Showing papers on "Inductive sensor published in 1999"

Shielded flat-plate proximity/dielectric properties sensor

Abstract: A shielded flat-plate proximity/dielectric properties sensor includes a dielectric substrate leaving a planar configuration and a pair of spaced sensing electrodes mounted on one surface of the substrate. A pair of shield electrodes limit the electric field produced by the sensing electrodes. A first shield electrode on the back of the substrate intercepts field lines behind the sensor to prevent detection of objects from behind the sensor. A second shield electrode co-planar with and between the sensing electrodes intercepts field lines very close to the sensor to prevent the dense electric field near the sensor from dominating measurements of objects within the field.

Electronic throttle control position sensor

Abstract: An electronic position sensor for determining position as a function of magnetic flux density. The position sensor includes a magnetic flux sensor and a movable magnet, the sensed magnetic flux density by the magnetic sensor being a function of the relative air gap, magnet thickness, and magnetic field direction between the magnet and the magnet sensor element. The relationship between the magnetic flux density sensed by the magnetic sensing element and the positional disposition of the moved magnet component of the sensor is geometrically defined and optionally linear between two defined points of the range of articulation or motion of the sensor. The magnetic flux sensing element is a Hall-effect integrated circuit, magnetoresistor, magnetodiode, magnetotransistor, or similar sensing element with associated electronic circuitry having adjustable or programmable features including ratiometry, gain, offset voltage, temperature coefficient, and output signal range limiting.

Ac current sensor having high accuracy and large bandwidth

Abstract: A method and apparatus for processing an output of an inductive sensor, including integrating the output of the inductive sensor with an integrator, having a transfer function with at least two zeros, and at least three poles having characteristic frequencies above the zeros, having a greater number of said poles than said zeros, wherein an integration is performed at frequencies above the characteristic frequencies of the poles, and low frequency noise is substantially rejected at frequencies below the poles. The inductive sensor may be, for example, a Rogowski coil.

Method for evaluating signals of magnetoresistive sensors with high band width

Abstract: The invention relates to a method for evaluating signals while eliminating an interference signal on magnetoresistive sensor elements which is preferably proportional to the zero offset. The sensor elements can form a sensor element array such as a sensor bridge. According to the invention, the direction of magnetization of the sensor elements is modulated or shifted by applying a magnetic pulse field of a modulated or variable direction, and the output signals of the sensor elements or of the sensor element array are fed to a differential amplifier. Due to the modulation or shift of the operating voltage of the sensor bridge, the modulation or shift resulting at the same time as the magnetization of the sensor elements, a signal often arises which includes a direct component that is proportional to the magnetic field to be measured, and has an alternating component that is proportional to the offset voltage of the sensor element array. The latter is minimized by a feedback or is adjusted to zero. The bandwidth, with which the direct voltage that is proportional to the magnetic field to be measured can follow changes of the input signal, is greater in magnitude than the magnetization frequency of the sensor elements.

First integrated inductive proximity sensor with on-chip CMOS readout circuit and electrodeposited 1 mm flat coil

Abstract: The first fully integrated inductive proximity sensor has been realized with a 75 nH, 1 mm side gold electrodeposited squared coil and with on-chip 1 μm CMOS readout circuit. The measured nominal frequency output is of 8.95 MHz and increases up to 11.60 MHz with an aluminum target placed at 50 μm of the coil. The on-chip electronic interface is based on a differential relaxation oscillator designed to be fast and to have a frequency output increase when approaching a conductive non-ferromagnetic target, thus enhancing strongly the sensor sensitivity. The new sensor microsystem has been successfully applied for angular position measurements.

Highly versatile occupancy sensor

Abstract: An occupancy sensor is provided that can operate within an extended range of AC and DC input voltages, enabling the sensor to be used in different electrical environments. The sensor draws substantially only an amount of current required by the sensor at the moment, which reduces power waste. The sensor includes a relay that de-energizes when occupancy is sensed and energizes when occupancy is not sensed. This reduces peak sensor current, permitting the sensor to maintain a more constant average current. A shutdown mode is provided to prevent sensor damage or destruction should excessive output current be drawn from the sensor. The sensor also includes a second output at which occupancy signals are provided when an occupancy signal is present at the first output.

Turning center with integrated non-contact inspection system

Abstract: A non-contact inspection system (110) has one or more pairs of non-contact sensors (112-1, 112-2), pointing at the braking surfaces and a non-contact sensor pointing at the outer diameter of a disc. The non-contact sensors can be inductive sensors, capacitive probes and/or laser sensors. A controller (118) is connected to each sensor for signal processing and measurement output. The system (110) measures various features and characteristics, such as braking surface (102, 104) thickness variation, lateral run-out, flatness, parallelism and diameters. Measurements are made while the disc rotates at a specified speed or while the disc is stationary. The pairs of non-contact sensors (112-1, 112-2) continuousl y measure the distance from the sensor or calibrated surface to the pointed surface. Thereby the run-out and thickness variations can be calculated from the measurements at different radii. By combining the measurements on the same braking surface, the flatness and parallelism are calculated. The other two sensors (115 and/or 117) continuously measure the distance from the sensor or the calibrated surface to the pointed surface. A diameter can be calculated knowing the center of the disc. The lateral run-out, thickness variation, flatness and parallelism can be measured on each brake disc within the turning center for final inspection and/or statistical process control. The diameter measurement and its run-out can be fed back to the turning center to monitor and compensate tool wear.

Localization and characterization of buried objects from multifrequency array inductive data

Abstract: The problem of mine localization and characterization form electromagnetic induction data is addressed We consider processing techniques based on an inductive sensor model originally proposed by Das et al Given this model we examine estimation-theoretic methods for determining an object's center, its orientation, and scattering characteristics from low frequency spectroscopic data obtained over a grid of spatial locations Under this model, the data are linear functions of the multiple moment spectra and non-linearity related to object's location and rotation angles An estimation procedure based on a low-dimensional non-linear optimization routine for the determination of the object center and rotation angles is employed with a linear lest squares inversion method used to estimate the multiple moment spectra Examples are provided for ellipsoidal objects

Inductive sensor arrangement and method for detecting ferrous objects

Abstract: The inductive sensor arrangement for detecting metal objects hidden in a surrounding medium comprises a pair of field coils for generating an alternating magnetic flux by a sequential excitation with an AC-current and a pair of sense coils respectively mounted inside each associated field coil in an orientation to the axes of each of said field coils such that essentially no voltage is induced in said sensor coils in an environment free of a metallic object. If a metallic object comes into the vicinity of the inductive sensor four characteristic voltage value sets are produced by the sense coil pair which become subject of an algorithmic processing for defining a position and distinction criterion in respect to said hidden metallic object. The sensor arrangement has the advantage of a single point measurement resulting in an accurate position discrimination for a hidden metallic object like a rebar in concrete.

High-integrity inductive sensor detecting metal parts and e.g. revealing occupied rail track section, has additional testing coil enabling periodic proof testing of sensor coil

Abstract: The sensor is a conventional inductance (5), in an oscillatory circuit. It has a second coil (8), a test coil with its own oscillatory circuit, which can be activated for the purpose of testing the sensor, over a predetermined interval.

Partial discharge measurement in transmission-class cable terminations

Abstract: This paper describes on-line and off-line partial discharge (PD) measuring techniques applicable to transmission cable terminations. The on-line technique can be utilized for both extruded and pipe-type cable terminations. In pipe-type cable terminations, the on-line technique is only applicable to newly installed terminations, as it requires an internal inductive sensor. In the case of extruded cable terminations, on-line testing is made possible by using an external inductive coupler around the ground connection at the base of termination. Off-line PD measurements utilize high-frequency capacitive couplers. The coupler is attached to the overhead line within 4-feet from the termination under test. The off-line testing is applicable to new and existing cable terminations.

Method for the generation of an electrical signal sensor device for executing the method and the use of the sensor device

Abstract: A method for generating an electrical signal and a sensor device (10) for executing the method. The signal is generated because of a change in a fluid-filled space. A sensor element (12) of the sensor device (10) detects the heat transfer over time between the sensor element (12) and the fluid. The sensor element (12), which has a temperature-dependent electrical conductivity and to which a voltage has been applied, is brought to a temperature which lies outside the range of the fluid temperatures. In the passive phase, the fluid is brought to a constant passive temperature by a heat transfer between the sensor element (12) and the surroundings. The sensor device (10) provides a constant passive output voltage. A heat transfer between the sensor element (12) and its surroundings takes place in the active phase by changes in the fluid-filled space. The sensor device (10) provides an active output voltage, which is different from the passive output voltage. When a difference between the output voltages is exceeded, the signal is generated. The device can be used for triggering the flushing action in sanitary installations, and for keeping a level constant, for example in aquarium installations.

Magnetic impedance effect micro-magnetic sensor

Abstract: PROBLEM TO BE SOLVED: To provide a magnetic impedance effect micro-magnetic sensor the temperature characteristic of which is stabilized and, at the same time, the power consumption of which can be reduced. SOLUTION: A magnetic impedance effect micro-magnetic sensor is provided with a head 2 which is excited in the peripheral direction by a pulse conducting current and is made of a magnetic material having high magnetic permeability, a coil 5 wound around the head 2 in the peripheral direction, and an electronic switch 4 which detects the first pulse of the voltage induced in the coil 5. Therefore, the temperature characteristic of the sensor can be stabilized and, at the same time, the power consumption of the sensor can be reduced. In addition, the sensor can obtain a high-linearity hysteresis-free magnetic field sensor characteristic due to a negative feedback effect.

System and method for controlling a self-heated gas sensor based on sensor impedance

Abstract: The present invention contemplates a system and method for controlling or adjusting the accuracy of an exhaust gas sensor utilizing the impedance of the sensing element. In one embodiment, a periodic AC signal is superimposed over low frequency or DC output signal produced by the gas sensor. The AC current flowing through the gas sensor is a function of the actual impedance of the sensor, which is in turn a function of the temperature of the sensor. Thus, the invention further contemplates an impedance sensor circuit connected to an output of the gas sensor. The output of the impedance sensor circuit is a peak voltage that is indicative of the AC voltage drop across the sensor, and ultimately the impedance of the sensing element. This peak voltage is utilized to control the operation of the heating element in a closed loop control system in which the thermal output of the heating element is continuously varied as a function of the magnitude signal to accurately maintain a consistent temperature for the exhaust gas sensor. In a specific embodiment of the invention, the impedance sensor circuitry includes a bandpass filter centered around the frequency of the superimposed AC signal to eliminate spurious noise. The output from the bandpass filter is provided to a half-wave rectifier, the output of which is the peak voltage signal indicative of the sensor impedance.

Method of sensing rotational information of shaft with toothed wheel

Abstract: A method for more accurately sensing the rotational position of a shaft having a toothed sensor wheel with a missing tooth is disclosed. The method includes employing an inductive sensor to produce a signal in response to the passing of the teeth on the sensor wheel. The sensor signal is altered by the geometry of the wheel about a gap formed by the missing tooth in order to correct for residual stored energy in the sensor at this location, and thus correct the signal for the timing measured by a processor in communication with the sensor.

Image sensor with increased pixel density

Abstract: An image sensor is disclosed that provides improved image resolution, for a given integrated circuit die size, by eliminating one or more dedicated power supply lines that feed each sensor element of the sensor array, thereby allowing greater sensor element density. Each sensor element has a first switch that is coupled to a photodetector to alternatively, under the control of a reset signal, (1) provide a first current to reset the photodetector and (2) present high impedance to the photodetector. A reset line is coupled to the first switch in each of the sensor elements to provide the reset signal and to both control the first switch and supply the first current. Such an image sensor may be particularly desirable when built using a metal oxide semiconductor (MOS) fabrication process. The image sensor may be used in a variety of imaging systems, including digital cameras.

Inductive sensor head for metal detectors

Abstract: An inductive sensor head for detecting of ferrous or non-ferrous electrically conducting objects, in particular rebars in a surrounding medium like concrete or a brick wall, comprises as essential sensing elements at least one field coil (Fl) with a small axial length compared to its diameter and at least one twin pair of sense coils (A, B) with a small diameter compared to the diameter of the field coil. The number of turns of wire on the field coil is small compared to the number of turns of wire on the sense coils. The common axis of the sense coils (A, B) is arranged perpendicular to the axis of the field coil so that there will be no component or a minimum component of maximum flux that is coaxial with the sense coils. For giving not only positional but also depths information, a twin pair of coaxially arranged identical field coils (F 1 , F 2 ) is provided which are excitated time sequentially. In a center plane between the field coils an orthogonal arrangement of two twin pairs of sense coils (A, B and C, D) is provided enabling a three-dimensional hidden object positioning. The sensor head according to the invention can be automatically calibrated, controlled and read out under control of a microcontroller.

Displacement and/or angle sensor with a meander-shaped measuring winding

Abstract: An inductive sensor for determining a position of a body moveable on a fixed housing includes an inductive transmission element in the body, the transmission element being operative for generating an alternating magnetic field flux The body is movably arranged such that the flux passes over a flux path area of the housing At least one conductor loop is arranged on the housing along a measuring length on the housing which measuring length can extend in a linear course or a circular course At least one conductor loop is arranged on the housing extending along the measuring length, the conductor loop including a feed line and a return line The return line has a path which at regular intervals of said measurement length alternates into and out of said flux path area A permeation of the return line at a given measurement path location by the flux of the flux region induces a loop output voltage indicative of a body measurement length position on the housing or of a body angular position on the body

Magnetic rotary position sensing

Abstract: A rotational sensing assembly including a ferromagnetic sensor wheel rotationally fixed to a shaft having a tooth pattern including a missing tooth. An inductive sensor is mounted adjacent the periphery of the sensor wheel and in communication with a processor. The sensor produces a generally sinusoidal signal in response to the wheel rotation, with voltage zero crossings that are time stamped by the processor. The geometry of the sensor wheel around the missing tooth location is altered to equalize the induced voltage in the sensor for fixed time intervals in order to maintain proper timing of the zero crossings in the sensor signal.

Proximity sensor method and apparatus that is insensitive to temperature, noise and length of wire

Abstract: A proximity sensor for determining the gap between a sensor and a metal target which is insensitive to noise, changes in temperature of the sensor and different lengths of wire by measuring the AC conductance, DC conductance and susceptance of the sensor and using the measured values with a predetermined data base to derive the desired gap distance.

A capacitance sensor for safeguarding operators of industrial robots

Abstract: To increase operator safety in robotic working cells, a capacitive sensor for the detection of humans has been developed. The sensor consists of two electrically conducting planes, insulated electrically from the ambient. When the dielectric or conductive conditions in the space between the planes are altered, e.g. a person enters, the sensor will indicate the presence of the person. The strength of the electric field caused by the sensor is kept low by lock-in amplifier technique. In the article the basic detection principle, the sensor electronics and the sensor signal handling are described and some practical experiments are presented.

Document validator having an inductive sensor

Abstract: A document validator includes a document path along which a document is conveyed and an inductive sensor for sensing features of the document. The sensor has a first inductive element disposed on a first side of a plane of the document path and a second inductive element disposed on a second side of the plane of the document path. Circuitry coupled to an output of the inductive sensor processes signals relating to a determination of at least one of the presence, authenticity and denomination of the inserted document. The sensor need not physically contact a document, such as a banknote, as it is conveyed along the document path.

Method and apparatus for force sensors

Abstract: The present invention relates to the design and use of multi-axis force sensors for applications such as human-robot interaction. A compliant and easily constructed flexure element for use in controlling the range of motion of a force sensor in response to applied forces and torques is presented. Two- and three-axis embodiments of the flexure element are disclosed. Devices and methods for reading out the deflection of the flexure element to determine an applied force along a single axis are presented as well. The read-out mechanism can employ optoelectronic measurement devices and methods. The optoelectronic sensor can be implemented with the two- or three-axis embodiment of the flexure element. Additionally, a force sensor based on an inductive read-out technique is presented. The described inductive sensor uses the two-axis flexure element.

Proximity sensor operation method of

Abstract: The proximity sensor cooperates with a trigger (4), an LC resonant circuit (1) and a frequency generator (3). The sensor has an analysis circuit (5) for determining a component, independent of the trigger material, of a complex system parameter dependent on the position and the material of the triggering object (4). The system parameter can be e.g. the impedance of the LC circuit, the amplitude of oscillation or a voltage distribution between the oscillation circuit and a series resistance. An Independent claim is included for a proximity sensor.

Inductive proximity switch with a one-piece housing

Abstract: An inductive proximity switch is provided which comprises a coil, means for supplying the coil with periodic transmitting current pulses, and means for processing signals which correspond to voltages induced in said coil after the end of a transmitting current pulse by the decaying current which previously flows in the detected body due to the voltage induced therein by the transmitting current pulse. In order to improve the robustness of the proximity switch so that it is suitable for durable use in an aggressive environment, the coil, the means for supplying the coil with a periodical transmitting current, and the signal processing means are arranged in a cylindrical housing which is closed on the side of the active surface of the proximity switch and consists of a metal which is not ferromagnetic and whose specific electric resistance is relatively high.

Simulation and calibration of an open inductive sensor for pulsed field magnetization measurements

Abstract: The relation between the voltage induced in an open sensor and the magnetic moment of a sample during pulsed field magnetization measurements has been calculated. The calculation takes into account the size of a sample, its internal flux distribution, and its position with respect to the center of the sensor. It has been found that the behavior of the response signal with respect to the sample position is the same for homogeneously magnetized Ni samples and high temperature superconductors. Because of this universality, it is possible to calibrate the open sensor even in the case of an unfavorable sample geometry. The calculations have been experimentally verified by using Ni samples with different geometries. Our results can easily be extended to samples with an arbitrary local field distribution.

Feasibility of Inspecting Defects in Printed Circuit Boards by Using Eddy-Current Testing Techniques.

Abstract: The inspection of etching defects in an as-made printed circuit boards (PCBs) is an attractive application of eddy-current testing (ECT) technology, since ECT inspection has various advantages such as non-contact, low stress, conductive testing, and fast scanning. When the technique is applied to high-density PCBs, the difference from conventional approaches becomes more remarkable. This paper describes the relationship between the shape of the inductive sensor and the width of printed wiring. The evaluation of signal-to-noise ratio results obtained by experiment clarifies the limits of detection. To improve inspection for higher-density PCBs requires a finer ECT sensor, but it was confirmed the defects in the printed wiring with a width less than one third of the sensor pitch can be detected.

Non contact inductive sensor for measuring rectilinear or angular displacements

Abstract: The inductive sensor has a magnetic circuit (2) with an airgap and excitation winding (1). A movable part (3) slides in the airgap and a measuring circuit (4,5,v), see Fig. 2a,2b, measures the reluctance of the magnetic circuit so as to deduce a position of an object mechanically linked to the moving part (3). the part (3) has a section, measured perpendicular to the sense of sliding which is variable along the slide direction. The excitation winding can include a series connected primary winding (7) see Fig. 5, and a secondary winding (8) mounted respectively on the first and second pole either side of the airgap. The measuring circuit includes an a.c. and d.c. current source connected in parallel with the winding. The circuit also includes: - a low and high pass circuits and a multiplier circuit; - an analogue - digital converter which has a reference input connected to the low pass circuit.

Sensor for measuring electrical conductivity of a liquid

Abstract: The sensor (1) has device (5) for measuring changing signal at the entrance of an excitation coil (3). Inductive sensor (1) to measure the electrical conductivity of liquid medium (2) has an excitation coil (3) which is driven by an entrance signal and a receiving coil (4) coupled to the excitation signal (3) via the liquid medium. The receiving coil (4) delivers an output signal (Iind) which is a measure of the conductivity of the liquid medium (2).

Method for automatically adjusting the switching threshold of capacitive and inductive proximity sensors, requires constantly re-compensating the proximity sensor should the environmental conditions change or another object be detected

Abstract: Adjustment of the switching threshold of the proximity sensors can be individually adapted to the prevailing environmental conditions and properties of the object being detected by continually measuring and sampling (evaluating) the capacitances C12(t) and C23(t).