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: Systems and methods for determining characteristics of geologic formations between conductively lined wellbores. At least one transmitter is axially disposed at a selected depth in a first wellbore and is attached to an external surface of a conductive liner. At least one receiver is axially disposed at a selected depth in a second wellbore and is attached to an external surface of a conductive liner. Both the transmitter and the receiver are attached to a surface control station. The transmitter generates a first magnetic field, and a formation magnetic field induced by the first magnetic field is detected by the receiver. The detected formation magnetic field is used to determine characteristics of the geologic formations.

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 sensing apparatus which has an electromagnetic transmitter, at least one receiver device, at least one calibration device, a switch and a processor. The transmitter generates a transmitter signal. The receiver device is spaced from the transmitter, senses an electromagnetic field proximate thereto and generates a receiver signal. The calibration device senses an electromagnetic field proximate thereto and generates a calibration signal. The calibration device is positioned such that the distance between the transmitter and the receiver device is greater than the distance between the transmitter and the calibration device. The switch is connected between the receiver device and the calibration device. The processor includes a first input for receiving a signal from one of the at least one receiver device and the calibration device and a second input for receiving a signal from the switch and compares the first input and second input and monitors distortions in the transmitter signal.

Abstract: A magneto-optical microscope magnetometer capable of simultaneously measuring a hysteresis loop and activation magnetic moment of a submicrometer-scale local area (about 0.3×0.3 &mgr;m). An electromagnet capable of applying a magnetic field to a magnetic material is attached to a polarizing optical microscope capable of observing a magnetized state of the magnetic material, such that images of the microscope varying with the strength of the applied magnetic field are grabbed in real time by a charge coupled device camera and then analyzed. The magneto-optical microscope magnetometer can measure a hysteresis loop and activation magnetic moment in a submicrometer-scale local area observed by the polarizing optical microscope. Further, the magneto-optical microscope magnetometer can measure hysteresis loops and activation magnetic moments simultaneously with respect to all CCD pixels of the camera and observe coercivity and activation magnetic moment distributions of the entire magnetic material.

Abstract: A system and method for programming a Hall effect sensor while the sensor is connected into the circuitry for a given application. The system includes a fixture for receiving the printed circuit board to which the sensor is mounted. A plurality of contacts, such as pogo pins, are arranged to contact the circuit board at desired pads that permit programming of the sensor, reduction of the voltage applied to the overall circuit during programming, and measurement of the sensor and circuit output. The system includes a voltage limiting circuitry that is electrically connected, via appropriate pogo pins, to the circuitry intermediate the subject sensor and potentially damaged circuit components.

Abstract: A hand tool has a ground-piercing probe, which is manually insertable in the soil. The probe has a chamber in which an inductor is positioned and connected to metal detection circuitry. A pulse generator applies current pulses to an inductor for inducing eddy currents in a buried target object. After the pulse terminates, the decaying coil voltage is sampled at different times to detect both the presence and range of the object, as well as the type of metal in the object. The coil voltage samples are applied to signaling circuitry, which provides an audible signal which is a series of bursts of an audio tone. The pitch of the audio tone signals the presence, range and bearing of the buried metal object, while the pulse rate of the bursts signals the metal type. Signal variations resulting from temperature changes when the probe is inserted into soil are compensated for by detecting a signal proportional to the coil current during the pulse and subtracting a scaled portion of that signal from voltage samples.

Abstract: A drive circuit for driving the transmitter windings of an inductive position transducer includes an oscillating power source. A resonator section is connected to the power source. The resonator section includes an impedance transforming section, a transmitter winding of the inductive position transducer, and feedback loops which cause the power source to oscillate at the resonator frequency. The resonator operating frequency and the load impedance imposed on the power source by the resonator can be independently selected. In various exemplary configurations of the drive circuit, the resonator operating frequency adapts to variations in the impedance of the transmitter windings. The drive circuit is particularly well-suited for driving low-impedance and/or miniaturized inductive position transducers with enhanced efficiency and accuracy. In various exemplary configurations of the drive circuit, the peak operating voltage of the transmitter windings can exceed the power supply voltage.

Abstract: A process for resetting or initially establishing the magnetic orientation of one or more spin valves in a magnetoresistive read head with improved robustness. The spin valve includes subcomponents such as an antiferromagnetic layer, a ferromagnetic pinned layer, a conductive layer, a free layer, and a hard bias layer. A first external magnetic field is first applied to the spin valve sensor, this field having a first orientation relative to the spin valve sensor. During application of the first external magnetic field, a pulse of electrical current is directed through the spin valve sensor in a first direction, preferably parallel to the magnetic orientation of the external field. The current waveform brings the antiferromagnetic layer of the spin valve past its blocking temperature, freeing its magnetic orientation. The first external field exerts a robust bias upon the antiferromagnetic layer in the desired direction.

Abstract: An angular position sensor includes a rotor attached to a shaft. A first magnet and a second magnet are attached to the surface of the rotor. Moreover, a first concentrator and a second concentrator are disposed around the perimeter of the rotor opposite each other. A space is established between the first concentrator and second concentrator, and a magnetic field sensing element is disposed in the space. As the rotor rotates with respect to the sensing element, the sensing element outputs a linear signal representing the location of the rotor with respect to the sensing element over a range between negative ninety degrees and positive ninety degrees.

Abstract: A vehicle rollover sensor 10 is provided, including a movable member free 12 free to rotate about a single axis 14. The movable member 12 includes an inertial mass 18. A magnet 22 is mounted to the movable member 12. The vehicle rollover sensor 10 further includes a magnetoresistive sensor 24 capable of sensing changes in the magnetic field due to changes in the orientation of the moveable member 12.

Abstract: Apparatus for detection and measurement of agglutinations of magnetic particles employing Hall sensors. A low frequency AC signal is employed to excite or bias the Hall sensors which reside in a DC magnetic field. The particles are moved into operative relationship with the Hall sensors in order to generate a signal representing the number of particles on the substrate. The method for such detection and measurement is also part of the invention.

Abstract: To make it possible for a rotation angle sensor to be manufactured and assembled more easily and more accurately, the part components of a stator element (21) made of a ferritic material are held in a sintered stator body, made by a sintering technique, by at least one holding element in a holding recess of a base element made of a non-magnetizable material. A magnetic holding device (26, 27) is a holding element made by a metal injection molding (MIM) technique with an at least partly formed magnetic isolation zone and at least one recess. An annular magnetic element (24) is attached inside the MIM holding device by means of at least one slit-shaped recess and at least one compatible linking element, and positioned at a given angle &agr; in relation to a gap, between the sintered stator bodies.

Abstract: Apparatus for determining the distribution of the electric polarization of a vessel in water, comprises an array of electric potential sensors (22) which are located in the water beneath the vessel and each generates a signal corresponding to the amplitude of the electric potential at the sensor as effected by the vessel, a signal processor unit (48) and cables (42) connecting each sensor (22) to the signal processor unit (48) to deliver each respective signal to the signal processor unit, the signal processor unit (48) serving to determine the potential difference between respective pairs of sensors (22) from the respective signals they generate, and the signal processor unit (48) processing multiple such potential difference determinations to deduce the distribution of electric polarization in the vessel which would cause said electric potential at each of the electric potential sensors (22).

Abstract: An ultrasensitive displacement sensing device for use in accelerometers, pressure gauges, temperature transducers, and the like, comprises a sputter deposited, multilayer, magnetoresistive field sensor with a variable electrical resistance based on an imposed magnetic field. The device detects displacement by sensing changes in the local magnetic field about the magnetoresistive field sensor caused by the displacement of a hard magnetic film on a movable microstructure. The microstructure, which may be a cantilever, membrane, bridge, or other microelement, moves under the influence of an acceleration a known displacement predicted by the configuration and materials selected, and the resulting change in the electrical resistance of the MR sensor can be used to calculate the displacement. Using a micromachining approach, very thin silicon and silicon nitride membranes are fabricated in one preferred embodiment by means of anisotropic etching of silicon wafers.

Abstract: The invention relates to a method for applying to a carrier a marking serving to measure length, angle cr the like, such as, for example, a magnetic tape (4), by means of which the accuracy of the measurements is improved. In the case of such methods, in one marking step a means for producing a track with markings, for example a writing head (9), is guided over the carrier and, by virtue of the fact that the carrier is acted upon, markings, for example magnetic north and south poles, are applied therein at predetermined positions of the carrier.

Abstract: A magnetic sensing device that senses low frequency magnetic fields by using movable flux concentrators that modulate the observed low frequency signal. The concentrator oscillates at a modulation frequency much greater than the observed magnetic field being sensed by the device. The modulation shifts this observed signal to higher frequencies and thus minimizes 1/f-type noise. This is preferably accomplished by the oscillatory motion of a microelectromechanical (MEMS)—type magnetic flux concentrator operated with a magnetic sensor, preferably made on a common substrate. Such a combined device can be used in a magnetometer. Such a device is small, low-cost and has low-power-consumption requirements. The magnetic sensor can be a Hall effect or other type of magnetic sensor. At least one modulating flux concentrator is used with the magnetic sensor.

Abstract: An improved Hall position sensor comprises a Hall effect sensing device having its leads soldered directly to an exposed electro-conductive portion of a flexible multiconductor circuit. The Hall position sensor further comprises a Hall magnet disposed proximate to the soldered Hall effect sensing device/flexible circuit unit.

Abstract: A locator is described for tracking the position of a boring tool and/or one or more buried lines within a region. A flux plane is used to establish a flux vector to guide the portable locator to locate points in a dipole field. A locate line is located in the dipole field by determining a predicted locate line angular orientation based upon horizontal flux vector determinations. The predicted angular orientation limits possible directions to and orientations of a predicted locate line relative to the portable locator. Cable line locating measures a local flux intensity of the locating signal using the portable locator. A cable line angular orientation limits the possible directions to the cable line. A display is configured for periodic updates such that displayed positional relationships are essentially continuous, including accommodation of positional and/or orientation changes seen by the portable locator in dipole or cable line tracking.

Abstract: A magnet is provided on a detection member that moves on a straight line. A Hall element serving as a magneto-electric element is provided on a fixed member that opposes the magnet. A surface of the magnet that opposes the Hall element is formed into a radius or trapezoidal shape. With this arrangement, linear outputs can be obtained at any rotational angles even when a rotator rotates a plurality of times.