Showing papers on "Inductive sensor published in 2001"

System for a machine having a large number of proximity sensors, as well as a proximity sensor, and a primary winding for this purpose

Abstract: A system for a machine, in particular an automated production machine, has a large number of proximity sensors. Each proximity sensor has at least one secondary winding that is suitable for drawing power from a medium-frequency magnetic field. At least one primary winding, which is fed from a medium-frequency oscillator, is provided for supplying the proximity sensors with electrical power without using wires. Each proximity sensor is equipped with a transmitting device that emits radio signals, which contain sensor information of interest, to a central receiving device that is connected to a process computer for the machine. A proximity sensor and a primary winding for this purpose are also proposed.

On-chip eddy current sensor for proximity sensing and crack detection

Abstract: In this paper, we present a new integrated eddy current sensor for proximity sensing and for the detection of microcracks on the surface of metals. The device consists of two stacked planar coils fabricated onto a glass substrate and encapsulated on one side by a Ni/Fe permalloy magnetic core. Fabrication of the device is achieved by a UV–LIGA thick photoresist lithography process, which involves the lithographic patterning of 15–25 μm thick molds using AZ-4000 series photoresist. The introduction of the permalloy core coupled with the thick conductor lines produces a high inductance, low resistance device capable of generating large magnetic fields at low driving currents. The device has been tested in the frequency range of 10–500 kHz and has been shown to work as both a proximity sensor and crack detector at input powers of 30 mW or less. When used as a proximity sensor, the unamplified output voltage on the sensing coil changes by as much as 75 mV with an aluminum target placed at a distance of 400 μm from the coil. The device has also shown the capability of clearly detecting cracks with depths of as little as 8 mil (200 μm) in both aluminum and titanium. Results show an extremely linear relation between crack depth and output signal voltage with an unamplified signal strength of several millivolts.

Methods and apparatus for compensating a radiation sensor for temperature variations of the sensor

Abstract: In one example, the radiation sensor is a thermal sensor having at least one property that varies as a function of temperature. The thermal sensor outputs signals based on thermal radiation of interest from a particular radiating body in its view. These signals may contain significant undesirable components due in part to changes in temperature of the sensor itself. Methods and apparatus of the invention compensate the sensor for temperature variations of the sensor that are not due to the radiation of interest, so as to significantly reduce undesirable components in the instantaneous signals output by the sensor. In one example, this is accomplished without thermally stabilizing the sensor itself (i.e., dynamic temperature compensation). In another example, the sensor is thermally stabilized selectively at various predetermined temperatures as a function of the ambient temperature in the proximity of the sensor.

Inductive proximity sensor for detecting ferromagnetic, non-permeable or magnet targets

Abstract: A core (120; 120'; or 1220) of a proximity sensor (100; 1200; or 1500) is made of a highly permeable metal and is shaped and sized to operate as a saturable core proximity sensor, a variable reluctance proximity sensor, and an eddy current proximity sensor. The core (120; 120'; or 1220) has a cross-sectional shape including a head portion (220 or 1231), two legs (222 or 1232) extending from the head portion (220 or 1231), and two foot portions (224 or 1233) (feet) extending from the two legs (222 or 1232). The head portion (220 or 1231) forms a substantially planar section along the upper surface and is perpendicular to the sectional direction created by the two legs (222 or 1232). The sectional direction of the two legs (222 or 1232) are perpendicular to the sectional direction of the two feet (224 or 1233). The two feet (224 or 1233) are in a common plane along the bottom surface. Both foot portions are also parallel to the head portion. The cross-sectional shape of the core may further comprise two tail portions (1234) (tails), wherein each tail extends from one of the two foot (1233) portions in a direction toward the upper surface (1221).

Methods and systems for capacitive motion sensing and position control

Abstract: A system for detecting motion and proximity by determining capacitance between a sensor and an object. The sensor includes sensing surfaces made of a thin film of electrically conductive material mounted on a non-conductive surface. In another embodiment, the sensor is a human body. The sensor senses the capacitance between a sensor's surface and an object in its vicinity and provides the capacitance to a control system that directs machine movement. Because the sensor does not require direct contact or line-of-sight with the object, a machine can be controlled before harm occurs to the object.

Proximity input detection system for an electronic device

Abstract: A proximity input detection system for an electronic device. In one embodiment, the present invention utilizes an inductive field sensor to detect a change in a magnetic field when an input device with a coil is within a threshold distance. In another embodiment, the present invention utilizes a capacitive sensor which can locate the position of an electrically conductive object which is within a threshold distance. The capacitive sensor can also be used, for example, as a switch to activate the device if a user picks it up. The present invention allows user inputs to be detected without actually touching the electronic device. The present invention can also be used to detect inputs through intervening non-metallic layers such as a protective cover or another display of the device without using additional input sensors.

Method and apparatus for measuring thickness of conductive films with the use of inductive and capacitive sensors

Abstract: The invention relates to an apparatus for measuring thickness and deviations from the thickness of thin conductive coatings on various substrates, e.g., metal coating films in semiconductor wafer or hard drive disks. The thickness films may be as small as fractions of microns. The apparatus consists of an inductive sensor and a proximity sensor, which are rigidly interconnected though a piezo-actuator used for displacements of the inductive sensor with respect to the surface of the object being measured. Based on the results of the operation of the proximity sensor, the inductive sensor is maintained at a constant distance from the controlled surface. Variations in the thickness of the coating film and in the distance between the inductive sensor and the coating film change the current in the inductive coil of the sensor. The inductive sensor is calibrated so that, for a predetermined object with a predetermined metal coating and thickness of the coating, variations in the amplitude of the inductive sensor current reflect fluctuations in the thickness of the coating. The distinguishing feature of the invention resides in the actuating mechanism of microdisplacements and in the measurement and control units that realize interconnection between the proximity sensor and the inductive sensor via the actuating mechanism. The actuating mechanism is a piezo actuator. Measurement of the film thickness in the submicron range becomes possible due to highly accurate dynamic stabilization of the aforementioned distance between the inductive sensor and the object. According to one embodiment, the distance is controlled optically with the use of a miniature interferometer, which is rigidly connected to the inductive sensor. According to another embodiment, the distance is controlled with the use of a capacitance sensor, which is also rigidly connected to the inductive sensor.

Device for contactless measurement of a displacement path, especially for the detection of position and movement

Abstract: The invention relates to a device (10) for contactless measurement of a displacement path, especially for the detection of position and movement, comprising a sensor electronics system for the provision of an alternating current and the evaluation of alterations therein, in addition to an inductive sensor (13) comprising at least one flat coil (15), whereby each coil (15) is configured with a helicoidal conductor (22) disposed on a plane and one of the two flat surfaces (19) thereof forms a measuring surface (14) which variously covers a measuring object (11), arranged at a distance, according to the movement thereof parallel to the measuring surface (14).

Inductive position measuring system

Abstract: In order to provide a position measuring system, comprising a transmitter, a sensor with an inductive element to which the transmitter is coupled electromagnetically and an evaluating unit, wherein the sensor and the transmitter are adapted to be positioned relative to one another, whereby said position measuring system will be of simple construction and can thus be manufactured economically while being employable universally, provision is made for the inductive element to be coupled to an oscillator which is affected by the Q factor and/or the effective inductance of the inductive element, for the Q factor and/or the effective inductance of the inductive element to be determined by the size of an effective sensor region to which the transmitter is coupled, and/or by the size of an effective transmitter region which is coupled to an effective sensor region, and for the sensor and/or the transmitter to be formed in such a manner that the size of the effective sensor region to which the transmitter is coupled, and/or the size of the effective transmitter region which is coupled to the effective sensor region is dependent upon the relative position between the transmitter and the sensor in a direction transverse to a direction of separation therebetween.

Method and apparatus for active isolation in inductive loop detectors

Abstract: An oscillator circuit (10) for use with a wire-loop inductive sensor (100) and method of use. The oscillator circuit (10) highly attenuates common-mode noise detected by wire-loop (100) and differential noise from both ambient and crosstalk sources are filtered by active isolation.

Inductive measuring transducer

Abstract: The invention relates to an inductive measuring transducer, comprising elements that can be displaced relative to one another. One of said elements (generator element (2)) comprises at least one inductive generator (6) that generates a magnetic alternating field, and the other element (sensor element (1)) comprises one or more inductive sensors. An electronic circuit (3) supplies the inductive generator (6) with an alternating current. The sensor element (1) has a closed conductive loop (10) in which the inductive generator(s) of the generator element (2) induce(s) a voltage in such a manner that a voltage profile is created that depends on the position of the generator element (2) with respect to the sensor element (1). Resistors (11) are connected along the conductive loop (10).

Inductive or capacitive detector

Abstract: The proximity detector includes a reference oscillator (11) and a measurement oscillator (10) whose frequency depends on the proximity of an object - especially a metal object. A correction is applied in order to compensate for temperature difference between the time of calibration and the time of use. The proximity detector includes a reference oscillator (11) and a measurement oscillator (10) whose frequency depends on the proximity of an object - especially a metal object. A counting value (A) which is a function of the reference frequency (F) of the measurement oscillator (10) is compared with a reference counting value (B) in order to produce the output signal. The value of the reference counting signal (B0) determined at the time of calibration is corrected by a quantity (C), which is dependent on the difference between the temperature at the time of measurement and that at the calibration time.

Inductive sensor having a sensor coil in the form of a structured conductive layer

Abstract: In order to so improve an inductive sensor comprising at least one sensor coil in the form of a structured, conductive layer of a carrier board, and an evaluation circuit comprising a printed circuit board with conductor tracks provided thereon and being connected to the sensor coil, that it is manufacturable as cost-efficiently as possible, it is proposed that the carrier board carrying the sensor coil be mechanically rigidly and electrically connected to the printed circuit board by at least two soldered joints.

Gage thickness measurement by use of inductive sensors

Abstract: A measuring gage for determining the thickness of a non-metallic material utilizes an inductive sensor positioned on one side of the material to be measured and a metallic object placed on the opposite side. The output of the sensor is used to determine the distance between the sensor and the metallic object, and hence the thickness of the material. The movement of the sensor and the metallic object can be computer controlled to map the thickness of the material along a predetermined path and produce a cross-sectional thickness profile. The output of the sensor can be used in conjunction with a computer controller responsible for adjusting the size of a score line to prepare an airbag deployment section in a vehicle trim panel.

Inductive and capacitive sensor arrays for in situ composition sensors

Abstract: Advances in electromagnetic sensor design provide the potential for high resolution imaging of subsurface objects and material properties at the microscopic (micrometer) and mesoscopic (meter) scales. With quasi-static, capacitive and inductive sensor arrays, objects are detected, identified, and imaged via their perturbations to the applied electric and magnetic fields, rather than through time delays of reflected electromagnetic waves as in ground penetrating radar. Building on the successful application as nondestructive quality assessment and monitoring tools as well as land mine detectors, several subsurface in situ sensors are enabled by this technology. Examples include: an electronic 3D microscope, enabling examination of cell level structures and composition; examination of near surface structures such as soil moisture, permafrost dynamics, soil properties with depth, root growth carbon sequestration, Martian surface aquifers, and buried deposits of carbon dioxide or methyl hydrides.

Power cable on-line diagnosis using partial discharges ultra wide band techniques

Abstract: A noninvasive ultra-wide band (UWB) partial discharge technique was employed in cable diagnosis of Mexico City underground distribution feeders. The technique presented here was applied to over 2000 joints, 400 terminals and thousands of meters of installed paper insulated impregnated cables rated at 23 kV. The technique allowed circuit classification according to electromagnetic field levels produced by partial discharges and recorded on each manhole with a joint along the circuits evaluated in 12 substations. The PD detection technique employs near field sensors working within the 80 MHz range and whose information is digitized and fed to a conventional PD digital detector, where a PD pattern is obtained. This pattern is correlated to the phase current by using an inductive sensor; therefore corona and interference problems could be disregard during measurements. To attain repetitive values, calibration was performed using a very fast pulse (less than 50 ns front) injected in a small cable loop. Results demonstrate a great signal to noise ratio, high selectivity and great noise discrimination. The large amount of measurements allowed the determination of limit values to differentiate areas in acceptable state from those requiring attention. Those results include detection of bad joints, cable deformation due to ducts collapse and damaged terminals, besides aged cable detection caused by overheating operation conditions. The results obtained had been confirmed by subsequent faults following the detection of very high levels of PD.

Comparative study of alternative circuit configurations for inductive sensors

Abstract: We study three different electronic circuit configurations for the excitation, recovering and analysis of the response of magnetic sensors based on inductive changes. The best characteristics are sought: maximum output, stability, linearity and large sensibility together with an economic design. To simulate the sensible element, we use a general coil with mobile magnetic core that resembles any real case where variations of induction take place. Three parts are readily distinguished in the circuits: oscillator, filter and rectifier. In one of the tested configurations the variable inductance is part of the oscillator, whereas in the other two, it is used in the filter. In turn, two different types of common oscillators are investigated: Colpitts and Wien bridge. The best option turns out to be the one composed by a Wien bridge oscillator with the variable inductance in the filter.

Inductive proximity sensor and related methods

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.

Device for monitoring and forecasting the probability of inductive proximity sensor failure

Abstract: A device for monitoring the probability of inductive proximity sensors (1) which are used to monitor the position of moveable points parts or rail parts. The proximity sensor (1) comprises at least one coil (5) which is fed by an oscillator (7) . The sensor current flowing as a function of alterable attenuation is measured and fed to an evaluation circuit. Characteristics (18,22) of the sensor for the profile of the sensor currents as a function of the distance of the moveable points or rail parts, i.e. mechanical attenuation, are stored in an electric, non -additionally attenuated state and an electric, additionally attenuated state. The measuring currents (22) corresponding to a mechanical attenuation state and the corresponding additionally electrically attenuated measuring currents are cyclically scanned. The respective measuring currents or pairs of measuring values are supplied to a comparator and evaluation circuit wherein differences arising from the characteristic curves are compared with the measured differences.

Non-contact position sensor having helicoidal conductor forming a measuring surface covering a measuring object

Abstract: A device for contactless measurement of a displacement path, especially for the detection of position and movement, includes a sensor electronics system for the provision of an alternating current and the evaluation of alterations therein, in addition to an inductive sensor including at least one flat coil. Each coil is configured with a helicoidal conductor disposed on a plane and one of the two flat surfaces thereof forms a measuring surface which variously covers a measuring object, arranged at a distance, according to the movement thereof parallel to the measuring surface.

Device and method for system and process supervision in a magneto-inductive sensor

Abstract: The invention relates to a method and to a device ( 1 ) for system and process supervision in a magneto-inductive sensor. A medium ( 6 ) flows through a measuring tube ( 2 ) substantially in the direction of the axis ( 5 ) of the measuring tube. A magnetic field extends through the measuring tube ( 2 ) in a direction substantially perpendicular to the axis ( 5 ) of the measuring tube. A measuring voltage is induced in at least one measuring electrode ( 3; 4 ) that is disposed substantially perpendicular to the axis ( 5 ) of the measuring tube. Said measuring voltage or the measurement data provide information on the volume flow of the measuring medium ( 6 ) in the measuring tube ( 2 ). The aim of the invention is to provide a method and a device which allow, in addition to the determination of the volume flow, the detection of the modification of a system and/or process parameter. To this end, the measurement data are acquired and stored over a predetermined period and the actual measurement data are compared with predetermined desired measurement data. If there is a deviation between the actual measurement data and the desired measurement data, a message is output.

Inductive Sensor for determining the position of a metallic workpiece

Abstract: Inductive sensor comprises a flat coil (4) for detecting the position of a metallic workpiece (2) relative to a first direction (X). The coil generates an output signal that is dependent on its impedance. The sensor measures workpiece position together with its contours, such as any holes or edges. The invention also relates to a corresponding transport system with a drive for transport of a workpiece using an inventive inductive sensor in conjunction with a drive controller for positioning the workpiece.

Inductive measuring transducer for determining the relative position of a body

Abstract: An inductive measuring transducer having bodies movable relative to one another, one of the bodies being a sensor component including an inductive sensor that produces an alternating magnetic field. Another of the bodies is a pickup component including an inductive pickup into which the alternating magnetic field is injected. The pickup component includes a conductor loop in which the inductive sensor induces a voltage. A voltage curve independent of position of the sensor component relative to the pickup component develops over the conductor loop. Resistors have first ends connected along the coductor loop and second ends connected together in groups at connection points. Voltage can be picked off from the connection points that correspond to functions of the position of the sensor component relative to the pickup component and permit the position to be clearly determined, the position and value of the resistors defining the functions of the position.

Inductive sensor and method of use

Abstract: An apparatus and method for measuring the inductance of a wire-loop without direct reference to any particular time-constant or frequency. Low-frequency noise induced into the wire-loop is canceled within the detector circuit and crosstalk between a plurality of adjacent wire-loops is nullified using passive transformers. New wire-loop configurations utilize the permeability-modulated carrier referencing to provide repeatable inductive signatures with less intrusive, and non-intrusive installations.

Sensor with a wireless power supply

Abstract: A sensor with a wireless power supply comprising an oscillating circuit which acts as a sensor unit, consisting of a capacitor and a coil. The coil is used for measurement purposes and to receive electromagnetic waves in order to supply the sensor with power. In a first preferred embodiment, the sensor is provided with a filter for frequency-based separation of the sensor signal into a supply component and a useful signal component. The sensor can be supplied with power during measurement. In a second preferred embodiment, the sensor is provided with a transfer switch for time-based separation of the sensor signal into the supply component and useful signal component. The sensor is alternately supplied with power and used to carry out a measurement.

Electromagnetic finite element analysis for designing high frequency inductive position sensors

Abstract: We used a commercial electromagnetic finite element analysis program to assess the performance of a noncontact inductive position sensor. The sensor's primary and secondary coils are laid on a printed circuit board, and are constructed in between a conductive target and a ground plane. It was found that the higher the conductivity of the target, the better the performance. Other simulation results, such as linearity, temperature effect, and contamination errors were also reported, and were used in design.

Calibration of nanosensors with direct traceability to the meter

Abstract: Nanosensors are a new class of sensors that has recently appeared. These sensors are characterized by nanometer or sub-nanometer resolution over a range of at least several micrometers. The most well known examples are capacitive and inductive sensors but also laser interferometers, holographic scales, and scanning probe microscopes (SPM's) belong to the class of nanosensors. The accuracy of these nanosensors is not necessarily of the same level as the resolution. Effects like sensitivity errors, non-linearity, hysteresis and drift may cause deviations of many nanometers. In order to determine these errors in a traceable way, a new measuring instrument was developed. The heart of the system is a Fabry-Perot interferometer, which consists of two parallel mirrors separated by a distance L from each other. Light of a so-called slave laser is directed into this Fabry-Perot cavity and stabilized to the cavity length L. When one of the mirrors of this cavity is displaced the frequency of the slave-laser will follow its movement. The frequency of this slave-laser is then compared to the frequency of a primary length standard. In this way the displacement of the mirror is measured. When a nanosensor is placed on top of the mirror it will also follow the movement of the mirror. In this way the nanosensor is calibrated. The range of the instrument is 300 micrometers and the uncertainty is approximately 1 nm. Measurements of different sensors, such as an inductive and a capacitive sensor as well as a laserinterferometer will be presented. A detailed description of the uncertainty budget will also be given.

Component movement direction monitoring method, uses detection of unsymmetrical magnetic field generated in component movement direction

Abstract: The movement direction monitoring method uses at least one cooperating signal source and signal sensor for providing signals correlated with the component movement to a control device (1) for automatic cut-out of the component movement upon detection of the incorrect movement direction. The signal source provides an unsymmetrical magnetic field in the component movement direction (R), detected by a Hall sensor (2) and/or an inductive sensor. An Independent claim for an automobile heater with a movement direction monitoring device is also included.

Offset hall-effect sensor

Abstract: A proximity sensing assembly for sensing the proximity of a metallic workpiece to a work holding device includes Hall-effect sensor. The magnetic field generated by the magnet is altered when a metallic workpiece is in close proximity to a magnet. Due to an offset relationship between the sensor and the poles of the magnet, the polarity detected by the Hall-effect sensor is analogous to a reversal when a metallic workpiece is proximate the magnet rather than simply detecting a change in strength. Thus the polarity detected by the Hall-effect sensor sends an clearly defined signal indicating the presence or absence of a workpiece in the work holding device.

Sensor-independent oscillation amplitude control

Abstract: The invention relates to a device (100, 200) for generating an electric voltage by means of which a body of a capacitive and/or inductive sensor, such as especially a capacitive micromechanical rotation rate sensor, can be oscillated, whereby said body is capable of oscillating. The aim of the invention is to produce the sensor in a cheaper manner. A voltage generation device (109) is provided which causes a constant mechanical excursion of the body that can oscillate, whereby said excursion is independent of the process tolerances of the sensor.