Abstract: A magnetic sensor 10 includes GMR elements 11-18, and heating coils 21-24 serving as heat generating elements. The elements 11-14 and 15-18 are bridge-interconnected to constitute X-axis and Y-axis sensors, respectively. The heating coils 21, 22, 23, and 24 are disposed adjacent to the elements 11 and 12, the elements 13 and 14, the elements 15 and 16, and the elements 17 and 18, respectively. The heating coils 21-24, when electrically energized, heat mainly the adjacent elements. Therefore, the elements can be heated and cooled in a short period of time in which constant geomagnetism can be ensured. Data for compensation of temperature-dependent characteristic (ratio of change in sensor output value to variation in element temperature) is obtained on the basis of the temperatures of the elements before and after the heating, and the magnetic sensor outputs before and after the heating. Subsequently, the temperature characteristics of the elements are compensated on the basis of the data.

Abstract: A method and apparatus are provided for measuring a thickness of a nonconductive coating disposed over portions of first and second conductive surfaces that intersect at an intersection angle. The apparatus is a thickness measurement gauge having an eddy current sensor. The thickness measurement gauge includes an eddy current sensor and electronic analyzer. The thickness gauge may be provided with a pressure enclosure. A method of calibrating a thickness measurement gauge and a calibration stand are also provided. The calibration stand has third and fourth conductive surfaces intersecting at the intersection angle. The conductivities of the third and fourth surfaces correspond to the conductivities of the first and second surfaces.

Abstract: A method of determining a surface profile of an electrically conductive object, using a probe having a transmitter adapted for inducing transient eddy currents in the object, and a receiver which is adapted for providing a signal indicative of a magnetic field property wherein the surface profile is determined by measuring a characteristic value at selected inspection positions at a selected set of inspection points to obtain a set of inspection values, and correcting for any offsets using a calibration function determined from a set of calibration values taken at a set of calibration positions at a calibration point.

Abstract: A method which compensates errors resulting from offset voltages and external magnetic fields when a magnetic sensor is used to measure coating thickness. The method also allows compensation of a temperature dependent change for output voltages of the magnetic sensor.

Abstract: A proximity sensor circuit of a powered dispenser for dispensing individual sheet segments from a continuous roll of sheet material includes an antenna, an oscillator circuit and an automatic sensitivity control circuit. The antenna has a baseline stray capacitance. The oscillator circuit is coupled to the antenna and generates an oscillation signal having a predetermined oscillation amplitude corresponding to the baseline stray capacitance of the antenna. Preferably, the oscillator circuit has a Colpitts oscillator-type topography. The oscillation amplitude of the oscillation signal increases in response to an increase in stray capacitance from the baseline stray capacitance of the antenna and decreases in response to a decrease in stray capacitance from the baseline stray capacitance of the antenna. The automatic sensitivity control circuit is coupled to the oscillator circuit and detects a change in the oscillation amplitude of the oscillator signal.

Abstract: A conductivity meter for measuring conductivity of terrain, including a first transmitter coil, a signal generator connected to the first transmitter coil to supply a time-varying current thereto for inducing eddy currents in the terrain, a first receiver coil horizontally spaced from the first transmitter coil, a temperature sensing device for measuring temperature, and a signal processor, including a memory storing a plurality of temperature dependent correction values, for isolating from a signal received by the first receiver coil a secondary signal representative of a secondary magnetic field generated in the terrain by the eddy currents, and determining an apparent terrain conductivity based on the isolated secondary signal and a selected temperature dependent correction value selected from the stored temperature dependent correction values according to a measured temperature received from the temperature sensing device.

Abstract: A magnetic field probe includes a substrate and a conductive layer provided on the substrate. The conductive layer has a coil, lead wires, and pads. The coil has at least one turn and outputs a signal indicative of a magnetic field from a device under test in a vicinity of the magnetic field probe. The lead wires extend from the coil to the pads, the signal from the coil being transmitted to the pads through the lead wires. An isolating layer of a dielectric material is provided on the lead wires to protect the lead wires between the coil and the pads in the conductive layer. A shielding layer of a conductive material is provided on the isolating layer to protect the isolating layer. The shielding layer prevents distortion of the magnetic field at the lead wires in conjunction with the isolating layer.

Abstract: A sensor includes a Hall cell and a compensation circuit for subtracting a magnet background field from the Hall cell output to provide a signal corresponding to rotations of a toothed ferrous gear.

Abstract: A method and measuring device for the in situ detection of the &ggr;-&agr; phase transformation of strip steel. The detection takes place on the basis of the eddy currents of the nonmagnetic phase, which are caused from the workpiece when an electromagnetic excitation field is applied, and on the basis of response fields which are generated by the magnetic phase which may be present. At least one electromagnetic excitation field which acts on the workpiece is generated by means of at least one excitation coil, and a response field which results from the application of the excitation field is measured by means of at least one detector measurement coil. The resulting measurement signal, which is dependent on the distance between the measuring device and the workpiece, is used to detect the degree of transformation.

Abstract: Frequency-dependent cancellation separates a plurality of interfering signals received by a plurality of receivers. Received wideband single-carrier signals or multicarrier signals are separated into a plurality of narrowband subcarriers. Sub-carrier frequencies and frequency-band characteristics may be selected with respect to channel characteristics (e.g., coherence bandwidth, interference, etc.). A cancellation circuit provides complex weights to the sub-carrier components. Weighted components associated with each sub-carrier frequency are combined to separate a plurality of interfering signals. Optionally, a plurality of the separated subcarriers may be combined to reconstruct at least one transmitted single-carrier signal from a plurality of frequency components.

Abstract: A magnetic sensing transducer device that senses low frequency magnetic fields by using flux concentrators that modulate the observed low frequency signal, thereby shifting this observed signal to higher frequencies and minimizing 1/f-type noise. This is accomplished by the oscillatory motion of a microelectromechanical (MEMS)-type magnetic flux concentrator operated with a magnetic sensor, preferably made on a common substrate. Such a combined device can be used in a magnetometer. Such a device is small, low-cost and has low-power-consumption requirements. The magnetic sensor can be a Hall effect or other type of magnetic sensor. At least one MEMS-type fabricated flux concentrator is used with the magnetic sensor. The concentrator oscillates at a modulation frequency much greater than the observed magnetic field being sensed by the device.

Abstract: A self referencing eddy current probe for determining conductive coating thickness includes a housing having a reference sample area, for accommodating a reference sample, and a testing edge, for positioning on a component during a coating thickness measurement. The eddy current probe further includes a reference eddy current coil situated in the housing adjacent to the reference sample area and a test eddy current coil, which is located at the testing edge. A self referencing eddy current measurement system, for measuring a thickness of a conductive coating on a component, includes the self referencing eddy current probe. The system further includes a signal generator for energizing the test and reference coils and a comparison module for comparing a test signal received from the test coil and a reference signal received from the reference coil and outputting a compared signal.

Abstract: A magnetic flux detector has a core member and an armature member. The core member generates a magnetic flux by an exciting coil receiving an excitation current controlled by an excitation current controller. The magnetic flux detector also has a search coil provided in a magnetic path for the magnetic flux, and a magnetic flux calculator, which determines the magnitude of the magnetic flux by measuring an electromotive force induced in the search coil by a change in the magnetic flux. The excitation current controller controls the excitation current to increase from zero to a predetermined value during a first predetermined time period and then to decrease to zero during a second predetermined time period. The magnetic flux calculator determines the magnitude of the magnetic flux based on the integrated electromotive forces during the first and second time periods.

Abstract: The support that bears and positions the head in a head holding apparatus is further supported by a heat-compensating member, so that when the support is expanded by the heat source of the head holding apparatus, the heat-compensating member expands in the direction opposite to the direction of expansion of the support. Moreover, supplying of heat to the support and heat-compensating member is further alleviated by insulating said heat source with an insulating material. The amount of displacement of the recording element per unit of time with exposure to heat is controlled by the above-mentioned structure and effects.

Abstract: A thin-film magnetic field sensor is provided which includes two arms of a bridge circuit formed of a first element having a giant-magneto-resistant thin-film, and soft magnetic thin-films disposed one on either side thereof, with electrical terminals, and a second element having a giant-magneto-resistant thin-film, and conductive films disposed one on either side thereof, with electrical terminals. The electrical resistance value of the second element has sensitivity relative to the magnetic field, such that it is substantially zero when the magnetic field is small, but it changes equally to the first element due to causes other than the magnetic field. Since the output of the bridge circuit is in proportion to the difference in electrical resistance values between the first and second elements, part of a change due to causes other than the magnetic field is canceled in the output of the bridge circuit, whereby the magnetic field value can be accurately measured.

Abstract: A sensor apparatus having a sensor for generating an analog sensor signal with successive minima and maxima is provided. The apparatus can include a first output signal generating device for generating a first alternating output signal in accordance with the zero crossings of the sensor signal; a sequence controller for defining a normal operating phase, in which the first output signal can be output, and a calibration phase, in which a second alternating output signal can be output; and an extremum defining device for the phase-shifted definition of the successive minima and maxima; the sequence controller furthermore having a zero crossing establishing device for establishing fictitious zero crossings of the sensor signal which follow the respective extrema defined by the extremum defining device.

Abstract: An inductive proximity sensor or switch and a method of using same. The sensor or switch includes an Application Specific Integrated Circuit (“ASIC”) and a plurality of external components. The ASIC is implemented in CMOS technology and has an oscillator. A switch point of the sensor or switch is predetermined by selection of a bias voltage to a potential node of the oscillator.

Abstract: A method for compensation of dynamic error signals of a chopped Hall sensor that comprises at least one Hall sensor element comprising a plurality of terminal pairs for impressing an excitation current through the Hall sensor element and for taking a Hall voltage. The terminal pairs for impressing the excitation current and for taking the Hall voltage are switched in a first and/or second rotational sense. In order to compensate dynamic error signals caused by the switching, the Hall voltages taken at the terminal pairs when switching in the first rotational sense are supplied to a summation and/or averaging analysis unit together with the Hall voltages taken at the terminal pairs when switching in the second rotational sense.

Abstract: A magnetic flux detector comprises a core member 12 and an armature member 11, and the core member 12 generates a magnetic flux by an exciting coil 13 when the exciting coil receives an excitation current controlled by an excitation current controller 30. The magnetic flux detector further comprises a search coil 14, which is provided in a magnetic path for the magnetic flux, and a magnetic flux calculator 40, which determines the magnitude of the magnetic flux by measuring an electromotive force induced in the search coil 14 by a change in the magnetic flux. The magnetic flux calculator 40 has a potential setup resistor 43, whose resistance B is sufficiently larger than the internal resistance A of the search coil 14 (approximately A=B/3˜B/30).

Abstract: A magnetic encoder includes a magnetic drum having, on the outer peripheral surface thereof, magnetized portions spaced at equal pitches; a magnetic sensor unit opposed to the outer peripheral surface of the magnetic drum; magnetic sensors are provided in the magnetic sensor unit spaced at a distance smaller than one pitch of the magnetized portions; a calculation device for calculating two sets of vectorial signals, from detection-signal output levels of the magnetic sensors generated upon rotation of the magnetic drum or the magnetic sensor unit, using the following equations (1) and (2): Aout=&Sgr;Wm=1Vm×sin &thgr;m  (1); and Bout=&Sgr;Wm=1Vm×cos &thgr;m  (2); wherein W designates the number of the magnetic sensors; Vm designates the detection-signal output levels of the magnetic sensors generated upon rotation of the magnetic drum or the magnetic sensor unit; Aout and Bout designates one and another set of vectorial signals.

Abstract: Measuring the wall thickness of an electrically conductive object using a probe comprising a transmitter coil, a first receiver and a second receiver, which method comprises arranging the probe near the object; inducing transient eddy currents in the object and recording the signals of the receivers with time; measuring the wall thickness from a characteristic of one of the signals; calculating a characteristic value from a combination of the signals; and correcting the measured wall thickness for the distance between the probe and the object using a pre-determined relationship between the wall thickness and the characteristic value for different values of the distance between the probe and the object.

Abstract: An apparatus for and a method of measuring material thickness with magnetics. The thickness monitoring system includes a thickness monitor, a probe, and a target. In a preferred embodiment, the probe is positioned on one side of an article for which the thickness is to be determined. The target is positioned on the opposite side of the article from the probe. The probe includes an excitation coil, a field compensation coil, and a magnetic sensor. The method includes energizing the excitation coil to excite a response from the target, compensating for the effect of the excitation coil on the magnetic sensor, measuring the response of the target with the magnetic sensor, and determining the thickness of the article from the measured response. The preferred mode of energizing the excitation coil is with an AC waveform; however DC, multi-frequency AC, or a combination of AC and DC waveforms may be used.

Abstract: Metal detector and method in which soil mineralization effects and responses to other undesired materials are eliminated. A periodic excitation signal is transmitted into an area where a target is to be detected, and signals returned by the target are processed to provide an output signal corresponding to the target. A plurality of signals are extracted from the output signal during different phase intervals in the period of the excitation signal and processed to provide signals which are free from ferrite response and/or response to other undesired materials. The signals which are free from response to ferrite and/or other undesired materials are then compared to identify the target.

Abstract: An axial direction groove is formed in a high permeability toroidal core taking the form of a pot core half with a mounting hole, a high cross-section ratio copper casing being tightly fit around core circumference, having poly-phase excitation windings shuttled through the mounting hole to encompass both the copper casing and the pot-core, forming an integral driving-sensing eddy current probe. A naked pot-core is wound as an integral driving-sensing probe. Poly-phase excitation of the probe is mesh-connected as a gramme-ring.

Abstract: A method and system for calibrating a magnetic sensor having at least one magnet and at least one sensing element incorporated therein is disclosed. A magnetization direction of a magnet is altered in at least one axis until a sensing element is balanced. The magnet can be calibrated separately from the electronic components associated with the magnetic sensor to thereby achieve an improved calibration over temperature variations associated with the magnetic sensor. The magnetic sensor can be configured to include one or more magnets and one or more sensing elements. Such magnets may be calibrated according to the methods and systems disclosed herein, in association with such sensing elements. Each magnet may be calibrated separately from the electronics associated with the magnetic sensor. The magnetization direction of the magnet may be altered in one or more axis until the sensing element is balanced. The magnetic sensor may, for example, comprise a gear tooth sensor or a wheelspeed sensor.

Abstract: In a non-destructive inspection device of the present invention which detects in a non-destructive manner a defect of a member to be inspected, based on a change in magnetic fluxes due to eddy currents that are generated by an inspection probe having a coil, a driving section which adjusts a position of the inspection probe, and measuring device for, based on a detection signal of the inspection probe, measuring a lift-off between the inspection probe and the member to be inspected are disposed. The driving section is controlled in accordance with a result of measurement of the measuring device, whereby a control of making the lift-off constant is performed.

Abstract: The invention relates to a process for testing of a workpiece by means of eddy currents induced by a field coil in the workpiece and from which a measurement signal is obtained by means of a measurement sensor, a pattern signal representative of a workpiece fault being generated, a correlation function of the measurement signal acquired by the sensor with the pattern signal being determined, and the correlation function being evaluated in order to detect a fault in the workpiece. The invention furthermore relates to a device for executing the process.

Abstract: A method and apparatus for non-destructively measuring the depth of a crack with precision and accuracy in a workpiece using an eddy current process. The method involves empirically creating a response curve of the eddy current response produced from crack(s) in a sample workpiece(s), wherein the depth of the crack(s) in the sample workpiece(s) may be modified a plurality of times and an eddy current response reading is taken at each different crack depth. The response curve is then used to interpolate the depth of a crack in a workpiece composed of the same material non-destructively by measuring the eddy current response in the workpiece crack and then obtaining the predetermined crack depth value form the response curve.

Abstract: An apparatus and method for determining linear and angular velocity of a moving body. A magnet is attached or fixed to the body, the velocity of which is to be determined. The apparatus comprises a sensor comprising a core of magnetic material and a coil wound about the core. The movement of the body and magnet relative to the core effects a time-varying magnetic field between the magnet and the core thereby producing Barkhausen effect time-varying voltage signals in the coil. The apparatus further comprises a system for detecting and processing the time-varying voltage signals so as to effect a transformation of the signals into data defining the velocity of the moving body.

Abstract: In the inductive motion sensor, there are provided magnetic field generating means (4, 5, 7, 8) for generating a magnetic exciting field and a measuring device for measuring a mutually induced measurement magnetic field as a measure of the motion. The measuring device is arranged with an offset from the magnetic field generating means in the motion direction and is thereby no longer subjected to the temperature-dependent variations of the exciting field.

Abstract: A method for identifying metal layer thickness of an inspection sample according to one embodiment utilizes an eddy current probe to obtain initial resistance and reactance measurements from the inspection sample. Once these measurements have been obtained, the relative distance between the eddy current probe and inspection sample is increased and terminating resistance and reactance measurements are obtained. An inspection sample intersecting line may then be calculated using the initial and terminating resistance and reactance measurements. An intersecting point between a natural intercepting curve and the inspection sample intersecting line may also be determined. A reactance voltage of the intersecting point along a digital calibration curve is calculated to identify a closest two of a plurality of calibration samples. The metal layer thickness of the inspection sample may then be calculated by performing an interpolation between the identified closest two calibration samples.

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

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

Abstract: The invention relates to measurement technology and can find application for nondestructive testing electrically conducting and/or ferromagnetic materials and products. The differential eddy-current transducer comprises a primary detector (1) which incorporates two similar search coils (2, 3) and an additional coil (4) having its leads connected in series aiding to respective first leads of the search coils (2, 3) to second leads of which voltage is applied in antiphase. The transducer further comprises an electronic unit (5) which is electrically connected to the primary detector (1) and incorporates a potentiometer (6), a capacitive element (7), and an operational amplifier (8). Two leads of the potentiometer (6) are connected to common connection points of the leads of the search coils (2, 3), and its midpoint lead is connected to the capacitive element (7) which in turn is connected to the inverting input of the operational amplifier (8) whose noninverting input is grounded.

Abstract: A geometry for a pickup coil assembly that improves the balance of a hysteresis loop tracer is described. First and second balance coils are placed on either side of a pickup coil. The first and second balance coils are wired in series to form a symmetric balance coil that senses the magnetic H field on either side of the pickup coil. The voltage produced by the symmetric balance coil is subtracted from the voltage produced by the pickup coil. This geometry reduces susceptibility to external electromagnetic fields and also reduces susceptibility to changes in the uniformity of the drive field. Mechanical and thermal stability is improved by physically connecting the balance and pickup coils together. Mechanical and thermal stability is further improved by winding the coils on alumina coil forms.

Abstract: A method and apparatus is described for making multichannel signal measurements of weak signals in noisy environments, wherein the elimination of background interference signals from the multichannel signal measurement is performed. The method is based on an adaptive compensation technique in which the large interfering background signals are first recorded. By a statistical analysis of this multichannel measurement, independent components of the interference are determined. The apparatus is provided with compensator elements which are coupled to individual sensors for both collection and distribution of information on the interference signals during the measurement. In this way the output of a device can be made immune to the large amplitude interference components present in the device's environment. This reduces the dynamic range requirement for the data transport and storage systems.

Abstract: A self-adjusting assembly and method are disclosed. In the disclosed embodiments, a support assembly for supporting a device comprises a pair of support members for supporting the device. One of the members is adapted to help support the device from a ground, and another of the members is adapted to provide lateral support for the device and to permit free longitudinal movement of the device as it expands or contracts due to temperature variations.

Abstract: A hand tool has a ground-piercing probe, which is manually insertable in the soil. The probe has a chamber in which an inductor is positioned and connected to metal detection circuitry. A pulse generator applies current pulses to an inductor for inducing eddy currents in a buried target object. After the pulse terminates, the decaying coil voltage is sampled at different times to detect both the presence and range of the object, as well as the type of metal in the object. The coil voltage samples are applied to signaling circuitry, which provides an audible signal which is a series of bursts of an audio tone. The pitch of the audio tone signals the presence, range and bearing of the buried metal object, while the pulse rate of the bursts signals the metal type. Signal variations resulting from temperature changes when the probe is inserted into soil are compensated for by detecting a signal proportional to the coil current during the pulse and subtracting a scaled portion of that signal from voltage samples.

Abstract: A system and method for programming a Hall effect sensor while the sensor is connected into the circuitry for a given application. The system includes a fixture for receiving the printed circuit board to which the sensor is mounted. A plurality of contacts, such as pogo pins, are arranged to contact the circuit board at desired pads that permit programming of the sensor, reduction of the voltage applied to the overall circuit during programming, and measurement of the sensor and circuit output. The system includes a voltage limiting circuitry that is electrically connected, via appropriate pogo pins, to the circuitry intermediate the subject sensor and potentially damaged circuit components.

Abstract: The present invention provides a sensor apparatus having a sensor (2) for generating an analog sensor signal (200) with successive minima and maxima, and a corresponding method for generating an output signal of a sensor apparatus.

Abstract: A device and a method to detect a broken tooth in a pulse signal by measuring one pulse cycle and another pulse cycle, determining whether a ratio of one pulse cycle and another pulse cycle is a multiplied number while wheel speed is constant.

Abstract: A magnetic field sensor includes: a Hall element; a voltage amplifier for amplifying an output voltage from the Hall element so as to output an amplified signal; a voltage comparison circuit for receiving the amplified signal; a switch circuit provided between the voltage amplifier and the voltage comparison circuit for inverting a polarity of the amplified signal; and a latch circuit for holding an output signal from the voltage comparison circuit. The voltage comparison circuit inverts a polarity of a hysteresis voltage that determines a reference value of a magnetic field intensity in response to a first synchronizing signal, which triggers a detection of a magnetic field, and a second synchronizing signal following the first synchronizing signal.

Abstract: The invention relates to a method for applying to a carrier a marking serving to measure length, angle cr the like, such as, for example, a magnetic tape (4), by means of which the accuracy of the measurements is improved. In the case of such methods, in one marking step a means for producing a track with markings, for example a writing head (9), is guided over the carrier and, by virtue of the fact that the carrier is acted upon, markings, for example magnetic north and south poles, are applied therein at predetermined positions of the carrier.

Abstract: A magnetic sensing device that senses low frequency magnetic fields by using movable flux concentrators that modulate the observed low frequency signal. The concentrator oscillates at a modulation frequency much greater than the observed magnetic field being sensed by the device. The modulation shifts this observed signal to higher frequencies and thus minimizes 1/f-type noise. This is preferably accomplished by the oscillatory motion of a microelectromechanical (MEMS)—type magnetic flux concentrator operated with a magnetic sensor, preferably made on a common substrate. Such a combined device can be used in a magnetometer. Such a device is small, low-cost and has low-power-consumption requirements. The magnetic sensor can be a Hall effect or other type of magnetic sensor. At least one modulating flux concentrator is used with the magnetic sensor.

Abstract: Apparatus for generating magnetic fields includes a plurality of radiator coils. Driver circuitry drives the coils so as to generate magnetic fields at a plurality of driving frequencies. Each of the coils is driven by a respective current that comprises a basic current at a respective one of the driving frequencies and cancellation currents at one or more of the other driving frequencies, so that each of the radiator coils generates a field substantially only at the respective driving frequency.

Abstract: Disclosed is a method for improving the sensitivity of a fluxgate magnetometer for which high-order harmonics are detected and utilized in determining a weak external magnetic field expressed in the core region. These harmonic signals are processed coherently so as to increase the signal-to-noise ratio, since noise can only add to the signal incoherently at these harmonic frequencies. Also disclosed is a method for improving the sensitivity of a fluxgate magnetometer for which the technique of waveform autocorrelation is used in determining a weak external magnetic field expressed in the core region. By convolving the gated signal with a waveform duplicating the signal itself, noise content is effectively suppressed, thereby increasing the resolution power of the fluxgate magnetometer.

Abstract: An inductive magnet sensor has two identically wound magnetic antennae connected in series, out of phase, spaced axially from one another, and placed outside and parallel to the axis of a magnetic pipe so that induced noise voltages from the symmetrical noise magnetic flux of the pipe mostly cancel, leaving the responsiveness of the antennae undiminished to sense the non-symmetrical magnetic flux from a permanent magnet or a signal from a transmitter passing through the pipe. The enhanced signal of each of these antennae is then resistively attenuated, one fixed and the other adjustable, to further enhance the cancellation after placement of the sensor outside of the pipe. This balance adjustment improves the signal to noise ratio of the combined signal and the sensor is adjustably resistively attenuated to set the gain to enhance the dynamic range after mounting on the pipe.

Abstract: A method for determining the direction of an external magnetic field (B) using a magneto-resistive sensor comprises the following steps: superimposing a fluctuating magnetic field on the external magnetic field (B); creating a first and second signal dependent on the sine and cosine of the angle between the external magnetic field and a reference vector by decoupling or disregarding the respective signal components which are dependent on the fluctuating magnetic field; determination of a third signal which is dependent upon the angle between the external magnetic field and a reference vector on the basis of the first and second signal whereby said third signal has a periodicity of 180°; determination of a logic correction signal (K5) with regard to the signal component which is dependent on the fluctuating magnetic field decoupled from either the first or second signal and which adopts a value for the angle of the external magnetic field in a first angle range, in particular between 0° and 180° an

Abstract: A method of removing bias drift from the output signal of a sensor is provided. The method includes sensing a condition with a sensor and generating an output signal, differentiating the output signal, and comparing the differentiated output signal with a threshold change. The method also includes the steps of determining the presence of bias drift based on the comparison, generating a bias adjustment command signal based on the determined presence of bias drift, and adjusting the sensed signal generated by the sensor in accordance with the bias adjusted command signal so as to remove bias drift from the output signal.

Abstract: A method for tracking the ON/OFF state of a 2D MEMS optical switch is based on comparing the output property of a magnetic sensor deployed on a micro machined optical element with fixed values predetermined by the property the sensor when said element is known to be in the ON and OFF states.