Abstract: An apparatus is provided for measuring the test current in magnetoelectric fault detection, for instance by the magnetic particle method. A sensor comprising a Hall generator or a magnetoresistor is movably mounted on a diamagnetic support which clamps the sensor at a variable distance from a conductor carrying the test current. Alternatively, a plurality of sensors can be fixed to the support and the appropriate sensor selected for use.

Abstract: A method and apparatus for testing steel components for temper embrittlement uses magneto-acoustic emission to nondestructively evaluate the component. Acoustic emission signals occur more frequently at higher levels in embrittled components. A pair of electromagnets are used to create magnetic induction in the test component. Magneto-acoustic emission signals may be generated by applying an AC current to the electromagnets. The acoustic emission signals are analyzed to provide a comparison between a component known to be unembrittled and a test component. Magnetic remanence is determined by applying a DC current to the electromagnets, then turning the magnets off and observing the residual magnetic induction.

Abstract: A transducer in the form of an integrated circuit comprising a Hall cell, first and second differential amplifiers, an output driver stage, a threshold voltage-generating circuit between said amplifiers, and a control circuit for selectively enabling and disabling the threshold voltage-generating circuit. The second amplifier provides an output signal representative of the enabled-disabled condition of the threshold voltage-generating circuit. A permanent magnet having a temperature coefficient is movable with respect to the transducer between given field-applying and field-removing positions. The transducer operates to change switching states between "operate" and "release" in response to the two different levels of applied magnetic fields, respectively, resulting from the two given operating positions of the magnet.

Abstract: When an electrically conducting material is subjected to an alternating magnetic field local changes in the magnetic field adjacent to the conducting material are detected by a detector comprising a magnetoresistor or Hall crystal which generate an electrical signal when subjected to the magnetic field.The process and apparatus can be used to identify, classify and locate electrically conductive material.The detectors can be of the order of a few millimeters in size and so can be used to detect local changes in the magnetic field over correspondingly small areas of the material.The invention is particularly useful in identifying coins used in coin operated machines.

Abstract: The invention relates to an apparatus consisting of a device for generating a magnetic field mounted for movement relative to a product sitting in or moving through its field which is suspected of carrying at least one metal component which will cause the generator to move either toward or away therefrom because of either the attractive or repulsive forces, or both, caused by the presence of this metal or these metals. A load-responsive element in the form of a load cell is connected to the field generator so as to sense its movememnt if any and output a signal evidencing such movement. A detector is connected to receive the output signal from the load cell and use this information to initiate an appropriate response to the presence of the metal or metals causing the displacement of the generator.

Abstract: The present invention is a proximity sensor employing a magneto resistive structure. This proximity sensor includes a toroidal magnet having a central aperture, an inner circumference and an outer circumference. This toroidal magnet has a first magnetic pole at the inner circumference and a second magnetic pole at the outer circumference thereby creating a magnetic field null at a center portion of the central aperture. A magneto resistive structure is disposed at the magnetic field null in the central aperture of the toroidal magnetic. This magneto resistive structure has a resistance dependent upon magnetic flux. The proximity of a magnetically permeable target to the toroidal magnet shifts the position of the magnetic null, thereby causing a large change in the magnetic flux through the magneto resistive structure. An electrical detection circuit detects changes in this resistance for indication of the proximity of the magnetically permeable target.

Abstract: A magnetic head characteristic measuring device for determining the recording and reproduction efficiencies of a magnetic head, which uses an MR block consisting of plural parallel magnetoresistive elements disposed on opposite sides of a reference plane aligned with the center of the gap of the magnetic head. The MR elements detect a change in the vertical component of the magnetic field caused by a change in a leakage magnetic field generated in the gap, to gauge the recording efficiency of the head. The measuring device also includes a further MR element or other conductor capable of generating a test magnetic field when supplied with a current. When this test magnetic field is being generated, a measurement of the response of the magnetic head is taken in order to gauge the reproduction efficiency of the same.

Abstract: A method and an apparatus are provided for detecting magnetic discontinuities, for example corrosion pits, in a specimen of magnetizable material. A horseshoe shaped magnet (32) is supported with its poles just clear of a surface of the specimen (12) by a wheeled frame (20), and is moved over the surface. An array of sensors (48) between the poles detects the leakage flux near the surface. The signal from any one sensor at a particular location is corrected by subtracting from it the average of the signals from the same sensor at a plurality of other locations preceding and following that location. If the corrected signal exceeds a threshold value, this indicates abnormally large localized leakage flux, and so indicates metal loss from the specimen.

Abstract: This invention relates to a process and an apparatus for the non-distructive examination of ferromagnetic bodies having sections of their surface adjoining along edges. The bodies or body parts are examined for structural faults or disturbances, including the regions along the edges and/or at the corners. A magnetic field is produced in the given body or body section. This field is stationary with respect to magnetic field sensors provided for measuring the stray fields on the surface. In a first measuring phase, measurements obtained for stray flux which are characteristic for the various positions of the magnetic field sensors along the surface of the body or body section are stored as reference values. In a second measuring phase, the reference values allocated to the various positions are subtracted from the stray flux values measured at these positions. The differences are then compared with predetermined threshold values.

Abstract: In a magnetic field sensor comprising at least one magnetic-field-dependent resistor disposed in the vicinity of an outer side of a housing that is open on at least one side and further comprising a permanent magnet that is adjacent to said magnetic-field-dependent resistor, the magnetic-field-dependent resistor(s) (6), arranged on a support (4), are in a contacting relationship with the inside of a detector side wall (2) of the housing (1), and the thickness (x) of said detector side wall (2) is, at least in the area of the active surface of the magnetic-field-dependent resistors (6), smaller than that of the other housing walls (17, 18, 19) and/or the housing base (20). A rugged, high-resolution magnetic field sensor is thus obtained.

Abstract: A magnetic field detector has a sensor arrangement which is disposed in a housing and includes a plurality of stripe-magnetic-field-dependent resistors arranged on the underside of a dielectric support. A permanent magnet is oriented perpendicularly to the upper side of the support and to the magnetic-field-dependent resistors. In one embodiment, the sensor arrangement is located approximately in the center of the housing and a plurality of electrical contact means are attached on both sides of the permanent magnet and adjacent thereto within the housing. In another embodiment, the sensor arrangement is located laterally from the center of the housing and the electrical contact means are attached within the housing and adjacent to only one side of the magnet.

Abstract: A non-oriented direct coupled sensor for gear teeth or similarly shaped discontinuities of a ferrous magnetic or magnetic target uses a single magnet and a direct coupled Hall cell integrated circuit to detect the presence or absence of gear teeth. The sensor incorporates techniques for flux steering and flux reversals independent of the orientation of the sensor to the target to overcome the operate or release point of a Hall switch, latch or other device. The use of spaced apart, offset flux concentrators provides a sensitive device with favorable tolerances in temperature and air gap.

Abstract: An apparatus for detecting substantially longitudinal flaws in the end area of a tubular member is disclosed. The apparatus comprises magnetizing-detection units, means for moving-said units along a helical path about the surface of the end area of the tubular member, and means for centralizing and securing the apparatus on the end of the tubular member being inspected. Magnetic detection transducers on the magnetizing-detection units detect perturbations in the applied magnetic field in the area of any substantially longitudinal flaws. The magnetic detection transducers are mounted so as to remain remote from the surface of the tubular member during operation of the apparatus. The field is generated in the tubular member by said magnetizing-detection units. The magnetizing-detection units are pivotably mounted to allow for movement over both flat and tapered surfaces. The signals generated by the magnetic detection transducers are transmitted to an external indicating device through slip rings.

Abstract: The subject of the invention is a method and a device for non-destructive testing of ferromagnetic bodies (1) for structural faults. The bodies (1) are magnetized. Structural faults cause changes in the magnetic field pattern which are measured with magnetic field detectors (6). Surface waves are generated electro-dynamically utilizing the magnetic field generated for magnetizing the body (1). Those structural faults extending up to the surface can be detected with the surface waves. To distinguish between the structural faults extending to the surface of the body at one point and those structural faults inside the body (1), it is determined whether the measured values gained both from the leakage flux and from the surface waves indicate structural faults or whether only the measured values gained from the leakage flux indicate structural faults.

Abstract: An improved method and device for measuring magnetic particles in a liquid wherein a known amount of liquid is contacted with a bed of ferromagnetic fibers maintained in the magnetic field of a magnet with sufficient strength to substantially completely magnetize said particles for a time long enough for said particles to migrate to and be substantially completely captured by said fibers and having a magnetic flux sensor positioned between a pole face of said magnet and said bed wherein the distance from said sensor to the fibers farthest from said sensor is not greater than about 6 millimeters.

Abstract: The object of the invention is a device with two Hall generators (12, 14) for measuring the gradients of magnetic leakage fields in the non-destructive testing of materials. The two Hall generators (12, 14) are arranged at a distance from each other with their broad sides on a flat carrier substrate (18). They are positioned along a common line (36) with respect to which they each have the same alignment. Furthermore the two Hall generators are arranged close to the edges (40) of two opposite sides of the carrier substrate (18) that are free of connections.

Abstract: Disclosed is an improved method and apparatus for sensing magnetic reluctance variations. The invention may be used for magnetic ink character reading, such as is employed on bank checks, or for any of a variety of magnetic reluctance pickup applications. An improved magnetic reluctance sensor head utilizes an essentially U or C-shaped magnetically permeable member having a magnetizing coil encircling it. The coil is arranged to deliver essentially a constant magnetic flux to the U or C-shaped member. The tips of the U or C are placed adjacent to the element whose variation of reluctance is to be detected and a magneto resistive or other similar magnetic sensor is connected in the magnetic circuit either in parallel or in series with the variable reluctance which is to be sensed.

Abstract: The invention relates to an analog non-contact distance sensor which includes a fixed stationary annular magnetized armature. The stationary armature member is provided with an air gap into which is disposed an element which is sensitive to a magnetic field. The moving portion is a rod-shaped magnetic core member which can be inserted into the annular armature member. Depending on the depth of insertion of the core member, the amount of diversion of the magnetic field from the air gap of the armature is controlled. Consequently, the magnetic sensing element emits an electrical signal which corresponds to the distance travelled by the movable core member.

Abstract: The present invention concerns devices with probes for measuring magnetic potentials. Potential differences between two points of a material in a magnetic field are measured with a plurality of Hall probes arranged on a curved line which connects the points. The voltage of each Hall probe is connected with the summation point of an operational amplifier whose output voltage is proportional to the potential difference P=.intg.H.multidot.ds. A similar arrangement may also be used to measure the current in a conductor.

Abstract: A method for the direct visualization of surface and near surface cracks, voids, flaws, discontinuities, etc. in materials is disclosed. The detection of flaws or the like is accomplished by the visualization of the static and/or dynamic magnetic fields, either ambient or induced, associated with various flaws in a target material. A magnetic garnet epitaxial film is deposited on a non-magnetic substrate. In one embodiment, a reflective coating or material is provided adjacent to the epitaxial film, and the substrate with its associated layers is placed over the target material. A magnetic field is then applied to the target material and substrate. Polarized light is directed onto the through the substrate and associated epitaxial layer, and is reflected by the reflective coating such that the polarized light passes back out of the substrate.

Abstract: A movable part of a robot, such as the fingers of the robot hand, are provided with an array of tactile elements mounted on a substrate. Each element includes a magnetic dipole embedded in a compliant medium on one side of the substrate and a magnetic sensor on the other side of the substrate. The dipole and sensor are in parallel planes. A force or torque deforms the compliant medium and displaces the magnetic dipoles with respect to the sensor. The sensor detects the change in magnetic field and produces an electrical signal which is used to control the robot. Magnetoresistive sensors are preferred. To detect torque, each element illustratively includes four sensors arranged at 90.degree. to one another and a magnetic dipole oriented at 45.degree. to each sensor.

Abstract: A method of inspecting the reinforcing members in prestressed concrete beams by generating a magnetic field close to the beam and measuring the field by means of a Hall effect sensor located between the pole pieces of the magnet. A partial or total break in a reinforcing member produces an anomaly in the magnetic field, which in turn registers as a voltage "spike" in the output of the Hall effect sensor. The method further includes a method for enhancing the data by substantially reducing or eliminating the effects of transverse reinforcing steel or support members located at the site of a break in the prestressed member.

Abstract: An apparatus for non-destructively testing ferromagnetic bodies to determine structural irregularities by means of magnetization of the respective object, comprises detectors for magnetic fields arranged close to the surface of the body, by which detectors any changes of behaviour of the magnetic field caused by structural irregularities can be determined. At least two stationary magnetic fields are arranged one after the other on the body that can be displaced in its longitudinal direction, the center axes of these magnetic fields being inclined toward each other at an angle. This angle is determined by the number of magnetic fields and is equal to the quotient from one hundred and eighty degrees and the number of magnetic fields. In the space between the poles of the magnetic field generators, the magnetic field detectors are stationarily arranged and in rows, each extending over a zone being equal to a body section to be tested, vertically to the shifting direction of the body.

Abstract: A device for measuring the position of a moving body. A detected member made of magnetic material is secured to the moving body and an E-shaped magnet is arranged adjacent the measured member transverse to the direction of motion. A Hall IC for converting the variation of magnetic flux density of the magnet to the variation of voltage is secured to an end of a central leg portion of the magnet. The measured member is an elongated bar and is provided with a series of projections on the elongated bar at both sides. The projections of both sides are arranged in staggered relation. The Hall IC is adjacent to an inner portion of one of the projections when the moving body travels in the elongated direction. The Hall IC produces an output having a waveform with a zero level interval between inverted waves.

Abstract: A paper note containing a magnetic strip is transported along a path and adjacent a magnetic detector. This magnetic detector comprises a magnet and a magnetic resistance element provided in the magnetic field generated by the magnet. When the magnetic strip passes through this magnetic field, the change in the field is detected by circuitry. This circuitry detects the change in resistance of the magnetic resistance element. By checking the change in resistance of the resistance element and comparing it with a predetermined value, the existance or non-existance of the magnetic strip can be determined.

Abstract: Apparatus for detecting flaws in the threaded end of a ferromagnetic pipe is disclosed. The apparatus comprises means for applying a magnetic force to produce a field generally axially through the threaded end of the pipe, first and second means adjacent successive crests of a thread for sensing a generally radial magnetic field and generating a first and second signal corresponding to the sensed magnetic fields, and means for differentially connecting the signals generated by said first and second sensing means, whereby a differential output signal is produced in response to a flaw between the crests of the thread being inspected. The apparatus also comprises means for helically rotating said sensing means to follow a path corresponding to the threads of the pipe, whereby the first and second signals vary with time.A method for detecting flaws in the threaded end of a ferromagnetic pipe is also disclosed.

Abstract: A rotational angle detection device having two magnetoresistive sensing elements positioned at a 45.degree. angle with respect to each other senses the rotary position of a permanent magnet. Sine and cosine waves are applied to first and second bridge circuits respectively incorporating the two sensing elements. The resulting bridge circuit outputs are differentially combined to provide an output whose phase relative to either of the input sine or cosine waves is dependent upon the rotational position of the permanent magnet. The phase difference is detected and the rotational position is calculated therefrom.

Abstract: A Hall effect device test circuit which detects Hall effect device operate and release point failures. A magnetic field circuit, a voltage switching circuit, a comparison circuit, a retriggerable monostable multivibrator circuit and a visual indicator circuit are included. The comparison circuit compares the Hall effect device switching voltage to a predetermined threshold and controls the multivibrator circuit which causes a visual pass/fail signal to be provided.

Abstract: To determine the rotary speed of a toothed element (1), for example the starter gear of an internal combustion (IC) engine, or a toothed wheel coupled to a wheel of a vehicle for evaluation of the speed, and change in speed thereof, for use in a brake anti-block system, a magnetic field is generated, for example by a permanent magnet (3) which has both radial and tangential components with respect to the teeth (2) of the rotary element. A magnetic field dependent sensor (4) such as a Hall generator or a thin-film permalloy-type magneto-resistive sensor is positioned to respond to the tangential component of the magnetic field, to thereby eliminate shifts in the null or center line about which the field strength undulates as the disk rotates to permit ready evaluation of the output from the sensor by threshold circuitry.

Abstract: A method of and apparatus for non-destructive investigation of the surface properties of a body of ferromagnetic material such as a pipeline in which a non-saturating source of magnetic flux is placed adjacent to said surface to create a magnetic circuit having a substantial proportion in non-ferromagnetic material and a sensor is used to measure the magnetic flux in said circuit, an indication of the surface properties of the body being derived from a plurality of such measurements.

Abstract: This disclosure is directed to an acoustic Barkhausen stress detector apparatus and a method of obtaining measurements of stress in or determination of the microstructure of ferromagnetic materials. In the preferred and illustrated embodiment, stress or microstructure information in a ferromagnetic specimen is tested and measured through application of a variable magnetic field. A sensitive acoustic detecting device including an input transducer(s) and amplifier(s) forms a signal based on Barkhausen acoustic phenomena which arise from a change in the magnetic field strength. Barkhausen acoustic information is in the form of vibrations produced within the material which occur as magnetic domain walls shift. The domain wall shifts occur at various locations within the material of interest, and the acoustic vibrations are propagated through the material and are observable at the surface by one or more transducers.

Abstract: An electromagnetic system is provided to monitor the activity of a ferrous debris detector of the type which uses electric discharges to automatically disintegrate magnetically concentrated accumulations of micron sized wear particles in hydraulic systems. The data provided are used to detect instances of abnormal wear as shown by either an unusually large number of such discharges or an excessive rate of discharge. Where such abnormality occurs the monitor will provide an audiovisual alarm to warn of the problem in time to prevent catastrophic failure of the system.

Abstract: A probe for sensing energizations of electrical components and particularly the energization of a relay or solenoid, the probe utilizing a magnetic switch as a sensor, a light-emitting diode as an indicator and a battery as a power source, the elements encapsulated as a unit in an epoxy material.

Abstract: A probe and method for detecting surface flaws in metals. The probe operates at microwave frequencies and uses a ferromagnetic resonator. The resonator experiences a frequency shift when brought into proximity with a metal because of the perturbations of the demagnetizing fields at the boundaries of the resonator. A crack in the metal additionally disturbs the field and causes additional perturbations of the frequency. The perturbations in frequency are detected to provide an indication of flaws in the surface of the metal.

Abstract: A method is proposed by which defects in workpieces are detected magnetically, which method comprises the following steps being performed concurrently: scanning the test surface of a workpiece utilizing magneto-sensitive elements; magnetizing the workpiece perpendicularly to its test surface in the test zone; exciting magneto-sensitive elements; and measuring the tangential component of the magnetic field strength in the test zone. An apparatus for magnetically detecting defects in workpieces according to the proposed method comprises an electrical signal excitation/measuring unit and a detector. The latter has a housing which accommodates a core-type magnet rigidly fixed to it and adapted to be magnetized prependicularly to its working surface which mounts magneto-sensitive elements separated from each other and oriented in a prescribed manner. The elements connect each other and the electrical signal excitation/measuring unit as well.

Abstract: Apparatus for locating the position of at least one magnetic member relative to a nonmagnetic member includes a probe assembly movably disposed within the nonmagnetic member and including a nonmagnetic head having a pair of spaced permanent magnets mounted thereon. Each magnet has a variable resistor connected thereto, the resistance of each resistor varying directly with the strength of the flux field emanating from each magnet. The resistors are connected to a source of electrical energy for providing an electrical control signal, the magnitude of which varies in response to the movement of the probe assembly including the magnets and resistors relative to the magnetic member.

Abstract: A ferrous metal detecting apparatus is disclosed for detecting metal particles in a flowing fluid, such as engine oil. The detecting apparatus has soft-iron pole pieces with a bridging gap therebetween. The soft-iron pole pieces are electrically insulated from each other and magnetized by direct current through an electromagnetic coil. After a sufficient amount of ferrous metal has accumulated on the bridging gap, a level detector will give a warning signal and cause the electromagnetic coil to degauss the soft-iron pole pieces by applying an alternating current to the electromagnetic coil. After the flowing fluid has washed away the ferrous metal, the direct current will remagnetize the soft-iron pole pieces. If repeated warning signals are within predetermined time intervals, an indication of the amount of ferrous metal contained in the fluid can be interpolated. The recycling for repeated warning signals may be automatically provided through a timing circuit and control logic.

Abstract: A magnetic testing device for detecting defects in elongated objects is disclosed. The testing device comprises 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 which is strong enough to saturate such section of the object, a tubular pole piece substantially centered on the elongated object adjacent each pole of the permanent magnet assembly for directing the magnetic flux radially into the object at one pole and out of the object at the other pole, Hall effect devices spaced around at least one pole piece in the path of the magnetic flux for sensing the radial flux entering into the elongated object, and means for sensing the variations of such magnetic flux as an indication of loss of metallic area in the object.

Abstract: A transducer for identifying and quantitatively measuring the presence and location of ferromagnetic material, which is specifically suitable for remotely mapping ferromagnetic deposits on pressurized water reactor steam generator tubing. The transducer employs a first source of a magnetic field which is positionable in magnetic communication with and is mounted to be movable over the surface area of the workpiece. Perturbations produced in the magnetic field as a result of ferromagnetic discontinuities associated with the workpiece are sensed by a Hall element fixedly positioned with respect to the source in magnetic communication with the workpiece. Means are provided for altering the magnetic field of the source in communication with the Hall element to substantially null the output of the Hall element in the absence of magnetic material within or on the workpiece within proximity of the Hall element.

Abstract: A method and apparatus for detecting flaws in conduits or the like which prises positioning an annular array of Hall-effect devices transversely around the conduit, applying an electric current to the conduit to flow longitudinally therethrough so as to create a magnetic field around the conduit, sequentially scanning the Hall-effect devices to produce a series of output signals corresponding to the portions of the magnetic field sensed respectively by them, and comparing the output signals for nonuniformities among them, the nonuniformities being indicative of the existence and location of flaws.

Abstract: Two magnetoresistive (MR) elements are connected with two matched impedance elements in a bridge arrangement for sensing magnetic flux manifesting information recorded on magnetic media. An alternating current (AC) bias is applied to the bridge's input, and short-term variations in the bridge output signal envelope are detected as representing recorded information. Long-term (average) variations in the signal envelope are also detected and used to adjust the AC bias to maintain a constant average envelope. Additional bridge inputs may be connected in parallel with the first, and the additional bridges' outputs used to derive additional information signals without any additional AC bias adjustment circuits.

Abstract: A solid state Hall effect sensor is disposed between two magnets having their fields in quadrature with flux from the magnets at least partially cancelling in the Hall element to thereby enable a ferrous element relatively movable with respect to the magnets and sensor to control the output of the sensor.

Abstract: An inductively coupled oscillator method for inducing eddy currents in a semiconductor PN junction wafer while irradiating said wafer with pulsed light of selected intensity. The oscillator loading due to the pulsed light modulated eddy current losses is monitored and displayed on an oscilloscope in the form of a decay time plot of voltage amplitude, the plot being a function of the pulsed light intensity and the recombination rate of light-induced electrons and holes on each side of the junctions. The leakage characteristics of the junctions which are desired to be measured are one of the factors determining said rate. Leakage characteristic is made the predominent factor by setting the intensity of the pulsed light to a value which produces a nearly straight line decay time plot on the oscilloscope display. The slope of the line then is a measure of the leakage characteristic.