Abstract: An apparatus for detecting a potentially dangerous ferromagnetic object carried inadvertently by a person approaching the magnet of a magnetic resonance imaging system (14) uses the fringe field (16) of the magnet and provides guide members (11) defining a path along which the person is prescribed to pass. The path (11) is generally or approximately parallel to the field the path. At least one sense coil and generally two sets of sense coils (12, 13) are located on respective sides of the path (11) s the movement of the ferromagnetic object in the field of the magnet causes a voltage to be generated in the sense coil.

Abstract: A magnetic detection device includes a mode switching section capable of switching over a 1-output mode in which a (+) magnetic-field detected signal and a (?) magnetic-field detected signal are both outputted from a first external output terminal, and a 2-output mode in which the (+) magnetic-field detected signal and the (?) magnetic-field detected signal are outputted respectively from the first external output terminal and a second external output terminal. The provision of the mode switching section in an integrated circuit makes it possible to perform mode selection, in particular to realize the mode selection with a simple circuit configuration resulting in a reduction of the production cost.

Abstract: Apparatus and methods for detecting passing magnetic articles using a first, True Power On State (TPOS) detector during a first time interval and transitioning to a second, running mode detector after the first time interval, when the output of the second detector is accurate. A phase comparator is responsive to the output signal of the first and second detectors and provides a control signal indicative of a change in the phase relationship between the two output signals. An output switch controlled by the phase comparator provides, as the detector output signal, the first detector output signal during the first time interval and the second detector output signal thereafter.

Abstract: Apparatus and methods for detecting passing magnetic articles using a first, True Power On State (TPOS) detector during a first time interval and transitioning to a second, running mode detector after the first time interval, when the output of the second detector is accurate. A phase comparator is responsive to the output signal of the first and second detectors and provides a control signal indicative of a change in the phase relationship between the two output signals. An output switch controlled by the phase comparator provides, as the detector output signal, the first detector output signal during the first time interval and the second detector output signal thereafter.

Abstract: A blind spot targeting system for establishing a cutting point includes a locator with a housing having an indicator and a signal-sensing device. The housing has a hole therethrough, and the indicator is in electronic communication with the signal-sensing device for indicating a cutting point on a first side of a structure. A transmitter is also included, which has a complementary hole therethrough. The transmitter is for placement on a second side of the structure for emitting a signal, which the signal-sensing device senses. The indicator in communication with the signal-sensing device indicates alignment of the hole and the complementary hole to establish the cutting point for cutting through the hole into the first side of a structure and possibly through the second side of the structure in a direction of the complementary hole.

Abstract: A blind spot targeting system for establishing a cutting point includes a locator with a housing having an indicator and a signal-sensing device. The housing has a hole therethrough, and the indicator is in electronic communication with the signal-sensing device for indicating a cutting point on a first side of a structure. A transmitter is also included, which has a complementary hole therethrough. The transmitter is for placement on a second side of the structure for emitting a signal, which the signal-sensing device senses. The indicator in communication with the signal-sensing device indicates alignment of the hole and the complementary hole to establish the cutting point for cutting through the hole into the first side of a structure and possibly through the second side of the structure in a direction of the complementary hole.

Abstract: A proximity detector includes a fine DAC and a coarse DAC, outputs of which are summed to provide a tracking signal for tracking a magnetic field signal. The proximity detector provides two mode of operation. In a first mode of operation the coarse and fine DACs operate in combination as one higher order DAC. In a second mode of operation, the coarse DAC is provided with one or more extra counts, allowing the tracking signal to move more rapidly to track a rapidly changing magnetic field signal. In another embodiment, the proximity detector also includes an offset circuit for bringing at least one of the magnetic field signal and the tracking signal towards the other one of the magnetic field signal and the tracking signal.

Abstract: Apparatus for detecting vibration of an object adapted to rotate includes one or more vibration processors selected from: a direction-change processor adapted to detect changes in a direction of rotation of the object, a direction-agreement processor adapted to identify a direction of rotation of the object in at least two channels and identify an agreement or disagreement in direction of rotation identified by the at least two channels, a phase-overlap processor adapted to identify overlapping signal regions in signals associated with the rotation of the object, and a running mode processor adapted to identify an unresponsive output signal from at least one of the at least two channels.

Abstract: Apparatus and methods for detecting passing magnetic articles using a first, True Power On State (TPOS) detector during a first time interval and transitioning to a second, running mode detector after the first time interval, when the output of the second detector is accurate. A phase comparator is responsive to the output signal of the first and second detectors and provides a control signal indicative of a change in the phase relationship between the two output signals. An output switch controlled by the phase comparator provides, as the detector output signal, the first detector output signal during the first time interval and the second detector output signal thereafter.

Abstract: A first measured value is determined which is associated with the proximity of a target to an inductive sensor. A first voltage signal having a first amplitude is generated. The first voltage signal is provided as a driving signal to the inductive sensor. A sensor current signal is received as a return signal output from the inductive sensor. The sensor current signal has an amplitude proportional to a proximity of the target to the inductive sensor. The sensor current signal is converted to a corresponding second voltage signal having a second amplitude. A differential measuring technique is used to determine the first measured value in accordance with relative amplitudes of said first voltage signal and said second voltage signal.

Abstract: A proximity sensor assembly includes a multilayer printed wiring board proximity sensor, the proximity sensor being operable as either a variable-reluctance sensor or an eddy current loss sensor. The proximity sensor includes a plurality of layers configured to form at least one wound coil disposed about at least a portion of a core. The coils are electrically driven to generate an alternating magnetic field such that the inductance of the coils changes when a permeable or conductive object is moved in relation to the magnetic field. The change in inductance is recognized and used to detect the proximity and presence of an object relative to the sensor.

Abstract: A new approach for locating an underground line described herein remains accurate in the face of bleedover by including both amplitude and phase from at least two magnetic field strength sensors in the measurement set. A numerical optimization step is introduced to deduce the positions and currents of each of several cables, of which one is the targeted cable and the others are termed bleedover cables. Furthermore, some embodiments of the method accounts for practical problems that exist in the field that relate to reliable estimation of cable positions, like the phase transfer function between transmitter and receiver, the estimation of confidence bounds for each estimate, and the rejection of false positive locates due to the presence of noise and interference.

Abstract: A magnetostrictive level sensing instrument is used for sensing level in a process vessel and comprises an elongate tube having a near end and a distal end. A magnet is selectively positionable proximate the tube responsive to level of the processed material. A magnetostrictive wire in the tube has first and second ends. The second end is operatively secured at the tube distal end. A pair of shear mode crystals are mounted proximate the tube near end. The crystals sandwich the magnetostrictive wire proximate the first end. A sensing circuit is operatively connected to the magnetostrictive wire and the pair of crystals for generating an electrical pulse on the magnetostrictive wire whereby a magnetic field produced by the magnet interacts with the electrical pulse to produce a torsional wave on the magnetostrictive wire sensed by the pair of crystals.

Abstract: A magnetic detector arrangement includes two equally polarized magnets positioned next to each other with the polarization in the same direction, and a magnetic detector element, wherein the magnets are arranged at a predefined distance apart such that the magnetic field from the magnets will superimpose. A magnetic detector arrangement with an improved tolerance towards deviations in the magnetic field of the comprised permanent magnets can be provided.

Abstract: A digital based two wire proximity transmitter system and a method for calibrating the system, wherein the transmitter includes a customized linearization table uniquely generated during calibration to take into account the unique impedance properties of a particular probe/coaxial cable configuration. During calibration, the probe is positioned adjacent a calibration target. The calibration target is selected to have the same material characteristics as the target to be monitored during actual operation of the transmitter in the field. At a fixed distance between the probe and calibration target, the resonant frequency of the probe/cable system is determined. Thereafter, utilizing this resonant frequency to excite the probe, the voltage response of the probe/cable system is determined as the distance between the probe and the target material is incrementally changed.

Abstract: A sensor element (30) measures a Hall voltage generated by a movable magnet (16). For this purpose, the sensor element (30) comprises a ceramic base element (40) which has connected therewith a detector element (46). The detector element (46) is protected with the aid of a cover element (42) against an aggressive environment produced by fuel or fuel vapors in a fuel tank (34) of a motor vehicle. The detector element (46) has connected therewith electric conductors (60) which are routed through the cover element (42) and/or the base element (40) for connecting the detector element (46) with a voltage source and/or an evaluation unit. The cover element (42) and possibly the base element (40) reliably encapsulate the detector element (46) against the aggressive environment such that by simple constructive measures the service life of the sensor element (30) is increased.

Abstract: A leaky cable having radiation directivity which varies with frequency transmits electric waves in different frequency bands. A measurement apparatus outputs measurement information including signal intensity and phase of a reflected electric wave in each frequency band which is reflected by a target and is received by another leaky cable, and propagation delay time A calculator groups the measurement information by target on the basis of signal intensities and phases of the reflected electric waves in different frequency bands, and calculates the position of the target with respect to the longitudinal direction of the leaky cables and the distance between the target and the leaky cables.

Abstract: A system that senses proximity includes a magnet producing a magnetic field and a sensor having a switch. The switch includes a cantilever supported by a supporting structure. The cantilever has a magnetic material and a longitudinal axis. The magnetic material makes the cantilever sensitive to the magnetic field, such that the cantilever is configured to move between first and second states. The switch also includes contacts supported by the support structure. The switch can be configured as a reed switch. When the magnet moves relative to the sensor, the cantilever interacts with a respective one of the contacts based on the position of the magnet during movement.

Abstract: A vehicle occupant sensing system that includes a sensor assembly. The sensor assembly has a housing that includes a base and an upper slide member. The upper slide member is moveable toward and away from the base. A sensor is operatively fixed relative to at least one of the upper slide member and the base and is operable to detect movement of the upper slide member toward and away from the base. Additionally, the vehicle occupant sensing system includes a variable biasing member adapted to bias the upper slide member away from the base with a force that is non-linearly related to movement of the upper slide member toward and away from the base. The vehicle occupant sensing system of the present invention may be employed in a vehicle seat assembly to detect a condition of the vehicle seat assembly.

Abstract: A motion transducer comprising one or more electromagnetic coils provided on a first element, each of the coils having a magnetic axis of symmetry.

Abstract: An apparatus includes a first circuit, a second circuit, and a capacitor. The first circuit includes a sense element. The capacitor couples the first circuit to the second circuit. The first feedback path couples the second circuit to the first circuit. And the second feedback path couples the second circuit to the first circuit. A method includes generating, for an oscillator signal having an amplitude and a gain, a substantially direct current signal related to an amplitude, and controlling the gain with the substantially direct current signal.

Abstract: A method of fabricating a multilayer wiring board proximity sensor includes forming a laminate, and fabricating a plurality of through-conductors through the layers of the laminate. The laminate has a plurality of layers including one or more core layers and a plurality of coil layers. Each core layer includes a core pattern formed of a permeable material, and each coil layer comprises at least one coil trace formed of a conducting material. Thus, the through-conductors may be fabricated through the layers of the laminate such that the coil traces are interconnected by the through-conductors to thereby form one or more coils disposed about at least a portion of the core patterns of the core layers.

Abstract: A process and a device for contactless measurement of rotational speed with a proximity sensor operating according to the eddy current principle. The proximity sensor comprises an inductor and a capacitor connected in parallel that form an oscillating circuit which can be excited from outside, and where the resonant frequency of the oscillating circuit experiences a detectable change when an object to be measured approaches the proximity sensor. In various embodiments, the resonant frequency of the oscillating circuit or the excitation frequency of the oscillating circuit is controlled as a reaction to slow changes of the resonant frequency in such a manner that the oscillating circuit is always excited with its resonant frequency or with a frequency close to its resonant frequency and that rapid changes are detected as a measurement signal for the measurement of rotational speed.

Abstract: An inductive proximity sensor for sensing the presence of target based on a change of inductance in the sensor. The sensor includes a coil and a core formed of a permeable material so as to form an electromagnetic field when the coil is electrically driven. The core has a base, a central post, an outer wall, and at least one slot. The central post extends distally from the base and through the coil and defines a distal end. The outer wall extends distally from the base and around the coil and also defines a distal end. The slot or slots are for enhancing the performance of the sensor by reducing eddy current losses in the core. Each slot extends at least partially along a path defined from the distal end of the outer wall to the base and from the base to the distal end of the central post.

Abstract: A proximity detector has a sequential flow state machine to identify states associated with a magnetic field signal provided by a magnetic field sensing element. The proximity detector can include a vibration processor to identify a vibration in response to the states.

Abstract: Exemplary embodiments of the invention provide a sensor attachment mechanism capable of attaching a position detecting sensor having directivity in a proper direction to a fluid pressure cylinder having a rail extending along the length of a cylinder tube on the outer surface thereof. Embodiments include a position detecting sensor for sensing the operating position of a piston is attached with a sensor holder to a grooved rail extending along the length of a cylinder tube on the outer surface thereof. The position detecting sensor has directivity in magnetic detection. The sensor holder includes a base mounted on the rail and a sensor holding part extending from the base. The sensor holding part is close to or in contact with the surface of the cylinder tube outside rail walls.

Abstract: Methods and systems a method of assembling a proximity probe are provided. The method includes determining a coil wire dimension and coil geometry for the probe such that a resistance versus temperature profile of the coil is approximately constant when the coil is excited with an excitation frequency of approximately 150 kilohertz to approximately 350 kilohertz, and adjusting the coil geometry such that a resistance versus temperature profile of the coil is substantially constant.

Abstract: A proximity detector includes a fine DAC and a coarse DAC, outputs of which are summed to provide a tracking signal for tracking a magnetic field signal. The proximity detector provides two mode of operation. In a first mode of operation the coarse and fine DACs operate in combination as one higher order DAC. In a second mode of operation, the coarse DAC is provided with one or more extra counts, allowing the tracking signal to move more rapidly to track a rapidly changing magnetic field signal. In another embodiment, the proximity detector also includes an offset circuit for bringing at least one of the magnetic field signal and the tracking signal towards the other one of the magnetic field signal and the tracking signal.

Abstract: A micro-position sensor and sensing system using the Faraday Effect. The sensor uses a permanent magnet to provide a magnetic field, and a magneto-optic material positioned in the magnetic field for rotating the plane of polarization of polarized light transmitted through the magneto-optic material. The magnet is independently movable relative to the magneto-optic material so as to rotate the plane of polarization of the polarized light as a function of the relative position of the magnet. In this manner, the position of the magnet relative to the magneto-optic material may be determined from the rotated polarized light. The sensing system also includes a light source, such as a laser or LED, for producing polarized light, and an optical fiber which is connected to the light source and to the magneto-optic material at a sensing end of the optical fiber.

Abstract: Systems and methods are disclosed that facilitate determining coil temperature in a proximity sensor, such as an extended range inductive proximity sensor. Voltage measurements can be taken before, and during, damped oscillatory decay of a voltage in a resonant circuit in the proximity sensor to determine a value, ?, associated with an inductive time constant for the resonant circuit. The gamma value comprises information related to both inductance and resistance in the sensor coil, and can be employed to determine coil temperature. Derivation of the gamma value, and thus of coil temperature, can utilize a current pulse of a duration of approximately one RC time constant of the resonant circuit, thus mitigating current consumption by the proximity sensor during temperature assessment.

Abstract: Systems and methods are disclosed that compensate for temperature drift in a proximity sensor, such as an extended range inductive proximity sensor. Voltage measurement can be taken before, and during damped oscillatory decay of a voltage in a resonant circuit in the proximity sensor to determine a value, ?, associated with an inductive time constant for the resonant circuit. A target-induced inductance value can be isolated, via manipulation of the gamma value, and compared to a predetermined threshold value to determine whether the target has been sensed by the proximity sensor.

Abstract: A sensor device includes the ability to determine part presence and at least one physical characteristic of the part. A drive coil and sense coil are arranged so that a voltage applied across the drive coil causes a response in the sense coil, which is influenced by the presence of the item of interest. In a first mode, a controller determines whether the item is present by determining an amount of coupling between the drive coil and the sense coil, which is indicative of whether a part is present near the sense coil. In a second mode, the controller determines an amount of magnetic flux that is indicative of a thickness of the material. In another mode, constant current applied to the drive coil instigates a voltage across both coils. The amplitude of the sense coil voltage and a phase shift of the sense coil voltage relative to the drive coil voltage provides material thickness information.

Abstract: Improving reducing or eliminating the effects of variation in characteristics of the resonance circuit in a resonance type displacement detection apparatus, so as to improve displacement detection accuracy. In a displacement detection system 10, the resonance frequency range assumable by the resonance circuit 21 is estimated in advance, there is determined a drive frequency variation range f1–f2 such that the estimated resonance frequency range is included therein, and by means of a variable oscillator 30, drive frequency is repeatedly varied between the first frequency f1 and the second frequency f2. Accordingly, where the resonance frequency of the resonance circuit 21 is fr1, when the drive frequency has changed to fr1, resonance voltage Vgl1 may be obtained in the case of large gap G. Where the resonance frequency of the resonance circuit 21 is fr2, when the drive frequency has changed to fr2, resonance voltage Vgl2 may be obtained in the case of large gap G.

Abstract: A position detector includes a magnet, a pair of Hall effect devices, and a processing circuit for detecting relative positions of the magnet and the pair of Hall effect devices. The processing circuit detects a difference in magnitude between output values of the Hall effect devices, as position outputs, with an input value to each of the Hall effect devices being controlled such that a sum of magnitudes of respective output values of the Hall effect devices is constant.

Abstract: A method of non-intrusive, inductive proximity sensing of a target through a conductive barrier comprises the steps of: disposing an inductive proximity sensor on one side of a barrier of conductive material; disposing a target on the other side of the barrier; determining an appropriate drive frequency for operating the proximity sensor based on the conductive material and thickness of the barrier; and operating the proximity sensor with the appropriate drive frequency to non-intrusively sense the proximity of the target through the conductive barrier.

Abstract: A magnetoresitive sensor comprising at least one sensor element for measuring a magnetic field, and a magnet assigned to the sensor element is disclosed. The magnet (14) has structures (18) which lead to a perpendicular guidance of magnetic flux lines (25) from the supporting magnet (14) in the sensing direction (y direction) at least in the sensitive area (26) of the sensor (100). The inventive sensor has a simple structure and does not require subsequent trimming for compensating an offset as in the prior art.

Abstract: An apparatus for detecting ferromagnetic objects in the vicinity of a magnetic resonance imaging scanner. The apparatus comprises primary sensor means adapted to measure a magnetic field, arranged in communication with signal processing means configured to identify temporal variations in the measured magnetic field due to the movement of a ferromagnetic object within an ambient magnetic field and to provide an output indicative of the presence of a ferromagnetic object in the vicinity of the primary sensor means. The apparatus further comprises secondary, non-magnetic, sensor means adapted to detect the movement of objects in the vicinity of the primary sensor means in order to reduce false alarms. The output from the signal processing means may be used to operate an audible alarm, a visual alarm, an automatic door lock or a physical barrier.

Abstract: Inductive proximity switch has a first transmitting coil (S1) and a first receiving coil (E1) of a receiving coil arrangement. The transmitting coil (S1) transmits an exciting field inducing eddy currents in a metallic trip (1) brought into the vicinity of the proximity switch. The eddy currents generate a voltage-inducing eddy current field in the first coil (E1) of the receiving coil arrangement. The first coil E1 and a second coil (E2) of the receiving coil arrangement are disposed and connected so that the exciting field generates a differential voltage (3), in the receiving coil arrangement. A pair of compensating coils includes the second coil (E2) of the receiving coil arrangement and a compensating coil (S2) connected in series with the transmitting coil (S1), the pair of compensating coils being isolated from the eddy current field.

Abstract: A magnetic linear displacement sensor. In accordance with one embodiment, the displacement sensor includes a Hall transducer element having a sensor plate surface and at least one magnet having a lengthwise dimension along which said Hall element detects a magnetic field component orthogonal to the sensor plate surface during displacement sensing. The magnet includes first and second pole faces disposed on opposite lengthwise sides thereof and a polarization axis aligned orthogonally with respect to the lengthwise dimension. The first pole face opposes the Hall, element and is characterized as having a non-planar surface contoured to generate a substantially linear orthogonal magnetic field component sensed by said Hall element during linear displacement sensing.

Abstract: An inductive measurement is carried out of the distance between a workpiece (3) and a working head (1), which bears an induction coil (8), through which an alternating current flows and which is part of a resonance circuit whose oscillation frequency is monitored for changes which occur as a consequence of changes in the distance between the workpiece (3) and working head (1). In this case, the working head (1) acts on the workpiece (3) with a material (2) having a dielectric constant greater than 1. The frequency of the alternating current is in the megahertz region or just therebelow. Last but not least, the induction coil is screened from external electric fields in order to avoid the influence of parasitic capacitances.

Abstract: A method and system for detecting a position of a metallic object are disclosed. The method includes (a) exciting a coil with an electrical signal to produce an electromagnetic field enveloping the object, (b) allowing a frequency of the electrical signal to be at the resonant frequency of the coil as affected by the object, and (c) adjusting a control signal controlling a characteristic of the electrical signal so that the characteristic substantially equals a predetermined standard level. The method further includes (d) periodically coupling and decoupling a resistive element in parallel with the coil while performing (a)–(c), and (e) deriving a signal based upon the control signal. The derived signal is indicative of a difference between first and second values of an intermediate signal functionally related to the control signal, which are obtained when the resistive element is coupled in parallel with the coil and decoupled, respectively.

Abstract: A preamplifier portion 2 is arranged between a head portion 1 containing a detecting coil and an amplifier portion 3, wherein a detecting circuit and a controlling circuit and the like are arranged. The preamplifier portion 2 is connected to the head portion 1 via a shielded cable 5 of fixed length, while connected to the amplifier portion 3 via multi core cables 6a and 6b having connectors 7a and 7b. In the preamplifier portion 2, in addition to an oscillating circuit, an EEPROM containing a compensating table for compensating the relation between the oscillation output of the oscillating circuit and a detected distance is arranged. This EEPROM is connected to the controlling circuit at the side of the amplifier portion 3.

Abstract: A sensor with a carrier board which is arranged in a housing is at least partly produced by an injection molding process and fitted with electronic, optical, electromechanical and/or opto-electronic components. A region of the carrier board and at least some of the components disposed thereon are arranged in a hollow space formed inside the at least partly injection molded housing.

Abstract: A method and apparatus for providing information from a speed and direction sensor is disclosed. The method and apparatus detect the presence of a ferromagnetic object as it moves past a sensor. The sensor determines speed and direction information regarding the ferromagnetic object, and further provides information relating to the environment surrounding the sensor or object, such as the status of an air gap between the sensor and the moving object, and the temperature of the environment in which the sensor or object is disposed.

Abstract: A stationary arranged sensor (4) is provided in the region of one of the dead centers of the piston movement to monitor the position of the path of motion of a piston (1) relative to a cylinder (2) whereby the sensor (4) measures the lateral distance (a) to an indicator unit (6) arranged on the piston (1). The sensor (4) is arranged in a recessed position relative to the inner surface of the cylinder (2) and is sealed toward the cylinder chamber (9) by means of a cover (8), and the indicator unit (6) on the piston (1) is designed as an anomaly (10) that is non-sensitive to contaminating deposits in the area of the face (11) of the piston (1).

Abstract: A magnetic sensor system and a method for installing magnetic sensors for detecting metal objects that allows ease of manipulation, control and access. A carrier conduit is used to position a magnetic sensor in an outer conduit. The outer conduit may be disposed beneath a surface where objects to be detected may be positioned. Alternatively, a conduit having multiple channels may be placed in a pathway. Magnetic sensors may be placed in the channels and a top placed over the conduit. Multiple embodiments for orienting the magnetic sensor systems are provided.

Abstract: A position detecting sensor includes a magnet, a magnetic detecting element, and a yoke adjacent to or near the magnet. A detected member is positioned at one side of the position detecting sensor so as to be adjacent to or away from the position detecting sensor. The magnet is oriented to generate a magnetic line of flux which flows in a direction complying with an extending direction of the detected member. The magnetic detecting element is positioned in an area in which a magnetic flux density generated by the magnet is relatively low when the detected member is positioned away from the position detecting sensor and a magnetic flux density is relatively high when the detected member is positioned adjacent to the position detecting sensor.

Abstract: A combination Hall effect position sensor and switch for sensing the position of a moveable object. The sensor has a magnet that is attachable to the moveable object. The magnet has a pair of ends and a central portion. A linear magnetic flux sensor is positioned about the central portion of the magnet. The linear magnetic flux sensor generates an electrical signal indicative of a specific position of the movable object. A switch type magnetic flux sensor is positioned about one of the ends of the magnet. The switch type magnetic flux sensor generates an electrical signal that is indicative of the movable object reaching a pre-determined location.

Abstract: A path and/or position measuring device is provided, including a magnet and a sensor for detecting the magnetic field intensity. The magnet and/or the sensor cooperate with a movable element. The magnet is formed such that the magnetic field intensity varies along an axis of the magnet and is not constant. The relative movement between the sensor and the magnet is substantially in the direction of the axis of the magnet. The path and/or the position of the movable element can be determined based on the magnetic field intensity detected by the sensor.

Abstract: A displacement sensor for sensing the relative position of an object to be detcted is provided. The displacement sensor includes a core body having a core center portion and core end portions that are continuously formed on both sides of the core center portion. Magnetizing coils and detecting coils are wound around the core body such that they are lined on an axis of the core body. One of the magnetizing coils and detecting coils is placed at the core center portion while the other ones of the magnetizing coils and detctin coils are placed at the core end portions in the axial direction. The width of the core end portions in the direction perpendicular to the axial direction of the core body is substantially the same and is smaller than the width of the core center portion.