Abstract: An eddy current sensor (1) has at least one measuring coil (2) that can be supplied with an alternating current, and an evaluation circuit (3). The eddy current sensor allows the temperature influences on the impedance of the measuring coil to be reliably compensated with a simple design and an evaluation circuit. For this purpose, the eddy current sensor has a compensating coil (4) which can also be supplied with an alternating current and which is arranged closely to the measuring coil, i.e. in thermal contact therewith, in such a way that the electric fields of compensating coil (4) and measuring coil (2) are orthogonal to each other. More particularly, the measuring coil (2) is in an annular form and the compensating coil (4) is wound around the measuring coil in the form of a torus.

Abstract: Arrangements, specific apparatus and associated methods for skin depth compensation in underground boring applications are described. Compensation for skin depth error is accomplished by measuring a locating signal transmitted from a boring tool such that measurements of the locating signal include skin depth error introduced as a result of the electrical conductivity characteristic of the earth. Thereafter, the measurements are used in a way which determines a skin depth corrected position of the boring tool. In one aspect, a multi-frequency approach is provided which utilizes measured intensities of the locating field at two or more frequencies to extrapolate a zero frequency value of intensity. The zero frequency value of intensity is then used in position determination.

Abstract: A rotation angle sensor is provided, including a casing, and a magnet positioned in the casing. The magnet has a first magnetic pole end and a second magnetic pole end. First and second yokes are positioned at a first predetermined space relative to the first magnetic pole end of the magnet, and a third yoke is positioned at a predetermined space relative to the second magnetic pole end of the magnet. The third yoke is further positioned between the magnet and an extending portion of the first yoke, and is also positioned between the magnet and an extending portion of the second yoke. A first signal output element, which is positioned between the third yoke and the extended portion of the first yoke, outputs a first signal corresponding to an area ratio between the magnet and the first yoke. A second signal output element, which is positioned between the third yoke and the extended portion of the second yoke, outputs a second signal corresponding to an area ratio between the magnet and the second yoke.

Abstract: A measuring device for determining the position of a control element, such as a throttle valve in which a temperature-resistant Hal sensor (4) cooperates with a permanent magnet (2), which is connected to the control element by a spindle (3), in order to obviate the need for a conventional mechanical potentiometer. By virtue of the Hall effect, the Hall sensor (4) produces during movement of the control element and thus of the position of the permanent magnet (2) relative to the Hall sensor (4), an output signal (Ua) that is preferably linearly proportional to the movement of the control element. The Hall sensor (4) is programmed to correct temperature, related measurement errors in the permanent magnet.

Abstract: An improved position encoder system for providing an output signal representative of the position of a movable body, relative to a reference position, includes at least one magnetic element fixedly attached to the movable body. The system further includes a first spatially orthogonal fluxgate sensor pair and a second spatially orthogonal fluxgate sensor pair for detecting the magnetic field. The first sensor pair is disposed adjacent to the polar axis at a first predetermined distance, and the second pair is disposed adjacent to the polar axis at a second predetermined distance, preferably twice the first predetermined distance. The system further includes a signal processor for receiving a signal from the first sensor pair and a signal from the second sensor pair.

Abstract: An inductive linear encoder (10) has a position sensor (1) and scale (2) which are movably disposed relative to each other. The sensor (1) is with a drive wire (3) to which an alternating current is supplied, and one set of detection wires (4a-4d) at right angles to the drive wire (3) in the same plane. The scale (2) is configured including an elongate substrate (7) having its surface on which a series combination of conductive closed loop patterns (8) are periodically arranged at equal intervals. These conductive closed loop (8) are linearly laid out on the substrate (7) in the relative movement direction. Each loop (8) consists essentially of a reception conductor segment (8a) and signal transmit conductor segments (8b, 8c) integral with the former (8a). The receive conductor segment (8a) is responsible for generation of an induced current due to a first variable magnetic field creatable from the drive coil (3).

Abstract: A magnetic detector to detect a magnetic object's rotation and movement using a magnetoresistive element having hysteresis. The magnetoresistive element is set so as to tilt from the magnetizing direction of a magnet up to a predetermined angle &thgr; between the rotational magnetic object to be detected and the magnet. The magnetic detector provides a high accuracy signal that corresponds to the distance between the rotational magnetic object to be detected and the magnetoresistive element. The signal obtained is independent of the rotational direction or rotational speed of the magnetic object to be detected or the atmospheric temperature of an apparatus. Moreover, the temperature dependency of the output signal (amplitude) of the magnetoresistive element is decreased.

Abstract: A sensor for detecting the angular position of a rotary drive shaft is disclosed which includes a stator, a rotor connected to the stator by a ball joint and including a moving target, and a drive shaft connected to the rotor. The moving target passes through a detection system and produces a signal as a function of its position. Variations in the sensor output signal due to misalignment of the rotor and the drive shaft are minimized by locating the moving target close to the axis of rotation of the ball joint.

Abstract: Magnetic resistive elements 4 and 5 cooperatively detect the change of the magnetic field responsive to the rotation of a gear 2 fixed to a shaft 1. An amplification circuit 6 comprises an operational amplifier 7 having an input terminal to which a gain-determining input resistor 8 is connected. A gain-determining feedback resistor 9 is provided in a feedback path of the operational amplifier 7. The gain-determining resistors 8 and 9 are formed by a P well region and a P+ region of a MOS process element. The temperature characteristics of the gain-determining resistor 8 and 9 are opposed to that of the magnetic resistive elements 4 and 5. The temperature characteristics of the gain of the operational amplifier 7 cancel the temperature characteristics of the magnetic resistive elements 4 and 5.

Abstract: Disclosed is a magnetic detector in which a GMR device is operated within the limited range of a magnetic field so as to optimize a temperature characteristic of changes in resistance value and to improve noise resistance. The magnetic detector comprises a magnet (4) for generating a magnetic field, a rotary member (2) of magnetic material arranged with a predetermined gap left relative to the magnet and provided with projections capable of changing the magnetic field generated by the magnet, and a giant magnetoresistance device (3) of which resistance value is changed depending on the magnetic field changed by the rotary member of magnetic material. The giant magnetoresistance device is arranged to have such a predetermined gap relative to the magnet that the giant magnetoresistance device operates under a magnetic field applied to change in a predetermined amplitude range, e.g.

Abstract: A rotary control valve includes a flow control element having a lower valve shaft rotatably received in a non-magnetic body portion. A magnet is coupled with a lower valve shaft and rotatable therewith to produce an external magnetic field that varies in accordance with the angular position of the flow control element. A magnetic field detector, positioned in the external magnetic field, is operable to detect the external magnetic field and to produce position signals representative thereof, such being indicative of the angular position of the flow control element.

Abstract: A noncontacting displacement sensor (1) is proposed with a measuring coil (2) to which alternating current can be applied, the measuring coil (2) having at least two voltage taps (3), with an electrically and/or magnetically conductive measuring object (5), and with an evaluation circuit (4) for evaluating and, if need be, determining an output voltage that corresponds to the position of the measuring object (5) with respect to the voltage taps (3). To provide the displacement sensor of a structural form that is as compact as possible, the measuring object (5) is arranged and displaceable in the interior of the measuring coil (2), the total impedance of the measuring coil (2) being independent of the position of the measuring object (5).

Abstract: A position sensor or controller generates a response signal in existing armature windings of an actuator and detects the response signal to determine the position of the armature. To generate the response signal, the actuator includes a sensor excitation winding near the armature. Two sensor excitation windings can be provided, above and below the armature, to cancel out z components and thus allow for a variable gap. The sensor excitation winding or windings are supplied with an excitation signal to induce the response signal in the armature windings. The response signal is derived by differentially amplifying and frequency filtering a raw output of the armature windings. The response signal is demodulated to determine position. If a position controller rather than a mere sensor is desired, the position signal can be buffered, PID compensated, amplified, and fed back to the armature windings.

Abstract: A magnetoresistive sensor for use in a rotary encoder with a drum having a circumference covered with a magnetic track at a predetermined pitch includes a plurality of magnetoresistive elements positioned opposite the drum and connected in a bridge circuit such that when the drum rotates an output signal from the bridge indicates a rotary angle of the drum. The magnetoresistive elements include one or more complementary pairs of elements positioned 180° out of phase. Each of such pair of complementary magnetoresistive elements is connected in one leg of a bridge circuit such that jitter effects caused by asymmetric magnetic fields and physical differences between sensor elements are cancelled. Magnetoresistive sensor element configurations for minimizing the impact of temperature gradients across the magnetoresistive sensor are also disclosed.

Abstract: A method and apparatus for controlling temperature stability of an inductor by using a magnetically coupled metallic object is disclosed in which a metallic object is magnetically coupled to the inductor by a magnetic field emanating therefrom. In one embodiment, the apparatus is tailored for use in a proximity probe of a machine monitoring system and includes the metallic object magnetically coupled to a sensing coil for controlling a resistance versus temperature profile including compensating for a proximity effect resistance of the coil.

Abstract: A method for detection of passing magnetic articles which includes an initial step of sensing an ambient magnetic field and generating a voltage, Vsig, proportional to the magnetic field. A threshold voltage is generated as a percentage of the peak-to-peak voltage of Vsig. The method further includes the step of generating a detector output voltage that becomes one binary level when Vsig rises to exceed the threshold voltage and another binary level when Vsig falls to below the threshold voltage. The threshold voltage is updated to track the positive and negative peaks of the Vsig voltage and is further updated by a predetermined amount upon each transition of the Vout voltage.

Abstract: Methods and systems for calibrating an absolute position encoder where a read head is moved relative to a scale of the absolute position encoder and the absolute position encoder is comprised of a fine scale and a coarse scale. An absolute position of a coarse scale is determined which corresponds to the measurement in a fine wavelength. An ideal coarse absolute position is determined from the fine scale measurements. A deviation between the determined coarse absolute position and the ideal coarse absolute position is then determined. The mean of the maximum positive and negative deviations from the ideal coarse scale absolute position for different intervals of the scale are then stored for the entirety of a measured range. These stored correction values are then used to correct the coarse scale values. The concept can be utilized also in a system with more than two wavelengths, for instance a fine wavelength, a medium wavelength and a coarse wavelength.

Abstract: An electromagnetically actuated machine balancer including a plurality of peripherally placed magnetic circuits and a power driver which selectively interrupts the magnetic flux through the circuits, thereby moving unbalanced rotors in a desired manner to compensate for machine unbalance.

Abstract: A magnetic-field-to-voltage transducer includes a Hall element and a digitally gain-controlled Hall-voltage amplifier that produces an analog voltage Vsig having excursions of one polarity corresponding to the passing of magnetic articles. Vsig is applied to the input of a peak-referenced-threshold signal detector that generates a binary proximity-detector output voltage, Vout, having transitions of one direction upon approaches of gear teeth down to zero speed. A digitally gain-controlled amplifier is connected to the Hall element. A comparator circuit generates a binary signal Vbig (or Vtoobig) that changes from one to another binary level each time that Vsig exceeds a DC target voltage, VTG. The AGC circuit incrementally changes the transducer gain in the direction to bring the peaks in Vsig to just below the target value TTG. Reference voltages VP2 and VN2 are generated that are equal respectively to the most recent peak positive and negative going excursion in Vsig.

Abstract: A method and apparatus wherein a single element sensor, preferably a single element magnetoresistive sensor, is utilized to sense crankshaft position and rotational speed from the passage of single tooth edges of an encoder or target wheel and determines its offset voltage by measuring the MR voltage over a slot in the target wheel. This is accomplished by inclusion of a valley detector in the sensor circuit. Subtracting the signal of the valley detector from the MR signal yields an MR signal with a zero offset utilizing a comparator with an appropriate fixed reference (hysteresis) to generate the desired output signal. The accuracy of the sensor can be improved by amplifying the MR signal prior to feeding it into the comparator. The amplification simply increases the slopes of the signal and permits the use of a higher threshold voltage level in the comparator.

Abstract: A catheter tracking system as depicted in FIGS. 1,2, and 3 for locating and tracking a position of a catheter head 16 within a part of a human or animal body 1. The catheter tracking system including of a catheter 10 having a head 16 which is arranged to be conveyed through a human or animal body to a desired location, a plurality of magnetic field transducers, at least one of which is disposed on the catheter 18, and others of which are located in/or around a body and which serve as reference transducers 19, and a control unit which energises the plurality of magnetic field transducers. Upon processing of the magnetic field signals the position of a catheter head 16 with respect to reference transducers 19 is determined.

Abstract: A non-contacting position sensor having radial bipolar tapered magnets. The sensor has a semicircular first plate and a second plate. Four semicircular magnets are affixed to the first plate and second plate. Each magnet has a thick end and a thin end. Two magnets generate a linearly varying magnetic field having a first polarity, while the other two magnets generate a linearly varying magnetic field having a second polarity. An air gap is formed in the space between the four magnets. A magnetic flux sensor is positioned within the air gap. The object whose position is to be monitored is rigidly attached to the magnet assembly, causing the magnetic flux sensor to move relative to the magnets within the air gap as the component moves. A varying magnetic field is detected by the magnetic flux sensor, resulting in an electrical signal from the magnetic flux sensor that varies according to its position relative to the four magnets.

Abstract: In so-called active sensors which transmit an output signal to an electronic controller, the amplitude of the output signal depending neither on the speed of the encoder nor on the distance between the sensor and the encoder, the problem is that the output signal does not permit identifying whether the air slot size set between the sensor and the encoder is chosen sufficiently small to ensure an appropriate amplitude of the input signal, generated in the sensor, even when dynamic increases in the air slot occur. If the input signal induced by the encoder in the sensor is too low, a sensor-inherent hysteresis threshold is not exceeded, and no output signal is generated. To prevent the sensor from being inadvertently operated at the limits of its maximum permissible air slot, according to the present invention, the sensor-inherent hysteresis threshold is changed over to the higher hysteresis threshold for testing purposes.

Abstract: Disclosed is a magnetic detector in which a GMR device is operated within the limited range of a magnetic field so as to optimize changes in resistance value of the GMR device and to improve noise resistance. The magnetic detector comprises a magnet (4) for generating a magnetic field, a rotary member (2) of magnetic material arranged with a predetermined gap left relative to the magnet and provided with projections capable of changing the magnetic field generated by the magnet, and a giant magnetoresistance device (3) of which resistance value is changed depending on the magnetic field changed by the rotary member of magnetic material. The giant magnetoresistance device is arranged in such a position with a predetermined gap relative to the magnetic field generating means that the giant magnetoresistance device is subject to a bias magnetic field applied with the intensity of magnetic field in a predetermined range, e.g.

Abstract: A system to analyze the impedance of interference-tolerant proximity sensors. A lock-in amplifier (LIA) is implemented as a resonance-tracking oscillator. The control loop of the amplifier monitors the response of sensor in relation to the output of a local oscillator to adjust the oscillator's frequency to resonance. The nature of the sensor acts as a pre-filter of noise for a synchronous demodulator, which demodulates the sensor's response with the local oscillator's driving signal. The output of the system is a filtered version of this demodulated signal. This system is effective in sensing objects in the presence of electromagnetic noise that is many times stronger than the signal produced by the local oscillator.

Abstract: The present invention is capable of more accurately tracking an invasive device in a subject's body in the presence of eddy current inducing structures. Current patterns applied to the tracking system's transmit coils are modified to compensate for the effect of the eddy currents. The current supplied to the coils is a linear combination of the current needed to create the desired electromagnetic field in the region of interest; and one or more error terms. These terms are determined experimentally during system calibration and are mathematically modeled as a series of exponential functions having a given amplitude and time constant. The error terms in the current applied to the transmit coils cancel the magnetic fields created by eddy currents within the tracking region and result in an actual electromagnetic field which is close to the desired ideal electromagnetic field.

Abstract: An electronic circuit for automatically compensating for errors in the output signal of a displacement sensor. The electronic circuitry includes an analog to digital converter for converting an analog output signal from a linear displacement type sensor. The digital output signal from the sensor is processed by a microcontroller which automatically compensates for errors in the output signal. Ideal values, stored in an electronic memory, are used for compensation.

Abstract: A magnetic detector is disclosed with a power-on function which can essentially eliminate temperature characteristics of a magnetic field sensing device and improve edge detecting accuracy of alternately projected and recessed portions of a moving member of magnetic material. The magnetic detector comprises a magnet for generating a magnetic field, a rotary member of magnetic material disposed with a predetermined gap remaining relative to the magnet and having alternately projected and recessed portions to change the magnetic field generated by the magnet, a magnetoresistive device comprising a plurality of magnetic field sensing elements and detecting changes in the magnetic field by movement of the rotary member of magnetic material, and a magnetic guide for adjusting changes in the magnetic field caused by the alternately projected and recessed portions of the rotary member of magnetic material.

Abstract: A geartooth sensor utilizes an algorithm for establishing an adaptive threshold for the switch point of the sensor to minimize drift in the point at which the sensor output changes in relation to the target features it is tracking. The algorithm utilizes measured waveform peak and average outputs and applies a separate empirically derived constant to each value to quickly obtain the major portion of the adaptive threshold value from the product of the first constant and the peak output, and to refine the threshold value further with the product of the second constant and the average output.

Abstract: A sensor for measuring linear or angular dimension. The sensor can be moved with respect to a magnetized scale with a period &lgr;. It is equipped with magnetoresistive electrodes provided with barber-pole structures and connected so as to form n measuring bridges, each measuring bridge formed by four sets of magnetoresistive electrodes. The magnetoresistive electrodes making up each set are connected in series, the magnetoresistive electrodes being distributed spatially so as to constitute x groups. Each group being formed by more than eight consecutive magnetoresistive electrodes coming from two sets of a same measuring bridge.

Abstract: Apparatus for generating magnetic fields, including a plurality of radiator coils (22, 24, 26) and driver circuitry (30, 32, 33) coupled thereto, which drives the coils so as to generate magnetic fields at a plurality of driving frequencies, wherein each of the plurality of radiator coils (22, 24, 26) generates a field substantially only at a single, respective driving frequency. Preferably circuitry is associated with at least one of the plurality of radiator coils (22, 24, 26) for substantially eliminating magnetic fields generated by the other coils.

Abstract: This micromachined inductive sensor is used to detect, without contact and through the intermediary of a radiated alternating magnetic field, the position and/or the movement of an object capable of modifying this magnetic field and including for this purpose at least one discontinuity. The sensor comprises a planar transmitter coil for transmitting the alternating magnetic field and planar receiver coils located so as to sense a determined portion of said field and the variations of this magnetic portion sensed due to the discontinuity of the object. The coils are disposed on a common substrate and obtained by selective photolithography operations. According to the invention, in the areas of the substrate in which the transmitter coil is contiguous with a receiver coil, there is provided at least one shielding band electrically independent of the coils and connected to a reference potential. The shielding band is formed from a metallization layer deposited on the substrate.

Abstract: A method and apparatus for determining the absolute position of a rotor in a permanent magnet synchronous machine (e.g. motor or generator) at standstill wherein short positive and negative voltage pulses are separately provided to each stator winding and the rate of current change with respect to time for each current is determined, the rates are used to determine general rotor position angle and thereafter are used to determine correction angle for correcting the general angle.

Abstract: A device is disclosed for measuring the position (location and orientation) in the six degrees of freedom of a receiving antenna with respect to a transmitting antenna utilizing multiple frequency AC magnetic signals. The transmitting component consists of two or more transmitting antenna of known location and orientation relative to one another. The transmitting antenna are driven simultaneously by an AC excitation, with each antenna occupying one or more unique positions in the frequency spectrum. The receiving antennas measure the transmitted AC magnetic field plus distortions caused by conductive metals. A computer then extracts the distortion component and removes it from the received signals providing the correct position and orientation output to a high degree of accuracy.

Abstract: A sensing device capable of obtaining an output signal corresponding precisely to a predetermined position (angle), for example, of a protruding or recessed portion of a moving magnetic-material member without being affected by temperature change.