Abstract: A diagnostic debris sensor operating on the inductive pulse is triggered by ferrous particles floating by or attracted to a permanent magnet within a pulse-sensing coil and the entire sensor at that, the pulse-sensing coil is equipped with a second winding for either continuous monitoring or an occasional push-to-test checking of the pulse-sensing coil.

Abstract: The buildup of slag or ash on the interior surface of a furnace wall is monitored by disposing two coils to form a transformer which is secured adjacent to the inside surface of the furnace wall. The inductive coupling between the two coils of the transformer is affected by the presence of oxides of iron in the slag or ash which is adjacent to the transformer, and the application of a voltage to one winding produces a voltage at the other winding that is related to the thickness of the slag or ash buildup on the inside surface of the furnace wall. The output of the other winding is an electrical signal which can be used to control an alarm or the like or provide an indication of the thickness of the slag or ash buildup at a remote location.

Abstract: A novel method and system for measuring AC magnetic characteristics is disclosed, in which the loss of a magnetic core is measured by defining the change rate of magnetic flux density, and for this purpose, the duration of a voltage induced in the coil of an object magnetic core during the gate period is detected and controlled by an input voltage, a reset current and a load resistor.

Abstract: A coil assembly for a metal detector of the type used for detecting metal fragments in foodstuffs and pharmaceuticals, the assembly comprising a frame of non-metallic material, the frame have an aperture therethrough for the passage of material undergoing inspection, a coating of carbon material applied to the exterior of the frame, a layer of plastic material applied over the carbon material, electrically conductive strands wound over the plastic material, the frame being fixed to a rigid metal housing providing an enclosed void around the exterior of the coated frame and strands, and foam plastic enveloping the frame and strands, the void being filled with the foam plastic.

Abstract: A transucer is encapsulated within a stainless steel housing in a recess opening within one of the grinding surfaces of a pair of opposed grinding surfaces between which material to be ground (e.g., wood chips to produce mechanical paper pulp) is disposed. Pole pieces formed of a material having wear properties corresponding to the wear properties of the grinding surfaces project through the cover of the housing to terminate flush with one of the grinding surfaces. Consequently, energization of the primary winding establishes a magnetic field through the core, pole pieces, across the gap and into the opposed grinding member, the strength of which is proportional to the distance betwen the pole pieces and the opposed grinding surface. The induced voltage from the secondary coil serves as a measure of the gap distance.

Abstract: The thickness of the layer of remaining molten metal at the bottom of a container is measured on tapping molten metal from the container. An alternating magnetic field is generated with a frequency such that the penetration depth (.delta.) in the metal is of the same order of magnitude as the residue thickness of the melt layer of interest for measurement. The alternating magnetic field is generated such that to begin with field components are reflected at a horizontal surface of the melt layer and towards an alternating magnetic field detection position. When the thickness of the melt layer decreases and approaches the residue thickness, less and less field components will be reflected at the surface of the melt and pass instead through the remaining melt layer. The resulting change in detected alternating magnetic field is utilized, e.g. for triggering an alarm or breaking off tapping in some other way.

Abstract: An improved method and apparatus for monitoring the thickness of a film includes a sensor roll which cooperates with a compliant roll to form a nip through which the film passes. As the two rolls rotate relative to each other, magnets disposed in the sensor roll are sequentially moved to and from the nip. As a magnet moves by the nip, the field emanating from the magnet is concentrated by a body of material having a relatively high magnetic permeability and disposed in the compliant roll. This results in an induced voltage being generated in a sensor coil. The output from the sensor coil is transmitted to control circuitry which effects operation of a suitable apparatus to control the thickness of the film.

Abstract: A method of and apparatus for measuring the degree of transformation of the structure of an object. An object is placed between a transmission coil and a receiving coil. An A.C. current or a pulse current or a combination of the A.C. current and the pulse current are supplied to the transmission coil, and the degree of transformation is detected by means of an electric signal obtained through the receiving coil.

Abstract: Shown is an apparatus for mounting an inductive transducer in position over an intermittently moved belt carrying easy open ends for a beverage container and designed to detect whether or not the tabs for easy opening are provided on the ends. The apparatus is designed to resiliently bias the detection transducer towards the ends with a predetermined gap therebetween such that an electrical signal will result that can be used to evaluate whether a tab is in place. The apparatus includes a camming ramp designed to trigger a limit switch to turn off the system should there be multiple ends positioned below the detector. The detector mounting on a resilient support is designed to back away from any obstruction therebeneath to protect the apparatus during the detection operation. The transducer face is protected by about 1/16 inch of the plastic material.

Abstract: In a metal detector, such as may be used in a bakery, an adjustable phase shifter is provided to adjust the detectors for different products. The adjustable phase shifter is controlled electronically from the output signal so that the arrangement is self-adjusting.

Abstract: Various electrical coin testing arrangements are described which may be used in coin sorters or in coin validators for example. In each arrangement a transmit coil is pulsed with a rectangular voltage pulse and the eddy currents in an adjacent coin under test are monitored, either by monitoring the resulting current in the same coil or in a different coil. In one arrangement, FIG. 7particularly suitable for a coin validator, a single coil acts as both a transmitter and receiver and is successively pulsed with voltage pulses of different lengths, and the decaying eddy currents are measured by measuring the coil voltage after delays which are longer for longer voltage pulses, in order to reduce the dynamic range requirements of the monitoring circuitry. In a second arrangement, FIG. 4two transmit coils are used, the larger coil being larger than each of the coins to be tested, and the smaller coil being smaller than each coin.

Abstract: A gear rattle detector is adapted for use with a gear set having meshing drive and driven gears. The gear rattle detector comprises a magnetic pick-up including a base, a first arm extending from the base and defining a north magnetic pole, a second arm extending from the base and defining a south magnetic pole, and a coil wound around the base. The poles are spaced sufficiently such that they span the root circles of the gears.

Abstract: A brazing apparatus and process which utilizes a dual function heating and eddy current probe coil is disclosed herein. The apparatus generally includes a radiant heater assembly having a coil which is capable of both generating radiant heat to effect a braze joint between a reinforcing sleeve and a surrounding tube, as well as serving as an eddy current probe which locates the sections of this sleeve to which the brazing heat should be applied to effect the desired joint. A switching means selectively connects the coil to either a relatively high, heat-generating current, or to the aforementioned alternating current which induces eddy currents within the metal forming the reinforcing sleeve. The apparatus further includes eddy current detection circuitry for monitoring changes in the coil impedance which result from these eddy currents while the coil is slid along the longitudinal axis X of the reinforcing sleeve.

Abstract: An apparatus for determining the position of an object has an outer fixed field winding extending along an axis, a source for energizing the field winding with alternating current and thereby creating a magnetic field, and an inner coreless detecting winding displaceable coaxially in the field winding. Thus the field induces a voltage in the inner winding. A link displaces the detecting winding axially in the field winding with the object and thereby changes the voltage induced by the field in the detecting winding. An equalizing winding coaxial between the field winding and the detecting winding is fixed in the field winding. The field also induces a voltage in the equalizing winding. An electronic unit divides the voltages induced in the detecting and equalizing windings into each other and derives a detection signal corresponding to the position of the object and inner winding relative to the outer winding.

Abstract: An improved method and apparatus for monitoring the thickness of a film includes a sensor roll which cooperates with a compliant roll to form a nip through which the film passes. As the two rolls rotate relative to each other, magnets disposed in the sensor roll are sequentially moved to and from the nip. As a magnet moves by the nip, the field emanating from the magnet is concentrated by a body of material having a relatively high magnetic permeability and disposed in the compliant roll. This results in an induced voltage being generated in a sensor coil. The output from the sensor coil is transmitted to control circuitry which effects operation of a suitable apparatus to control the thickness of the film.

Abstract: Metal detection apparatus includes an oscillator coil 101 driven by an oscillator 101, which induces in detector coils 103,104 equal and opposite E.M.F.s such that a nominally zero output is produced at terminals D.E. When metal is detected the E.M.F.s in coils 103,4 move out balance to produce a voltage at D.E., which is detected by circuit IC11 and fed to output circuits 111. Drifts in the nominally zero output at D.E. are corrected by combining quadraphase balancing signals on lines 109,110 with the detector coil output by means of amplifier IC10. The combined signal from IC10 is fed to phase sensitive detectors IC1,2 which respectively detect the quadraphase components of the combined signal from IC10. The outputs of IC1,2 are stored by capacitor circuits 112,113 and used to adjust variable capacity diode bridges 106,7 which adjust the amplitude of the balancing signals to maintain a nominally zero output from IC10 when metal is not being detected.

Abstract: For characterizing coating compositions with magnetic particles the coating composition is subjected to an alternating magnetic field of variable frequency. The field induced by the coating composition after energization is recorded, and thus the susceptibility of the coating composition is measured. Depending on the variable frequency, conclusions can be made regarding the degree of dispersion, particle density, and viscosity of the coating composition. The variable frequency is between 1 and 100 cps, and the field intensity of the energizing field should be lower than 10 Oerstedt. The coating composition is fluid or stagnant in a pipe *1, 11 which is surrounded by field coil and measuring coil.

Abstract: An accuracy control subsystem for an object examination (OE) system is disclosed. The OE system is of typical frequency-based type and includes a drive unit for generating an excitation signal of preselected frequency, a transducer for receiving the excitation signal and for applying it to the object and for generating an output signal indicative of interaction of the excitation signal with the object and a detector for receiving the transducer output signal and for generating first and second output signals respectively indicative of components of the transducer output signal at first and second different phases thereof, typically zero degrees and ninety degrees, i.e., in-phase and quadrature, respectively.

Abstract: According to the process, a toroidal sample of ferrimagnetic material to be analyzed is placed in a thermostatically-controlled enclosure fitted with temperature regulation and detection means. The toroidal sample is submitted to an electro-magnetic magnetizing field of given frequency and the flux induced in the sample is measured directly using a measuring loop, around the sample and which is connected to a vectorial voltmeter.

Abstract: A method comprises repeatedly magnetizing a test article by a pulsed axially symmetric magnetic field normal to the surface of the test article, and reading the gradient of a residual field. Magnetizing the article is effected by two trains of pulses in two steps: first until a first instant of discontinuance in the growth of the gradient of a remanent magnetic field and then until a second instant of discontinuance, the pulse amplitude of the second pulse train being lower than a maximum amplitude of the second pulse train.An apparatus to carry out the proposed method comprises a pulse shaper 1 for forming pulses of an axially symmetric magnetic field and a measuring circuit for measuring the gradient of a remanent field normal component. According to the invention said apparatus is further provided with a working storage 4, a comparison circuit 5 and a pulse amplitude measuring device 2 for measuring pulse amplitude at the output of the pulse shaper 1.

Abstract: An invention is disclosed which supports an eddy curent probe at a predetermined distance from a surface to be scanned. In another embodiment, the probe is scanned by rotation about an axis and along an arc of predetermined length and position.

Abstract: A method comprises magnetizing a portion of the test piece by a pulsed magnetic field and forming as a result of said magnetizing two regions of remanent magnetization, which are magnetized to saturation in opposite directions, determining the magnitude of the remanent induction, which magnitude is used to judge the mechanical properties of the test piece. The magnitude of the remanent induction is determined by converting its gradient along the magnetized portion to an electrical signal, selecting from said signal a one-polarity pulse indicative of the change in the remanent induction between said regions, and integrating said selected pulse. A device comprises a pulse generator 1, magnetizing coils 2 connected to said generator in antiparallel relationship and arranged along the test piece, a transducer 4 for converting a gradient to an electrical signal, a measuring circuit including a key 5 and an integrator 6.

Abstract: The metal detector circuitry for a forage harvester is provided with a socket for receiving a pluggable unit, the arrangement being such that a resistor in the pluggable unit is connected into the detection circuitry of a metal detector whereby the sensitivity of the metal detector may be changed by inserting into the socket a pluggable unit containing a resistor of a different value. A metal detector test assembly connected to the metal detector through the socket, provides a means for testing the sensitivity of the metal detector and its associated circuitry. The test assembly includes a signal unit which is placed adjacent the metal detector sensing unit and generates a magnetic field that is sensed by the sensing unit, and a test box with circuitry, indicators and switches for selectively checking the sensitivity of the metal detector and correct operation of its associated circuitry.

Abstract: A procedure for nondestructively determining a physical characteristic of a test object (10) involves introducing an electromagnetic energy pulse into the test object, and measuring elapsed time before the signature of a time-dependent function of the energy thereby propagated through the test object (10) reaches a value larger than a pre-set threshold value. For example, the volume density of graphite fibers in a graphite-epoxy composite material can be determined by introducing a pulse of radio-frequency electromagnetic energy into the composite material, and by measuring the elapsed time before the voltage signature of the energy propagated through the composite material reaches a value larger than the threshold value.

Abstract: A piece of the magnetic material to be tested is coupled to the device by primary and secondary windings. The material is then exposed to varying polarities of a controlled electrical current, such as a ramped current, through the primary winding causing the magnetic flux of the material to vary with respect to the controlled current; and creating varying voltage levels across the secondary winding. When this process has been completed the data is made available to a computer which now has data for the current levels transmitted through the primary winding and the corresponding voltage levels across the secondary winding. The computer can then utilize this data to provide a variety of magnetic property values of the magnetic material.

Abstract: A method and apparatus are provided for effecting the inspection of a ferromagnetic element, or piping, and particularly piping that is already installed. The invention incorporates a device for indicating wall thickness of a length of the ferromagnetic element, including means for producing a value of magnetic flux extending longitudinally through a portion of the element. A voltage generating device is disposed in surrounding relationship to the element and is movable axially relative to the length of the element containing the value of the magnetic flux. Means for indicating the voltage generated in the voltage generating means by the value of the magnetic flux also are provided. Preferably, an axially split spool is provided which may be closed in surrounding relationship to an installed pipe. A saturation level of magnetic flux is induced in the pipe by a flexible cable which is wrapped around the spool in a multi-turn configuration and supplied with electrical current sufficient to produce saturation.

Abstract: An eddy-current loop detector operates to sense the presence of an electrically conductive object by applying D.C. onto a conducting loop so that a permanent magnetic field is induced, which field partly penetrates into the object; ensuring the quick cessation of self-inductive transient operation of the loop when the D.C. is switched off; and measuring the change in the part of the flux passing through the measuring loop arising from eddy-currents induced in the conductive object, and evaluating such change while the relatively slowly decreasing flux is maintained. By repeating these operations with the desired frequency, the eddy-current detector is well suited for continuous measuring of the position of the object.

Abstract: A method of measuring hardness in steel casing to detect soft spots. A magnetizing force is generated and traversed along the length of the steel casing. A flux density is created along those portions of the steel casing traversed by the magnetizing force. The flux density is monitored to detect any change in such flux density caused by the presence of a soft spot in the hardness of the steel casing.

Abstract: An induction voidmeter for detecting voids in a conductive fluid may comprise: a four arm bridge circuit having two adjustable circuit elements connected as opposite arms of said bridge circuit, an input branch, and an output branch; two induction coils, bifilarly wound together, connected as the remaining two opposing arms of said bridge circuit and positioned such that the conductive fluid passes through said coils; applying an AC excitation signal to said input branch; and detecting the output signal generated in response to said excitation signal across said output branch. The induction coils may be located outside or inside a non-magnetic pipe containing the conductive fluid.

Abstract: Metal detection apparatus includes an oscillator coil 101 driven by an oscillator 101, which induces in detector coils 103,104 equal and opposite E.M.F.s such that a nominally zero output is produced at terminals D.E. When metal is detected the E.M.F.s in coils 103,4 move out balance to produce a voltage at D.E., which is detected by circuit IC11 and fed to output circuits 111. Drifts in the nominally zero output at D.E. are corrected by combining quadraphase balancing signals on lines 109,110 with the detector coil output by means of amplifier IC10. The combined signal from IC10 is fed to phase sensitive detectors IC1,2 which respectively detect the quadraphase components of the combined signal from IC10. The outputs of IC1,2 are stored by capacitor circuits 112,113 and used to adjust variable capacity diode bridges 106,7 which adjust the amplitude of the balancing signals to maintain a nominally zero output from IC10 when metal is not being detected.

Abstract: A device for detecting metallic objects in a material flow, comprising as sensing member a scanning coil consisting of a primary coil and, for example, two oppositely connected secondary windings arranged symmetrically around the primary winding so that the voltage induced in the secondary winding becomes zero as long as no conducting objects appear in the scanning area. To eliminate irrelevant signals from conducting objects in the vicinity of the scanning coil but not in the material flow or from weakly conducting objects in the material flow, the primary winding is fed with at least two alternating currents having different frequencies. The corresponding secondary voltages are rectified in phase-controlled rectifiers, and in a calculating circuit the difference is derived between the output of one rectifier voltage and the output of another rectifier multiplied by a constant factor which includes the relation between the frequencies of the corresponding alternating voltages.

Abstract: A method and apparatus are provided for effecting the inspection of a ferromagnetic element, or piping, and particularly piping that is already installed. The invention incorporates a device for indicating wall thickness of a length of the ferromagnetic element, including means for producing a value of magnetic flux extending longitudinally through a portion of the element. A voltage generating device is disposed in surrounding relationship to the element and is movable axially relative to the length of the element containing the value of the magnetic flux. Means for indicating the voltage generated in the voltage generating means by the value of the magnetic flux also are provided. A saturation level of magnetic flux is induced by a multi-turn supplied with electrical current sufficient to produce saturation. The voltage induced in a central pickup coil is amplified, integrated and correlated to average thickness of the pipe.

Abstract: The metal detecting device includes first and second coils provided on both sides of a passageway for paper money. This metal detecting device is designed for use in detecting a metal strip embedded in the paper money in order to determine whether the paper money is genuine or counterfeit. The first coil is connected to a high frequency AC source to generate an AC magnetic field. The second coil is connected to a capacitor to form a resonance circuit which resonates at the same frequency as the AC current. The variation of the Q factor of the resonance circuit due to eddy-current losses produced in the metal strip of the paper money is used by a detecting circuit to determine whether the paper money passing through the space between the first and second coils is genuine.

Abstract: The present invention relates to a method and apparatus for non-destructive comparative investigation of physical characteristics affecting the reluctance of different parts of a body having magnetic permeability. In accordance with the present invention a first saturating magnetic flux is induced in the body or a part thereof giving rise to a flux distribution pattern determined by the reluctance of the body or part thereof which in turn is determined by the physical character of the body or body part. A second magnetic flux is also induced generally opposing the first magnetic flux in a selected region of the flux distribution pattern, outside of the body or body part while maintaining substantial first flux saturation of the body or body part such that any resultant magnetic flux in that region is at a readily measureable flux level.

Abstract: Metal detector apparatus includes a controlled phase responsiveness to allow operation with reduced ground effects while discriminating between different types of metals. A phase relationship is predetermined that will reject unwanted signals from mineralized ground and trash metals and will be responsive to the signals from desired metals. The algebraic relationship between two signals is determined so that only input signals falling within the desired algebraic relationship are used to provide an output signal.

Abstract: Parameters of electrically conductive material at high temperature are measured by generating, by means of a transmitter coil, an electromagnetic alternating field which induces currents in the material and by detecting, by means of a receiver coil, a specific component of the secondary electromagnetic alternating field generated by the induced currents and dependent on the measured parameter, the frequency of the generated electromagnetic alternating field being such that the penetration depth of the field into the material is of the same geometrical order of magnitude as the characteristic geometrical dimension of the system, such as the distance between the receiver coil and the material. The specific component of the secondary electromagnetic alternating field is detected by means of a synchronous detector connected to the receiver coil and controlled by a phase-shifted signal from the transmitter.

Abstract: A synchronous demodulator subsystem produces a ground balance pulse and a discriminate pulse each time a detector head housing the receive coil and an associated transmit coil passes over a metallic object (e.g., a target) buried in the ground. In one form, a pair of synchronous demodulators produce V.sub.X and V.sub.R signals, each of which includes a pulse each time the detector head passes over a target. The V.sub.X and V.sub.R signals are combined to produce the ground balance and discriminate pulses. Alternatively, a pair of synchronous demodulators are used to directly produce the ground balance and discriminate pulses. The polarity of the discriminate pulse is dependent upon on whether the target is a desirable or an undesirable target. Contrariwise, the polarity of the ground balance pulse is always the same.

Abstract: The present invention discloses both a method and apparatus whereby the integrity of elongate magnetically permeable member(s) can be determined even if coated with a non-magnetic substance or embedded in a non-magnetic body. A magnetic yoke having field winding(s) and sensing winding(s) is used to induce a time varying magnetic field in the magnetically permeable member(s). Changes in the reluctance experienced by this magnetic field alter the output of the sensing winding(s). The invention finds particular application to testing conveyor belts, but is also applicable to steel cables, and both rubber and concrete bodies, including steel reinforcing.

Abstract: A reflection type probe for an eddy current testing instrument comprises a ferromagnetic core 2, 3 and a driver coil system 8 and a pick-up coil system 9 mounted on the core, the core having four limbs 4 to 7 each with a free end. One of the coil systems 9 is wound on the four limbs with its turn equally distributed between the four limbs and the other coil system 8 is wound on a core part remote from the turns of the coil system 9 and which interconnects the core limbs at least in pairs. Advantageously the coil system which is wound on the limbs 4 to 7 is the pick-up coil system. A detector coil section of the pick-up coil system can then have its turns equally distributed between one pair of limbs and a balancing coil section having its turns equally distributed between the other pair of limbs.

Abstract: A metal detector is disclosed which has a transmit coil, a receive coil, and circuit means for detecting metal object due to a change in the magnetic coupling between the coils. Circuit board arrangement techniques are disclosed which enable the close placement of the transmit and receive coils and the circuit board, thereby allowing packaging of the metal detector in a small package. A low battery voltage indicator circuit is provided to warble an audio indicator signal to indicate sufficient battery voltage. In the event the battery voltage drops below a certain level, the warbling of the indicator signal ceases and a steady tone is generated thereby indicating a low battery voltage condition.

Abstract: A process and apparatus for controlling the level of a molten metal surface in a continuous casting mould uses a probe located either in the molten or above the surface of the molten metal. The probe is connected to a high-frequency transmitter which is arranged to induce voltages in each of two secondary receiver-coils, the receiver-coils being in coupling relationship with a compensating coil and a further coil connected to the probe. The receiver-coils are connected in opposition to one another so that a difference voltage of zero is arranged to be produced when the molten metal surface is at the required level but that the difference voltage is used, when departing from zero, for control purposes of the height of the molten metal surface.

Abstract: A crankshaft position sensor having a reluctance sensing magnetic pickoff cooperating with sense features on a nearby, rotating sense wheel. The sense features are filled with a nonmagnetic electrically conductive material to enhance uniform eddy current flow within the sense wheel and where the magnetic pickup contains two coaxial magnetically polarized pole pieces.

Abstract: Apparatus for detecting ferromagnetic material such as is present in an explosive cartridge being loaded into a borehole, e.g., according to the method described in U.S. Pat. No. 3,986,430, which includes an inductance coil connected in series with a resistor, separately rectifies and amplifies the AC voltages across the coil and resistor and connects them in series opposition. The value of the balancing resistance is adjusted so that the two rectified voltages are equal and opposite when no ferromagnetic material is present. When the unbalance voltage exceeds a threshold value, a signalling device is actuated.

Abstract: A tire pressure monitoring system includes a tuned circuit with a pressure sensitive switch which is closed when the tire pressure is normal, connected across it, the tuned circuit and switch being mounted on the vehicle wheel. Mounted on a part of the vehicle is a detector circuit including an oscillator which includes an inductor which is at least intermittently coupled to the inductor of the tuned circuit. When the switch is closed the oscillator runs normally and its output is detected to indicate that all is well. When switch is open, however, the oscillator output is suppressed whenever the inductors are coupled together. The circuit can also be used in other applications where it is required to detect the state of an isolated switch.

Abstract: This invention pertains to two forms of verifier of the grade of oil field tubular goods. The first form can be thought of as a sorter in that it will indicate when a particular length of tubular goods is of a different grade than its companions in a lot. The second form will identify the grade of a length. Both forms depend upon magnetizing or inducing magnetic eddy currents in the pipe which are detected and handled by the invention circuitry to sort or to identify.

Abstract: A cable detecting system with a cable ship, a cable detector towed by said cable ship via a towing wire and said cable detector dredging the water bottom to find a buried cable, has been improved. When the cable detector detects a buried cable, and the cable is engaged with the cable detector, the towing wire between the cable ship and the cable detector is released either by drawing out a wire from the cable ship or by extending an auxiliary wire from the cable detector, thus, the cable detector stops just when a cable is detected, even when the cable ship continues to move by inertia, and no damage is caused to the cable. The presence of a cable is sensed either through a mechanical means which detects the cable by contact between the cable and the detector, or through electromagnetic means. The detection of a cable triggers the above release of the towing wire.

Abstract: Disclosed is a metallic imaging system for detecting and visually displaying the shadow projection of a diamagnetic metallic object immersed in a point source magnetic induction field. In a preferred embodiment of the invention, the object is located intermediate a magnetic induction point source transmitter operating, for example, in the 100kHz range and a magnetic receiver consisting of a scanner adapted for two dimensional movement in a projection plane substantially normal to the axial projection of the magnetic induction field. The output of the scanner comprises magnetic phase and amplitude variation signals which are converted to video signals and thereafter fed to an imaging device for producing a display in the form of a television like visual presentation of the projected magnetic shadow image.

Abstract: Method and apparatus for the nondestructive determination of the amount and quantitative distribution of a paramagnetic additive such as gadolinia in nuclear fuel elements. Changes in paramagnetic susceptibility of the material in the element are detected as the element is passed through a constant magnetic field and compared to the changes in susceptibility produced by a standard element of known additive content.

Abstract: A sensor for measuring the change of a magnetic field comprises a magnet for generating a constant magnetic flux, and magnetically conductive members magnetically coupled to the magnet for producing first and second magnetic fields, the first magnetic field passing through an object and the second magnetic field not passing through said object, the object being of a material which influences the first magnetic field. A magnetic field measuring device located in the second magnetic field to measure the second magnetic field and to indicate a change in the second magnetic field as a result of the first magnetic field being influenced by the object. A magnetically conductive outer shielding member, which may be one of the magnetically conductive members, is provided.

Abstract: A method apparatus for qualitatively detecting remnant magnetic fields in matched pairs of magnet cores. Equal magnitude and oppositely oriented magnetic flux is induced in the magnet cores by oppositely wound primary windings and current source. Identically wound secondary windings generate output voltages in response to the induced flux. The output voltages generated should be of equal magnitude and opposite polarity if there is no remnant field in the cores. The output voltages will be unequal which is detected if either core has a remnant field.