Abstract: Eddy current based method and apparatus uses a repetitive square wave signal applied to an excitation coil and operates in a pulse echo mode by gating the detected field signal at synchronized intervals to generate one or more sequences of like gated slices obtained from respective detector positions on a circular scan path. Suitable time gating to exclude surface and near-surface reflections overcomes surface clutter and flaws are detected by examination of the sequence of slices for characteristic changes in level. Both method and apparatus have special application for crack investigations at rivet fasteners or similar, e.g. in airframes, and have ability to cope with ferrous fasteners in non-ferrous material. Excitation coil and magnetic detector are combined in a probe and the latter is driven around a circular scan path. A centering display is derived by examination of the near-surface reflection signal to determine the position and level of the peak slice level on the scan path sequence of slices.

Abstract: Method for locating metal studs hidden from view by wall board members fastened thereto by screw-type fasteners characterized by a magnetic field of force which attracts particulate magnetic material, by first locating the screw-type fasteners which are hidden from view by spackling compound or other wall surface finishing material. The screw-type fasteners are located by depositing particulate magnetic material on the outer surface of the wall board, the particulate magnetic material being attracted to a screw-type fastener by the magnetic field of force and associating with the head of the fastener in a surrounding manner on the outside surface of the wall board.

Abstract: An apparatus for locating magnetizable material (5, 6) within a structure (4) includes a scanning head (1) with a permanent magnet (28) for producing a magnetic field in the structure (4). Two field plates (30, 31), adjacent one another on only one pole face of the permanent magnet (28), are interconnected by a differential circuit and measure the magnetic field of the magnet disturbed by the magnetizable material (5, 6). The differential values measured by the pair of field plates form a differential measured signal for establishing, after differentiation, the location of the magnetizable material (5, 6) within the structure (4). The location of the magnetizable material (5, 6) within the structure can be shown on a monitor (7) of an evaluation unit (3).

Abstract: In equipment for recognizing misfire in an internal combustion engine, a first voltage waveform is obtained at an intermediate point (A) between a high impedance element (41) and a low impedance element (42). The first voltage waveform has a capacitive discharge component and an inductive discharge component during the spark and a voltage component after completion of the spark. The first voltage waveform is inversely amplified by a comparator (51) and divided by a shunt circuit (52) to obtain a second voltage waveform. In an integration circuit (53), a condenser (C1) is electrically charged by an output voltage from the comparator (51) to obtain a third voltage waveform. The second voltage waveform and the third voltage are compared by a comparator (54) to generate an output pulse.

Abstract: A magnetometer comprising a superconducting loop including a magnetic flux detecting coil and a SQUID (Superconducting QUantum Interference Device) connected to the superconducting loop via magnetic flux. A negative inductance generating device is provided having two terminals for generating a negative inductance defined by the value of the derivative of generalized magnetic flux between the two terminals with current flowing between the terminals (d.PHI./dI) being negative. The inductance of the superconducting loop is decreased by the negative inductance generating device and input signals intensified by the negative inductance generating device are detected by the SQUID. A plurality of the superconducting loops may be provided to construct a gradiometer and a variable negative inductance generating device is provided to the respective superconducting loop to equalize and intensify the sensitivities of the detection coils.

Abstract: An instrument for non destructive evaluation (NDE) is called an electromagnetic microscope, formed by superconductive microprobes arrayed in parallel rows. When moved over a test piece, the array generates a scanned image of flaws, stress variations or changes in composition. Each microprobe has a drive coil a few mm in radius that encircles pickup loops forming a concentric, coplanar gradiometer 1 mm or less in diameter, coupled to a superconducting quantum interference device (SQUID). Drive coils transmit an oscillating magnetic field that induces eddy or magnetization currents in conductive or ferromagnetic materials, respectively. The gradiometer senses distortions in paths of induced currents. The sensitivity of SQUIDs increases sensitivity, penetration depth, and spatial resolution of flaws.

Abstract: A calibration fixture for an MWD logging tool consists of a plurality of concentric co-planar conductive calibration loops are mounted around the logging tool mandrel coaxially with the usual transmitter(s) and receivers that are mounted on the tool. The calibration loops are terminated with a multiple-tap impedance quantizing means for discretely varying the impedance of the calibration loops. When a transmitter is activated to emit an electromagnetic signal, the calibration loops are excited to reradiate a portion of that signal into the receivers with an intensity that is a function of the loop impedance thereby to simulate the effects of formations having known resistivities.

Abstract: A multichannel weak magnetic field measuring system for neuromagnetic diagnosis is provided having a plurality of dc-SQUID magnetometers. Bias current setting circuits are provided for detecting an even harmonic component of the output across the terminals of the corresponding SQUID and automatically adjusting a DC bias current to the SQUID. Accordingly, the level of the component becomes a predetermined value. Circuitry is also included for equalizing the magnetic flux detection sensitivities of these dc-SQUID magnetometers. Abnormal operation detecting circuits are also provided for producing abnormal operation detected outputs when the level of the corresponding even harmonic component is smaller than a certain threshold value.

Abstract: A meter drive apparatus using a counter for counting reference clocks and a comparator for comparing the output value of the counter and the data indicating a directive target of a meter. The output of the comparator is supplied to steering logic where the sign of a current flowing a drive coil of the meter is determined. When supplying the counted value of the counter to the comparator, parallel bits indicating the counted value are cyclically changed. The output of the comparator is PWM-modulated to drive the meter. The effective frequency of PWM waveform is increased, compared to the direct PWM modulation based on the data indicating the directive target of the meter. With this meter drive apparatus, the frequency of the reference clocks may be relatively low.

Abstract: A method of operating an induction distance sensor employs a sensor having a vane or tongue of magnetic material disposed movably between two inductive coils for changing their inductances in the opposite sense upon movement of the tongue. With respect to sensor signals U.sub.s and U.sub.e, the method employs the portion U.sub.sL of U.sub.s which is in phase with the imaginary part U.sub.eL of U.sub.e. Furthermore, the value U.sub.sL measured in this way is to be further increased by U.sub.e /U.sub.eL in order to compensate for the temperature influences on the ohmic resistances. Furthermore, the errors which can be caused by erroneous controls U.sub.e1 and U.sub.e2 are also corrected. For this purpose, the total voltage is applied at intervals to a reference sensor which consists of a precision resistance divider. In this way, the exact middle point M of the total voltage U.sub.e =U.sub.e1 and U.sub.e2 can be determined by measurement, and the middle-point voltage U.sub.

Abstract: In a system for processing signals responsive to the position of an object, a pair of position sensors are mounted to produce sinusoidal wave signals corresponding to positioning scale markings on the object. The output of the sensors are pulse-width modulated with high-frequency sinusoidal waves. The pulse-width modulation is carried out in a selected section of the sinusoidal waves that does not include regions proximate the peak values of the sinusoidal output of the sensors.

Abstract: A circuit configuration for editing, or processing the output signal of a speed sensor (5) includes a trigger circuit (1, 22), the changeover points or "hysteresis" of which are controllable, with the circuit configuration being furnished with circuits for determining the coupling factor (k), and with circuits for adjusting the hysteresis in response to the coupling factor. The coupling factor (k)--multiplied by the frequency of the sensor signal corresponding to the speed--forms the amplitude of the sensor output signal. With the coupling factor (k) being high, the hysteresis will be high, while it will be low with a low coupling factor.

Abstract: Apparatus and method for accurately timing speed of aquatic vehicles, particularly for water skiing competition and the like. Floating magnetic generating transmitters are placed under one or more linearly aligned buoys configured to accommodate an aquatic vehicle's path. Water-tight detection means is placed on the aquatic vehicle for receiving a series of signals which are induced when the vehicle cuts through the magnetic field produced at a plurality of such buoys. The signals, responsive to the vehicle speed, are amplified and extraneous high frequencies attenuated, and speed or course traverse time calculated and displayed.

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: An improved locator system is provided which transmits digital and analog information over an electromagnetic field that is radiating from an underground source. The locator system includes a transmitter that modulates its output signal by turning its output signal on and off in response to a sequence of digital words. The transmitter also modulates an analog signal onto the transmitted signal. The modulated analog signal can include an audio frequency or voice signal. The improved locator system also includes a receiver that senses and detects the transmitted digital or analog signal impressed on the radiated electromagnetic field. The receiver also demodulates the transmitted audio frequency signal and provides an audio output signal to an operator.

Abstract: A sensor assembly for a two-wheeled vehicle having a sensor housing for holding a sensor receiver having a rod body supporting a reed switch. An O-ring is provided on the exterior wall of the rod body for sealing the inside of the sensor housing from the outside when the rod body is inserted into the sensor housing. The sensor housing is attached to a sensor support that is fixed to a part of the bicycle frame, for example, the fork that supports the front wheel. The reed switch will sense the rotation of the front wheel.

Abstract: A device for detecting speed in a braking system between two relatively rotatable elements, such as, the inner and outer rings of a roller bearing used to support a vehicle wheel. The device includes a first deflector mounted on one of the bearing rings having a magnetized ring member and a plurality of radially outwardly facing poles separated by non-magnetized spaces and a serrated annular member having a plurality of radially inwardly facing ribs. The device further includes a second deflector integral with a fixed ring of the bearing having at least one magnetic sensor engageable between the two bearing rings and spaced to intersect the magnetic fields to produced a plurality of signals per revolution. The signal produced by the sensor has a frequency proportional to the relative speed of the inner and outer bearing rings.

Abstract: An apparatus for near surface, nondestructive eddy current scanning of a conductive part using a multi-layer eddy current probe array. Such structures of this type, generally, employ an ultra-thin, flexible, film-like, multi-layer eddy current probe array which is adapted to provide routine inspection of conductive parts while also providing improved signal integrity, signal transmission and isolation.

Abstract: A magnetoresistive sensor having a magnetization vector M and a current density vector J which form an angle of approximately 45.degree.. Magnetic flux, which enters an active region of the magnetoresistive sensor approximately perpendicular to the magnetization vector M, propagates across the active region with substantially constant length thereby producing a rectangular shaped read sensitivity function. The current density vector J is directed with electrical contacts adjacent the active region which have high resistance regions and low resistance regions.

Abstract: Magnetic poles are provided continuously with a pitch .lambda. on the peripheral portion of a drum rotated in accordance with a movement of a moving body. A magnetic sensor is provided in opposition to these poles. The sensor is formed of two magnetoresistive element pairs which are spaced from each other at .lambda./6, and the two elements in each pair are arranged in positions spaced from each other at .lambda./2. The two elements in each pair are connected in series to form a bridge circuit. The signals obtained from the nodes of the series-connected elements in the two element pairs are differentially amplified so that third harmonic wave components are eliminated, and a signal having no distortion and representative of the position or speed of the moving body can be obtained.