Abstract: A meandering winding magnetometer (MWM) includes a meandering primary winding and at least one sensing winding or coil on a membrane to be pressed against a test surface. The membrane may be supported on a flexible carrier which is translatable into a probe. Abutments in the probe press the carrier against the test surface but allow the carrier and membrane to conform to the test surface. One MWM circuit includes meandering primary and secondary windings. The return leads from the secondary winding return to connector pads in close alignment with the test array, while leads from the primary winding are spaced at least one wavelength from the array. In another MWM circuit, individual sensing loops are positioned within the meandering primary winding. The MWM circuit may be provided on an adhesive tape which may be cut to length.

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: In a method for measuring a distance between a conducting reaction track and a functional surface moving relative to the reaction track a sensor with two signal transmitters is provided on the functional surface. An alternating field is generated in the sensor. The alternating field changes as a function of the distance between the conducting reaction track and the functional surface. Each of the two signal transmitters detects the changes of the alternating field as distance information. Each signal transmitter produces decoupled distance information values. These decoupled distance information values are processed in separate distance measuring channels to provide processed signals. The processed signals are constantly fed to and compared in a comparator. A distance information signal is emitted only when the processed signals of the separate distance measuring channels are identical within a predetermined tolerance range.

Abstract: A method for excitation and detection of magnetic resonance elements (10) in an interrogation zone (11), whereby a magnetic excitation signal is generated by at least one excitation means (12) and is supplied to the resonance element, so as to force the resonance element (10) into mechanical self-oscillation, and whereby a magnetical signal caused by the self-oscillation is detected. The excitation signal is generated by at least two excitation means (12) being located at a distance from each other, whereby a symmetry plane (14) for the excitation signal is obtained between the excitation means (12). The magnetic signal caused by the self-oscillation is symmetrically recorded at both sides of the symmetry plane (14), and the resonance elements are placed between an excitation means (12) and the symmetry plane (14), the recorded signal thereby containing the magnetic signal caused by the self-oscillation, but lacking the excitation signal.

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.

Abstract: A magnetic inspection device for detecting structural faults in elongated magnetically permeable objects has two primary and opposite poles which induce a magnetic flux to place the object at least near magnetic saturation. At least one auxiliary pole is positioned on the inspection device between the primary poles and serves to change the level of the magnetic flux induced by the primary poles so as to induce eddy currents during relative movement of the inspection device and the object. At least one sensor positioned on the inspection device detects eddy current changes which are representative of structural faults.

Abstract: A leakage flux flaw detection apparatus in which an object material is magnetized and leakage fluxes derived from a flaw are detected to thereby search for a flaw of the object material in a predetermined flaw-detection direction. The apparatus has a pair of magnet poles for magnetizing the object. material in a direction different from the flaw-detection direction, another pair of magnet poles for magnetizing the object material in a direction different from the magnetization direction and flaw-detection direction of the first pair of magnet poles at a predetermined distance in the flaw-detection direction from the magnetization area of the two magnet poles, and two leakage sensors each of which is interposed between each of the two pairs of magnet poles.

Abstract: A leakage flux flaw detection apparatus in which an object material is magnetized and leakage fluxes derived from a flaw are detected to thereby search for a flaw of the object material in a predetermined flaw-detection direction. The apparatus has a pair of magnet poles for magnetizing the object material in a direction different from the flaw-detection direction, another pair of magnet poles for magnetizing the object material in a direction different from the magnetization direction and flaw-detection direction of the first pair of magnet poles at a predetermined distance in the flaw-detection direction from the magnetization area of the two magnet poles, and two leakage sensors each of which is interposed between each of the two pairs of magnet poles.

Abstract: A system for locating objects in space, such as medical instruments within the body of a patient, based upon transmission of magnetic fields from coils in a fixed frame of reference to sensors on the object or visa-versa. The current supplied to the coils is adjusted to assure that the sensors receive fields within a preselected range of magnitudes regardless of the location of the object in space. This assures that the sensor operates within its optimum range, and permits use of compact transmitters and sensors.

Abstract: A method and apparatus for testing an integrated magnetic head assembly for normal operation. The head assembly includes an inductive write element and a MR read element. The method includes a step of applying an external alternating magnetic field to a plurality of magnetic head assemblies which are aligned on a head block and are not yet individually separated from the head block, in a direction perpendicular to an ABS of the head block, and also applying high frequency current to the inductive write element so that alternating leakage magnetic field from the inductive write element is applied to the MR read element, and a step of measuring varying resistance characteristics of the MR read element with respect to the variation of the external alternating magnetic field and to the variation of the alternating leakage magnetic field.

Abstract: A proximity sensing circuit is provided with various attributes, including the connection of a proximity sensor coil in a feedback loop of an amplifier, the frequency hopping technique that periodically changes the two frequencies used by its proximity sensor circuit to avoid deleterious interference by constant frequency EMI sources and the provision of a self diagnosis technique. The connection of the proximity sensor coil in the feedback loop of an amplifier results in several advantages including the connection of the coil to a virtually infinite impedance, the reduction of the number of components needed in the proximity sensing circuit and decreased temperature sensitivity of the overall circuit. The frequency hopping technique that periodically changes the two frequencies used by the proximity sensor significantly decreases the likelihood that a constant frequency EMI source in the vicinity of the circuit will have a continually adverse affect on its accuracy and reliability.

Abstract: An electromagnetic-induction type inspection device for inspecting a test specimen by placing the specimen in electromagnetic fields produced by exciting coils, detecting induction currents from induction coils set in the electromagnetic fields, and analyzing a composite signal composed of the amplitude and phase components contained in a differential current between the induction currents. The composite signal is expressed as a waveform which is displayed on a display unit, so that deformed portions of the waveform, which represent internal defects or other abnormalities in the specimen, can be identified.

Abstract: An apparatus for accurately inspecting an electroconductive film using an eddy current and an apparatus for production of an optical fiber which measures on-line the electrical resistance, which shows the state of formation of the electroconductive hermetic coating of the optical fiber by an electroconductive film inspection method and reflects back the measurement results to the hermetic coating forming conditions. Optical fiber is made up of a core, a cladding, amorphous carbon film or other electroconductive hermetic coating formed on the outer surface of the cladding, and a protective coating. The electrical resistance of the hermetic coating generates an eddy current at the coating, the eddy current generated is detected, and the phase angle of the complex impedance is detected to enable calculation.

Abstract: There is provided a transient electromagnetic method and apparatus for inspecting objects. The apparatus includes a sensing portion, which has a transmitting antenna and at least one receiving antenna thereon. The sensing portion is located adjacent to the object which is to be inspected such that the antennas are adjacent to the object. There is also a magnet located adjacent to the sensing portion. The magnet has poles located adjacent to the object, so as to provide a steady-state magnetic field to the object. By applying a steady-state magnetic field to the object during inspection, increased inspection speeds and improved spatial resolutions can be achieved. In addition, casing can be inspected from inside of tubing.

Abstract: An eddy current surface measurement array structure for complete coverage of an underlying inspection surface without requiring mechanical scanning is disclosed. A three-dimensional array of eddy current sense elements is organized as a plurality of layers of two-dimensional sub-arrays. The sub-arrays, although in different layers, are essentially identical in configuration, and are staggered such that the sense elements of one layer provide at least partial coverage of portions of the inspection surface not covered by the sense elements of another layer. As many staggered layers are included as are necessary to ensure that no "blind spots" remain, for complete coverage of the underlying inspection surface. The sense elements are disposed in a layered flexible structure fabricated employing high density interconnect fabrication techniques or other photolithographic techniques.

Abstract: A device for and method of testing toroidal magnetic cores for magnetic anomalies which prevent uniform performance of the cores. The core is positioned on a drive device which can rotate the core through 360.degree.. The core passes through an input winding which receives the test signal and an output winding coupled to a display device which shows the presence or absence of such magnetic anomalies.

Abstract: A system for detecting metal targets located in a background environment such as the ground evaluates metal targets by processing components of signals at two or more different frequencies. A component of the received signal induced by the ground can be eliminated by subtracting signal components measured at two different frequencies. The received signal can be processed to account for changes in the background response with frequency. The type of an unknown target can be identified by processing background excluded components to produce data characterizing the target type.

Abstract: A magnetic telescope utilized to detect flaws in underground articles such as underground piping, implements multiple stages in the form of geometric and electronic configurations to enhance noise suppression. The geometric configuration includes a differential configuration of two pair of source coils which generate the magnetic flux, and gradiometers which pick-up the magnetic flux. A superconducting quantum interference device (SQUID) is utilized to detect the magnetic flux. The electronic configuration includes circuitry to adjust the current in the source coil pairs to minimize the signal seen by the SQUID when no underground article is present. The electronic configuration also includes feedback circuitry to feed back magnetic flux to the SQUID based on the signal detected by the SQUID. Combining the geometric and electronic configurations provides enhanced noise suppression so that the SQUID is capable of detecting smaller flaws in the underground piping for the same amount of source magnetic flux.

Abstract: A sheet inducer carrying a uniformly distributed ac current induces a sheet eddy current generally parallel to a generally smooth surface of an electrically conductive object. A magnetometer, preferably a superconducting quantum interference device (SQUID) magnetometer, detects the component of a magnetic field generally perpendicular to the generally smooth surface resulting from disturbances in the sheet eddy current caused by a flaw. Through appropriate selection of the phase angle between the detector signal and the applied current, the response can be adjusted to suppress surface flaws and enhance detection of flaws below the surface. The sheet eddy current is induced in multiple directions to detect flaws of all orientations and at multiple frequencies to refine determination of the size, shape, and depth of a flaw.

Abstract: In one aspect of the present invention, an apparatus for detecting particles within a fluid is disclosed. A bobbin defines a debris collection chamber. A first coil is wound in a helix about the bobbin in the proximity of the debris collection chamber, wherein the induction of the first coil is responsive to the particle accumulation within the collection chamber. A reference coil is wound in a helix about the bobbin to compensate for changing fluid temperature. An oscillator is coupled to the first and reference coils for selectively energizing the coils with an oscillating waveform at a frequency that induces eddy currents in the particles. The frequency of the oscillating waveform is indicative of the amount of accumulation of both the ferrous and nonferrous particles.

Abstract: In one aspect of the present invention, an apparatus for detecting particles within a fluid is disclosed. A bobbin defines a debris collection chamber. Spaced apart first and second coils are wound about the bobbin in the proximity of the debris collection chamber, wherein the inductance of the coils are responsive to the particle accumulation within the collection chamber. An electromagnet is wound about the second coil to attract ferrous particles into the proximity of the second coil. A reference coil is wound about the bobbin to compensate for the changing temperature of the fluid. An oscillator is coupled to the first, second and reference coils for selectively producing an oscillating waveform at a frequency that induces eddy currents in the particles. The frequency of the oscillating waveform is indicative of the amount of accumulation of both the ferrous and non-ferrous particles.

Abstract: A method and apparatus for investigating various parameters of biofluids, such as blood, particularly protein and cellular concentrations and cellular volume utilises the application of at least two a.c. frequencies, preferably simultaneously, in the range 0.1 to 60 MHz to a sample of the fluid and receiving and resolving the frequencies after passage through the fluid. The received frequencies are processed to derive corresponding d.c. voltage amplitudes which are mathematically processed to provide a numeric output correlating with a parameter under investigation, A new parameter named Instant Sedimentation Rate (ISR) is disclosed.

Abstract: An apparatus to detect anomalies in a member, such as a conveyor belt, having reinforcing cables therein made of a magnetically permeable material. There is coil means arranged to create a magnetic field as two longitudinally spaced first and second field components at longitudinally spaced locations. There are Hall effect sensors arranged to respond to modifications in each of the first and second field components. In a first embodiment, there is one set of sensors positioned between the first and second field components. In a second embodiment, there are two sets of sensors spaced at said first and second field components.

Abstract: A method and system for accurately inspecting an electroconductive film using an eddy current and a process and apparatus for production of an optical fiber which measures on-line the electrical resistance, which shows the state of formation of the electroconductive hermetic coating of the optical fiber by the electroconductive film inspection method and reflects back the measurement results to the hermetic coating forming conditions. Optical fiber is made up of a core, a cladding, an amorphous carbon film or other electroconductive hermetic coating formed on the outer surface of the cladding, and a protective coating. The electrical resistance of the hermetic coating generates an eddy current at the coating, the eddy current generated is detected, and the phase angle of the complex impedance is detected to enable calculation.

Abstract: An apparatus and method for detecting anomalies in ferrous pipe structures is presented. A sensor having one or more sensor shoe members is placed in the interior of a ferrous pipe structure to be inspected. Each sensor shoe member has one or more magnetic field generating apparatus, with a three-axis fluxgate magnetometer for detecting magnetic fields in the region of the ferrous pipe structure adjacent to which the sensor shoe member is placed. Any magnetic fields in the pipe structure, whether imposed externally, or remnant, which are detected, are sensed and resolved into components in three mutually orthogonal directions for enhanced accuracy.

Abstract: A plurality of magnetic field members are provided, each for selectively generating a time-varying magnetic field for combination into a o time-varying composite longitudinal magnetic field with magnetic flux lines which are substantially aligned with the central longitudinal axis of the cylindrical ferromagnetic member. Additionally, a traverse magnetic field member is provided which selectively generates a time-varying traverse magnetic field with magnetic flux lines which are substantially traversed to the central longitudinal axis of the cylindrical ferromagnetic member. The plurality of magnetic field members and the traverse magnetic field member are maintained out of contact with the cylindrical ferromagnetic member. Magnetic particles are placed on selected portions of the cylindrical ferromagnetic member. A time-varying composite longitudinal magnetic field and a time-varying traverse magnetic field are applied to the cylindrical magnetic member, while it is being rotated.

Abstract: A magnetic field generator positioned externally of a non-ferrous metallic tructure being examined, is rotated at a relatively low speed to produce a rotating magnetic field penetrating the metallic structure to a selected depth as a function of spacing between magnetic poles of the generator parallel to a planar surface of the metallic structure. Traction between the metallic structure and the magnetic field accompanying its rotation is measured. Corrosion of the metallic structure at subsurface depths is detected and quantified from such traction measurements.

Abstract: An apparatus for detecting surface flaws in cylindrical articles by means of asymmetric magnetic detection, utilizing a rotating magnetic field, said articles having central longitudinal axes, apparatus having a guide assembly for guiding the cylindrical articles along a displacement path having a central longitudinal axis extending coaxially of the central longitudinal axes of the articles and a pair of multiple polar sensor assemblies positioned in annular relationship with the displacement path for producing a plurality of phase/amplitude modulated signals representative of the surface geometry of the inspected cylindrical article, also disclosed are two embodiments of cylindrical container flange imperfection detector apparatus utilizing multiple polar sensor assemblies.

Abstract: A device for testing elongated objects, particularly wires, optionally with cross-sectional irregularities, which has a rotating test head traversed by the object and on which is provided a probe, particularly an eddy current probe, provided on rotary probe holding means and guided on circular paths about the object. For the change of the radial spacing between the object and the probe with the test head rotating, externally controllable e.g. by a sensor for irregularities, the device has a switching device with two inherently stable switching states, whereof one can correspond to a testing position near the object and another to a raised position further removed from the object and which can be rapidly set for protecting the probes.

Abstract: An eddy current probe for insertion into a tube to be inspected includes a transmitter coil and a pair of sensing coils. The pair of sensing coils have opposite polarity relative to one another and are series connected to provide a differential output. The pair of sensing coils and the transmitter coil are disposed on the surface of the probe. The pair of sensing coils being equally spaced from the transmitter coil and separate from each longitudinally on the probe. Each sensing coil in the pair of sensing coils is thereby angularly displaced from a plane transverse to the probe as measured from the transmitter coil with which a multi-coil unit is formed. Bracelets of coils are formed from plural multi-coil units aligned around the probe to improve sensitivity of the probe. Additional bracelets of coils may be added to the probe, offset rotationally, to improve coverage of the tube.

Abstract: A metal detector apparatus and a metal detection method for detecting and discriminatory interrogating a metal target buried in the ground. The detector includes a transmitter for providing a first varying magnetic field including at least two frequency components and a receiver for providing a resultant voltage dependent upon a second magnetic field resulting from the combined effects of the ground and metal targets buried in the ground, upon the first alternating magnetic field. The detector samples at least three voltage measurements of the resultant voltage over three different time periods to provide three sampled values which are then processed by a microprocessor to provide three average ground balanced signals from which at least two ratios are calculated and compared against a pre-defined response.

Abstract: An induction logging tool is disclosed for utilization in conjunction with surface electronic equipment for measuring a characteristic of subsurface formations. A transmit signal which is comprised of a repetitive sequential series of at least three transmit frequencies is generated by coupling an oscillator to a transmitter coil and a plurality of selectable tuning capacitors. A signal characteristic of the response of the formation to this transmit signal is detected at a receiver coil array and two phase sensitive detectors are then utilized to generate output signals indicative of the magnitude of the X and R components of the formation signal which is in phase with a reference phase signal. The output signal of each phase sensitive detector is then utilized to accurately determine the X and R component of the receiver coil signal for each frequency by nulling the output of the phase sensitive detector utilizing a closed loop conversion circuit which eliminates errors due to phase and gain variations.

Abstract: A Metal Detector with windings placed so as to originate multipolar electromagnetic fields, including two or more pairs of transmitter Tx and Receiver Rx windings, in which the different pairs are characterized by having a different number of poles so that the simultaneous passage of two or more metal masses on parallel trajectories will never cause equal and opposite inducted signals in the Rx windings, with a zero resultant so that such masses are detected in any case.

Abstract: An adjustable scanning range is provided for vehicle-activated measuring equipment of the type which includes receiver coils positioned on opposite sides of a transmitter such that voltages induced in the received coils from the transmitter are altered as the vehicle passes, the measuring occurring through the application of the induced voltages to a comparison circuit. Altering the input(s) to the comparison circuit by a constant voltage value allows the scanning range to be adjusted.

Abstract: Apparatus for non-destructive examination of a plate for defects existing in one of both of opposed first and second surfaces thereof includes a rotatable support platform, an eddy current coil structure for inducing eddy currrents in the plate located at a first location in the platform, a first magnetic flux generator disposed at a second location in the platform, the second location being opposite the first location on a line extending from the first location through the platform center. A drive unit rotates the platform relative to the plate.

Abstract: Apparatus and methods are disclosed which provide increased sensitivity, selectivity and dynamic range for non-contact measurement of actual physical and/or kinematic properties of conducting and magnetic materials. The apparatus and methods are based upon various methods for increasing sensitivity, selectivity and dynamic range through proper construction of a magnetometer sensor and for proper selection of operating point parameters for the application. A measurement apparatus for measuring one or more MUT properties includes an electromagnetic winding structure which, when driven by an electric signal, imposes a magnetic field in the MUT and senses an electromagnetic response. An analyzer is provided for applying the electric signal to the winding structure. A property estimator is coupled to the winding structure and translates sensed electromagnetic responses into estimates of one or more preselected properties of the material.

Abstract: Defects such as corrosion located on either the inner diameter or outer diameter of a covered metal component are detected through eddy current inspection. At least two concentric magnetizing yokes are held fixed with respect to each other and are scanned over the cover of the component. A magnetic flux sensor on the leg of each yoke detects changes in the magnetic flux that penetrates at different depth regions in the covered metal component, depending on the relative postion of each magnetizing yoke.

Abstract: A device for and method of testing toroidal magnetic cores for magnetic anomalies which prevent uniform performance of the cores. The core is positioned on a drive device which can rotate the core through 360.degree.. The core passes through an input winding which receives the test signal and an output winding coupled to a display device which shows the presence or absence of such magnetic anomalies.

Abstract: In order to improve product quality control through quantitative determination of a defect and quantitative judgement of the quality of a product, an alternating current is applied to a standard product coil into which is inserted a standard object, and to a test object coil into which is inserted a test object, and eddy currents are measured by means of a bridge circuit. If the test object coil is at a location removed from a flaw, the bridge circuit output voltage is zero, while if the test object coil is at the location of the flaw, a predetermined voltage is output. A determination of torsional breakage torque of the shaft inspection is carried out by correcting the output voltage for dependence on the cross sectional area ratio of the test object relating to the cross sectional area of the coil and for the influence of flaw size depending on the location.

Abstract: Eddy-current response voltages, generated during inspection of metallic structures for anomalies, are often replete with noise. Therefore, analysis of the inspection data and results is difficult or near impossible, resulting in inconsistent or unreliable evaluation of the structure. This invention processes the eddy-current response voltage, removing the effect of random noise, to allow proper identification of anomalies within and associated with the structure.

Abstract: A magnetic inspection device for detecting structural faults in elongated magnetically permeable objects has two opposite magnetic poles, at least one pole being an end pole, that induce a first magnetic flux axially in a first section of an object between the poles, and an oppositely directed magnetic flux in another section adjacent the end pole. As the device and object move relative to one another, eddy currents induced in the object by the changing longitudinal fluxes at the end pole are detected to locate structural faults in the object.

Abstract: Device to detect surface faults in a hot metallic bar or wire rod (11) travelling at speeds up to 130 meters per second, the device comprising upstream and/or downstream rough alignment lead-in means (38), in which device are included first coils (29) and at least one pair of second coils (13) coaxial with the first coils (29), the first coils (29) generating an alternating magnetic flow which causes on the surface of the bar (11) parasitic currents that generate in the second coils (13) a magnetic feedback flow, the first (29) and second (13) coils defining a measurement assembly (12), at least two measurement assemblies (12) being included and having their lengthwise axis able to move from an open position defining an intake hole (15), in which the various lengthwise axes coincide substantially with the nominal axis of the feed of the bar (11), to an inspection position defining a resulting inspection hole (15R), in which inspection position the lengthwise axes are substantially parallel to the nominal axis

Abstract: A magnetic interferometer for performing nondestructive magnetic induction testing and inspection of wire rope and cable. The device concentrically surrounds a wire rope or cable to be tested and includes means for inducing a magnetic field in the rope or cable as well as means for detecting flux changes in the induced magnetic field. By detecting flux changes in the magnetic field the condition of the rope or cable can be determined.

Abstract: An eddy current probe for detection of cracks in multi-layered structures. The probe includes a body of a material having high permeability and is shaped to include a central core and an additional wall. A central core drive coil is wound around the central core of the body and a plurality of sense coils are located in an array in association with the additional wall. An outer drive coil is wound about the outside of the additional wall. The central core drive coil is excited with a first alternating current high frequency signal producing eddy currents primarily in the top of the layered structure. These eddy currents are sensed with the sense coil array and analyzed for structural defects in the top surface of the layered structure. The central core coil is excited with a second alternating current signal of a lower frequency than the first signal producing eddy currents in deeper layers of the structure. Such eddy currents are sensed by the sense coils and the signals so sensed are stored.

Abstract: Disclosed are methods for processing and interpreting data acquired from an eddy current probe array inspection system, based on a background subtraction technique. Test and reference waveform data sets are acquired, and subsequently combined. However, the data sets are first normalized and registered to the same position, registering on characteristic signals produced when scanning over edges. Specific techniques are disclosed for normalizing, correcting for spatial offsets, determining the actual locations of edge signals by peak detection and correlation, and adjusting for variations in the number of points in the test and reference data sets.

Abstract: A gauge probe for a handheld combination coating thickness gauge allows the combination coating thickness gauge to measure both nonferrous coatings on ferrous substrate and nonconductive coatings on conductive nonferrous substrate. The gauge probe enables the combination coating thickness gauge to determine automatically, with a single probe, the substrate characteristics, and to effect a measurement of the coating thickness on that substrate. The technique used to measure coatings on a ferrous substrate utilizes a permanent magnet to provide a constant magnetic flux and a Hall sensor and thermistor arranged to measure the temperature-compensated magnetic flux density at one of the poles of the permanent magnet. The flux density at the magnet pole can be related to a nonferrous coating thickness on a ferrous substrate. The technique used to measure nonconductive coatings on a conductive nonferrous substrate utilizes eddy current effects.

Abstract: A non-destructive inspection apparatus includes a magnetic field applying device and a magnetic sensor. The magnetic field applying device is adapted to apply DC and AC magnetic fields to an object to be inspected. Degradation/damage of the object is detected by measuring a magnetic characteristic of the object in a state in which the DC and AC magnetic fields are applied. Also, a non-destructive inspection apparatus includes as a magnetic sensor a plurality of pickup coils and a SQUID(s) connected to the pickup coils and decides the form of a defect of an object to be inspected by producing a difference between outputs of the pickup coils or SQUIDs.

Abstract: An eddy current device for inspecting a component includes an eddy current array circuit having respective pluralities of drive and sense elements and having an active face for positioning on a surface of the component during the inspection operation. A backing is disposed on a face of the eddy current array circuit opposite to the active face for concentrating an electromagnetic flux from the eddy current array circuit into the component when each of the plurality of drive elements is being energized. A mechanical arrangement is provided for supporting and deploying the backing and the array circuit to substantially conform with the surface portion under inspection and to cause each of the pluralities of drive and sense elements to be maintained at their respective substantially constant distances from the inspection surface during scanning, preferably at a controlled rate of scan.

Abstract: The method and the apparatus relate to the detection of faults in the wall of a passing metal tube. A solenoid or solenoids generate two alternating magnetic fields of different frequenceis, the frequencies being chosen from the range of medium and high frequencies, in order to produce in the wall of a tube eddy currents which interact with the faults. The signals resulting from these interactions are detected by at least one detection solenoid and each difference in amplitude D between the signals obtained at the two frequencies for one and the same fault is compared with a specific difference which constitutes a threshold for rejection of the corresponding tube. Application of the method and of the apparatus to the inspection of ferrous or non-ferrous magnetic and non-magnetic metal tubes.

Abstract: A gauge probe for a handheld combination coating thickness gauge allows the combination coating thickness gauge to measure both nonferrous coatings on ferrous substrate and nonconductive coatings on conductive nonferrous substrate. The gauge probe enables the combination coating thickness gauge to determine automatically, with a single probe, the substrate characteristics, and to effect a measurement of the coating thickness on that substrate. The technique used to measure coatings on a ferrous substrate utilizes a permanent magnet to provide a constant magnetic flux and a Hall sensor and thermistor arranged to measure the temperature-compensated magnetic flux density at one of the poles of the permanent magnet. The flux density at the magnet pole can be related to a nonferrous coating thickness on a ferrous substrate. The technique used to measure nonconductive coatings on a conductive nonferrous substrate utilizes eddy current effects.