substance portions and passes the magnetic sensitive devices. The amount of magnetic flux passing each magnetic sensitive device is substantially proportional to the rotational angle of the ring-shaped permanent magnet.

Abstract: A method and system for detecting electrostatic noise in a magneto-resistive head which may be caused by a plurality of conditions manifesting in the frequency domain as either an amplitude spike or an unstable baseline. In one embodiment, the signals generated by the head when reading a DC-erased track are compared. When viewed in the frequency domain the spectrum gap between the signals is used to determine if the head being tested suffers from defects causing an unstable baseline or from defects causing an amplitude spike.

Abstract: A device for detecting changes of resistivity or dielectrical properties due to changes of fluid composition in the near-well area about a well in a geological formation, comprising an electrically conductive tubing string, an electrical energy source, a signal generator, at least one transmitting antenna for emitting electromagnetic waves along the tubing string, one or more receiver antennas for receiving electromagnetic waves reflected along the tubing string, devices for receiving signals induced in the receiver antennas, signal processing means for processing the received signals, and communication devices for transmitting signals representing the electrical signals and for receiving control signals.

Abstract: A position sensor to determine the absolute position of an object features a rotary position sensor with a tooth gear, which is resiliently and elastically tensioned against a toothing on the moving object.

Abstract: A method and apparatus for high speed magnetic detection of surface fatigue cracks in railway rails. The magnetic material of the rail is magnetized by touch magnetization using a permanent magnet (31), leaving a remanent magnetic field. A sensor head (30, 50) having a plurality of Hall effect sensors (32) senses stray flux generated in the vicinity of surface fatigue in the rail head by the remanent magnetic field. The sensor head (30, 50) may incorporate a proximity sensor (60) to compensate for variations in sensor height. The apparatus may be mounted on a conventional track recording vehicle (TRV) for use in routinely monitoring the surface fatigue severities in rail along a railway.

Abstract: A Hall-effect semiconductor device is formed on a metal-made baseplate, as of nickel-plated copper, via a magnetic layer of Permalloy or the like. Higher in magnetic permeability than the baseplate, the magnetic layer is designed to reduce the magnetic resistance of the flux path. A plastic encapsulation thoroughly encloses the semiconductor device, magnetic layer, and baseplate.

Abstract: The invention concerns a method and apparatus for determining the hydride content in an electrically conductive substrate by generating a first electromagnetic alternating field that at least partly penetrates the substrate which in turn produces a second alternating field that reacts with the first field. The first field is set at at least two different frequencies and measurement at the frequencies of the combined alternating field formed by the interaction of the first and second fields determines the hydride content in the substrate.

Abstract: A wheel speed sensor and bearing assembly for use in a wheel end assembly of a vehicle. The assembly includes an outer race, an inner race, a bearing unit, a spindle, a wheel speed sensor and a tone wheel. The outer race includes an opened inboard end, an opened outboard end, and at least one bearing seat. The inner race includes at least one bearing seat. The bearing unit is disposed between the bearing seats of the outer race and inner race. The spindle is adapted to be secured to a fixed component of the vehicle and includes an inboard end, an outboard end, and an opening formed therethrough. The wheel speed sensor is operatively connected to the spindle adjacent the outboard end thereof. The wheel speed sensor includes an outer magnet surface. The tone wheel is operatively secured to the outer race adjacent the opened outboard end thereof. The tone wheel includes an inner surface which is positioned in a spaced apart relationship relative to the outer magnet surface of the wheel speed sensor.

Abstract: A method and system for the rapid automatic screening of GMR heads for Barkhausen noise during production. This system rapidly and repeatedly measures associated noise in a GMR head subjected to a smoothly-varying external transverse magnetic field. The repeated Transverse Magnetic-field Excited Noise (TMEN) measurements are automatically sorted into bins to form a histogram, which is then automatically evaluated to develop TMEN range and weighted sum measures, which are then compared with predetermined standards for automatic acceptance or rejection of the GMR head under test. The GMR sensor Barkhausen noise is quantified through the use of a bandpass filter to remove all direct sensor responses, leaving only the noise signals, which are then repeatedly sampled to develop valid statistical Barkhausen noise measures suitable for automated analysis.

Abstract: A multi-mode resistivity tool for use in a logging-while-drilling (LWD) system includes an asymmetric transmitter design with multiple transmitters capable of generating electromagnetic (EM) signals at multiple depths of investigation. An array of at least three receivers is positioned amongst a transmitter array to detect the EM signals after they have traversed the region in the vicinity of the borehole. In a first mode, two pairs of receivers combine with the asymmetrical transmitter array to produce a plurality of compensated resistivity measurements. In an alternative mode, one pair of receivers, consisting of a receiver from each of the previous pairs, combines with the array of transmitters to create a plurality of non-compensated measurements. This multi-mode capability enables the resistivity tool to operate successfully in a wide variety of drilling formations and under a broad scope of drilling conditions.

Abstract: In a device for measuring an angle &phgr; between a magnetic field and an MR sensor (1) which supplies at least two electrical sensor signals x and y mutually 90° phase-shifted, which are supplied to an A/D converter (4) whose output is connected to an angle calculating device (6), the absolute sensor signal value |r| of the two sensor signals x and y is determined from the equation |r|={square root over (y2+x2)} in a total calculation device (7) for the purpose of an automatic and continuous offset compensation of the static and dynamic offsets, and the change in the absolute sensor signal value is determined therefrom in dependence on the calculated angle, whereupon an offset control of the sensor signals x and y is carried out in dependence on said change in absolute value.

Abstract: A rotary position detector includes first and second members, the first member generating a magnetic field which spatially varies around the axis of rotation in a cyclic manner and the second member sensing the generated magnetic field. In response to the generated magnetic field, first and second signals are generated by first and second sensors respectively, which signals vary with the relative angular position of the first and second members and the relative angular position of the first and second members is determined from the first and second signals.

Abstract: Spin stand platform. The platform includes an air bearing puck forming a micropositioning stage. The puck is constrained for two dimensional motion on a surface. The micropositioning stage supports a read head element under test. At least one actuator moves the puck to a desired location on the surface and apparatus is provided for removing air from the air bearing puck to lock down the puck to the surface at the desired location. It is preferred that the air bearings be vacuum preloaded and that linear motors be used to move the puck.

Abstract: An electromagnetic antenna extension assembly for connection downhole into a pipe string between a data transmission unit and an electromagnetic antenna. Further, a method for connecting the data transmission unit with the antenna utilizing the assembly. The antenna includes an outer antenna member and an inner antenna member having a lower electrical connector. The data transmission unit includes an outer transmission member and an inner data transmission tool having an upper electrical connector connectable with the lower connector of the inner antenna member.