Abstract: A non-destructive testing equipment comprises a magnetic field generator for generating a uniform magnetic field, and a magnetic sensor accommodated in a thermal insulation container and filled with a liquid nitrogen. The thermal insulation container is located within a magnetic shield container having an opening. The magnetic sensor includes a SQUID that is a magnetic sensor having very high sensitivity. The magnetic sensor can detect, through the opening, an appreciable variation of the magnetic field that is caused by small impurities or minor defects contained in the object to be tested.

Abstract: A method and apparatus for the inspection of ferromagnetic and non-ferromagnetic pipes, tubes or other cylindrical shell structures utilizing the magnetostrictive effect to detect defects such as corrosion pits, wall thinning, and cracks within the structure under evaluation. The apparatus and method constitute an active testing application, wherein 1) a transmitting coil element generates a mechanical pulse within a cylindrical shell structure through the magnetostrictive effect and a second coil detects reflected mechanical waves within the pipe, this by the inverse magnetostrictive effect, or 2) a single sensor functions as both transmitter and detector. The present invention also anticipates a passive monitoring application with a detection coil that continuously monitors ferromagnetic or non-ferromagnetic tubes, pipes, etc.

Abstract: A process and apparatus for the non-destructive checking of the condition of a metal reinforcement element of magnetic material in a tire (11) whereinthe metallic reinforcement element is subjected to a magnetic field in order to magnetize it;relative movement is produced between the metallic reinforcement element of the tire (11) and at least one conductor (31) of a detecting device (30) placed opposite the metallic reinforcement element in such a manner than any variation in magnetization of the element produces an electromotive force in the conductor (31);the electromotive force is detected in order to obtain information as to the condition of said magnetized metallic reinforcement element.

Abstract: An electromotive induction current which is detected by an induction coil placed in an electromagnetic field generated by applying an alternating current to an exciting coil distinctively changes with the frequency of the applied alternating current in accordance with the conditions of an object placed in the electromagnetic field. By analyzing the change in amplitude and/or frequency phase of the electromotive induction current, the physical properties, size and relative position of the object and internal defects such as a crack and pin hole in the object can be measured precisely.

Abstract: A nondestructive inspecting apparatus is arranged to have an exciting magnet for applying an ac magnetic field to a sample and a SQUID for converting change of a magnetic characteristic of the sample occurring when the ac magnetic field is applied to the sample into an electric signal. The exciting magnet is a cancelled coil assembly composed of plural coils having respective polarities.

Abstract: A magnetic detector includes a magnetizer generating a magnetic field; a first magnetic sensor for detecting a leakage flux resulting from a magnetically defective portion of an object moving in and relative to the magnetic field; a low-pass filter for extracting a low-frequency signal component contained in the signal output by the magnetic sensor, the low-frequency signal component being indicative of a floating flux which crosses the magnetic sensor and is a result of the object moving through the magnetic field; an amplifier for amplifying the extracted low-frequency signal component; a compensating coil excited by the amplified low-frequency signal component output by the amplifier, for generating a magnetic flux which cancels out the floating flux crossing the magnetic sensor; a high-pass filter for extracting a signal resulting from the magnetically defective portion and contained in the signal that is output by the first magnetic sensor; an output amplifier for amplifying a signal output by the high-p

Abstract: A test head through which passes a test object has at least one test probe guided in a circular orbital path around the test object. The shape of the circular orbital path of the probe, when considered in the travel direction of the object, diverges in a predetermined manner from a circular shape. A rotor guides the probe on a circular path, and the rotational axis of the rotor can be tilted with respect to the travel direction of the test object. The rotor is driven by a driving unit positioned laterally to the travel direction on a base plate by a belt drive which runs in a transmission element carrying the test head and linking it with a drive unit.

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: 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 inducing eddy currents into the object, families of cracks, such as caused by environmental conditions, can be detected. In addition, magnetic flux leakage methods can be used in combination with the transient electromagnetic method to further assisting detecting crack families in pipeline inspection applications.

Abstract: The detection of an internal damage in an FRP member constituted by reinforcing fibers, a matrix resin and magnetic members having a magneto-mechanical property is conducted by disposing the magnetic members in the FRP member, and measuring a change in the magnetic properties of the magnetic members by a non-destructive inspection method.

Abstract: A system for searching and sensing reinforcing steel in reinforced concrete is provided. The system comprises a means for magnetizing the reinforcing steel in the reinforced concrete with lines of magnetic force generated by a magnetic field and a means for sensing the lines of magnetic force radiated from the magnetized reinforcing steel to detect an existence and a condition of the reinforcing steel in the reinforced concrete. The sensing means includes a coil for sensing a magnetic force and the magnetizing means is positioned remote from the sensing means.

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: The present invention provides an eddy current sensing device capable of in-situ operation within a high temperature and high vibration environment of a combustion turbine engine. The eddy current sensing device is preferably utilized in an eddy current sensing system for monitoring crack formation and displacement of rotating members of the combustion turbine engine. The method according to the present invention provides inducing eddy currents in the rotating member, detecting the eddy currents, providing a signal indicative of the detected eddy currents, filtering the signal based on the condition to be monitored and evaluating the filtered signal to determine whether the condition, such as the formation of a crack in the surface of the rotating member exists, and if so, determining whether the condition is critical or routine.

Abstract: An inspection device has an exciting coil for generating an electromagnetic field and an induction coil which are integrally connected to each other a coaxial relation so as to induce mutual inductance in the induction coil by the electromagnetic field. The mutual inductance caused in the induction coil varies with a given object to be inspected which is present in the electromagnetic field. The object can be inspected by analyzing the change in inductance.

Abstract: A microcomputer or PC based non-destructive coated-object testing system and method combines thermoelectrically measured surface coating thickness data with flaw/crack depth data determined from eddy current measurements of the surface of the object to locate and selectively identify faults or cracks which penetrate the surface coating. The microcomputer controls scanning of eddy-current and thermoelectric probes over the object surface and stores measured data along with surface coordinate information to provide a color-keyed graphics display of surface conditions for visual analysis.

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 method for nondestructive examination of an object of type having localized permeability variations therein and varying surface conditions and grain structures comprises the steps of AC flux saturating a localized surface area of the object so as to magnetically saturate the surface area to quiet localized permeability variations therein and to set up a stabilized high level primary field on the surface substantially unalterable by the varying surface conditions and grain structures in the object and detecting eddy currents in the surface area. Coil structure and apparatus for implementing the method are also defined. Further, the method is disclosed as being implemented in part by the use of components of a pre-existing object evaluation device.

Abstract: A fluxmeter includes an application unit for applying a magnetic field, a superconducting quantum interference element and a flux transmitting circuit. The flux transmitting circuit includes a pickup coil formed of a superconducting print coil and a core for the pickup coil. The core is formed of a soft magnetic material. The core serves to suppress the leakage of magnetic flux to magnetically couple the pickup coil and the superconducting quantum interference element efficiently to improve the sensitivity and resolution of the fluxmeter. The pickup coil may be manufactured by photolithography, sputtering, laser beam deposition, MBE deposition, MOCVD or spray pyrolysis.

Abstract: A multiparameter magnetic imaging system and method to be used in the localized measurement of the magnetic properties of a material and the display of those properties in the form of a false color image indicating the occurrence of those properties across the surface of a sample specimen. The system includes an inspection probe to measure certain magnetic parameters across the surface of the specimen and means to determine a multiplicity of magnetic property values based on the measured data. The system also includes a visual display system which selectively displays the data relating to the determined magnetic properties in the form of a false color image indicating the presence and variation of these magnetic properties across the specimen surface.

Abstract: A method and apparatus for nondestructively detecting a flaw such as a hairline crack or defect within a conductive object to be inspected. Surface flaws can be distinguished from deep flaws. The pulse duration of the pulse voltage induced in the secondary coil of a sensor is measured at two separate time instances. At one time instance, the pulse duration is affected by variations in the distance between the sensor and the object but is not affected by the flaw. At the other time instance the pulse duration is affected by said variations and also by the flaw. The effect of said variations is cancelled, using these two measured pulse durations. Only a signal correctly indicating the flaw is extracted to detect the presence of the flaw.

Abstract: An improved eddy current probe array having means to compensate the entire array for varying different element liftoff, is described. An array consisting of a plurality of sense elements and means for compensating these sense elements is scanned across an inspection surface to produce respective scan responsive signals wherein the scan responsive signals of the sense elements are proportionately normalized or calibrated against the scan response of said compensating means during routine signal processing of the array signals in order to compensate for any lift off experienced by the sense elements. Array lift off compensation is attributable to sense element design cooperating with at least one lift off compensating sense element and a method of normalization/calibration performed during signal processing of the array signals.

Abstract: A method for inspecting a component of a gas turbine engine or the like having a plurality of similarly shaped structural portions, such as the gear teeth of a gear, the dovetail slots of a turbine disk or the like, includes the steps of: scanning a surface of at least one of the similarly shaped structural portions with an eddy current probe to induce eddy currents in the component; generating a two-dimensional image of the at least one portion from eddy current signals received during scanning, the image including a multiplicity of pixels arranged in a two-dimensional array and each pixel having a gray scale intensity responsive to the eddy current induced in the component at a component location corresponding to a position of the pixel in the matrix array; preprocessing the image to substantially reduce any signals or changes in the gray scale intensity of any pixels relative to the background pixel intensities of the image caused by geometrical characteristics and background noise common to all similarly

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: A magnetic inspection device for non-destructively testing elongated objects such as large diameter wire cables is constructed with a number of flux carrying components that are assembled and disassembled in sections with a magnetic flux detector for detecting the loss of metallic cross-section and local discontinuities in the cable. The inspection device is moved bodily along a cable during the inspection process and in another embodiment the flux detector itself is the only component movable along the cable. Jack screws are utilized to mechanically separate or bring together the flux carrying components which are normally attracted to one another by powerful magnetic forces. Draw screws are also employed to pull together flux carrying components which are naturally repulsed from one another by the magnetic forces. Alignment pins are utilized to guide the components together in predetermined positional relationships during assembly processes.

Abstract: A system and a related method for non-destructive evaluation of the surface characteristics of a magnetic material. The sample is excited by an alternating magnetic field. The field frequency, amplitude and offset are controlled according to a predetermined protocol. The Barkhausen response of the sample is detected for the various fields and offsets and is analyzed. The system produces information relating to the frequency content, the amplitude content, the average or RMS energy content, as well as count rate information, for each of the Barkhausen responses at each of the excitation levels applied during the protocol. That information provides a contiguous body of data, heretofore unavailable, which can be analyzed to deduce information about the surface characteristics of the material at various depths below the surface.

Abstract: A pipe electromagnetic field simulation apparatus used to simulate a current produced by flaw in a pipe when the flaw is subjected to the electromagnetic field of a transmitting coil. The apparatus includes a system for determining an electromagnetic field distribution of a represented pipe without a flaw, a system for determining an equivalent current source of a represented flaw in the represented pipe, and a system for determining the electromagnetic field distribution of a represented pipe with a flaw. The apparatus may also include a system for determining a signal received by a detector which indicates a flaw.

Abstract: In a non-destructive method for the detection of surface cracks in metals, an eddy current is induced in the surface region of a workpiece under test, at a frequency sufficiently high to generate an alternating magnetic field solely in the skin region of the workpiece. That alternating surface magnetic field is interrogated by means of a relatively small electro-magnetic induction sensor, having regard to the overall area of the induced magnetic field. The sensor provides a voltage output which is analysed, preferably in real time, to yield an indication sensor. Also described is a probe for performing such a method.

Abstract: A method and apparatus for measuring the temperature and heating rate of a workpiece during the induction heating cycle by inducing and detecting a plurality of eddy current pulses at varying frequencies during a short power interruption to the induction coil and correlating the pulses to generate a workpiece profile which is compared to a reference profile to determine whether to reject the inductively heated workpiece.

Abstract: A method for improving eddy current flaw detection by simultaneously exciting a select plurality of eddy current probe elements with a multiplicity of select frequencies in a simultaneous parallel or serial manner to form a corresponding multiplicity of direct and/or differential images which can be processed together for improved eddy current image resolution. Select eddy current probe elements when driven at select multiple frequencies further provide a capability for simultaneous flaw detection and characterization by dual resolution scanning. Dual flaw resolution is accomplished by first locating a flaw using low resolution frequencies; and thereupon, switching to higher resolution frequencies to characterize the flaw.

Abstract: There is provided a transient electromagnetic method and apparatus for inspecting objects using moving sensors. 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. The sensing portion is moved along the object at the same time the transmitting antenna is inducing current in the wall and the receiving antenna is producing a received signal of the induced current diffusion in the wall. Because the antennas are moving during data acquisition, the speed of inspection is increased. The data is then interpreted to determine the thickness of the object.

Abstract: A method for rapidly detecting and locating reinforcing steel corrosion in concrete structures using non-linear harmonic and intermodulated frequencies of electromagnetic signals. The method comprises transmitting either a single primary frequency or two primary frequencies into the concrete structure in the general direction of the reinforcing steel. The reflected/generated signal, which is composed of the primary frequencies and of various harmonics and intermodulation components, is received, filtered, and amplified. A third order harmonic frequency is isolated with a band pass filter, is amplified, and is compared with the amplitudes of the primary frequencies. Intermodulation frequencies, primarily the combination of the primary of a frequency and the second harmonic of a second frequency, or the primary of a second frequency and the second harmonic of a first frequency, are isolated by appropriate band pass filter, are amplified, and are compared with the primary frequency or frequencies.

Abstract: An eddy current flaw detecting endoscope apparatus has an endoscope having an elongate insertable part and an objective optical system provided on the tip side of the insertable part. A flaw detecting device is provided on the tip side of the endoscope. A signal processing device processes a signal for the flaw detecting device. An eddy current flaw detecting apparatus detects a flaw in an object to be inspected and generates a flaw detecting signal. A controlling device generates a control signal controlling a controlled device with a flaw detecting signal of the eddy current flaw detecting apparatus.

Abstract: On the basis of a finding that a magnetic hysteresis of a metal material, among magnetization characteristics changing with secular degradation of the metal material, shows a clear correspondence with the degree of degradation of the metal material, a change in such a magnetization characteristic is measured to estimate the degree of secular degradation of the metal material. In a typical embodiment, a superconducting quantum interference device is used to detect the magnetization characteristic of a measuring object. According to the present invention, the degree of embrittlement of a metal material used in an environment of high temperatures can be quickly detected in a non-destructive fashion so that the danger of brittle fracture of the metal material can be reliably prevented.

Abstract: An AC magnetic flux leakage type flaw detecting apparatus for use in flat surface flaw detecting comprises AC exciting means having a pair of magnetic poles for exciting a steel material to be flaw detected, a leakage magnetic flux detecting element, and rotatably scanning means for rotatably scanning the magnetic flux leakage detecting element in a surface substantially parallel to the flat surface oppositely to the flat surface to be flaw detected of the steel material in a plane of an exciting magnetic field between the pair of magnetic poles.

Abstract: A method for operating a computer to control the manufacture process of zirconium tubes in a pilger mill operation, the computer including an electronic memory and being coupled to the pilger mill to receive, as input, data related to the operation of the mill. The method comprising, in one embodiment, the steps of storing in the computer memory respective test signals, each test signal corresponding to a signal obtained by inspecting a tube manufactured by the mill with a respective, known defective operation condition, inspecting a zirconium tube finished by the manufacture process and generating a signal representative of the physical dimensions and material configuration of the tube, comparing the generated representative signal of the zirconium tube with the stored test signals, alerting an operator if the generated representative signal of the zirconium tube correlates to a stored test signal, and identifying the defective operation condition which corresponds to the correlated stored test signal.

Abstract: On the basis of a finding that a magnetic hysteresis of a metal material, among magnetization characteristics changing with secular degradation of the metal material, shows a clear correspondence with the degree of degradation of the metal material, a change in such a magnetization characteristic is measured to estimate the degree of secular degradation of the metal material, In a typical embodiment, a superconducting quantum interference device is used to detect the magnetization characteristic of a measuring object. According to the present invention, the degree of embrittlement of a metal material used in an environment of high temperatures can be quickly detected in a non-destructive fashion so that the danger of brittle fracture of the metal material can be reliably prevented.

Abstract: A read/write head particularly suitable for mapping the superconductive properties of a sample of superconducting material. The head is arranged so that the reading and writing gaps are coaxial. Although the gaps are coaxial, the reading gap and the writing gap may be optimized in length and width to provide efficient reading and writing performance. The coaxial disposition of the heads eliminates parallax error to permit detailed mapping of the properties of the surface of a sample of superconductive material.

Abstract: A method of nondestructively inspecting a magnetic substance such as metal pipe and bar stocks, wherein the method provides a detection coil having a diameter which is specified based on the length of existent peripheral surface flaws such that the directional sensitivity of the detection coil relative to those flaws is improved. The magnetic substance is moved along an axis thereof and has an eddy current induced therein. Relative rotation of the detection coil around the magnetic substance is effected to permit detection of surface flaws.

Abstract: A method and apparatus is provided for electromagnetically testing an elongate object such as a wire rope for cross-sectional area variations. The elongate object is magnetized over adjacent sections in opposing directions along a longitudinal axis of the elongate object. Variations in axial magnetic flux, which have been observed to be coincident with variations in the cross-sectional area of an elongate object, are measured by a plurality of non-inductive transducers. The transducers are interconnected to produce a composite signal. The composite signal is compared to a reference signal.

Abstract: High-T.sub.c superconductor quantum interference devices (SQUIDs) for noise-free, accurate measurements of defects and flaws in metal shapes and forms by measuring changes in the secondary magnetic field intensity around any point which is excited by a primary excitation current or by measuring changes in the impedance of the exciting coils. These measured changes are correlated to defects and flaws present in the metal.

Abstract: A transient electromagnetic method for detecting irregularities on container walls by measuring wall thickness. The method utilizes a transmitting antenna and a separate receiving antenna arranged in a loop-loop configuration. The transmitting antenna induces current into the container wall and the receiving antenna and the receiver detect the decay of the induced current, which is then analyzed to detect wall thickness. A receiving antenna array of many receiving antennas is used to increase the spatial resolution. Simultaneous measurement of the induced current by the receiving antennas reduces noise that is coherent across the array. Use of a noise antenna located so as to be unaffected by the transmitting antenna further reduces noise. The received signal from the receiving antenna array is displayed on a two-dimensional display in a spatial arrangement that corresponds to the spatial arrangement of the receiving antennas.

Abstract: The invention relates to a method for the determination of the condition of the insulation of an object (1) made of an electrically conducting material, coated with an electrical insulation (2) and positioned in an electrically conducting medium. According to the invention, the determination of the condition of the insulation is carried out without any electric contact with the object to be monitored in such a way that a first electromagnetic field (6) is created in the conducting medium (3), which field induces eddy currents (7, 8) both in the medium (3) and in the conducting object (1) positioned therein, a second electromagnetic field created by the eddy currents (7, 8) passing both in the conducting medium (3) and in the conducting object (1) is measured in the form of electrical information, essentially excluding the effect of the first electromagnetic field, and said electrical information is analyzed for detecting any changes in the condition of the insulation.

Abstract: A pulsed eddy current testing system for detecting defects in a part. A probe carries an exciting pulse in one coil and receives a measuring signal in a second coil. The measuring signal is sampled at two instants defined by short and long time lags. The two amplitudes obtained are plotted in a representative plane having two reference axes. The point having the signals as coordinates describes a figure eight, when the part has a defect. The size and orientation of the figure gives information on the defect in the part.

Abstract: Relatively minute changes in magnetic field intensity are sensed by a circuit including a wire coil connected to a Hall effect element to provide the bias current to the element. The Hall effect element is disposed in the magnetic field with the coil and the output signal of the element is proportional to the square of the intensity of the magnetic field. The circuit is included in a device for measuring magnetic anomalies such as stress or corrosion cracks in structures of magnetic material including fluid transmission pipelines.

Abstract: A method and apparatus for generating and detecting magnetization responses from ferromagnetic, ferrimagnetic, paramagnetic, or diamagnetic materials comprises a means for generating an alternating magnetic field. The cycle of the alternating magnetic field includes a first magnetization pulse and a second demagnetization pulse, the energy content of the magnetization pulse and the demagnetization pulse being approximately equal, the time duration of the magnetization pulse being substantially longer than the time period of the magnetization pulse, the demagnetization pulse having a higher magnetic field strength than the magnetization pulse magnetic field strength. The effect of the alternating magnetic field on the material to be tested is measured by magnetic field detectors. The field detectors generate electrical signals which are fed to an oscilloscope, a comparator, or a computer for analysis.

Abstract: A transient electromagnetic method for detecting irregularities on container walls by measuring wall thickness. The method utilizes a transmitting antenna and separate receiving antennas so as to form a loop-loop configuration. The transmitting antenna induces current into the container wall and the receiving antennas detect the induced current and produce received signals. The distance between the antennas and the container wall can vary, particularly where insulation is interposed therebetween. The variations in antenna distance affects the received signals. The affects are corrected by determining the maximum of the respective received signal and determining the arrival time of the maximum. The maximum and the arrival time are used to determine the thickness of the wall.

Abstract: A method and apparatus is provided for electromagnetically testing an elongate object such as a wire rope for cross-sectional area variations. The elongate object is magnetized over adjacent sections in opposing directions along a longitudinal axis of the elongate object. Variations in axial magnetic flux, which have been observed to be coincident with variations in the cross-sectional area of an elongate object, are measured by using saddle coils which are positioned adjacent the magnetized sections of the elongate object and which detect variations in radial flux. The saddle coils are positioned to have first half circumferential windings located where the magnetic flux density in the elongate object is at a maximum value and second half circumferential windings located where the magnetic flux density in the object is zero.

Abstract: A transient electromagnetic apparatus for use in detecting irregularities on conductive walls of containers forms a multichannel distributed system and includes at least one transmitting antenna, at least one transmitter unit, plural receiving antennas, plural receiver units, and a computer for controlling the transmitter and receiver units. The receiver units each include elements that suppress noise in the received signals. Each receiver unit has a preamplifier, first and second low pass Bessel type filters, a gain ranging amplifier, and an A/D converter. The gain ranging amplifier receives feedback from the output of the A/D converter and provides increased small signal resolution. Each receiver unit also rejects common mode noise with a choke and balanced input impedances in the preamplifier. The apparatus allows an arbitrary number of receiving antennas, receiver units, and even transmitting antennas, and transmitting units, so that the apparatus can be configured to a variety of containers.

Abstract: Various devices are constructed with gap-modified magnetic bridge circuits. In a magnetic bridge device for evaluation of samples, a magnetic bridge circuit has at least four arms, a driving leg and a sensing leg, one of the arms being utilized for evaluating a sample, pole pieces of a sample-evaluating arm having end faces defining between them a sample-evaluating gap. An electrically conductive gap insert produces an enhanced fringing flux exteriorly of it. The sample is placed in juxtaposition to the sample-evaluating gap for affecting the fringing flux. A driving circuit for the driving leg provides a time-varying flux path within the four arms of the bridge. A sensing device associated with the sensing leg senses changes in the sensing leg caused by changes in the fringing flux resulting from characteristics or movement of the sample. A specific single-side modification provides an accelerometer.

Abstract: A device for inspection by eddy current methods of materials exhibiting cumferential conductivity. This device finds application for the inspection of filament-wound carbon fiber reinforced composites which do not usually have sufficient conductivity in the axial direction to allow inspection by conventional surface probes while still providing the desired resolution. This device is also useful in inspecting thick-walled circumferentially conductive materials, including metal, where their thickness would require a surface probe of such diameter as to be impractical.