Abstract: A cancellation circuit provides active electromagnetic shielding for canceling inductive noise in electrical circuits caused by electromagnetic flux. The cancellation circuit includes amplitude-adjustment and phase-adjustment circuits for adjusting the amplitude and phase of electrical signals, and a combining circuit for combining electrical signals such that the effects of electromagnetic induction cancel. An electromagnetic pickup is provided with a cancellation circuit for canceling its response to electromagnetic flux. An electromagnetic drive coil is provided with a cancellation circuit for canceling electromagnetic flux in a predetermined region of space, and a compensation circuit compensates for frequency-dependent phase and amplitude variations in electrical pickup signals and transmitted electromagnetic flux. The cancellation and compensation circuits may be combined to provide a device that can simultaneously transmit and receive electromagnetic radiation.

Abstract: A process for determining a thickness of a layer of electrically conductive material, any measurement errors are converted into dimensionless norm values with the aid of a normalization process. In this conversion, measurement errors, for example due to temperature drift and different electrical and magnetic properties of the base material of the carrying body can be largely eliminated. These norm values are converted into layer thickness values with the aid of a calibration curve.

Abstract: An instrument and method for providing accurate and reproducible measurement of absolute properties of a material under test without using conductivity or crack calibration standards. The instrument has a sensor designed to minimize unmodeled parasitic effects. To accomplish this, the sensor has one or more of the following features: dummy secondary elements located at the ends of a primary winding meandering, setting back of the sensing element from a connecting portion of the primary winding, or various grouping of secondary elements. The sensing elements of the sensor can be connected individually or in differential mode to gather absolute or differential sensitivity measurements. In addition, the instrumentation is configured such that a significant portion of the instrumentation electronics is placed as close to the sensor head to provide independently controllable amplification of the measurement signals therein reducing noise and other non-modeled effects.

Abstract: A method and apparatus for calibrating a glide head and detector system performs a pre-screening to ensure the quality of the glide head and the piezoelectric sensor in the detection system. The glide head and the piezoelectric sensor detect a signal when the glide head makes contact with the disk, such as a magnetic recording disk. Calibration of the detection system utilizes a specially made bump disk that has asperities of desired height and size that protrude out of a flat disk surface. The glide head is flown over the bump disk, and by gradually reducing the disk spinning velocity, the head is brought closer to the disk and eventually into contact with the asperity. The onset of contact, as detected by the piezoelectric sensor, defines a disk spinning velocity for the head to fly at the desired height.

Abstract: A method of calibrating a three-axis magnetometer is provided. In accordance with the method, calibration is effected by first establishing a three-axis magnetic field simulator having a center position portion. Suitable measures are taken to substantially compensate for the earth's magnetic field at least at that center position portion. A three-axis magnetometer is then disposed in the magnetic field simulator and successively actuated in predetermined manner to generate a set of measured parameter values. The measured parameter values are normalized using a predetermined standard output factor, and a square pre-calibration matrix C is generated from the normalized measured parameter values. An inverse matrix operation is thereafter performed upon the pre-calibration matrix C to generate a square calibration matrix D having a plurality of coefficients respectively indicative of orthonormal compensation coefficients.

Abstract: A proximity detector that employs a Hall-effect flux sensor disposed between the like poles of two magnets. The opposing fields of the magnets define a null flux field at a sensing plane of the Hall-effect sensor. A proximate ferrous object will deflect the null point and will therefore apply flux to the sensor. The sensor generates a signal indicative of the presence or absence of the ferrous object. In manufacturing a preferred spatial position of the null point with respect to the Hall-effect sensor is defined by adjusting the field strength of at least one of the opposed magnets.

Abstract: The contactless magneto-resistive angle sensing device (1) includes two sensor components (10,11) oriented at a fixed angle relative to each other, a controllable power supply (PW) to heat and maintain the sensor components (10,11) at different temperatures, a magnet (MG) producing a magnetic field (B) in which the sensor components are arranged and an evaluating device (12) to receive output signals (U1,U2) from the sensor components (10,11). Each sensor component (10,11) includes magneto-resistive resistors (MR) connected in a respective bridge (B1,B2) having input terminals (I1,I1';I2,I2') for supply of current and output terminals (O1,O1';O2,O2') for the output signal (U1,U2).

Abstract: An opto-electronic scale reading apparatus includes a scale 10 and a readhead 14 movable one relative to another. The readhead produces a pair of quadrature pulses which enable the generation of an incremental count corresponding to the displacement of the readhead 14 relative to a reference mark 80. The reference mark 80 is a permanent magnet mounted on the scale substrate inside a non-ferromagnetic casing 90. A pair of differential Hall sensors 62A,B within the readhead, and associated processing circuitry generate a step-change ZERO pulse when the readhead 14 and scale 10 are in a particular relative position. This relative position can be adjusted to enable corresponding adjustment of the relative phase of the quadrature pulses emitted from the readhead and the ZERO pulse, by means of a ferromagnetic adjusting screw 92.

Abstract: A method for temperature calibration of an optical magnetic field measurement array and a measurement array calibrated by the method include an optical series circuit having a first optical transmission path, a first polarizer, a Faraday sensor device, a second polarizer, and a second optical transmission path. The optical series circuit is temperature-calibrated by adjusting the polarizer angles of the two polarizers in a special way. The calibration method functions even if the intrinsic axis of the linear double refraction in the sensor device is unknown.

Abstract: A pulsed eddy current (PEC) instrument acquires PEC pulse responses from different locations on a structure being inspected. The difference between the acquired PEC pulse responses and a reference PEC response is determined to obtain time-domain difference signals having a time value and a magnitude value. The time and magnitude values are stored in memory with location information. An image display is provided that is determined from the stored magnitude values, although magnitude values for difference signals whose time values do not meet a defined time condition are filtered from the display. The time condition filters from the display known conditions such as the presence of fasteners, the presence of air-gaps between layers of the structure, and excessive PEC probe lift-off from the structure and filters the display so that only information from a particular layer or depth of the inspected structure is displayed.

Abstract: A rotational speed sensor system which uses the sensor and a sensor electronic circuit to test the air slot between the speed sensor and an encoder to determine if the air slot falls within acceptable limits.

Abstract: Inventive electrical-computational method and system for aligning a magnetic gradiometer, and for determining magnetic gradients using a magnetic gradiometer which is inventively aligned. For each correlation of a correction magnetometer's vector with a reference magnetometer's vector, three correction coefficients and an offset coefficient are evaluated, using a mathematical approximation technique (such as least-squares) upon voltage outputs for various relative orientations of magnetic fields in relation to a magnetic gradiometer. An inventive matrix formula is used for determining magnetic gradients. A correction magnetometer matrix (matrix of voltages generated by each correction vector of the correction magnetometer) is multiplied by a coefficient matrix (matrix of correction and offset coefficients).

Abstract: A method is disclosed for calibrating a position error signal (PES) to overcome the problem of an amplitude signal that varies as a non-linear function of real displacement when the read transducer is positioned to either side of a null position where the PES equals zero. The amplitude signal and resulting PES is notably nonlinear while reading servo burst information with a Magneto-Resistive (MR) head which has nonlinear magnetic characteristics. The calibration according to this method may be performed at anytime without need for real displacement information from a servo track writer or any sort of special calibration track. The method involves positioning the MR head to a plurality of nominal partial track displacements on either side of the null position, measuring an open loop gain value for a particular frequency at each of the displacements, deriving the coefficients of a 3.sup.rd order polynomial "gain" curve that best fits the data, integrating the "gain" curve using the coefficients to obtain a 4.

Abstract: A flux sensitive device for creating electrical signals from magnetic flux produced by a magnetic piece has a first member defining a surface for sliding the magnetic piece. A conductive trace and a backiron are located proximate the first member such that the conductive trace is between the first member and the backiron. The position of the conductive loop is fixed relative to the backiron and the first member. The backiron forms a magnetic flux path with the magnetic piece and the conductive trace creates an electrical signal when magnetic flux crosses the conductive trace.

Abstract: A sensor arrangement (1) comprising at least one measuring coil (2), at least one voltage source (3) for the measuring coil (2), and an evaluation unit (4) with means for detecting, processing, and evaluating measured signals. This sensor arrangement (1) is used to measure distances and thicknesses substantially independently of the material involved, without the user having to know the physicomathematical relations between the influencing quantities and the measured values. In order to evaluate the measured signals, the evaluation unit (4) of the sensor arrangement comprises a neural network (5) with an input layer, at least one hidden layer, an output layer, and connection weights for the individual layers. The connection weights are determined and stored in a learning phase by measurements taken on a plurality of different suitable learning objects with known actual values.

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 vehicle door lock apparatus utilizes Hall-effect sensors for the position of an element in a latch or locking system and, according to the invention, the Hall-effect sensor chip or the evaluating circuitry enables the generation of first control signals when the first information signal current amplitude is above an upper threshold, the generation of second control signals with a second information signal below the upper threshold is above a lower threshold and an alarm signal when the information signal is between the lower threshold and zero. In this manner defects in the Hall-effect sensor, the conductive path between the Hall-effect sensor and the evaluating circuitry and in the current supply to the Hall-effect sensor can be detected simply and economically.

Abstract: A vehicle compass system including a magnetic field sensor from which the earth's magnetic field can be detected in two channels of measurement. The sensor is coupled to a processing circuit which samples the sensor data and determines the maximum and minimum signal levels in each channel of measurement during movement of the vehicle through a 360.degree. path of travel. Based on the spans between the maximum and minimum signal levels, adjustment signals are generated for adjusting the resolution of the compass system and the maximum and minimum signal levels of subsequent sensor data so that the system's sensitivity resolution may be adjusted and accurate heading information can be calculated and displayed regardless of the strength of the earth's magnetic field.

Abstract: A thickness gauging instrument uses a flux focusing eddy current probe and two-point nonlinear calibration algorithm. The instrument is small and portable due to the simple interpretation and operational characteristics of the probe. A nonlinear interpolation scheme incorporated into the instrument enables a user to make highly accurate thickness measurements over a fairly wide calibration range from a single side of nonferromagnetic conductive metals. The instrument is very easy to use and can be calibrated quickly.

Abstract: An improved proximity detector comprising a hall effect sensor affixed to a permanent magnet, where the improvement comprises tuning the operational gradient of the magnetic field normal to the face of the detector. An apparatus and method for tuning the operational gradient of the magnetic field normal to the face of the detector is also discloses and utilizes means for generating magnetic fields parallel and perpendicular to the face of the magnetic proximity detector. The tuning apparatus changes the gradient through the application of magnetic tuning fields to the sensor magnetic, thereby changing the operational gradient axis, the operational gradient strength or both.

Abstract: A meandering winding magnetometer (MWM) includes a meandering primary winding and at least one sensing winding or coil on a membrane to be pressed against a test surface. The membrane may be supported on a flexible carrier which is translatable into a probe. Abutments in the probe press the carrier against the test surface but allow the carrier and membrane to conform to the test surface. One MWM circuit includes meandering primary and secondary windings. The return leads from the secondary winding return to connector pads in close alignment with the test array, while leads from the primary winding are spaced at least one wavelength from the array. In another MWM circuit, individual sensing loops are positioned within the meandering primary winding. The MWM circuit may be provided on an adhesive tape which may be cut to length.

Abstract: The present invention features a method and a fixture for determining the asymmetrical character of a readhead prior to its installation in a check-validation machine. Such a machine that is used to validate checks uses a stepper motor drive to convey the check past the readhead. The magnetic field produced by the coil of the stepper motor interferes with the capability of the readhead to recognize the magnetic indicia on the check. Once determined, the asymmetrical sensitivity of the readhead towards the magnetic flux allows the manufacturer to mount the readhead with its sensitive side away from the stepping motor of the validating unit. The readhead asymmetry is determined by the method of this invention by measuring an output voltage pulse of the readhead, when it is excited by magnetic pulses both forward and rear of its read gap. The excitation is provided approximately one inch from the read gap.

Abstract: A system used with a system having a carrier delay to determine the phase of a signal before the delay and to recover the signal after the delay. Two signals at different frequencies are sent through the system having a carrier delay. One signal will be the signal that contains the phase information. The other signal is a reference signal to generate a reference for the first signal.

Abstract: Alignment during installation of an octant of a tokamak fusion toroidal magnetic takes place at room temperature or at low operating temperature of the magnet. In order to identify the magnetic center of the magnet, a toroidal magnet octant is electrically powered with equal but opposite flowing current and a spatially known probe is utilized to measure the magnetic field of such a powered octant.

Abstract: A variable differential transformer system (10), both linear and rotary (L/RVDT) includes a primary coil (12) drive by a primary drive (20) having a triangle wave generator whose frequency is set by an external frequency control (R.sub.osc and C.sub.osc) which includes compensation for gain temperature error. Secondary coils (14, 16) have a common connection for balanced loading with an input stage arrangement (R7, R8, R9, R10) providing low common mode range and a way to differentiate between normal operation and coil faults detected by a fault detection network (28). Synchronous demodulation (22) extracts both magnitude and direction from the secondary coil signals. Electronic calibration (24) is shown which compensates for sensor offset and gain. Sensor offset calibration is accomplished by adding a percentage of the synchronous demodulation reference wave form to the differential secondary signal.

Abstract: A vehicle compass system having a magnetic field sensor coupled to a processing circuit which samples the sensor data and implements a calibration routine that generates compensation signals to compensate the sensor for the effects of vehicular magnetism so that accurate heading information can be displayed on a display coupled to the processing circuit. If the signal levels detected are outside of a variable threshold, then the calibration routine is run. Also provided is a circuit for receiving vehicle position information in response to which the processing circuit adjusts the signals supplied to the display in order to account for magnetic variations between the true north and magnetic north.

Abstract: A method of electromagnetically measuring the distance between adjacent tube elements in a heat exchanger. A cylindrical, high magnetic permeability ferrite slug is placed in the tube adjacent the spacing to be measured. A bobbin or annular coil type probe operated in the absolute mode is inserted into a second tube adjacent the spacing to be measured. From prior calibrations on the response of the eddy current coil, the signals from the coil, when sensing the presence of the ferrite slug, are used to determine the spacing between the tubes.

Abstract: A magnetic sensor is provided which utilizes a molded magnet with a channel formed therein. A magnetically sensitive component, such as a Hall effect element, is attached to a substrate or printed circuit board. The printed circuit board, or substrate, is provided with an opening through its thickness that is shaped to accept a post with a certain amount of clearance therebetween. This allows the printed circuit board to be moved relative to the magnet during calibration procedures and then rigidly attached in a position relative to the magnet by soldering the post to the substrate or printed circuit board. This places the magnetically sensitive component at a desirable location relative to the magnet and within the channel formed in the magnet. The post can be molded into the magnet or formed as an integral portion of the magnet.

Abstract: A low-cost, portable, magnetic ink printer calibration system including a device which directly measures magnetic flux from recorded magnetic ink characters and provides an electrical signal representative of that flux, an amplifier to convert the electrical signal into a readable signal level, and a device to provide a measure of that signal level so that the signal can be compared to one produced by a reference character and the comparison results used for printer calibration.

Abstract: A calibration and measurement system for a multi-axial device is disclosed which includes a memory for storing a set of test measurement values obtained from the multi-axial device in a substantially uniform field; and a calibration transformation generator for generating from the set of test measurement values to calibrate the multi-axial device, with the set of test measurement values lying on a multi-dimensional surface.

Abstract: Apparatus for detecting ferromagnetic debris in a fluid medium in a container includes a plug attachable to the container and having an associated magnetic field preferably produced by a permanent magnet. The plug is at least partly exposed to the fluid to capture debris in the fluid. The apparatus further includes a portable sensor for optically sensing the captured debris, with the sensor having a probe that is connectable to the plug. A method for using such apparatus is provided, and in general a method of detecting ferromagnetic particles in a fluid medium in a container includes the steps of: a) magnetically capturing particles from the fluid using a plug with the container, and b) interrogating the plug with light for captured particles using a portable probe.

Abstract: An angular position sensor is provided with a rotatable magnet and first and second ferromagnetic pole pieces. The first ends of the ferromagnetic pole pieces are disposed on opposite sides of the rotatable permanent magnet and the second ends of the ferromagnetic pole pieces are arranged in overlapping association with a magnetically sensitive component disposed therebetween. First and second ferromagnetic inserts are provided which are movable with respect gaps between the permanent magnet and the first ends of the first and second pole pieces. By changing the relative positions between the first and second inserts and their respective gaps, the gain and offset of an output signal from the magnetically sensitive component can be altered to achieve predetermined characteristics.

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

Abstract: A metal detection device is disclosed and includes a housing defining a central aperture. An induction member is mounted to the housing and surrounds the aperture for generating an output voltage in response to the presence of a metal object near the induction member. A mechanism is provided for calibrating the induction member by comparing the output voltage to a reference voltage to establish a threshold voltage which is unaffected by transient fluctuations in the output voltage. A mechanism is also provided in the housing and spaced about the aperture for selectively sensing an object passing through the aperture. The sensing mechanism generates a detection signal in response to passage of an object through the aperture only upon activation of the sensing mechanism. A mechanism activates the sensing mechanism upon generation of an inductive member output voltage above the threshold voltage. Finally, a device is provided for triggering an alarm in response to the generation of the detection signal.

Abstract: An apparatus and method are provided for calibrating a densitometer based sensor for measuring the linear density of the shot particles passing through a shot peening system to ensure that mass flow rate readings and shot velocity readings calculated therefrom are accurate. The apparatus comprises a probe having a plurality of randomly distributed particles configured to have a linear density substantially equal to the linear density of shot which the sensor should experience during operation of the shot peening system at desired parameters.

Abstract: In a two-channel magnetic metal detector having first and second mutually inductively coupled detection coils connected to first and second detection channels, respectively, the inductance of the coils is tested by applying a square wave test signal to the first detection coil and determining if the resulting output signal from the second detection channel has a magnitude falling within a range of magnitudes defined by two threshold values stored in a non-volatile memory. A microcomputer applies digital signals to a digital to analog converter to generate the square wave. The output signal from the second detection channel is repetitively sampled and digitized and the digital values are transferred to the microcomputer which includes means for comparing the digital values with the threshold values.

Abstract: A method is provided to calibrate an angular position sensor by using an electrical coil to provide a magnetic field that simulates the presence of a permanent magnet. By successively selecting currents to flow through the electrical coil and by moving the electrical coil through at least two angular positions, the gain of an output relationship between a signal from a magnetically sensitive component and the angular position of the coil can be determined. By changing the intensity of the electrical current flowing through the coil, the intensity of the magnetic field emanating from the coil can be selected. In order to achieve the appropriate null offset characteristic of the device, the electrical coil is moved until a preselected output voltage is achieved. By comparing the angular position of the coil when the output voltage is achieved to an angular position of the coil for the desired output signal characteristic, a calibration angle can be determined.

Abstract: Apparatus and methods are disclosed which provide increased sensitivity, selectivity and dynamic range for non-contact measurement of actual physical and/or kinematic properties of conducting and magnetic materials. The apparatus and methods are based upon various methods for increasing sensitivity, selectivity and dynamic range through proper construction of a magnetometer sensor and for proper selection of operating point parameters for the application.A measurement apparatus for measuring one or more MUT properties includes an electromagnetic winding structure which, when driven by an electric signal, imposes a magnetic field in the MUT and senses an electromagnetic response. An analyzer is provided for applying the electric signal to the winding structure. A property estimator is coupled to the winding structure and translates sensed electromagnetic responses into estimates of one or more preselected properties of the material.

Abstract: An angular position sensor is provided with a rotatable magnetic structure that comprises a primary magnet and a secondary magnet. The primary and secondary magnets are adjusted in position relative to each other in order to achieve an adjustability of the gain and offset characteristic of an output signal from a magnetically sensitive component disposed within the magnetic field of the magnetic structure. The primary and secondary magnets are rigidly maintained in position relative to each other and disposed for rotation about an axis of rotation. Each magnet has a magnetic axis extending though its first and second magnetic poles. The two magnetic axes rotate within parallel planes that are each perpendicular to the axis of rotation of the magnetic structure.

Abstract: An apparatus and method for monitoring the condition at or near the surface of objects is disclosed. The apparatus is a vehicle which includes a housing which is supported and translated across the object surface by three wheels. The front or first wheel is associated with an encoder and sensor which magnetically determines the physical condition of the object. The apparatus includes a starter block which includes a series of metallic wires embedded at certain depths and locations within the starter block. The vehicle passes over the starter block prior to passing over the object in order that the vehicle be recalibrated by the starter block prior to observing the physical condition of the object.

Abstract: A dual sensitivity stud sensor senses studs through both thick and thin surfaces. Studs are sensed by detecting a change in the capacitive loading of plates as they are moved along a surface and into proximity with a stud. The sensor informs the operator when the sensor has (incorrectly) been calibrated over a stud. The sensor also informs the operator if the sensor is placed against a surface either too thick or too thin for stud detection. Through use of a digital register, the sensor remains calibrated indefinitely while the sensor is powered on.

Abstract: A test device for vehicles has a wheel rotation speed sensor which is sensitive to magnetic fields. The test device, having a wheel rotation simulation device, contains a sensor stimulating magnet coil, which can be positioned in the magnetic field region of the sensor such that a magnetic field coupling is provided. A control unit, drives this magnet coil with an AC voltage at a frequency which determines the wheel rotation speed. This allows the performance of functional tests of components which are sensitive to wheel rotation speed while keeping the wheels stationary. In addition, a compact roller unit, which is preferably transportable, is provided in order to carry out actual wheel rotations in order to make it possible to test further components, such as the brake system or electronic transmission control.

Abstract: A magnetic sensor device having output characteristics with high precision and a method of manufacturing the same. A thick film resistor is trimmed while a magnetic field is applied to a circuit board at a predetermined angle, thereby adjusting output characteristics of a hybrid integrated circuit on the circuit board and eliminating undesirable misalignment of the mounting position between an MR device and the circuit board. Subsequently, a dowel recess used as a first positioning member formed on the circuit board receives a dowel projection used as a second positioning member formed on a frame, the dowel projection complementary to the dowel recess, thus positioning and assembling the circuit board into the frame. The output characteristics obtained during trimming conform with those after assembly, thus obtaining a magnetic sensor device having output characteristics with high precision and achieving correct detection as a sensor.

Abstract: To suppress and compensate influences of disturbance variables, a method of calibrating a sensor is disclosed, in which at most as many so-called influence variables influencing the measuring result are considered as measurable quantities are detected by the sensor, the set of the influence variables being composed of at least one disturbance variable influencing the measurement and at least one target quantity to be determined from the measurable quantities.

Abstract: A method and apparatus for performing conductance measurements on a sample using an eddy current probe, without the need for measurement or knowledge of the separation between probe and sample. The probe comprises sense and drive coils mounted in close proximity to each other (or a single coil which functions as both a sense and drive coil), circuitry for producing AC voltage in the drive coil, and a meter for measuring in-phase and quadrature components of induced voltage in the sense coil. Look-up table data can be generated for use in subsequent measurements on samples of unknown conductance by performing eddy current measurements on samples having different known conductances to generate reference lift-off curves, processing the reference lift-off curves to determine a conductance function relating each known conductance to a location along a selected curve, and storing conductance values determined by the conductance function for different points on the selected curve as the look-up table data.

Abstract: A storm monitoring apparatus and method is described wherein two H-field antennas are oriented with respect to the heading axis of an aircraft or the like at an angle of 45.degree.. The signals developed by these two antennas are picked-up by small R-F transformers which serve the inherent function of integrating the signals and extracting the H-field current component. A printed circuit board structuring of the two antennas provides for consistency of fabrication and reliability as well as compactness. The monitoring apparatus exhibits broad band frequency response to evaluate lightning strike rate to determine storm range and intensity. A computer control test utilizing diagnostic coils at the antenna carries out periodic testing of the performance of the device and a component such as a gravity switch provides an indication to the control system as to the orientation of mounting of the antenna on an aircraft.

Abstract: A system and method is provided for positioning a take-up reel in a tape drive unit so that a leader block can be inserted therein. The take-up reel is driven by a motor having a rotatable shaft and a motor controller. A position encoder, mounted on the shaft of the motor, uses a Hall-effect device to generate a Hall voltage signal in response to rotational motion of the motor shaft. The Hall voltage signal is amplified to provide a motor phase signal which is then compared to a reference level (usually zero volts) to generate encoder pulses. The encoder pulses are counted using a counter/state machine to determine a position and direction of rotation of the take-up reel. A feature of this system is that it is calibrated using a processor that determines the DC level of the motor phase signal and subsequently adjusts the motor phase signal so that it is substantially symmetrical about the reference level to which it is compared.

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

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

Abstract: A storm monitoring apparatus and method is described wherein two H-field antennas are oriented with respect to the heading axis of an aircraft or the like at an angle of 45.degree.. The signals developed by these two antennas are picked-up by small R-F transformers which serve the inherent function of integrating the signals and extracting the H-field current component. A printed circuit board structuring of the two antennas provides for consistency of fabrication and reliability as well as compactness. The monitoring apparatus exhibits broad band frequency response to evaluate lightning strike rate to determine storm range and intensity. A computer control test utilizing diagnostic coils at the antenna carries out periodic testing of the performance of the device and a component such as a gravity switch provides an indication to the control system as to the orientation of mounting of the antenna on an aircraft.