Abstract: An antenna assembly for an induction logging tool for use in a drilling operation. The assembly includes an outer pressure housing, a coil former within the pressure housing, magnetic cores mounted in the housing, a core carrier within the coil former and the pressure housing which carries the magnetic cores, and shock-absorbing mountings on the core carrier for the magnetic cores.

Abstract: A pair of cores is arranged so that their respective first end portions are opposed to each other across a given gap with a transfer path (M) for the passage of a medium between them. Coils wound individually on the respective first end portions of the cores are connected in series with each other to form a first coil. Coils 5a and 5b wound individually on second end portions of the cores are connected in series with each other to form a second coil. Coils wound individually on respective intermediate portions of the cores are connected in series with each other to form a third coil. A signal processing circuit is provided for AC-energizing the third coil to process a detection signal from the first coil and a detection signal from the second coil.

Abstract: An eddy-current probe according to the present invention comprises: a substrate having a first surface facing to a subject to be tested and a second surface opposite to said first surface; an exciting coil formed on the second surface, having a pair of current lines in parallel with each other through which exciting currents flow in opposite directions to each other during testing, for generating an alternate magnetic field applied to the subject by the exciting currents; and at least one eddy-current sensor positioned on a central axis between the pair of current lines on the second surface of the substrate, for detecting a magnetic field generated newly from the subject by an eddy-current induced by the alternate magnetic field.

Abstract: A non-contact type position sensor enhanced in characteristics. A first magnetic element has a first magnetic detecting part at one end side thereof. A first magnet has one pole thereof fixed to the other side of the first magnetic element. A second magnetic element is positioned underneath the first magnetic element, and has a second magnetic detecting part at one end side thereof, and has the other pole of the first magnet at the other end side thereof. A third magnetic element is positioned substantially on circles concentric with the first magnetic element, and has a third magnetic detecting part at the one end side thereof. A second magnet has one pole fixed to the other end side of the third magnetic element. A fourth magnetic element is positioned underneath the third magnetic element, and has a fourth magnetic detecting part at one end side thereof, and also has the other pole of the second magnet at the other end side thereof.

Abstract: A method of estimating target signals (dc or low frequency signals) by a dynamical fluxgate sensor and a low-power fluxgate magnetometer operating according to the method. The sensor is pre-biased with a periodic bias signal in the form of a superposition of a square wave and a triangular wave. The change in residence time statistics in the stable state of the sensor is analyzed for estimating the target signals.

Abstract: A constant current termination is provided for cable locating tones on communication and control cables that may be buried or placed in underground duct structures. The constant current termination limits the current on each branch of the cable to that required for cable location, thus ensuring that branches furthest from the tone source have adequate current for location purposes. The termination is the same for each branch, regardless of its position along the cable system. This eliminates the need to calibrate and recalibrate termination distances for a cable on installation and when branches are added. It also allows the location of damaged cables where the tone signal strength on a damaged branch is less than that for which the termination was designed.

Abstract: A transducer comprising a fixed part and a mobile part which are mounted for relative motion about a given axis. On the shaft of the rotor part there is fitted a magnetized element consisting, for example, of an annular element diametrically magnetized at a single pair of poles. Mounted on the fixed part is a pair of Hall-effect sensors which are set angularly staggered by 90° about the axis of rotation of the shaft. The Hall-effect sensors generate corresponding output signals having values that vary in a continuous range. The values of the output signals generated by the transducer uniquely identify the relative positions of the aforesaid fixed and mobile parts with respect to the axis of rotation.

Abstract: The present invention provides a method for detecting missing servo patterns on printed recording media. In general, the method first comprises the step of generating a map of anticipated servo burst patterns for a magnetic medium. The magnetic medium is typically a magnetic storage disc. Next, the magnetic medium is placed onto a disc reading assembly. Using the disc reading assembly, individual servo bursts on the magnetic medium are identified. In one embodiment, signals from the magnetic medium are processed through a frequency down conversion process, coupled with band pass filtering and rms-to-DC conversion. This enables higher throughput of signal processing. A map of identified servo bursts on the magnetic medium can then be generated. The map of identified servo bursts is then compared with the map of anticipated servo burst patterns. In this way, missing servo bursts can be detected.

Abstract: A highly accurate rotation angle detection device is realized by correcting a detecting position error caused by a machining error such as deterioration of roundness of an internal diameter of a stator. The rotation angle detection device is provided with a stator (12), which is provided with an exciting winding of one phase and two-phase output windings, and a rotor (13) having salient poles, in which the stator (12) has a plurality of teeth (11), the two-phase output windings are wound around the plurality of teeth, and the plurality of teeth include teeth for which the number of turns of the output windings is N and at least one of teeth for which the number of turns of the output windings is N±m (it is assumed that N and m are positive integers and N>m) and teeth for which the number of turns is m.

Abstract: A position sensor including a magnetic circuit comprising a magnet having opposite first and second magnetic poles, a first pole piece having a proximal portion positioned adjacent the first magnetic pole and a distal portion positioned adjacent the second magnetic pole to define a first air gap area with a first magnetic field provided adjacent thereto, and a second pole piece having a proximal portion positioned adjacent the second magnetic pole and a distal portion positioned adjacent the first magnetic pole to define a second air gap area with a second magnetic field provided adjacent thereto. A first magnetic flux sensor is disposed within the first magnetic field to sense varying magnitudes of magnetic flux density and to generate a first output signal. A second magnetic flux sensor is disposed within the second magnetic field to sense varying magnitudes of magnetic flux density and to generate a second output signal.

Abstract: A non-contacting position sensor detects relative displacement between two objects. A magnetic flux source is provided by a plurality of discrete magnets selectively determined to produce a highly configurable flux source that is easily adapted to rotary or rectilinear displacement. The interaction of the individual flux fields generated by the discrete magnets is controlled to produce both linear and non-linear relationships with respect to changes in displacement. A flux-gathering pole piece is dimensionally optimized to integrate the plurality of individual flux fields directed to a magnetic sensor.

Abstract: A magnetic sensor system and a method for installing magnetic sensors for detecting metal objects that allows ease of manipulation, control and access. A carrier conduit is used to position a magnetic sensor in an outer conduit. The outer conduit may be disposed beneath a surface where objects to be detected may be positioned. Alternatively, a conduit having multiple channels may be placed in a pathway. Magnetic sensors may be placed in the channels and a top placed over the conduit. Multiple embodiments for orienting the magnetic sensor systems are provided.

Abstract: A method and apparatus performs high resolution imaging. The disclosed apparatus includes a low temperature SQUID sensor mounted in close proximity to a dewar thin window. A radiation shield has an extension surrounding the detection coil.

Abstract: An airborne exploration system used with an aircraft for shallow and deep exploration for oil and gas, mineral deposits and aquifers. The survey system uses natural electromagnetic EM fields as an energy source. The exploration system includes a pair of aerodynamic housing pods adapted for mounting on wing tips of the aircraft. The housing pods include electric field sensors with three orthogonal electric dipoles oriented along an X, Y and Z axis. An optional third set of orthogonal electric dipoles can be mounted in the tail of the aircraft. The field sensors are electrically attached to angular motion detectors mounted inside housing pods. The motion detectors are used for compensating for errors caused by angular motion of the aircraft when in the presence of strong electric field gradients. The system also includes a total field magnetometer mounted in the aircraft.

Abstract: A rotation angle detecting device includes a magnet, a magnetic flux concentrator, a first magnetic sensor, and a second magnetic sensor. The magnet is provided in a rotary member and is substantially coaxially aligned with a rotational axis thereof. The magnet has a magnetic flux generation section and a magnetic flux absorption section oriented in radial directions vertical to the rotational axis. The magnetic flux concentrator is made of a magnetic material and rotates integrally with the magnet. The magnetic flux concentrator is substantially coaxially aligned with the rotational axis and disposed substantially parallel to the magnet. The first and second magnetic sensors are disposed between the magnet and the magnetic flux concentrator at a predetermined angle away from each other in a rotational direction. The rotation angle detecting device detects the rotation angle of the rotary member based on magnetic flux passing through the first and second magnetic sensors.

Abstract: A magnetoresistive sensor has at least one strip-shaped conductor that is formed from a magnetoresistive material and that is designed to determine its electrical resistance, which can be influenced by an external magnetic field, and/or to be acted on by an electric current. In order to construct a magnetoresistive sensor of this type in such a way that a further reduction in the hysteresis and an improved linearity are obtained, at least one screening strip is provided according to the invention that is disposed at least substantially parallel to and at a predetermined spacing from the conductor and is electrically separated from it.

Abstract: The present invention relates to the processes and devices for assessing the permeability of a rock medium 1 containing a fluid 2 in its interstices 3. The device and the process according to the invention are characterized essentially in that a given magnetic field is applied to the interstitial fluid 2 located in the rock medium 1, the variation in pressure of the interstitial fluid 2 resulting from the application of the magnetic field is measured, and the permeability of the rock medium is determined as a function of the value of the variation in pressure of the interstitial fluid.

Abstract: An electromagnetic gage sensing system having sensor heads positioned over each rail of a railroad track that measures both rail gage and height distance above the rails of a railroad track. Each sensor head includes an array of electromagnetic field generating coils and an array of electromagnetic field sensors positioned above each rail so as to extend substantially across the rail surface. A method of measuring gage distance is also provided in which lateral EM field output signal indicative of an edge surface of a rail is sensed.

Abstract: A sensor that characterizes welds in materials. The sensor includes a meandering drive winding with at least three extended portions and at least one sensing element placed between an adjacent pair of extended portions. A time varying electric current is passed through the extended portions to form a magnetic field. The sensor is placed in proximity to the test material and translated over the weld region. An electrical property of the weld region is measured for each sensing element location. The weld quality is determined using a feature of the electrical property measurement and location.

Abstract: A magnetic sensor provides an output voltage range having first and second linear slopes. Proper selection of magnetic sensor dimensions enables changes in magnetic flux density upon the passage of at least one tooth and one slot of a target wheel past the magnetic sensor to be represented as a linear magnetic sensor output comprised of at least one linear range whereby linear interpolation of position is possible with appropriate signal processing algorithms.