Abstract: The present invention provides an improved magnetometer to efficiently evaluate subsurface characteristics of conductive material without destroying the material. A white noise generator drives an induction coil to induce measurable currents in a work piece at multiple frequencies. Multiple super conducting quantum interference devices (SQUIDs) measure the magnetic filed created by the currents. The SQUIDs are housed in a liquid nitrogen Dewar. The SQUIDs are aligned along a Josephson junction and are manufactured on a single substrate. A mover moves the work piece adjacent the super conducting quantum interference devices. A computer analyzes the measured data.

Abstract: An apparatus is provided for quantitatively measuring combinations of magnetic particles combined with analytes whose amount or other characteristic quality is to be determined. The magnetic particles are complexed with the analytes to be determined and are excited in a magnetic field. The magnetizations of the magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to at least one sensor such as sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

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: An apparatus and a method of detecting wide spread fatigue damage (WFD) on aircraft using the absolute conductivity of the metal. A meandering winding magnetometer (MWM) having a plurality of parallel spaced linear conductor elements are placed in proximity to the aircraft. An electromagnetic field is imposed on the aircraft and the resulting response is sensed. The response is transformed to determine the conductivity of the aircraft structure. The mapping of the conductivity of the aircraft structure produces an indication where microcracks are located in the structure. These early indications of the density, spatial distribution and spatial orientation, as well as the size, of the microcracks give the user an indication of WFD.

Abstract: Apparatus for obtaining certain characteristics of an article (60, 62), the apparatus including an electromagnet inductor (10, 30) with a first end (20, 54) and a second end (20, 54) with an air gap (24, 58) therebetween, there being at least one arm (12, 32, 34) joining the first end (20) and the second end (20) having electrical windings (14, 52) to generate a magnetic flux in the air gap (24, 58), the arm (12, 32, 34) being a fixed return path for the magnetic flux.

Abstract: A system for characterizing coatings and substrates of a material under test. A sensor is positioned against a coated sample which is to be measured to obtain phase and magnitude measurements. Penetration depth of the magnetic waves of the sensor is a function of frequency. Measurements are made at each of a plurality of signal frequencies. The measured phase and magnitude data is applied with respect to a frequency independent parameter, such as conductivity, using a grid method. The conductivities of the coating and the substrate are determined by the limits of conductivity with respect to frequency. With the assumed conductivities of the coating and substrate, the sensor is once again placed over the material, and coating thickness and lift-off are determined. By examining the coating thickness versus frequency the accuracy of the measurement can be determined, since actual coating thickness does not vary with frequency in the material.

Abstract: A method of determining a time-dependent gradient of a shock wave in a percussion or subjected to a percussion load ferromagnetic element and including subjecting the ferromagnetic element to action of a magnetic flux, providing a voltage measuring instrument associated with the ferromagnetic element for determining a change of a magnetic flux velocity, which is determined as a change in a measuring voltage, during a percussion action, and determining the gradient of the shock wave by additive superimposition of the measuring voltage; and a device for effecting the method.

Abstract: The probe for inspecting electrically conducting parts (1) of the invention comprises a row of transmitter and receiver coils (27), (28) that form an array of energized coils. The receiver coils (28) are influenced by different magnetic fields created by several neighboring transmitter coils (27) at the same time, making them sensitive to different types of flaws. The array of energized coils is displaced along the row. The probes are usually used for inspecting steam generator tubes of nuclear power plants.

Abstract: A method for operating an eddy current sensor (10) with a measuring coil (2) and an evaluation circuit (4) for determining material or geometric parameters of a test object (5), in which the test object (5) is arranged at a distance (d) from the measuring coil (2). The impedance of the measuring coil (2) is evaluated, while the measuring coil (2) is being supplied with an alternating voltage of a predetermined frequency, and the evaluation circuit (4) determines the material and geometric parameters of the test object (5) based on the impedance of the measuring coil (2). The impedance of the measuring coil (2) is determined at an alternating voltage of a first frequency, and the impedance of the measuring coil (2) is determined at an alternating voltage of a second frequency, and the evaluation circuit (4) computes the material and geometric parameters of the test object (5) on the basis of the impedances of the measuring coil (2) at the first and the second frequencies.

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: A method of determining the number of magnetic particles within a sample using a tuned circuit having a capacitor and a coil.

Abstract: A hand tool has a handgrip attached to a ground-piercing probe, which is manually insertable in the soil. The probe has a chamber in which at least one inductor is positioned and connected to metal detection circuitry. The preferred circuitry has a pulse generator applying 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. An asymmetric magnetic field pattern about the probe is aligned with a direction pointing indicium on the handgrip and provides directional sensitivity. 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.

Abstract: In an apparatus for determining the contents of a battery or accumulator (10), the inductive coupling provided by the battery or accumulator (10) between an excitation coil (20) and a sense coil (30) is measured. To improve the selectivity of the apparatus magnets (41, 42) are provided that generate a quasi-static magnetic field during a measurement. The quasi-static magnetic field saturates the iron in an ornamental jacket of the battery or accumulator (10) so that the inductive coupling between excitation coil (20) and sense coil (30) is almost completely determined by the interior of the battery or accumulator (10). The inductive coupling at different frequencies, with and without the quasi-static magnetic field, yields a reliable identification. The excitation coil (20) can be energised by a current source (21, 22, 23) generating an alternating current with constant amplitude.

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: Eddy currents are generated in an object constructed of a conductive material by transmitting an electromagnetic signal to the object and detecting electromagnetic signals generated by eddy currents induced in the object, and an electromagnetic signal V(t) is described by a product of two factors F and G(t), wherein F is a function of the geometry and electrical and magnetic properties of the material and G(t) is a function of geometry of the material, the electrical and magnetic properties of the material, the thickness perpendicular to the surface of the material, and time.

Abstract: Apparatus for quantitatively measuring groups of magnetic particles. The particles are complexed with substances to be determined and are excited in a magnetic field. The magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: A device for detecting random objects that are being carried inside a container includes an excitation coil and a sensing coil with a gap therebetween. When the construction of the container includes a conducting loop, the container is positioned on a path between the two coils, with the plane of the loop substantially perpendicular to the path. The excitation coil is then activated to generate a magnetic field that is directed along the path. This magnetic field has both a sinusoidal component and a cosinusoidal component. Importantly, the cosinusoidal component is adjusted to match a characteristic dimension of the loop, to thereby cause zero mutual inductance with the loop in the magnetic field. On the other hand, conducting objects inside the loop will cause inductance perturbations in the magnetic field which can be detected to establish the presence of the objects in the container.

Abstract: A magnetic field excitation and detection coil arrangement is configured to produce an electrical output signal representative of a differential combination of responses from a plurality of magnetic fields, including the field emitted from the excitation coil, a response magnetic field emitted from an object-tagged transponder interrogated by the excitation coil, and other magnetic fields from extraneous sources, such as industrial machinery. This differential combination of the responses from the detection coils will contain only the desired signal (e.g., response from an object-tagged transponder), as the other far away fields cancel, and therefore produces a net output signal level for a downstream signal (transponder output) processor.

Abstract: A method and apparatus for the contactless determination of planarity and a ferromagnetic metal strip during transit of the strip through a strip-processing line or cold-rolling line. Hysteresis loops repetitively impressed in the metal strip and the tangential magnetic field strength is measured at a surface thereof and electromagnetic parameters are determined from the time course of the tangential field strength signal. The parameters are functions of the mechanical stress which is evaluated to determine residual intrinsic stress distribution and then the planarity or nonplanarity of the strip.

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: A method and a device for non-contacting measurement of the measures and position of objects of electrically conductive materials based on electromagnetic induction is provided. A measuring object, a transmitter coil and a receiver coil are placed in relation to each other such that a time-varying magnetic field generated by the transmitter coil at a measuring region of the measuring object is substantially parallel to the surface of the measuring region. The receiver coil is placed such that a conceived field line which touches the measuring region in its extension reaches the receiver coil. On the basis of the voltage induced in the receiver coil, the position and dimensions of the measuring region relative to a given reference point can be calculated.

Abstract: A support assembly for a metal detection device is disclosed. The detection device includes a housing with a central orifice, an induction member surrounding the orifice for generating an output voltage when a metal object is passed nearby, and a mechanism which includes pulse emitting and pulse receiving members for selectively sensing an object passing through the orifice. The support assembly includes a base member having front, rear and opposed side portions sized and shaped for positioning beneath the housing. The base member has a central aperture adapted for substantial alignment with the housing orifice when the base member is positioned beneath the housing. A mechanism secures the base member to the housing, and a plurality of mounting posts are disposed along the base member front, rear and side portions for positioning a metal detection device induction member about the central aperture.

Abstract: Disclosed are a method and an apparatus for easily, sensitively and reliably detecting the presence of a magnetic substance in a non-magnetic product, and even a minuted magnetized material such as a broken needle erroneously included in a sewn product. Magnetic sensors as a sensing unit are disposed at a prescribed position between a pair of opposed magnetic shielding members made of a soft magnetic material as a magnetic flux converging unit. A non-magnetic product including a magnetic substance is passed through between the pair of magnetic shielding members. A magnetic flux generated by the magnetic substance mingled in the product is converged to the magnetic shielding members, while shutting off a magnetic field due to external disturbance, and residual magnetization of the magnetic substance is detected by the magnetic sensors.

Abstract: An electromagnetic gradiometer generates a time varying primary electromagnetic field, such as by use of a transmitter coil attached to a waveform generator. The primary electromagnetic field induces a responsive, relatively weak, time varying secondary electromagnetic field about a hidden object. The combined primary and secondary electromagnetic field is measured simultaneously at two spaced apart detectors, such as at two distinct receiver coils. The detectors are configured such that they detect the primary field in equal magnitudes but in opposite sense and connected in series such that the primary electromagnetic field is automatically nulled. The difference in the secondary electromagnetic field measured at the two points is divided by the distance between the detectors to determine the electromagnetic field gradient therebetween.

Abstract: A device for non-contacting measurement of a measuring object is provided. The device includes at least one pair of associated coils, including a transmitter coil and a receiver coil. The transmitter coil generates a time varying magnetic field. In the receiver coil, a voltage is induced. The voltage is dependent on the location of the transmitter coil, the receiver coil and a measuring region of a measuring object. The device comprises a U-shaped structure with two branches. A retaining part is arranged between these branches. The transmitter and receiver coils are fixed to the branches of the U-shaped structure and the measuring object is intended to be arranged centrally in the opening of the U-shaped structure.

Abstract: Method to measure the variations in section of a hot rolled bar (12) as it is fed, the method including the generation of a variable frequency magnetic field by at least a generator device (14) defining an inner space (214) for the transit of the bar (12), the variations in section of the bar (12) in transit being measured by a receiver device (15) suitable to monitor the perturbations induced on the magnetic field by the variations in the area of section of the bar (12) in transit. The receiver device (15) is arranged coaxial and inside the generator device (14) and defines inside the same a surface for the transit of the bar. The (12) has a transverse section of (A.sub.S "), and the value ("f.sub.0 ") of the frequency of the magnetic field generated by the generator device (14) is suitable to minimize the influence of the real temperature of the bar (12) on the measurement.

Abstract: An electronic autoclave cycle passively records the number of thermal cycles to which an instrument has been subjected in a steam autoclave. When a sterilization cycle has been completed, and the instrument is next energized in use, a microprocessor is employed to read the sensor and record the occurrence of a sterilization cycle. Information as to the cumulative number of cycles through which the instrument has been subjected is stored in a non-volatile memory. This data is suitably displayed on a display panel. The sensor employed uses either the Curie temperature or a temperature near but below the Curie temperature of a ferromagnetic material by first magnetizing the material and then, later, checking its flux density to determine whether a thermal cycle has occurred. In a first embodiment, a Hall effect sensor is used to directly measure the magnetic field strength of the magnetizable material.

Abstract: A magnetic sensor for a magnetic anomaly detector includes a bobbin made from a layered printed circuit board material. A plurality of non-ferrous leads are attached to the bobbin for providing external connection to the sensor. A metal strip is attached to the bobbin. The strip is made from a material having a high permeability. First and second coils are wound around the bobbin and over the metal strip. The bobbin interconnects the first and second coils.

Abstract: A method and apparatus for identifying a coin in free fall employs a coin sensor that has a pair of drive coils for generating a horizontally elongated magnetic field across a free-fall path of the coin. The drive coils are driven by a square wave, and ringing waveforms induced in a pair of sensor coils disposed on the two sides of the free-fall path are measured when the coin passes through the magnetic field. A digitized signature is derived from the measured ringing waveforms and compared to a set of pre-stored reference signatures to find a match. A diverter mechanism directs the coin to an accept path when a match is found and to a reject path when a match is not found.

Abstract: A high frequency magnetic properties measuring system is used for measurement of high frequency magnetic properties, for example high frequency core-loss and magnetic hysteresis curve (coercivity force, magnetic flux density, permeability) in soft magnetic materials such as ferrites, permalloy and amorphous magnetic cores used in inductors, transformers and filters of various electric and electromagnetic systems and devices such as computers and multimedia devices. A digital oscilloscope is operated as a waveform detection unit for measuring magnetic fields and magnetic flux density. A signal generator and a power amplifier are operated as a signal input unit. The digital oscilloscope and the signal generator are remotely controlled through a General Purpose Interface Bus by the computer. The high frequency magnetic properties are measured by remote control and the resulting data can be outputted and stored by the computer.

Abstract: A unique time-domain electromagnetic system and data processing technique which, using low frequency electromagnetic fields, can localize, in three-dimensions, the position of buried metallic objects is disclosed. The measurement system uses time-domain electromagnetic techniques on a scanning frame similar to a X-Y plotter. The system collects magnetic data over a large area above the buried object. The spatial information of the field detected on the ground is then processed with an unique `nearfield holographic` data processing method to reconstruct the field image of the buried object.

Abstract: Apparatus and method for measuring the Barkhausen signal of a moving magnetic film, ribbon or fiber wherein first and second stationary electromagnet coils are arranged and separated by a distance, d, along the path of movement of the film, ribbon or fiber. The first and second coils are energized in a manner to generate first and second opposing DC magnetic fields through which the moving film, ribbon or fiber passes along its path of movement. As the film, ribbon or fiber moves through the first and second opposing magnetic fields at a velocity, v, it experiences one complete cycle of magnetization in a period of time equal to d/v. A stationary third signal pick-up coil is disposed between the first and second coils to detect the Barkhausen signal from the moving film, ribbon or fiber. The pick-up coil typically is disposed midway between the first and second coils where the Barkhausen signal will be approximately maximum.

Abstract: Method and apparatus for determining concentration of a trace of contaminant magnetic substances contained in a non-magnetic substance. A magnetic field (3) is applied to the non-magnetic substance (1) from outside a duct (2) through which the non-magnetic substance is advanced so that magnetic substances contained in the non-magnetic substance are magnetized. At a downstream in the duct, an intensity of magnetic field produced substantially only by the magnetized magnetic substance is detected by a magnetic sensor (8) having a superconducting quantum interference device (SQUID).

Abstract: Radio-interrogated surface-wave technology sensor, in which the sensitive element (12) is an impedance which is electrically connected as termination to a surface-wave structure (26) of the sensor.

Abstract: Apparatus for quantitatively measuring groups of magnetic particle. The particles are complexed with substances to be determined and are excited in a magnetic field. The magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: A magnetic anomaly detector for detecting the presence of ferrous metal objects such as firearms, knives, or other weapons. The detector contains a square wave generator, a sensor for sensing ferrous metal objects, a sensor amplifier, a main amplifier, and a display. When a ferrous metal object is detected by the sensor, the resultant anomaly in the magnetic field causes portions of a pulse train being input to the sensor amplifier extend past a preset threshold, causing an average input value of an integrator to change. The integrator then forces the average input value of the waveform to zero over an extended period of time to compensate for the changes in the magnetic field. The value at the integrator input represents the magnetic anomaly. The anomaly is also visually displayed in an LED bar graph display for easy detection of weapons by the operator.

Abstract: Banknotes printed with magnetic ink pass through a tri-color age detector 34, and then between a pair of premagnetization rollers (10,12) having opposite magnetic polarity of such strength that the magnetic signature of all banknotes is enhanced to the same level; the notes are then stacked 50 in an electromagnetic stacker 42. Such notes, having magnetic signatures of the same level, can also be recognized and/or validated by magnetic techniques also.

Abstract: A device for validating the authenticity of a document uses changes in capacitance due to the presence of an electrically conductive security thread extending across the document. The device uses a drive arrangement for moving of a document such as a bank note, past a sensing arrangement which senses changes in capacitance due to movement of a security thread therepast. A frequency generator produces a high frequency time varying oscillator signal and provides this signal to an elongate oscillator electrode extending across the path of movement. A lead elongate measuring electrode is electrically conductive and positioned in front of the oscillator electrode and extends across said path and a trailing elongate measuring electrode is positioned behind the oscillator electrode and extends across the path. The signals from the measuring and the oscillator electrode are provided to a signal processing arrangement.

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: 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 spectrogram of secondary magnetic field strength as a function of frequency and spatial relationship is used to identify hidden objects. A time-varying multi-frequency primary electromagnetic field is generated, preferably over the range 100 Hz to 300 kHz, which induces a time-varying multi-frequency secondary electromagnetic field about the hidden object. The strength of the secondary field, typically inphase and quadrature, is plotted as a spectrogram over a low frequency broadband spectrum as a function of frequency and spatial relationship between the hidden object and the secondary field strength detector. From this spectrogram, indications may be had of the hidden object's characteristics such as location, size and shape, and material composition. Preferably, the measured spectrogram is compared against a library of reference spectrograms by a computer to identify the hidden object.

Abstract: An openable ring assembly is externally centered around and moved parallel to the centerline of a stationary pipe. As a low-frequency EM source signal is applied to the ring assembly, the time and/or frequency shifts of a detected EM signal from the source signal can be correlated to pipe wall thickness without removal of external pipe insulation and metal cladding, if present. The ring assembly may be opened or expandably segmented to allow pipe thickness detection around obstructions or larger diameter pipe. Centering is preferably accomplished by using rollers circumferentially attached to the ring assembly.

Abstract: An eddy current sensor comprises a generally E-shaped core having three parallel legs joined together by a bridge. Current carrying coils are mounted on each of the outer legs and a signal coil is mounted on the central leg. Identical a.c. currents are caused to flow through the two outer coils for generating two magnetic fields which combine to form a sensing magnetic field extending outwardly from the ends of the legs for sensing purposes but which cancel one another within the central leg. The sensor is disposed within an E-shaped, hollow shield of an eddy current producing, electrically conductive material. The sensor fits within the shield as fingers in a glove with the parallel legs of the sensor magnetically separated from one another by walls of the shield. Only the ends of the sensor legs are exposed through apertures through the shield for emergence of the various magnetic fields. The shield cancels unwanted fringing fields and better guides the magnetic fields in desired directions.

Abstract: Poly-phase induction motor-stator rotating magnetic fields are utilized as driving cores coupled to polar coordinate sensors for higher driving flux utilization and size reduction. External internal and combinational driving core structures are disclosed. An unsegmented stator having an extended longitudinal coupling portion is also disclosed.

Abstract: The subject of the invention is a weak-field magnetic sensor with the following features: etched circuit coils are substituted for conventional coil technology. The sensor includes an amorphous core having epoxy bases stacked relative to one another on the top and bottom surfaces thereof. One epoxy base has a coil Y etched thereon. A second epoxy base has a coil X etched thereon. The remaining epoxy base has circular patterns etched thereon. The amorphous core is formed from at least two amorphous thin boards stacked on opposite sides of an epoxy base thin board. The epoxy base thin board has a particular pattern etched thereon and the capacity for vertical conductivity. The coil conductor size and position accuracy is controlled in increments of microns by the etching process. The range of detection errors and the level of reception has no non-uniformities. A thin and small sensor in terms of the structure is therefore enabled.

Abstract: Disclosed are a method and apparatus for detection of a magnetic substance erroneously included in a non-magnetic product. The non-magnetic product such as a sewn product is passed through a high magnetic field in which a magnetic field is applied to the product. The residual magnetization of a magnetic substance such as a broken needle mingled in the product is detected by a sensing unit and a signal of detection is transmitted to a measuring unit to measure the magnitude of detected residual magnetization. The presence or absence of the magnetic substance in the product is determined by a control unit based on the output from the measuring unit. Alternatively, a magnetic field may be preparatorily applied to a magnetic substance having the possibility of being mingled in the non-magnetic product thereby causing the magnetic substance to assume a state of possessing residual magnetization.

Abstract: A process is presented for the direct determination of characteristic magnetic values of thin magnetizable layers, in which an element creating a magnetic field creates the magnetization of a part surface in such a way that the thin magnetizable layer, the element creating the magnetic field, and a magnetic field sensor are located in a relative position of rest to one another. The magnetic field sensor is then positioned opposite the magnetized part surface by a relative movement of the element creating the magnetic field, the magnetic field sensor, and the thin magnetic layer. During the subsequent measurement of the magnetization of the part surface, the thin magnetic layer, the element creating the magnetic field, and the magnetic field sensor are in a relative position of rest to one another.

Abstract: A device for determining the effect of pulsed primary magnetic fields on an organism has a measuring pick-up for secondary magnetic field signals generated by the organism in response to the primary magnetic fields. An evaluation circuit for the secondary magnetic field signals is provided. The evaluation circuit has a first memory device with a memory unit. The evaluation circuit has a control device. The control device includes a device for processing sequential secondary magnetic field signals such that the sequential secondary magnetic field signals are combined to a cumulative signal in the memory unit. The cumulative signal is used as an output signal of the evaluation circuit.

Abstract: An acoustic monitor assembly for monitoring the particulate content of a liquid, comprising, a body having an electrically conductive portion, the body contacting a liquid whose content is to be monitored in use, a magnetic field generator for generating a magnetic field to which the electrically conductive portion of the body is exposed, the magnetic field generator being positioned such that magnetic particulates in the liquid are drawn on to said body, and a signal generator for inducing eddy currents which oscillate at an acoustic frequency in the electrically conductive portion of the body and in response to which the body is caused to vibrate, and a monitoring for observing the vibration condition of the body so as to provide an indication of the content of said particulates which are drawn onto the body in the liquid.

Abstract: Devices and analytical techniques are disclosed for measuring spatial profiles of complex permeability and conductivity of a material by multiple wavenumber interrogations. Coil array structures are disclosed which define a number of different fundamental wavelengths (or wavenumbers). Spatially periodic interrogation signals (of temporal frequency ".omega.") from the coil array structures are attenuated by varying degrees in the material undergoing analysis, depending on the wavenumber ("k"), thereby permitting the derivation of composite complex permeability/conductivity profile.