Abstract: A method and apparatus for high speed magnetic detection of surface fatigue cracks in railway rails. The magnetic material of the rail is magnetized by touch magnetization using a permanent magnet (31), leaving a remanent magnetic field. A sensor head (30, 50) having a plurality of Hall effect sensors (32) senses stray flux generated in the vicinity of surface fatigue in the rail head by the remanent magnetic field. The sensor head (30, 50) may incorporate a proximity sensor (60) to compensate for variations in sensor height. The apparatus may be mounted on a conventional track recording vehicle (TRV) for use in routinely monitoring the surface fatigue severities in rail along a railway.

Abstract: Apparatus for detecting a metal object comprises a transmitter for generating a pulsed or an alternating magnetic field in the vicinity of the metal object to be detected and a detector for detecting the secondary magnetic field induced in the metal object by the transmitted magnetic field. The detector measures at least three magnetic field gradient components of at least first order of the secondary magnetic field. The apparatus also comprises a processor for determining at least one of the position or the electro-magnetic cross-section or an estimate of the shape of the metal object from the measured magnetic field spatial gradient components. The processor fits the measured components to dipole, multiple dipole, multipole, or extended source models. In a preferred embodiment, the invention may comprise three or more pairs of gradiometric coils, or other sensing means.

Abstract: In a method and device for measuring at least one parameter of a metal bed, measuring is obtained by a magnetic field being generated from one side of the metal bed so that eddy currents are generated in the metal bed as the metal bed moves relative to the magnetic field. The metal bed and the magnetic field are made to move relative to one another. A force related to the eddy currents affects a body and the action of the force on the body is detected by a detecting device, the detected force being a function of a desired parameter of the metal bed.

Abstract: A magneto-optical microscope magnetometer capable of simultaneously measuring a hysteresis loop and activation magnetic moment of a submicrometer-scale local area (about 0.3×0.3 &mgr;m). An electromagnet capable of applying a magnetic field to a magnetic material is attached to a polarizing optical microscope capable of observing a magnetized state of the magnetic material, such that images of the microscope varying with the strength of the applied magnetic field are grabbed in real time by a charge coupled device camera and then analyzed. The magneto-optical microscope magnetometer can measure a hysteresis loop and activation magnetic moment in a submicrometer-scale local area observed by the polarizing optical microscope. Further, the magneto-optical microscope magnetometer can measure hysteresis loops and activation magnetic moments simultaneously with respect to all CCD pixels of the camera and observe coercivity and activation magnetic moment distributions of the entire magnetic material.

Abstract: A soft-magnetic material is installed on the opposite side of the magnetism sensing face of magnetism sensing devices. This soft-magnetic material is larger than the magnetism sensing face. Then the detection coverage per sensor is enlarged, and the number of sensors and signal processing circuits are reduced across the width of the strip.

Abstract: Apparatus for detection and measurement of agglutinations of magnetic particles employing Hall sensors. A low frequency AC signal is employed to excite or bias the Hall sensors which reside in a DC magnetic field. The particles are moved into operative relationship with the Hall sensors in order to generate a signal representing the number of particles on the substrate. The method for such detection and measurement is also part of the invention.

Abstract: The invention relates to apparatus and a method for detecting the condition of the material of a pipeline wall. The apparatus includes means for inducing and detecting magnetic flux at a location on the pipeline and, at said location, sensing means detect whether any change in material condition is on or near the external wall of the pipeline. By analysing the two sets of monitored values a change in condition, such as corrosion, can be detected, located and determined to be at or near the external or internal surfaces of the pipeline wall.

Abstract: A giant magnetoresistive (GMR) based eddy current sensor including a giant magnetoresistive sensor integrated on a silicon chip with a signal conditioning circuit and a circular coil.

Abstract: A magnetic non-destructive method and an apparatus for measurement of cross sectional area of elongated ferrous objects such as steel wire ropes and for detecting local flaws is disclosed. A section of a wire rope is magnetized by longitudinally spaced magnetic poles. A magnetic field parameter, e.g. magnetic flux density, is measured in, by at least, one pair of points between the poles of magnetizing device (in an inter-pole area) at the object under test surface. The pair of points is formed by two sensors placed in the inter-pole area along a direct line parallel to the rope axis. The rope cross sectional area corresponds to a sum of the sensor pair signals. Local flaws, such as broken wires and pitting corrosion in the rope, is detected by a first differences of signals of the sensor pair.

Abstract: An apparatus for the magnetic inspection of ferrous conduit for signs of wear includes a housing having a first end, a second end and a conduit travel passage extending through the housing from the first end to the second end. At least one coil is positioned within the housing encircling the conduit travel passage. The coil is disposed at an angle to the conduit travel passage so as to create a transverse flux component. Sensor supports are positioned along the conduit travel passage encircled by the coil. At least one sensor array is mounted on the sensor supports. The sensor array is oriented to detect flux patterns which extend transversely relative to the conduit travel passage. A computer is in communication with the sensor array to receive and interpret signals from the sensor array.

Abstract: A detector assembly and methods including a magnetoresistive sensor capable of detecting anomalies in the wall of a casing string disposed in a wellbore. Examples of anomalies include gaps between casings such as due to casing joints, air gaps in casing threads such as due to flush casing joints, enlarged casing wall thickness such as due to external casing collars, damaged casing, perforations, and other discontinuities or deformities in the casing. The detector assembly and methods detect perturbations in the earth's magnetic field caused by the anomalies. The detector assembly generates essentially no magnetic or electromagnetic field so that other downhole instrumentation is not affected by its presence.

Abstract: A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil's longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing.

Abstract: Magnetic characterization of the magnetic field emanating from an RWH device is presented using a magnetostrictive layer as a probe between the device and the scanned SFM tip. The findings suggest a very promising technique to resolve magnetic fields laterally at least in the 100 nm realm. Other magnetosensitive properties such as the magnetoelastic and the piezomagnetic effect can be used in a similar way to infer magnetic characteristics of microstructures or of magnetic multilayers.

Abstract: An electric current sensor for sensing an electric current flowing through a conductor comprises a single hall element having a magnetic-flux sensitive surface, and an angle adjusting mechanism. The angle adjusting mechanism changes an angle between the magnetic-flux sensitive surface and the direction of a magnetic flux induced by the electric current flowing through the conductor. The magneto-electric conversion element outputs an electric signal in response to a magnetic flux density at the magnetic-flux sensitive surface. The electric current sensor detects the electric current flowing through the conductor based on the electric signal output from the magneto-electric conversion element whose magnetic-flux sensitive surface is oriented with respect to the magnetic flux at a selected angle.

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

Abstract: A casing joint locator device and methods of use are described. The locator device includes a giant magnetoresistive (GMR) sensor that is capable of detecting joints between sections of casing in a wellbore. The methods and devices described detect perturbations in the earth's magnetic field caused by air gaps and discontinuities associated with a casing joint or with an external casing joint collar. As a result, they are capable of detecting flush and standard collared joints. The casing joint locator generates essentially no magnetic or electromagnetic field so that other downhole instrumentation is not affected by its presence.

Abstract: A scanning AC hall microscope and a method which measures the domain pattern of magnetic materials, such as magnetic storage media, by measuring the oscillatory motion of a domain boundary under the influence of an external applied AC magnetic field, which allows a differentiation between domains which are immobile and domains which are mobile.

Abstract: A method is disclosed for processing, optimization, calibration, and display of measured dielectrometry signals. A property estimator is coupled by way of instrumentation to an electrode structure and translates sensed electromagnetic responses into estimates of one or more preselected properties or dimensions of the material, such as dielectric permittivity and ohmic conductivity, layer thickness, or other physical properties that affect dielectric properties, or presence of other lossy dielectric or metallic objects. A dielectrometry sensor is disclosed which can be connected in various ways to have different effective penetration depths of electric fields but with all configurations having the same air-gap, fluid gap, or shim lift-off height, thereby greatly improving the performance of the property estimators by decreasing the number of unknowns.

Abstract: An apparatus for locating positions on a surface of a structural member indicating the presence of elements within and below the surface of the structural member by means of a detector (1) including a scanning head (3), a position measuring device (4) and an evaluation unit (5) all located within a housing (2). A marking device (6) is connected to and interacts with the evaluation unit (5) for automatically placing a visible marking on the surface of the structural member at the location of the elements scanned by the detector.

Abstract: An apparatus for reducing rotation of an article such as a bird for holding a superconducting quantum interference device for use in airborne transient electromagnetic mineral prospecting. The apparatus includes a support sphere having an inner shell and an outer shell. Liquid is contained between the inner and outer shells and a sphere has openings through which support strings project for locking to an internal point within the sphere. The strings have one end connected to an internal point within the support sphere and another end connected to a spring. The spring includes a damper for damping movement of the spring. Baffles are arranged in the cavity between the inner and outer shells in which the liquid is contained for damping movement of the liquid.

Abstract: A method and a measuring device for determining the spatial distribution of a magnetic field vector. At least a pair of sensor elements is provided. Each sensor element measures a component of the magnetic field vector. The sensor elements are aligned in a parallel, spaced-apart relationship along an axis parallel to the measured components.

Abstract: An active magnetic anomaly sensing system includes a transmitter for transmitting a magnetic field towards a target. The magnetic field induces magnetic moments in the target which cause a magnetic anomaly field to propagate from the target. A first sensor positioned a distance D from the target directly senses magnetic field strength and produces a first output. A second sensor positioned a distance (D+d) from the target directly senses magnetic field strength and produces a second output. A controllable power supply is coupled to the transmitter for selectively activating and deactivating the transmitter. The first and second outputs are produced when the transmitter is deactivated. The second output is subtracted from the first output to generate a differential output indicative of the magnetic anomaly field propagating from the target.

Abstract: A Barkhausen probe comprising a magnetizing field generator, a magnetoresistive magnetic field sensor, a direct current power supply for biasing the magnetoresistive magnetic field sensor and signal conditioning electronics is described. The Barkhausen probe being capable of generating and sensing the Barkhausen noise emanating from the surface of a cyclic magnetized specimen. The conditioned Barkhausen noise output of the signal conditioning electronics being usable as input to various analysis systems where textural analysis of the material can be performed.

Abstract: A method comprises manufacturing a read/write head for a disk drive; then testing the read/write head; and then mounting the read/write head to a suspension only after the testing step indicates that the read/write head is not defective. The testing may be performed by writing information to and reading information from a non-disc shaped media paddle that is caused to move back and forth with respect to the read/write head in oscillatory fashion.

Abstract: A current which will change an initial magnetization state of a shield layer for a MR element is applied to an inductive element, and output characteristics of the MR element is measured.

Abstract: A method and apparatus for detection of rare earth metal oxide inclusions in non-magnetic metal. The method utilizes a D.C. magnetic search field coupled with a magnetic field sensor for detecting the response of a rare earth metal oxide casting fragment inclusion through the bending and amplification of the ambient magnetic field at the defect location.

Abstract: An apparatus for detecting and measuring axially extending defects in ferrous tube includes a magnetizing coil for inducing a longitudinal magnetic field in the ferrous tube. Linear magnetic transducers are used to detect parallel non-linking flux leakage that occurs from axially extending defects. An analog to digital converter digitizes the measured signals representing the amount of parallel non-linking flux leakage detected. A processor subtracts signals typical of ferrous tube with no axially extending defects from the measured signals. The processor further processes the resulting signals after subtraction, by separating the alternating AC components from the constant DC components to remove the effects of perpendicular flux leakage, which may exist in the measured signals. The processor then calculates the percentage of missing material due to the axially extending defects by applying a proportionality equation to the remaining DC components of the measured signals.

Abstract: A magnetic sensor for detecting magnetic fields deriving from a magnetic body to detect any magnetic body on a non-magnetic body by moving relative to the non-magnetic body in prescribed relative moving directions along the surface of the non-magnetic body includes a magnetizing magnet in which a line connecting the N and S poles thereof is a direction substantially orthogonal to, and of which one pole is arranged either in contact with or in proximity to, the surface of the non-magnetic body; and a magnetism detecting element having two magnetic detectors arranged along a magnetic field detecting direction, the magnetic field detecting direction being orthogonal to the relative moving directions in a surface parallel to the surface of the non-magnetic body, wherein the magnetic body is magnetized by the magnetizing magnet along with the movement relative to the non-magnetic body, and magnetic fields according to the quantity of the magnetized part of the magnetic body are differentially detected by the two m

Abstract: A system for testing the read/write head elements of a head stack assembly (“HSA”). A completed HSA is placed in the test apparatus. Test probes are aligned and placed in electrical contact with the electrical leads coming from each head element, between the head elements and the preamplifier. The HSA is then placed in a changing magnetic field. A low frequency magnetic field can be applied to test the head elements. The changing magnetic field induces electrical signals within the head elements. By analyzing these electrical signals, the condition and characteristics of the each head element can be determined.

Abstract: The present invention relates to a device for continuously monitoring the junction of a conveyor belt which is made of rubber or a rubber-type plastic material and which comprises supports inserted therein for reinforcing the same. In an advantageous embodiment, the device essentially comprises the following constituent members for the junction area: mainly four reference marks, two addresses as well as four detection heads, the heads being located above the carrier surface of the conveyor belt. This invention further relates to other advantageous embodiments of this device.

Abstract: A surface profile detecting device comprises a plurality of bar-like cores disposed in a line with predetermined intervals in a predetermined disposing direction. Each core has tip ends that are arranged on a single plane and which face a surface of an object to be measured having recesses and protrusions in a magnetic field such that they are relatively movable in a direction orthogonal to said disposing direction. The detecting device also includes detecting arrangement provided in each of the bar-like cores for detecting changes in magnetic flux generated due to the uneven profile of the object to be measured. An A/D converting device is provided for A/D converting the output of the detecting arrangement with a predetermined timing. A memory is also provided for storing the output from the AND converting device. The uneven profile of the object to be measured in a predetermined range is detected from the data stored in the memory.

Abstract: The process first applies a magnetostatic field to a target magnetic body to magnetize the target magnetic body. The process then cuts the magnetostatic field off and measures a transient variation in a differential magnetic flux density at a plurality of positions in the vicinity of the target magnetic body. The process subsequently determines a time constant of the transient variation in the differential magnetic flux density at the plurality of positions. The process then determines a specific characteristic value relating to the internal structure of the target magnetic body, based on a distribution of the time constant over the plurality of positions. This arrangement enables a variety of internal structures of the target magnetic body to be examined in a non-destructive manner.

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

Abstract: The present invention relates to a detecting apparatus for detecting a magnetic minute substance. The detecting apparatus of the present invention can detect continually at a high sensitivity an entity of fine particle, without destroying an object to be inspected. The detecting apparatus comprises a magnetic field generator and a magnetic sensor. The magnetic field generator generates a magnetic field having a right angle to the traveling direction of the object to be inspected. The magnetic sensor includes a SQUID for inspecting a drift of the magnetic field that is parallel to the magnetic field.

Abstract: An apparatus and method for detecting defects in electrically conductive materials. A detection method and apparatus are provided for using applied magnetic fields to induce magnetic fields in the material under test, and then directly detecting changes in the induced magnetic field attributable to corrosion, cracks, flaws, or anomalies in the material under test. The invention features the use of one or more giant magnetoresistance sensors to detect directly the changes in the induced magnetic field, which changes provoke a response in the giant magnetoresistance sensors in the form of a change in resistance signal. The apparatus may be configured in various ways, including absolute field detection and differential field detection configurations, with either passive or active field compensation, and single sensor or multiple sensor arrays. A plurality of giant magnetoresistance sensors may be disposed upon a single substrate, or on multiple substrates.

Abstract: A method and an apparatus are provided for measuring the mechanical properties of ferromagnetic, elongated structures, such as cables, through the measurement of Barkhausen signals. The method comprises creating a magnetic field, that varies as a function of time or of position, and measuring the Barkhausen signals rate as a function of the magnetic field for each section of the structure to be tested. The mechanical properties are determined for each section from the Barkhausen signals relative to it. The apparatus comprises means for generating the variable magnetic field, a plurality of Barkhausen signal sensors distributed along the structure length, and means for comparing the signals relative to each section to be tested.

Abstract: A ferrous object detection circuit for use with automated document processing devices is provided for detecting and sorting documents affixed with ferrous objects such as staples and paper clips. A static magnetic field is positioned to intersect a document path. At least one inductive transducer is positioned relative to the magnetic field to detect changes in the magnetic field resulting from documents traveling along the document path. The movement of ferrous objects through the static magnetic field produces a detection signal in the inductive transducer, identifying the document as having a ferrous object.

Abstract: A helically movable system for the detection of cracks in a pipeline, capable of moving inside this pipeline, produces a magnetic flux that passes into a portion of the pipeline. Detectors measure local magnetic fields on the inner surface of the pipeline. These measurements are provided for processing and storage. The system is driven by the fluid flowing in this pipeline. Devices for the generation of flux and the measuring are arranged within at least one cylindrical housing having wheels to make this housing follow a substantially helical path inside the pipeline.

Abstract: Small metallic patches embedded in a mainly non-metallic surface may be detected and mapped by placing a wire coil at the free end of a cantilever, with a fine tip made of a ferro-magnetic material located at its center. An alternating current is passed through the coil so that when it is near a metallic patch eddy currents are induced in the patch. These produce a small magnetic moment in the patch which pulls the tip towards the surface. This movement of the tip is detected by observing a light beam that is reflected off the surface of the cantilever. By plotting the output of a photodetector, sensistive to small changes in the reflected beam's position, as a function of the tip's location over the surface, a map of the metallic patches is produced.

Abstract: A proximity switch with a magnetic field-sensitive sensor is formed of limbs of a U-shaped permanent magnet with a vertical direction of magnetization. A magnetic flux-free region, in which the sensor is fitted, is formed by three like poles. When a flat ferromagnetic triggering part is brought close to the two poles of the limbs of the U in a plane parallel to the base of the U, a switching signal which is triggered from the sensor by the cancellation of the magnetic flux-free region can be evaluated.

Abstract: A method of and apparatus for torque magnetometry in which a specimen, the magnetic moment of which it is desired to determine, is disposed on a support. A temporally varying, for example sinusoidal, magnetic field is generated in the region of the specimen so that interaction between the magnetic moment of the specimen and the magnetic field causes a torque to be exerted on the specimen. Consequently, the specimen and/or the support are deflected and typically exhibit a vibratory motion. The motion of the specimen and/or support due to the torque is measured. When the magnitude and direction of the magnetic field are known, the magnetic moment of the specimen can be determined from the results of the motion measurement. The frequency of the magnetic field can be adjusted so that the specimen and/or the support resonate. The support is typically a single silicon crystal having two orthogonal modes of vibration which have different resonant frequencies.

Abstract: A method and apparatus employs Hall probes for contactless, longitudinal and transversal homogeneity examination of a critical current density j.sub.c in a superconductor tape that is cooled to below a transition temperature T.sub.c. The cooled superconductor tape is pulled through an external, locally limited magnetic field that has a constant gradient and a fixed magnetic field axis. The magnetic field generated by a screening current induced in a region of the superconductor tape penetrated by the external magnetic field is scanned using a first Hall probe at a distance of a few tenths of millimeters to the superconductor tape. The external magnetic field outside of a field range of the induced persistent currents is measured with a second Hall probe. A compensated difference between the first and second Hall probe signals is used as a qualitative measure for a critical current density j.sub.

Abstract: A microelectric position sensor wherein an assembly of magnetic field sensitive elements assume first and second states when subjected to a magnetic field having an intensity below or above first or second predetermined values respectively. A magnet is selectively movable relative to the assembly, so that the elements are selectively subjected to the magnetic field. The magnet has focusing tongues for focusing the magnetic field at a region including substantially only one of the elements, so that the magnetic field within the region has an intensity above the second value, and the magnetic field outside the region has an intensity below the first value.

Abstract: An electromagnetic-field-focusing remote-field eddy-current probe for inspecting anomalies in a conducting plate. The probe is designed to have the electromagnetic energy released from an excitation coil penetrate through the plate twice, so that the signals received by one or more receiver units (pickup coils, magneto-resistors or SQUIDs) have passed twice through the plate wall; from one side of the plate at the excitation coil to the other side, then back to the original side at the receiver units. The probe detects flaws, with good and substantially equal sensitivity, irrespective of their depth in the plate. It can detect, from one side of a plate, flaws located on the other side of the plate, which is useful for inspecting the bottom plate of a huge tank which is sitting on the ground. The thickness of inspected plates can go up to one inch for aluminum plates and to 3/8" for ferromagnetic plates. The probe generates a periodic magnetic field.

Abstract: A magnetic sensor for detecting the presence of a magnetic sample proximate a sensing region. A magnetoresistive element is positioned in a biasing region of the sensor which is spaced apart from the sensing region. A magnetic circuit provides a magnetic field to the sensing region and the biasing region. The magnetic field biases the magnetoresistive element positioned in the biasing region. A circuit detects changes in the magnetic field in the biasing region as a function of changes in the resistance of the magnetoresistive element whereby changes in the magnetic field caused by the presence of a magnetic sample proximate the sensing region are detected.

Abstract: A circuit device for driving a SQUID magnetometric sensor. This device includes an FLL magnetometer circuit for driving the SQUID with an AC signal as a magnetometric sensor, an evaluator circuit for evaluating the SQUID characteristics, and a selector circuit for selecting a sensor function or an evaluator function. When the selection circuit selects one of the sensor and evaluator functions, only one of magnetometer and evaluator circuits is activated. Therefore, the circuit device can act alternatively as either a sensor or an evaluator.

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

Abstract: A magnetic sensor is provided with a permanent magnet structure, a magnetically sensitive component and a transparent plate through which the magnetically sensitive component can be selectively trimmed by a laser beam through the transparent plate. The magnetically sensitive component is attached to an under surface of the plate which is provided with conductive runs, conductive circuit points and conductive pads. The magnetically sensitive component is provided with solder bumps that are soldered to the conductive circuit points on the under surface of the transparent plate. The magnetically sensitive component is rigidly attached to the permanent magnet structure by an epoxy or other suitable material. This disposes the magnetically sensitive component between the transparent plate and the permanent magnet structure. The magnetically sensitive component can be calibrated by laser trimming resistors on an integrated chip through the transparent plate.

Abstract: A cryogenic apparatus for microscopy of physical properties of an object including a thin, stiff, transparent substrate or window within the outer wall of the vacuum space of a dewar and a cryogenic sensor within the vacuum space and spaced very close distances to the window. This construction allows for positioning a sample for measurement outside of the vacuum space, at room temperature or higher and for microscopy of physical properties of the sample by monitoring the output from the cryogenic sensor as it is scanned along the surface of the sample.

Abstract: The invention provides a sensing device capable of outputting a correct signal precisely corresponding to a particular position (angle) such as a protruding or recessed portion of a rotating member made of a magnetic material over the entire operating temperature range regardless of the temperature coefficient of the magnetic field sensing element. The sensing device includes: a magnet for generating a magnetic field; a rotary member of magnetic material for changing the magnetic field generated by the magnet, the rotary member being disposed at a predetermined distance apart from the magnet; a giant magnetoresistance device which changes in resistance in response to the magnetic field whose magnitude is changed by the rotary member of magnetic material; and an AC coupling circuit for performing an AC coupling process on the output of signal of the giant magnetoresistance device.