Abstract: An apparatus and method for measuring the gap, tram, deflection, and wear of rotating grinding plates wherein inductive sensors are mounted in a recessed manner inset from the surface of a first grinding plate and located opposite recessed non-wear surfaces of a second grinding plate, thereby providing data by which plate gap and plate wear may be derived. A plurality of such sensors provide data by which plate tram and/or deflection may be deduced.

Abstract: A method and an apparatus for the detection of slag co-flowing within a sam of molten steel being poured from metallurgical vessel, more particularly during continuous casting, makes it possible to detect even a small quantity of slag in the emerging flow of molten metal without requiring the removal of the shielding for the pouring stream, or without interfering with the pouring, by measuring changes in the electrical conductivity of the pouring system by means of electromagnetic fields. To this end, one or more transmitter coils and receiver coils are mounted fixedly around the pouring stream. The transmitter coils are fed with a current containing several frequencies, and the magnitude and phase position of the voltage induced in the receiver coils are evaluated frequency-selectively so as to increase the sensitivity, the measuring transducer being operated in a bridge circuit.

Abstract: A method and apparatus for use with a measuring and/or control device having at least one sensor based on eddy current induction and movable over a test piece and supplied with at least two carrier frequency signals. A determination is made on one of the carrier frequency signals with respect to those signal changes obtained at the transistion from measuring against the test piece to measuring against essentially empty space. When such signal changes occur an edge signal is generated which indicates that the measuring and/or control device has passed over an edge of the test piece.

Abstract: A sensor including an eddy current loop and an ultrasonic transducer transmitting along a common axis is placed against a second surface of a graphite/epoxy composite structure whose first surface has been formed over the surface of a steel model. The eddy current coil can produce a signal measuring the separation between the sensor and the surface of the steel model, and the ultrasonic transduer can produce a signal representing the thickness of the graphite/epoxy composite panel. The distance and thickness signals are passed to electrical circuitry that computes their difference and displays the calibrated result as a measure of the gap between the steel model and the graphite/epoxy tool.

Abstract: The invention concerns processes for immunizing nautical vessels against the disturbances that they cause to the magnetic field of the earth, consisting in supplying immunization loops of such a vessel with a set of alternating currents producing inside the volume of the vessel a homogeneous and alternating inductor field, isolating the alternating signal issuing from the alternating field at the measuring base and calculating the induced magnetization, wherein it allows to separate the induced magnetization from the permanent magnetization in the magnetic signature of a vessel while reducing the duration of measuring time required.

Abstract: Method and apparatus for monitoring a rod mill and flexible wire drawn and annealed from a stiff coil of rod in the rod mill are disclosed. The fault signals provided by an eddy-current tester are counted on a per unit time basis in order to permit the detection of rod mill problems before serious deterioration of the mill occurs. This is accomplished by direct observation of an increasing rate of fault signal occurrence. A totalized fault signal count is also provided to aid in detecting low quality wire. This is accomplished by direct observation of uniformly high levels of fault signals. A control function is disclosed whereby the rod mill is shutdown in the presence of a high rate of increase in fault signal occurrences. A "change coil" message may be sent upon detecting uniformly high levels of faults. Fault signals are stored and identified for purposes of traceability.

Abstract: A method and an apparatus for detecting a defect of a magnetic tape which is loaded in a dictating machine for recording and reproducing dictations. In the event of initialization, the tape is automatically transported in a fast forward mode for a predetermined period of time and, then, a counter is loaded with an initial value. Thereafter, the tape is rewound while, at the same time, the counter counts reel rotation detection pulses. The tape is decided to be defective when the count of the counter at beginning of tape does not lie in a predetermined range, and free from defects when the count lies in the predetermined range. In an operation mode after the initialization, presence/absence of the pulses is detected.

Abstract: A method for coupling liquid crystals and a magnetic field to monitor changes in local magnetic properties (e.g., direction of magnetization) is provided. A magneto-optical sensor is used to detect and observe inhomogenieties, impurity phases, of a high energy magnet by monitoring the response of liquid crystals to a magnetic and/or electric field applied perpendicular or antiparallel to the magnetic field supplied by the magnet. The intensity of field necessary to cause a rotation of the liquid crystals in the direction of the applied field, and hence a modification of the optical properties of the liquid crystals, can be used as a rapid, inexpensive quality control test for batch magnet fabrication. The method can be applied to both thin films and bulk specimens. The magnetically weak spots of the sample can be mapped out by noting the appearance of dark and light regions as the liquid crystals are rotated into positions which obscure the illuminating light.

Abstract: A method for determining force characteristic of a device for magnetically holding workpieces placed on a top plate (3) of the device, wherein a workpiece (1) cooperating with a source of magnetic field of the device is connected to a force pick-up (2) and is caused to move along the top plate (3), along a test line (4). The source of magnetic field remains permanently energized during the tests, the workpiece (1) is placed in parallel with the top plate (3) with a clearance which depends on sensitivity of the force pick-up (2), and is caused to move along the test line (4) continually while maintaining the amount of the clearance substantially unchanged.

Abstract: A coil assembly including primary coils disposed at predetermined locations axially spaced from one another and secondary coils provided in association with these primary coils is fixed at one end of a fluid powered cyliner. A piston rod is slidably disposed through a space in the primary and secondary coils. Rings made of magnetic substance are provided on the piston rod with a predetermined axial interval therebetween. Each of the primary coils is excited with one of reference AC signals which are out of phase with one another and an output signal which is electrically phase-shifted in accordance with the position of the piston rod is obtained as a sum of output signals from the secondary coils. Piston rod position data is obtained by measuring the amount of the phase-shifting and is utilized for positioning control of the cylinder.

Abstract: A method and apparatus for the determination of thickness of plastic materials, as well as of bonding and coating materials, by high frequency electric and magnetic alternating fields. The method enables a simple test of components, as well as of coatings and bondings, even if the plastic parts to be tested or the coatings or bondings to be tested are not yet completely cured and the surfaces to be tested are located, so as to be concealed or are accessible only with difficulty. The method and apparatus consists in that electrically conductive or ferromagnetic particles are added to the materials to be measured and subsequently the electrical conductivity or magnetic permeability is measured at the completed or coated test specimen by high-frequency electrical and magnetic alternating fields, whose progression in space and time is adapted to the measuring task.

Abstract: A method and apparatus for determining the extent of axially extending defects in ferromagnetic elements, such as tubing comprising a continuous string for use in an oil or gas well is disclosed. The tubing trip tool detects axial defects, such as sucker rod wear during removal of the tubing from the well. A saturating magnetic field and a fluctuating magnetic field are applied to the tubing and the magnitude of the induced fields and the changes are measured to quantify defects in the tubing.

Abstract: A magnetic detector for detecting the magnetic field of a magnetic field generating substance including an even number of saturable coils aligned in a straight line with the distance between adjacent ones larger than the width of the magnetic field generating substance. The saturable coils are separated into at least two pairs, and a high frequency oscillator is provided to supply a high frequency voltage through a resistor circuit to each pair of the saturable coils. A rectifying voltages circuit is arranged across the resistors in a differential manner as an output. When the magnetic field generating substance is displaced over an interval wider than the width thereof relative to the saturable coils, the magnetic detector generates a linear output voltage.

Abstract: A torque sensor comprising a first shaft having a fore end portion which is constructed such that a displacement of torsion thereof occurs; a second shaft connected to the first shaft through the fore end portion; a plurality of first magnetic segments each having a N-pole as a fixed magnetic pole and second magnetic segments each having a S-pole as a fixed magnetic pole; a plurality of first magnetism pickup path members and second magnetism pickup path members corresponding in number to the N-pole of the first magnetic segments and the S-pole of the second magnetic segments, respectively; and a magnetism detecting element provided in the first shaft so that it does not contact with the first shaft and adapted for detecting change in magnetic flux passsing through the first and second magnetism pickup path members.

Abstract: A feeder for supplying sheetlike items such as envelopes or the like to a processing machine such as an office printer. The feeder may employ a pickup such as a coil for detecting a change in magnetic field to thereby detect operation of an intake device in the processing machine. The feeder may pass an item downstream into the processing machine in response to such detection. The feeder may be arranged to move each item into a ready position and then advance each item downstream from the ready position while permitting realignment of the item by the processing machine.

Abstract: A noncontact ultrasonic transducer for studying the acoustic properties of a metal workpiece includes a generally planar magnetizing coil positioned above the surface of the workpiece, and a generally planar eddy current coil between the magnetizing coil and the workpiece. When a large current is passed through the magnetizing coil, a large magnetic field is applied to the near-surface regions of the workpiece. The eddy current coil can then be operated as a transmitter by passing an alternating current therethrough to excite ultrasonic waves in the surface of the workpiece, or operated as a passive receiver to sense ultrasonic waves in the surface by measuring the output signal. The geometries of the two coils can be varied widely to be effective for different types of ultrasonic waves. The coils are preferably packaged in a housing which does not interfere with their operation, but protects them from a variety of adverse environmental conditions.

Abstract: A metal detector is proposed, in which field coils and receiving coils are arranged on either side of a zone to be monitored. In order to bring about a more uniform sensitivity distribution within the zone to be monitored, alternately the field coil on one side and the field coil on the other side is excited for radiating a magnetic field.

Abstract: A method and apparatus for measuring the flying height of a slider supporting a magnetic transducer in-situ in a direct manner in an operational magnetic disk storage system. The method and apparatus produce relative motion between the magnetic transducer and a magnetic recording medium at a first velocity so that the resulting air bearing positions the magnetic transducer slider at a first flying height from the magnetic medium. A single signal of constant periodicity is written over a predetermined area of the recording medium by the magnetic transducer, and a readback signal is sensed from the predetermined area of the recording medium to produce a first signal. The flying height of the magnetic transducer slider is lowered to substantially zero, and a readback signal is sensed at the lowered flying height to produce a second signal. The first flying height is then calculated as the ratio, expressed in decibels, of the first and second signals times the wavelength divided by a constant.

Abstract: A process for determining the arrangement of the layered charges in a blast furnace prior to smelting. Positioned in the layered charges in the blast furnace are a plurality of upright tubes in each of which an eddy current probe is moved up and down. The layered charges are composed of alternate layers of coke and sintered iron ore. A first set of data indicating the position of the probe is obtained through an encoder, a position counter and a recorder. A second set of data indicating the content of the sintered iron ores in the charges at any level is obtained through an eddy current tester and the recorder due to the fact the sintered iron ores and the cokes are of different magnetic permeabilities. By contrasting the first set of data with the second set of data, the distribution of the sintered iron ores in the charges is detected.

Abstract: Apparatus for electromagnetically testing pipeline walls of steel or the like ferromagnetic material which is equipped, for example with a magnetizing coil for leakage-flux measurements, can be extended for ultrasonic measurement which is inductively excited and inductively measured with regard to the travel time as far as a reflecting surface and back, in the disposed in one or more of the pole regions there is a high-frequency current coil for the transmission and/or reception of steep-edged waves which are inductively coupled at the wall of the pipeline. The associated method starts from a stationary magnetic field in which high-frequency current pulses are produced in order to initiate vibrations in the pipe wall through induced currents. The travel time of these vibrations to a reflecting point and back can be measured in order to obtain an indication regarding the intact thickness of the pipe wall.

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

Abstract: A fuel channel flatness measuring system. A stationary measuring unit which allows measuring of two sides of fuel channels without detaching the fuel channel from the crane send warp and axial position electronic signals to conditioning electronics which amplify and digitize the signals for computer use. A computer analysis unit receives the signals and processes and corrolates them to generate a contour profile of the entire length of the measured fuel channel. Fixed and spring loaded rollers mounted on the measuring unit and in rolling contact with the fuel channel guide the fuel channel and allow the movement caused by warp which results in the generated signals.

Abstract: A magnetizing device includes a two-pole electromagnet with four rollers mounted in pairs on the poles of the electromagnet and interacts with a respective guide. These guides are made as rings. The rollers are mounted on the poles by means of half-axles which are secured on each roller with a displacement in relation to the rotation axle of the roller.

Abstract: An eddy current probe is supported against the force of gravity with an air earing while being urged horizontally toward the specimen being examined by a spring and displaced horizontally against the force of the spring pneumatically. The pneumatic displacement is accomplished by flowing air between a plenum chamber fixed with respect to the probe and the surface of the specimen. In this way, the surface of the specimen can be examined without making mechanical contact therewith while precisely controlling the distance at which the probe stands-off from the surface of the specimen.

Abstract: A device for detecting axial movement of a rotating member, for example a compressor rotor of a gas turbine engine, comprises a conducting wire spaced radially from the rotating member, and a magnet carried by the rotating member passes in proximity to the conducting wire when the rotating member is rotating. The conducting wire has a first limb a second limb and a third limb extending with axial and circumferential components, the first and third limbs extending in the circumferentially opposite direction to the second limb to increase resolution between pulsed e.m.f.'s produced when the magnet crosses the limbs. The first, second and third limbs are each formed from a pair of parallel connected bars to produce positive and negative pulsed e.m.f.'s which form zero crossing points which are more easily detected. This enables operation at greater radial clearance or lower rotating speeds.

Abstract: A device for transmission of signals between two units which are movable relative to each other without having to use rotating slip rings or the like. The signal transmitting conductors are disposed close to a point on the center axis of a rotating holder for the signal source. This results in minimum fatigue of the conductors, which in turn permits a long life of the conductors. The signal source is journalled in the holder and can be prevented from rotating around its center axis. The device can also be used to transmit a medium such as a coolant between two units.

Abstract: A method and apparatus for detecting the presence of magnetic ink within a package without opening the package or altering its contents. The method and apparatus detects items marked with magnetic ink, such as bank checks, in an unopened package independently of the item's location within the package and despite the presence of such magnetic clutter as staples and paper clips. The apparatus and method is designed to eliminate magnetic noise from the equipment itself and from the environment.

Abstract: The present invention relates to an improved position monitoring system for use in monitoring the positional relationship of two members mounted for relative movement with respect to each other. In such apparatus, a pair of magnetic fields are juxtaposed to each other such that they have opposite polarity and are of such a field strength that they provide for a generally linear variation in field strength extending over an elongated path which traverses the abutment of said fields. In a preferred embodiment, such a system is employed as an integral part of an electromagnetic actuator wherein the magnetic fields interact with the electromagnetic fields of a suitably positioned field coil. The monitoring is used to provide closed loop control of the positional relationship between the two members.

Abstract: The vertical and lateral displacement of sections of fluid transmission pipelines due to earth subsidence or heaving is determined using vertical and horizontal arrays of magnetometer sensors located spaced apart on a boom or support member for providing multiple readings of the earth's magnetic field intensity and the anomaly caused by the presence of the pipeline. True position of the sensors may be measured using stadia techniques or electromagnetic radiation signals transmitted from a reference point. The sensor array may be mounted on a landbased vehicle or suspended from a rotary wing aircraft to provide access to remote regions which may not be accessible to conventional equipment and techniques.

Abstract: A measurement system for remotely measuring a parameter and relative distance having a parameter sensor providing signals to control the pulse repetition rate of a pulse generator, the pulses from the pulse generator in turn controlling a switch to alternately connect and disconnect an energy storage device to the input of a sonic waveguide device. The output signals at the outputs of the sonic waveguide device control a driving device which provides a representation of these output signals on a transmission line arrangement.

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: A target adapted for use in a magnetomechanical transducer system is activated by an ac magnetic field and a variable dc bias field to produce a resonant frequency which corresponds to the effective strength of the dc bias field. The target includes an elongated ductile strip of magnetostrictive ferromagnetic material enclosed in a nonmagnetic container in a manner to allow the strip to vibrate freely. The strip has a magnetomechanical coupling factor, k greater than O, where K=zero.sqroot.(1-fr.sup.2 /fa.sup.2), fr and fa being the resonant and antiresonant frequencies, respectfully. The system is economical to construct and affords accurate and efficient measurement of pressure via displacements and angles of pressure sensitive devices at locations proximate to or remote from the signal source (target).

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

Abstract: A tubing trip tool for use in determining the extent of defects in tubular sections of a continuous tubing string used in subterranean oil and gas wells is disclosed. The tubing trip tool is mounted on a surface rig surrounding the tubing string and defects are magnetically detected during tubing removal from the well bore. The tool comprises a segmented expandable detector head containing elements for measuring average wall thickness and local and axially extending defects. The expandable head is spring loaded and pneumatically actuated. Coupling detectors are located on the ends of the head to count tubing sections and to detect the presence of obstructions on the tubing to prevent damage to the detector head.

Abstract: A combination of magnetics and a special geometric environment is employed to distinguish whether an instrument is positioned within a pipe formed of magnetizable or non-magnetizable material, and is the basis, in part, for a method and an apparatus used in controlling picture taking at the bottom of a well bore. A coil is energized repetitively in a circuit in which the voltage across the coil, or the current that flows through the coil, can be measured. Whether the coil is in a magnetic or non-magnetic environment is determined by the magnitude of the change in coil voltage or current.

Abstract: A magnetic sensor system for spindle orientation in which a magnetic body is attached to a rotating spindle and a magnetic signal from the magnetic body is detected by a sensing unit arranged on a mechanically stationary member to detect the rotational position of the spindle. A pair of wedge-shaped, annular fastening elements are fitted onto the circumferential surface of the spindle in such a manner that tapered portions thereof oppose each other, thereby rigidly securing an accommodating ring and a cover body together on the spindle.

Abstract: A tubing trip tool for use in determining the extent of defects in tubular elements comprising a continuous string used in a subterranean oil or gas well during removal of the string from the well is disclosed. Local defects and axially extending defects, as well as the average wall thickness of the tubular elements, are measured. The position of the defects is determined by measuring the variable velocity of the tubular elements as they are removed from the well. A noncontact velocity detector comprises detector elements generating a first signal dependent upon an applied magnetic field and the velocity of the tubular elements. The first signal is compared to a signal dependent only upon the magnetic field generated in a second element. A pickup coil and Hall effect probes can be used.

Abstract: A torque sensor for electrically detecting torque, such as the torque of an automobile engine, wherein a strain disk is provided in the path of torque transmission and the torque is magnetically detected in terms of the magnetostriction generated in the strain disk. The torque sensor comprises a magnetic rotating disk and a magnetic sensor disposed in the vicinity of and opposed to the strain disk. The magnetic sensor comprises a detection coil and an excitation coil oriented perpendicularly to each other with the excitation coil ordinarily being disposed outside of the detection coil. Supplying alternating current to the excitation coil causes an alternating field to be produced within the strain disk and the configuration of this alternating magnetic field is varied by the anisotropy of the strain caused within the strain disk by the transmitted torque.

Abstract: A method for testing electrostatic developer toners which comprises applying the toner to a stationary non-magnetic sleeve (4), moving the toner along the surface of the sleeve by an array of field lines generally normal to the surface produced by a multiple magnetic roll (1) rotating within the sleeve and determining the characteristics of the toner from the pattern (15) of the spread toner by reference to a calibrated scale (9) and a stop line (5) on the surface of the sleeve.

Abstract: A measuring device includes means for converting a physical quantity to be measured into a corresponding magnetic field. A magnetooptic element is aligned with a polarizer which passes incident light in one plane only. The part of the magnetooptic element which intercepts the transmitted magnetic field rotates the throughgoing light and the position of rotation is indicated on an optical indicator.

Abstract: Elongated ferromagnetic parts of cylindrical or polygonal cross-sectional outline are tested while rotating about their axes and while advancing longitudinally along a cushion of dry pulverulent magnetic material which is supplied by one or more pneumatic conduits into the range of one pole of a first U-shaped electromagnet whose poles extend in the longitudinal direction of but do not contact the parts. The electromagnet establishes a stray magnetic flux in the region of each defect on the ferromagnetic part which is being tested and such flux or fluxes attract pulverulent material which thereby pinpoints the locations of defects. A second electromagnet is placed next to the one pole of the first electromagnet and its poles are spaced apart from each other as considered in the longitudinal direction of the tested part.

Abstract: An electromagnetic communications and switching system provides for line-of-sight remote selection and actuation of a wide variety of apparatus. The system has a plurality of radiating antennas having independent components defining a reference coordinate frame. A transmitter is provided for applying electrical signals to the antennas which generate a plurality of radio frequency electromagnetic fields. The signals are multiplexed so that the electromagnetic fields are distinguishable from one another. An array of control positions is provided that is fixed with respect to the reference coordinate frame. A plurality of receiving antennas are provided which are adapted for mounting on the head of an operator. The receiving antennas are provided with independent components for detecting and measuring the components of the electromagnetic fields. A sight couples the eyes of the operator and the array of control positions.

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

Abstract: The contactless angular displacement and/or torque pickup is characterized in that it comprises two electrically insulating coaxial disks (7a, 7b) that can turn in relation to one another by an angle to be detected and that carry on their opposing faces conductive plane coils (8) in the shape of spirally wound sectors coiled alternately in both directions and whose mutual induction varies as a function of the relative angular position of the detection disks (7a, 7b). Also included is a rotary transformer (6a, 6b) to supply one of the detection disks (7a, 7b), a circuit (18) for supplying the primary (11a) of the rotary transformer and a circuit (17, 18) for processing the signal (S) collected on one of the detection disks (7a, 7b).

Abstract: Methods and apparatus for sensing, switching and modulating relying upon apparent resonant properties of thin conductive materials are provided in accordance with the teachings of the present invention. According to the present invention, an output of an oscillating circuit is selectively varied as a function of the relationship between a coil within the oscillating circuit, a thin conductive member and the apparent resonant condition of the thin conductive member to achieve appropriate sensing, switching and modulating conditions.

Abstract: A system for measuring the values of a parameter of a sheet of material is provided. The system includes a head system with sensors mounted therein and a distance correction system to correct the measured parameter for variations in the distance between parts of the head system.

Abstract: A method and apparatus is provided to embed paper drain material in water-laden soil by means of a mandrel driven into the soil by power means. The paper drain material is intermittently treated with a substance detectable by a signal emitted electronic sensing means secured to the lower end of the mandrel. When the paper drain is believed to be in place, the mandrel is withdrawn. During mandrel withdrawal, as each sensing means passes by each detectable substance, the signal from the sensing means is modulated, thereby indicating that the paper drain is embedded in place and the mandrel has disengaged from the paper drain. If the paper drain adheres to the mandrel and is being withdrawn with the mandrel, no modulated signal will be generated, thereby indicating that the paper drain is not properly anchored in the soil.

Abstract: A current location updating display for indicating the current location of moving members such as an automobile while updating from time to time based on output from a magnetic azimuth sensor adapted to detect the azimuth of terrestrial magnetism. Output signals from the magnetic azimuth sensor are stored in a data memory after A/D conversion and correction, and a predetermined amount of data read out from the data memory is subject to the averaging processing. With this, plural angle information (sin .theta. and cos .theta.) signals or plural angle (.theta.) signals are averaged out including a signal corresponding to disturbance magnetism. Thus average data signals are integrated by an integrator and then sent to a display portion. Through the averaging processing an azimuthal error is restrained as small as possible, so that the current location or running path of the moving member may be indicated correctly.

Abstract: To determine the relative positions of two bodies, an alternating current is passed through a conductive path in the first body, establishing an alternating magnetic field around the body, the amplitude of the field decreasing in inverse proportion to the distance from the conductive path. Coil pairs are supported on a second body so as to essentially surround the first body, the coils being used to produce voltages proportional to the intensity of the magnetic field, thereby providing differential distance information. The voltage differences of the coils can be used for establishing the shape of the first body or for positioning the second body to a coaxial location of the coil pairs with respect to the first body. The determination is largely free from interference.

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