Abstract: Measuring arrangement for contactless measurement of rotational speed. The measuring arrangement operates using a stationary pulse wire sensor (5) which is activated by the magnetic fields of several revolving, radially aligned magnets (4). The rotational speed of a component (3a) arranged on a shaft (3) is detected by each pulse being triggered in the pulse wire sensor (5) by two opposite poles (N, S) lying at an axial distance to each other. The measuring arrangement provides reliable measurements irrespective of the rotational speed, in particular in the lower measuring range.

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

Abstract: A position measuring device having a magnetic graduation scanned by a scanner unit which contains magnetic field sensitive elements as sensors. A high frequency alternating auxiliary field is generated to magnetically bias the magnetic field sensitive elements.

Abstract: A noncontact type rotation sensor, which can detect the rotational movement of a gear with high sensitivity and precision without causing any erroneous output, is disclosed. To a magnetic gear is applied a bias magnetic field by a bias magnet from the direction of the teeth of the gear. A sensor part disposed within the bias magnetic field comprises a substrate and a plurality of magneto-resistive elements mounted on the substrate in parallel to the teeth of the gear and electrically connected in series one after another. The sensor part detects the magnetic vector of the bias magnetic field varying according to the rotation of the gear as the composite value of the variations of the resistance values of the plurality of magneto-resistive elements connected in series one after another.

Abstract: To provide a nondestructive inspection apparatus with a reduced distance between a superconducting magnetic sensor and an object under inspection, a cryostat for cooling the sensor to a superconducting state is provided with inner and outer vessels. The inner vessel has a baseplate on which the magnetic sensor is disposed, and has an inner wall defining a central chamber for containing a refrigerant for cooling the magnetic sensor. The outer vessel has an inner wall defining a central chamber for containing the inner vessel, the magnetic sensor and the stage. A gap between the inner and outer vessels is evacuated to insulate the inner chamber from the ambient atmosphere. To facilitate ease of transferring an object to and from the stage for inspection, a load lock area is provided adjoining the outer vessel.

Abstract: A miniturized coil arrangement made by planar technology for the detection f material having a magnetic permeability other than zero, provided with a magnetizable core in a first plane of a substrate, an electrically energizable coil wound around a first section of a core to generate flux therein and at least one other coil in a second plane of the substrate adjacent another section of the coil responsive to disturbance in the flux.

Abstract: Apparatus for performing nondestructive magnetically testing and inspection of elongate objects. The apparatus concentrically surrounds the elongate object to be tested and includes means for inducing a magnetic field in the elongate object and a partial ferrous return path for the magnetic flux emanating from a pair of magnet arrays. The partial ferrous return path is engaged with a sensor for detecting variations or flaws in the elongate object.

Abstract: A magnetic testing device for obtaining a damaged index of an elongated magnetically-permeable object in real time includes a permanent magnet assembly with spaced-apart poles, a tubular pole piece adapted to surround the object, Hall effect devices placed in the magnetic flux path, a leakage flux sensor installed between the pole pieces, and a real time signal processing unit. The signal processing unit provides local fault (LF) signals generated by the leakage flux sensor, and loss of metallic area (LMA) signals generated by the Hall effect devices. The standard deviations of the LF signals are summed, the root-mean-square of the LF signals is summed, the absolute values of the LF signals are integrated, and the LMA signal is multiplied by a coefficient which is dependent on the object construction. The damage index is then determined using the thus-calculated values. Preferably, when a wire rope is passed through the monitoring device, the damage index is given to the user in a hand-held display means.

Abstract: The invention concerns magnetic field energy responsive position sensing apparatus and method. A Hall sensor has an element defining a generally planar active face and circuitry coupled to said Hall sensor for producing a two state electrical output signal in response to magnetic field energy in a region of said active face. A ring magnet has spaced apart annular end walls that are adjacent a north pole and south pole of the ring magnet and defines a magnetic field in a center region of the ring magnet. The ring magnet and the Hall sensor are mounted for relative linear movement in a direction substantially normal to the active face of the Hall sensor so that the active face moves through the center region of the ring magnet. One annular end wall of the ring magnet moves past the active face while avoiding mechanical contact with the active face. This causes the electrical output signal to change state as the end wall moves past the active face of the Hall sensor element.

Abstract: A method of magneto optic imaging to locate the presence of a crack around a circular drilled bolt hole wherein the circular bolt hole, because of its sharp corners, locally disturbs the magnetic field used to form the image and obscures the presence of a crack therearound. Initially, a magneto optic image is formed of the drilled circular bolt hole under test, wherein a crack near the circular hole will perturb the circularity of the hole image by driving the magnetic field away from the circumference of the circular hole to cause it to appear out of round and eccentric. A pattern recognition analysis is then applied to the image to check the image for circular shapes, wherein each circular shape image is correlated with a circle of similar diameter to check the circularity of the image, and an eccentricity of the circular image shape is indicative of a crack around the drilled circular bolt hole.

Abstract: Apparatus for detecting a magnetic pattern having a plurality of spaced magnetic areas includes an array of magnetic sensors which are configured and spaced from each other to detect the spaced magnetic areas of a magnetic pattern brought into contiguity with the array. Electrical circuitry connects the array of magnetic sensors in series and a single source is provided for supplying current to the array of magnetic sensors through the electrical circuitry.

Abstract: A magnetooptic device to be used in industrial applications to investigate articles for flaws or defects. The magnetooptic device is capable of revealing defects in articles of nonmagnetic and magnetic conducting material. These results are achieved by designing a magnetooptic device having a magnetooptic transformer element on its bottom surface and incorporating a front electrical contact and a rear electrical contact on the bottom surface of the MO device. The respective electrical contacts are connected by wire conductors to the respective positive and negative terminals of a source of electrical current. The defect pattern of an article can be either visually viewed or the defect pattern can be recorded on a tape or magnetic rubber sheet placed between the bottom surface of the MO device and the top surface of the article being analyzed.

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

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

Abstract: An apparatus for detecting a nugget for spot welding utilizing the magnetic after-effect which is generated when a variation in the magnetic field is applied to a nugget. The apparatus includes a driving coil, which applies a magnetic field variation to a spot-welded nugget, and a magnetism sensing element, which detects variations in magnetic flux density arising in the vicinity of the nugget as a result of the magnetic field variation. The magnetism sensing elements may be installed in an array form so as to face the nugget and the area around the nugget.

Abstract: The present invention involves enhancing machine-readable matrix symbol markings on substrate materials by the addition of magnetizable materials, and then, at a later time, taking advantage of the magnetic properties associated with the matrix symbol marking to read the marking using a magneto-optic reading apparatus. For example, the marking material may be mixed with a media having magnetic properties and applied to a component surface either via stencil or as backfill. The magnetic material enables detection with the aid of a magnetic-property detection apparatus. Once detected, the matrix symbol image is transmitted to a symbol decoder so that the information represented by the symbol can be provided to a user.

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

Abstract: A non-destructive testing equipment comprises a magnetic sensor located within a magnetic shield container. The magnetic sensor includes a SQUID that is a magnetic sensor having a very high sensitivity. A magnetically uniform inspection zone is formed in the magnetic shield container. While a rod-like material to be tested passes through the inspection zone at a uniform velocity, the magnetic sensor can detect an appreciable magnetic field variation that is caused by impurities or minor defects contained in the object to be tested.

Abstract: A magnetic device, comprises a first magnetic layer; a second magnetic layer on the magnetic layer and having a coercive force smaller than that of the first magnetic layer; a semiconductor layer between the first and second magnetic layers so that photo-induced magnetism occurs between the first and second magnetic layers when the semiconductor layer is irradiated with light, a third magnetic layer on the second magnetic layer, the third magnetic layer having a coercive force larger than the coercive force of the second magnetic layer, and a second semiconductor layer between the second and third magnetic layers, magnetism being induced between the second and third magnetic layers when the second semiconductor layer is irradiated with light.

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

Abstract: A monitoring apparatus is provided for determining permeabilities of a vacuum-deposited second pole piece of a magnetic head at the wafer level by providing wafer-mounted monitors which have layers formed by the same masking and deposition steps employed in making the magnetic heads so that the layers of the monitors are replicated layers, except for a shaping layer on top of a replicated second pole piece of some of the monitors. Each monitor is a transformer wherein each of a primary winding and a secondary winding comprises essentially a replicated magnetic head. The first and second pole pieces of the replicated magnetic heads are joined so as to magnetically couple the primary and secondary windings that constitute the transformer.

Abstract: In order to measure the permeability of a magnetic material, a permanent magnet is positioned at a distance from the surface of a magnetic material. A first magnetic field sensor is placed proximate the magnetic material on the magnetic axis of the permanent magnet. The axis of sensitivity of the magnetic field sensor is perpendicular to the field of the permanent magnet and in a plane perpendicular to the surface of the magnetic material. A second magnetic field sensor for compensating for temperature and stray field effects can be positioned perpendicular to the magnetic axis of the permanent magnet with its axis of sensitivity parallel to the axis of sensitivity of the magnetic field sensor.

Abstract: A method for determining through a test structure a longitudinal magnetic exchange field within a patterned exchange biased magnetoresistive (MR) sensor element. To practice the method, there is first provided a substrate. Formed upon the substrate is a patterned magnetoresistive (MR) layer which has a projected length upon the substrate and a projected width upon the substrate. There is formed at a pair of separated locations over the patterned magnetoresistive (MR) layer a pair of patterned conductor lead layers. The pair of patterned conductor lead layers is separated by a track width of the patterned magnetoresistive (MR) layer, where the track width is smaller than the projected width.

Abstract: A tester for measuring the resistance of magnetoresistive heads as a function of the magnetic field applied to the heads. The tester applies a time varying magnetic field to the magnetoresistive head to be tested and filters the resulting time varying (AC) voltage signal indicative of the resistance of the head with a capacitor to remove the DC component of the signal. The AC component of the signal is then amplified, digitized, and analyzed to obtain the resistance properties of the magnetoresistive head.

Abstract: In order to ensure an optimal position of a magnet (3) in relation to a Hall IC (2) or, respectively, its Hall effect elements (4, 5), the magnet (3) and the Hall IC (2) are displaceable in relation to one another and, namely, in the direction of the lateral distance of the two Hall effect elements (4, 5). It is preferred that the Hall IC (2) is retained stationarily in the rotational speed sensor, and the magnet (3) is retained so as to be displaceable and lockable in position, in particular in a base member (10) of the sensor housing.

Abstract: A magnetic assembly for detection and authentication of magnetic documents. The magnetic assembly includes a permanent magnet (PM), first and second magnetically soft high permeability pole pieces shaped to form a tapered, variable gap size magnetic circuit with the permanent magnet. The PM is located at a first gap between the first and second pole pieces. A magnetoresistive (MR) sensing element is located at or near the center of a second gap between said first and second pole pieces. The second gap and MR sensing element are proximate a magnetic document to be sensed. An electrical conductor is adjacent to the MR sensing element, but is electrically insulated therefrom. A direct current is passed through the electrical conductor to create a compensating bias field in the MR element which is combined with the bias field generated by the PM.

Abstract: A magnetoresistive element is used to detect a surface roughness of an object, such as a magnetic recording medium, a photomask blank, a semiconductor wafer, and is assembled into a reproducing head which moves along a surface of the object and which can produce an electric signal related to the surface roughness. The reproducing head may be incorporated with a recording head into a head unit. The head unit can monitor a magnetic characteristic of the magnetic recording medium in addition to detection of the surface roughness, by recording a predetermined signal by the recording head and by reproducing the predetermined signal by the reproducing head.

Abstract: In the simplest embodiment of the invention, the apparatus holds the edge of the magnetized film to be measured close to, and above, a linearly biased magnetoresistive (MR) element. Magnetic poles appearing at the magnetic discontinuity at the edge of the film generate a magnetic field which is incident on the MR element, and which results in a measurable change in the element's resistivity. In a preferred embodiment, a pair of MR elements are placed so that they are both linearly biased by a magnet; only one of the MR elements being in close proximity to, and influenced by the magnetic field emanating from the edge of the magnetized film. The second MR element, selected for matched characteristics with the first MR element, is located out of the field of the magnetized film, but still subject to the same temperature environment and field noise as the first MR element.

Abstract: An array of sensors is provided at or near the surface of a material arranged to detect magnetic flux leakage occurring when a magnetic field is induced in the material. The sensors in the array are coupled in respective pairs (differential pairs) such that when one partner of a respective pair overlies a discontinuity, a differential output signal is produced dependent on the difference between the output signals from the sensors of the respective differential pair. Because of the nature of the change of the flux leakage field produced by a discontinuity, respective partners of each pair of sensors are spaced relative to each other according to the invention. In one embodiment, partners of each sensor pair are spaced relative to one another both in the direction of travel of the apparatus and also in a direction transverse thereto.

Abstract: Magnetic flux leakage inspection apparatus systems with independently suspended magnetic sensor blocks. The apparatus includes a magnet and a sensor assembly. The magnet is disposed over a surface of a magnetizable material under inspection for inducing magnetic flux in the material, and the sensor assembly is disposed in a predetermined inspection position over the surface for detecting magnetic flux leakage from the material that may indicate a magnetic anomaly in the material. The magnet and sensor assembly are moved along over the surface while the sensor assembly scans for magnetic leakage flux. The sensor assembly is formed with one or more independently suspended sensor blocks, each block including a plurality of sensors rigidly held in the block for detecting magnetic flux leakage.

Abstract: A pair of Hall sensors are symmetrically positioned between the poles of a horseshoe magnet. The Hall sensors are mounted in a plane flush with the ends of the magnet faces, and are located equidistant from the centerline of the magnet. A small magnetic object in the field of the magnet, preferably located on the magnet axis, has an induced dipole moment which is detected by the Hall sensors. The small magnetic object dipole field is such that the flux at each Hall sensor is in opposite directions, and by differentially sensing the outputs of the Hall sensors, a signal proportional to the magnetic object is derived. Leakage flux from the magnet as well as the flux of the earth's magnetic field, are in the same direction at both Hall sensors, and their effects are zeroed out by the differential sensing of the Hall sensors' outputs. When the poles of the magnet are drawn across the surface of a non magnetic sheet of conductive material, eddy currents are induced in the sheet by the moving magnetic field.

Abstract: A method and sensor for sensing the rate of rotation of a fan in order to monitor and detect a variation in the rate of air flowing through the fan, such as to indicate a restriction in the air flow path or failure of the fan. A Hall-effect transistor (HET) is placed in the fixed field of a magnet adjacent the path of a preferably ferrous moving element capable of changing the magnetic field coupled to the HET. As the ferrous element passes the magnet and HET, the strength or alignment of the field changes sufficiently to produce an output pulse from the HET. The pulse rate decreases with slowing of the fan such as may occur with a restriction or blockage in the air flow path.

Abstract: A magnetic sensor including a magnetoresistance effect element directed to prevent deterioration in the detection sensitivity occurring due to inversion of the magnetization of a plurality of ferromagnetic thin film stripes forming the magnetoresistance effect element with respect to the initial direction during the repeated operations, the magnetic sensor being arranged in such a manner that the magnetoresistance effect element is disposed at a position deviating from the center of the magnetic pole surface of a cylindrical magnet, preferably at a position deviating in a direction perpendicular to a direction in which the magnetic object to be detected is moved. The thus-employed arrangement enables a bias magnetic field to be applied to the magnetoresistance effect element in parallel to the deviation direction. Therefore, the magnetization of all of the plurality of the ferromagnetic thin film stripes forming the magnetoresistance effect element can be caused to face the same direction.

Abstract: An anti-counterfeit security device for documents in general in the form of a tape-like or filament-like supporting element made of polyester. On the tape or filament, a first security element is provided which can be detected by devices and is constituted by regions made of a material which can be detected by magnetoresistors and are arranged in succession to generate a signal that can be decoded by the magnetoresistors, and a second security element is also provided, visually detectable in transmitted light, which is constituted by portions of the regions that are free from the magnetoresistor-detectable material in order to form graphic markings optically perceivable in transmitted light.

Abstract: In order to control the direction of a magnetic field induced by a current sheet in a sheet conductor, relative to anomalies in a test sample, the current sheet is either rotated relative to the sheet conductor, by using either electrical or mechanical commutation of the current sheet, or the phases of plural independent current sheets in the sheet conductor are shifted relative to each other.

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

Abstract: A magnetic testing device for detecting loss of metallic area and internal and external defects in elongated magnetically-permeable objects includes a permanent magnet assembly having poles adapted to be spaced apart in the longitudinal direction of an elongated object for inducing a longitudinal magnetic flux in a section of the object between the poles of the magnet assembly, the magnet assembly being strong enough to magnetically saturate the section of the object. A tubular pole piece is arranged to surround the object adjacent each pole of the permanent magnetic assembly for directing the magnetic flux into the object at one pole and out of the object at the other pole. Hall effect devices are placed in the path of the magnetic flux for sensing the reduction of the flux passing through the elongated object due to any reduction of cross-sectional area of the elongated object between the pole pieces caused by loss of metallic area in the elongated object.

Abstract: A magneto-optic layer of bismuth-garnet deposited on a thin transparent substrate is utilized in viewing very low amplitude magnetic field patterns. When subjected to a magnetic field perpendicular to the layer, the layer lowers its magnetic energy by breaking up into a series of reversed domains called meander patterns. As the magnetic fields to be viewed are too low in amplitude, (approximately equal to, or less than 1 Oe), to directly modify the meander pattern, the magneto-optic layer is excited with an AC magnetic field of more than 100 Oe which is then slowly reduced to zero; (a small DC bias field is simultaneously applied to control the background of the viewed field, and to cancel the earth's field). This causes the anhysteretic transfer of the pattern of the low amplitude field onto the magneto-optic layer, with the resultant meander pattern replicating the low amplitude field pattern.

Abstract: A polar coordinates sensor probe, having a plurality of circularly arranged pick-up poles driven by a rotating magnetic field originating in a hollow toroid core, for detecting the reflected rotating eddy current pattern in material (both ferrous and non-ferrous) surrounding fastener holes, wherein the flaw is detected by means of mutual phase-amplitude comparison and adjacent pick-up pole signal phase deviation. The second embodiment having an isolated multi-pole pick-up core, picking up a rotating figure 8 eddy current pattern. Also embodiments utilizing Hall effect and magnetoresistive devices with the rotating magnetic field for flaw detection.

Abstract: A magnetic assembly for detection and authentication of magnetic documents. The magnetic assembly includes a permanent magnet (PM), first and second magnetically soft high permeability pole pieces shaped to form a tapered, variable gap size magnetic circuit with the permanent magnet. The PM is located at a first gap between the first and second pole pieces. A magnetoresistive (MR) sensing element is located at or near the center of a second gap between said first and second pole pieces. The second gap and MR sensing element are proximate a magnetic document to be sensed.

Abstract: A preprogrammed controller, preferably a stored program computer such as an IBM PC computer, is programmed to automatically control all the steps in the testing of a MR reproduce head. First, the magnitude of the sense current is established by command of the controller, and a voltage proportional to the sense current flowing in the head is monitored by the controller. An electromagnet, having high permeability pole pieces, and whose current is programmed by the controller provides a the magnetic field for exciting the MR head. The MR device is placed on an measured magnetic equipotential of the field of the electromagnet, and a Hall sensor magnetic detector is placed on the same magnetic equipotential line but in a different physical position from the MR device. The output of the Hall sensor is fed into the preamplifier electronics, digitized by a converter and this digital output is stored in the controller memory for future processing.

Abstract: Tank bottom inspection apparatus of the magnetic flux leakage type having a powered release mechanism for reducing the magnetic attraction of the apparatus to the tank bottom. The apparatus is wheeled over the tank bottom surface and includes a magnet assembly disposed over the surface for inducing magnetic flux in the material under inspection and a sensor assembly for detecting magnetic flux leakage from the material indicative of magnetic anomalies. A powered actuator permits the operator to retract the magnet assembly away from the surface, reducing the magnetic attraction to the surface and thereby reducing magnetic resistance to movement of the apparatus over the surface. The operator retracts the magnet assembly for maneuvering the apparatus over and around obstacles on the surface with greatly reduced magnetic attraction to the surface. The operator is then able to return the magnet assembly to a precise inspection position for continued inspection of the surface.

Abstract: A wafer level test structure and method detects multiple magnetic domains and magnetic domain instability in a test magnetic element. The apparatus comprises a first MR sensor designed to be held in a single magnetic domain by shape anisotropy and a second MR sensor having a permanent magnet to hold the element in a single magnetic domain. A circuit connects the first and second MR sensors to detect differences between the changes in resistance between the first and second sensors in the presence of a magnetic field or differences in resistance after the application and release of a magnetic field. The circuit is preferably a balance circuit in which imbalance in the presence of a magnetic field indicates the presence of multiple magnetic domains in at least one of the test sensors.

Abstract: A magnetic sensor includes a member having a magnetic contour anisotropy. A counterpart yoke is disposed above a magnet. The thickness of the counterpart yoke is equal to or slightly smaller than the resolution. The counterpart yoke has a magnetic contour anisotropy for restraining the divergence of the magnetic flux from the magnet. The resolution can be prevented from being reduced depending on the distance between a medium and a magnetic sensing element. At the same time, the magnet can be miniaturized.

Abstract: An eddy current surface inspection array probe and method for detecting cracks and flaws in aircraft skin metal immediately surrounding rivets, without requiring rivet removal or manual scanning. The array probe includes a circular array of small sense coils positioned beneath a much larger drive coil encased in ferrite. The sense coils are differentially connected in pairs such that the signals from two sense coils located on opposite sides of the rivet (180.degree. apart) subtract to produce a resultant output signal. During operation, the probe is positioned concentrically over the rivet and data acquired from all sense coil pairs. If no cracks or other defects are present, all sense coil pairs produce a null (zero) signal. If a crack exists, some sense coil pairs (the exact number depending on the crack length, number of sense coils, and sense coil spacing) produce a non-zero signal.

Abstract: An apparatus for non-intrusively indicating the passage of a pipeline pig having a housing adapted to be supported adjacent the exterior surface of a pipeline through which a magnet carrying pig moves, the housing containing an armature formed of pole pieces of paramagnetic material having a narrow gap therein that receives a solid-state magnetic sensing member, the sensing member providing changing electrical characteristics in response to changes in ambient magnetic field intensities, and an indicator pivotally attached to the housing and normally held in a ready position by a latch, the latch being operated by a circuit controlled by the magnetic sensing member so that the flag is released to move to an operative position in response to a changed magnetic field intensity caused by the passage of a magnet carrying pig, the armature within the housing serving to increase the sensitivity of the magnetic sensing member.

Abstract: A sensor for measuring the density of a magnetic porous material such as foam. The sensor includes a load cell connected to a magnet. The magnet is spaced a predetermined distance away from the material. The load sensed by the pull of the magnet is translated into a perceivable density value.

Abstract: Defects such as corrosion located on the exterior of a component such as a metal pipe, tank, vessel or support structure which is insulated by a coating or cover, are detected by a low frequency eddy current (LOFEC) system. A magnetizing yoke in the shape of an inverted U is placed on the cover insulating a metal component. An excitation coil is wrapped around the magnetizing yoke for carrying an altering current in order to produce an alternating magnetic field by the magnetized yoke. The alternating magnetic field produced by the magnetized yoke induces an eddy current which runs through the metal component between the legs of the yoke. A pair of magnetic flux sensors are used in differential connection beneath one or more excitation coils which can be articulated to conform to varying pipe diameter. In addition, an absolute signal response can be obtained from one of the receiver coils.

Abstract: A magnetic flux microscope that measures the magnetic field about a sample surface. The apparatus uses a thin-film superconducting quantum interference device (SQUID) as the scanning device. Magnetic shielding is provided about the SQUID and is held stationary relative to the SQUID. The apparatus and method provides a very high magnetic image of the sample with a very high spatial and field resolution.

Abstract: A security circuit includes a Hall-effect sensor for generating an output signal in response to a sensed variation in magnetic field strength. A supply voltage source is connected to the Hall-effect sensor. A latch circuit receives the Hall-effect sensor output signal and generates a latched output signal. The latch circuit operates between a set and a reset state. Circuitry is provided for monitoring the supply voltage source and for generating an output signal applied to the latch circuit. The latch circuit generates the latched output signal in response to the Hall-effect sensor output signal and the output signal generated by the monitoring circuit when the supply voltage is at a predetermined level. The latch circuit is reset when the supply voltage is below the predetermined level.