Abstract: The invention concerns the field of devices and appliances for measuring the intensity and the direction of the magnetic field emitted by a plate or a structure, such as for example a ship's hull and it particularly concerns a method for determining the magnetisation and the magnetic field radiated by a ferromagnetic plate using magnetic field sensors distributed along said plate and at known positions relative thereto.

Abstract: A high-speed corrosion-resistant rotating cylinder electrode test apparatus for monitoring of corrosion rates of metals includes an electrochemical/permeation cell body adapted to contain a fluid whose corrosive effect is to be monitored, the cell body having a base at a lower surface thereof and the base having an aperture therethrough. A counter electrode/reference electrode complex is mounted within the cell. The system further includes a cylindrical working electrode and a rotatable system shaft having a lower portion below the base and extending therefrom through the aperture into the cell body, the working electrode being mounted on an upper portion of the system shaft to be positioned within the cell body for rotation. A cone-shaped cap formed from a corrosion-resistant polymeric material is positioned above the working electrode and extends upwardly a relatively short distance into the fluid to reduce vortex phenomena. A motor is connectable to the system shaft for rotating the system shaft.

Abstract: An unvulcanized raw rubber is provided, to which magnetic ferrite powder is added. A resulting mixture composed of the unvulcanized raw rubber and magnetic ferrite powder is passed through a rolling machine or an extruding machine such that the mixture is formed into a sheet blank that contains the magnetic ferrite powder aligned regularly in a particular orientation. Alternatively, the resulting mixture may be first passed through an extruding machine and then through a rolling machine. The sheet blank is then stamped across a planar direction such that a ring-like sheet is formed. The ring-like sheet, along with a supplemental ring, is placed inside a metal mold, where the ring-like sheet and supplemental ring are compressed in an axial direction, while applying heat thereto, so that the ring-like sheet is vulcanized and joined to the supplemental ring. Finally, the vulcanized ring-like sheet is magnetized so that S poles and N poles appear alternately around its circumference.

Abstract: An encoder made of rubber material in which the S-poles and the N-poles are alternately magnetized in circumference, whose magnetic force is strong and whose variation of the magnetic force is slight in the circumferential direction when it is magnetized. And a manufacturing method thereof. A ring shaped rubber compound made of unvulcanized rubber material into which magnetic powders are mixed and having thickness t1 of 1.5 times to 5 times thicker than the thickness t of the encoder made of rubber material as the final product is vulcanizingly molded. In this vulcanizingly molding process, the thickness of ring shaped rubber compound is reduced to one fifth (⅕) to two thirds (⅔) by compressing the ring shaped rubber compound in the axial direction under high temperature. And then, vulcanizingly molded one is magnetized S-poles and N-poles alternately in circumference.

Abstract: A memory module socket having a transposed pinout allowing the socket to be mounted on the second, or reverse, surface of a motherboard and connected to circuit traces configured for mounting of a memory socket on the first, or processor, surface of the motherboard to correctly accommodate signals between the motherboard and the memory module. A motherboard having at least one memory socket mounted on the second, opposing surface enhancing access to the memory socket or sockets for insertion and removal of memory modules for testing the memory modules in multimotherboard test systems. A method of converting a conventional motherboard and memory socket assembly for such testing.

Abstract: A technique for reducing acoustic noise emitted by a magnetic resonance imaging system includes providing energy dampening elements in the scanner, such as within the gradient coil assembly, between the gradient coil assembly and the primary magnet, and around the outer and inner peripheries of the primary magnet and RF coil. The elements may be formed to conform to the structures of the scanner, and may be tile-like elements which can be fitted to new scanners and retrofitted to existing equipment.

Abstract: An evolutionary program is used to calibrate a ship degaussing system with respect to one or more parameters relating to the ship's magnetic signature. Pursuant to the computer program, a mathematical vector lists electrical current values which correlate with the degaussing coils. A genetic algorithm is executed through a certain number of generational iterations in order to find a solution vector which will optimize the parameter(s). Every generational population has the same number of vectors. An initial population is randomly engendered, and successive populations are engendered through a biasedly random process wherein each vector has associated therewith a parenthood selection probability which is commensurate with its fitness. The offspring vectors are given birth to via crossover hybridization of parent vectors, and a small fraction of offspring vectors are randomly modified via mutation. The present invention is suitable for accomplishing optimization (e.g.

Abstract: A superconducting magnet assembly comprises a superconducting magnet (1) which, under working conditions, generates a magnetic field in a working volume, the superconducting magnet being connected in parallel with a superconducting switch (3), the switch and magnet being adapted to be connected in parallel to a power source (4) whereby under working conditions with the switch (3) open, the magnet (1) can be energised by the power source to generate a desired magnetic field in the working volume following which the switch (3) is closed, characterised in that the assembly further comprises a resistor (5) connected in series with the switch (3), the resistor (5) and switch (3) being connected in parallel to each of the magnet (1) and the power source (4).

Abstract: An apparatus for measuring the inductance of a wire-loop with noise-cancellation, auto-calibration and wireless communication features, or detector circuit. The apparatus measures the effective change in inductance induced in a wire-loop as a vehicle passes over the wire-loop to produce an inductive signature corresponding to a vehicle.

Abstract: Technical field: analysis of mixtures, predominantly of biologic origin, for the contents of biological and/or chemical components, and analysis of mixtures, which parameters determine vital functions of biologic objects.

Abstract: An angle sensor can be re-mounted properly. This angle sensor includes a detecting sensor that detects a turned volume of a rotary shaft, and a governor connected to the detecting sensor. The governor includes a comparator that compares a turned angle data obtained before the angle sensor is detached with a turned angle data obtained after the angle sensor is re-mounted. This angle sensor produces a remarkable advantage when it is used in cars which are governed using the data about a turned volume of the steering wheel or the shaft.

Abstract: A magnetic sensing element detects the presence of magnetic particles in a binding assay. The magnetic sensing element has at least one planar layer of electrically conductive ferromagnetic material that has an initial state in which the material has a circular magnetic moment within the plane of the layer. The magnetic sensing element has molecules of a first specific binding member attached to it. The device also includes a fluid test medium to which the magnetic sensing element is exposed during the course of a binding assay. The fluid test medium includes magnetizable particles that become immobilized during the assay in relation to the amount of analyte in the test medium.

Abstract: A memory device tester capable of testing for proper operation of reduced power states in memory devices. The memory device tester can include a processor or a state machine, each configured to send commands to the memory device, and to compare results. An example of a memory device that can be tested by the memory device tester is a Direct Rambus Dynamic Random Access Memory (DRDRAM). The described processing systems and other circuits can test a DRDRAM for proper operation in a standby (STBY) state. When the DRDRAM is in STBY, the column decoder is shut off to conserve power, and the DRDRAM should not respond to column packets on the column control bus. The method and apparatus provide for testing that the column decoder is shut off when in STBY with no banks active, which is the recommended usage pattern for the part.

Abstract: A method and apparatus are provided for detecting the degradation of a permanent magnet in a motor of an electric or hybrid electric vehicle. A voltage monitor (102) is directly coupled to a traction motor (38) and/or generator motor (30) to detect a permanent magnet induced voltage within the motor at a predetermined speed and no load condition (300). A controller (100) compares the detected permanent magnet induced voltage with an expected reference voltage that represents an expected permanent magnet induced voltage at full magnetization and the predetermined speed (302). The controller produces an indication of magnetization based on the reference voltage, the detected permanent magnet induced voltage, and the predetermined speed. The indication of magnetization is stored for future reference (306). Also, a safety indicator is produced for a user of the vehicle if the indication of magnetization is below a safety threshold.

Abstract: The invention includes an apparatus and method for determining the pass through flux of magnetic materials. The apparatus comprises one or more magnetic field sensors arranged in such a way as to collect field strength data in any or all the x, y, z directions. The apparatus also comprises a magnet field source or arrangement of magnet field sources which are placed beneath the material being characterized and includes a mechanism whereby the magnetic material can be mapped by the movement of any one or combination of: magnetic field source or sources, sensors and magnetic material. The invented method comprises the use of various configurations of magnetic sources in order to generate a magnetic field that emulates the open-loop condition found in magnetron sputtering.

Abstract: A speed sensor for sensing a rotating speed of a wheel is provided. The speed sensor includes a thermoplastic sensor body. A mounting ring is connected to the sensor body. The mounting ring can include a flange portion. A plastic insert is integrally molded into the sensor body adjacent the mounting ring. An active sensor element is located in a lower end of the plastic insert, a face of the active sensor element being vertically spaced a predetermined distance from the flange portion. A pair of terminals is electrically connected to the active sensor element. The pair of terminals extends from an upper end of the plastic insert. The flange portion, when pressed onto a hub associated with the wheel, is adapted to space the active sensor element an operating distance from a tone wheel mounted to the hub.

Abstract: To precisely determine easily a disconnection failure in bonding connection of a flip coil of a magnetic sensor. A wiring pattern for connecting a +FL terminal of an X-axis sensor and a wiring pattern for connecting a +FL terminal of a Y-axis sensor are arranged on a circuit wiring board. After MOS transistors are mounted on the board, the wiring patterns are connected to each other by wiring in the MOS transistors. The MOS transistors are mounted on the circuit wiring board so that a flip coil of the X-axis sensor and a flip coil of the Y-axis sensor are connected in parallel with each other. Before the MOS transistors are mounted on the circuit wiring board, the resistance of each of the flip coils and is measured. The disconnection failure in bonding connection of the flip coils can be inspected by using such a fact that a difference between a measured value in a case of good bonding connection and that in a case of bad bonding connection is large.

Abstract: A system and method for measuring volumes and areas using electromagnetic induction techniques. A current is generated and fed into one of two coil assemblies to induce voltage into another coil assembly to provide accurate values for volume or area.

Abstract: An Fe group-based amorphous alloy ribbon having a cross section having a width of from 100 to 900 &mgr;m and a thickness of from 8 to 50 &mgr;m and a magnetic hysteresis loop which exhibits a large Barkhausen discontinuity. The amorphous alloy ribbon is suitable for preparing magnetic markers for use in an anti-theft system and an article surveillance system, and as a pulse generator. A magnetic marker formed from the amorphous alloy ribbon is also disclosed.

Abstract: A semiconductor integrated circuit includes a memory cell array, a read circuit that reads test data from the memory cell array, a parallel test control circuit, a bit organization address control circuit, and a parallel test circuit. The parallel test control circuit, in response to a wafer test flag signal, a package test flag signal, and a bank activation signal, generates a first control signal and a second control signal. The bit organization address control circuit, in response to the wafer test flag signal, the package test flag signal, the bank activation signal, and a bit organization information signal, generates a third control signal. The parallel test circuit, in response to the first and second control signals, determines whether all bits of the test data read have the same logic levels. The first, second, and third control signals determines where the test data are read from in the memory cell array.

Abstract: A method for processing biomagnetic fields generated by biocurrents resulting from activities of human brain or myocardia and its mapping apparatus are provided, which features biomagnetic measurement and its analysis, magnetic field mapping and its imaging and their waveform generation by a simple operation. Biomagnetic fields emitted from the patient are measured at a plurality of measurement positions, and a contour map of magnetic field obtained as a result of processing of these measured biomagnetic fields is imaged in the magnetic contour map display apparatus, which display apparatus includes: the process function display area indicating process function items including measurement; and the analysis data display area which displays the waveform together with a designated measurement time, the waveform being generated during measurement at least based on the measured biomagnetic fields and during the designated measurement period of time.

Abstract: A proximity sensor for determining the gap between a sensor and a metal target which is insensitive to noise, changes in temperature of the sensor and different lengths of wire by measuring the AC conductance, DC conductance and susceptance of the sensor and using the measured values with a predetermined data base to derive the desired gap distance.

Abstract: A double-resonance coil for use in NMR spectroscopy and imaging having a coil element, a first input/output terminal coupled to the coil element, and a second input/output terminal coupled to the coil element. A first resonance means is coupled between the coil element and the first input/output terminal to cause the NMR coil to resonate at a first NMR frequency, and a second resonance means is coupled between the coil element and the second input/output terminal to cause the NMR coil to resonate at a second NMR frequency substantially different than the first NMR frequency. The double resonance coil includes a first frequency-blocking means coupled to the coil element for substantially preventing the second NMR frequency from being detected at the first input/output terminal and a second frequency-blocking means coupled to the coil element for substantially preventing the first NMR frequency from being detected at the second input/output terminal.

Abstract: The present invention relates to a method of manufacturing disc drives. Before a pivot cartridge is assembled into a disc drive, impedance readings of the pivot cartridge are taken, preferably, at more than one rotational position and across a frequency range. The pivot cartridge is accepted for assembly into the disc drive only if its impedance readings compare favorably with readings taken of a good pivot cartridge. Otherwise, the pivot cartridge is rejected and the impedance readings are analyzed to provide identification of the defect in the pivot cartridge. In addition, a system and a storage device readable by a computer system for implementing the method of screening pivot cartridges and identifying causes of defects is provided.

Abstract: A DEWAR for SQUID is provided. In the DEWAR for SQUID, an amount of leak gas discharged from absorbent arranged in the upper portion higher than the liquid surface level of liquid helium is small even if the liquid surface level of the liquid helium is lowered.

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

Abstract: Obtaining fast dipole size estimation with less influence of noise by using a regional dipole model. An artificial neural network section 30 executes regional dipole size estimation using a neural network having coupling coefficients representing coupling states among as plurality of units and thresholds thereof.

Abstract: Temperature sensing through observable, temperature-dependent effects on an interrogating magnetic field is facilitating by a sensing module having, first, a signal element that interacts with the interrogation field to produce a remotely readable magnetic response; and disposed proximate to the signal element, a temperature-sensitive component. This latter component may include a modulation element having a magnetic permeability varying with temperature in the operating range and/or a bias element comprising a magnet having a Curie temperature in the operating range. The temperature-sensitive component interacts magnetically with the signal element such that the remotely readable magnetic response is indicative of a temperature in the operating range.

Abstract: The highly efficient multi-frequency voltage regulating circuit is capable of converting magnetic field energy to electrical energy for charging either a battery or an energy storage device such as a capacitor. The invention provides a magnetic field sensor circuit that measures the strength of incoming magnetic field energy with respect to a reference current. The invention also provides for a programmable magnetic field detection circuit which is used to adjust the detection level of the inductor-capacitor magnetic field converter circuit. A discharge expediter circuit is provided to improve the efficiency of the magnetic field converter circuit by discharging excess energy.

Abstract: A magnetic field sensor for a keyless access system, particularly for motor vehicles, wherein the direction of incidence of electromagnetic radiation emitted by a transmitter in the short-range field can be detected. The magnetic field sensor has at least one first and at least one second conductor loop, which are disposed substantially concentrically with one another and are substantially symmetrical with respect to the center.

Abstract: An object of the present invention is to provide a magnetic powder for magnetic recording and a magnetic recording medium wherein stability of a coercive force of each of the magnetic powder and the magnetic recording medium is improved.The magnetic powder for magnetic recording and the magnetic recording medium having the magnetic powder used therfor are characterized in that the magnetic powder is composed mainly of a plate-shaped ferrite having a crystalline anisotropy and containing an element effective for reducing a temperature coefficient of coercive force of the magnetic powder, and that a difference between a coercive force (Hc) of the magnetic powder at a room temperature and a coercive force (Hc(s)) of the magnetic powder in such a state that the magnetic powder is dispersively deposited on the surface of silica (SiO.sub.2) powder particles is 100 (Oe) or less.

Abstract: A method of manufacturing a rotation sensor can effectively prevent a sensor element from moving during a resin molding process for forming a resin portion that covers the sensor element to provide excellent waterproofness and airtightness. During a first resin injection step, an end of a bobbin of the sensor element is fixed or held in place by a slide core. Thereafter the slide core is extracted and resin is again injected in a second injection step into a vacated portion that is formed by extraction of the slide core. In the finished rotation sensor, the resin completely surrounds and encloses the bobbin, except at an exposed end of a magnetic pole piece. A metal mounting bracket is embedded in the resin at a spacing away from the bobbin. The bobbin has a positioning cavity to receive the slide core during the molding. The resin covering an upper part of the bobbin is at least four times as thick as the resin covering the coil of the sensor element.

Abstract: Analysis of an electromagnetic field in a region including an electric conductor having an arbitrary shape is efficiently and accurately performed with a computer. A value of electric potential at a predetermined portion of the electric conductor or a value of the normal component of an electric current density vector to the cross section of a predetermined portion of the electric conductor is used as an initial condition. The distribution of exciting current density vectors in the electric conductor is obtained form the initial condition so as to meet the condition of continuity of electric current. The electromagnetic field of the region is analyzed by using the obtained distribution of exciting current density vectors.

Abstract: Mechanical stresses and deformations are applied directly to cell surface receptors or molecules and measured using a system including a magnetic twisting device in combination with ferromagnetic microbeads coated with ligands for integrins or any other surface receptors. The system can be used diagnostically to characterize cells and molecules and to determine the effect of transformation and compounds, including drugs, on the cells and molecules. The system can also be used to induce cells to grow or alter production of molecules by the cells.

Abstract: An encapsulatable sensor assembly includes an external housing with internal support components for retaining an active sensor element and associated electrical circuitry in a predetermined relationship while providing a plurality of internal sequentially interconnected cavities for facilitating a flow of an encapsulating material from an encapsulating material injection port to a vented overflow to assure a complete fill of the internal cavities to restrain the internal components. The sensor assembly provides a structure for a void free encapsulation and internal leadwire stress relief concurrently with location control of the internal components while also providing a combination which is easily adaptable to automatic assembly and encapsulation techniques.

Abstract: A magnetic rotary encoder which is reduced in overall size and production cost and wherein little torsional force around an axis of a rotary shaft is applied to a bearing for the rotary shaft from a force from an object member for detection and the detection sensitivity does not fluctuate even if the rotary shaft is yielded. The rotary shaft includes a fixed shaft fixedly supported at least at one portion thereof and having an inner race of the bearing secured to an outer periphery thereof, a cylindrical member having an outer race of the bearing secured to an inner periphery thereof, and a magnetic member provided on an outer periphery of the cylindrical member and having magnetic poles formed thereon. A magnetic sensor for detecting a magnetic flux from the magnetic member is supported on the fixed shaft by means of a mounting plate, and a detecting member is mounted in sliding contact with the cylindrical member and rotates, when it is rotated, the magnetic member around the axis of the rotary shaft.

Abstract: A method for the direct visualization of surface and near surface cracks, voids, flaws, discontinuities, etc. in a material 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 either side of 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 transmitted onto the target material and is reflected through the epitaxial layer and back out of the substrate. The existing magnetization within the epitaxial film interacts with nearby magnetic fields associated with near surface flaws in the target material, such that the domain structure of the epitaxial film is altered.

Abstract: Rapid nondestructive testing of a ferromagnetic workpiece for creep damage is carried out by placing an eddy current coil adjacent to the workpiece, passing an alternating current through the coil, measuring the eddy current response as influenced by the workpiece, and comparing the current measurement to a current calibrated to known creep damage for the given ferromagnetic material. Correlations of the eddy current response to creep rate and time to failure are generated from creep rupture tests performed on specimens of the given material subjected to varying conditions of time, temperature and stress. Qualitative tests can also be performed to identify the point of greatest creep damage by passing the eddy current coil over the workpiece to find the location of the lowest eddy current response. Conventional creep damage tests can then be performed at that location if desired.

Abstract: An electronic switch of the type having two external lines, one of which is connected to one pole of an operating voltage source in series with a load and the other of which is connected with the load. The switch comprises a sensor, e.g. an oscillator, responsive to proximity of an object thereto and has an output transistor operated by the sensor with blocking and conductive states selectively controlled by the transistor in response to the oscillator. A MOS-FET power transistor is in series with the output transistor and, to reduce the voltage drop in a conducting state of the electronic switch, a self-conducting MOS-FET is used as the MOS-FET power transistor.

Abstract: A method and apparatus for monitoring the state of the surface of a moving body wherein a four-terminal eddy-current coil circuit is connected in a feedback loop of an RC resonator. The eddy-current coil circuit is placed in proximity to the monitored surface of the moving body and connected in the feedback loop of an RC resonator such that a change in the state of the surface of the moving body results in a change in the conductivity thereof, which conductivity change produces a phase displacement changing the output frequency of the RC resonator. During operation, a first data set is obtained from the coil circuit and RC resonator presenting a first runout profile of the body when the monitored state is in an initial state. The first data set is stored in a memory, and a subsequent profile is derived to obtain a second data set indicative of the operational state of the surface of the moving body.

Abstract: A magnetometer is moved along the route of a pipeline and the output of the magnetometer is observed to identify pipeline characteristics. Used with a buried pipeline the magnetometer is moved over the surface of the overlay to identify and locate girth welds, pipeline fittings and accoutrements, changes in pipeline metallurgy such as occur with large hard spots and changes in wall thickness as occur in extensive and severe corrosion. Similar functions can be performed with underwater pipelines using a magnetometer which is located in an appropriate container and trolled along the route of the pipeline by a vessel. The pipeline is formed of pipe sections which are arranged in an identifiable pattern according to their magnetic characteristics to facilitate inspection and maintenance.

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

Abstract: A toner mixture comprising ferromagnetic carrier particles and non-magnetic toner particles are caused to flow through a conduit for measuring the toner density which is the ratio of toner particles to carrier particles in the mixture. The effective inductance of an electromagnetic coil disposed in the conduit varies in accordance with toner density. The coil is designed so that the magnetic lines of force thereof are substantially confined within the conduit and are not influenced by external bodies.

Abstract: This distance measurement system employs the principle of electromagnetic induction to sense distances between an inductive transducer and an object. The inductive transducer forms a part of a signal phase network, and a means for comparing the signal of the inductive transducer to a reference signal provides linear output of the dimension between the transducer and an object. A circuit element such as a capacitor is connected in parallel with the inductive transducer to enhance the sensitivity and resolution of the measurement, to significantly reduce or eliminate error due to temperature, and to provide a high degree of output linearity relative to the distance measured.

Abstract: A phase-controlled pulse signal generator, comprising a magnetic field source born by a rotating shaft, and a Hall effect sensor submitted to the field, the sinusoidal signal delivered being processed by a phase correcting circuit controlled by the speed of the shaft, followed by a triggered pulse circuit.

Abstract: A magnetic coin element sensor for sensing, detecting and identifying coin elements and the like interposed in a magnetic field wherein the metallurgical structure of each interposed coin element causes an identifiable change in the magnetic field responsive to the metallurgical structure of the interposed coin element and uniquely indicative of the interposed coin element, the change in the magnetic field being sensed, detected and utilized to uniquely identify each of the interposed coin elements. The magnetic coin sensor is particularly useful for identifying coins deposited in a coin handling apparatus such as a vending machine, a coin telephone or the like.

Abstract: An exciter for use with a shaft speed magnetic pickup includes a strip of flexible, stretchable, sheet material having a plurality of magnetic elements attached to it that are uniformly spaced along the strip, enabling the magnetic elements to be attached to the exterior of various diameter rotatable shafts by stretching and fastening the strip about the circumference of the shaft close to the magnetic pickup which generates an electrical pulse signal whenever a magnetic element passes by it. The pulse signal is processed to produce a readout of shaft speed. Two magnetic pickups circumferentially spaced about the shaft closer than the circumferential spacing of the magnetic elements are used to provide signals that can be processed to indicate shaft direction of rotation as well as shaft speed.

Abstract: A detector for measuring relative movement and/or displacement between two relatively movable members comprises a plurality of regularly shaped elements of magnetic material e.g. steel balls, periodically spaced along a path which is preferably linear, and a transducer which is movable relative to the elements in a direction parallel to said path. The transducer comprises a transmitter coil, or series of coils, disposed for producing a magnetic field parallel to said path, and at least two pick-up coils encasing the path and displaced along it. The pick-up coils sense the variation in the magnetic field due to the presence of the elements, so that the relative spacing of the pickup coils and the elements enable, on the production of the magnetic field, the generation by the pick-up coils of output signals denoting the relative movement between the members.