Showing papers on "Inductive sensor published in 1996"

The future of magnetic sensors

Abstract: The operation of magnetic-field sensors is based on many different physical principles ranging from induction to magneto-optical effects. This in turn leads to a vast range of possible magnetic sensor types. What will finally decide the commercial viability of a particular magnetic sensor is its performance as well as its compatibility with miniaturization and microelectronic circuits. The magnetic sensors with the most potential for future applications include: Hall devices, magnetoresistors, inductive coils and fluxgates. The Hall device, while very compatible with microelectronics, suffers from a limited sensitivity in silicon, a high level oof 1 F noise and a relatively large offset. Ferromagnetic magnetoresistors generally have a high sensitivity at a low field; associated problems are the flipping effect and hysteresis. Inductive coils find many applications in proximity and distance sensors, but the miniaturization of coils is difficult. The fluxgate is a highly sensitive magnetic sensor. In principle, it could be integrated, but the main challenges are the three-dimensional structure of the coils and the low magnetic permeability of integrated ferromagnetic cores. The performance of sensors can be considerably improved by incorporating them into a system and using synergistic relationships such as feedback and compensation. The future of magnetic sensor microsystems looks bright with many promising application areas.

Handbook of Chemical and Biological Sensors

Abstract: PREFACE FUNDAMENTALS OF SENSOR TECHNOLOGY: INTRODUCTION TO CHEMICAL AND BIOLOGICAL SENSORS by J.S. Schultz and R. F. Taylor PHYSICAL SENSORS by R.A. Peura and S. Kun Piezoelectric sensors Resistive sensors Inductive sensors Capacitive sensors Bridge circuits Displacement measurements Blood pressure measurements INTEGRATED CIRCUIT MANUFACTURING TECHNIQUES APPLIED TO MICROFABRICATION by M. Madou and H.L. Kim Photolithography Subtractive techniques Additive techniques Comparison of micromachining tools Acknowledgment PHOTOMETRIC TRANSDUCTION by D.G. Buerk Phototransduction based on interactions between light and matter Applications for photometric transducers ELECTROCHEMICAL TRANSDUCTION by J. Wang Amperometric transduction Potentiometric transduction Conductometric transduction MODIFICATION OF SENSOR SURFACES by P. Barlett Covalent modification of surfaces Self-assembled monolayers and adsorption Polymer-coated surfaces Electrochemically generated films Other surface modifications BIOLOGICAL AND CHEMICAL COMPONENTS FOR SENSORS by J.S. Schultz Sources of biological recognition elements Design considerations for use of recognition elements in biosensors IMMOBILIZATION METHODS by R.F. Taylor Immobilization technology Immobilization of cells or tissues BILAYER LIPID MEMBRANES AND OTHER LIPID-BASED METHODS by D.P. Nikolelis, U.J. Krull, A.L. Ottova, and H.T. Tien Experimental bilayer lipid membranes Electrostatic properties of lipid membranes Electrochemical sensors based on bilayer lipid membranes BIOMOLECULAR ELECTRONICS by F.T. Hong Advantages of using molecular and biomolecular materials Electrical behavior of molecular optoelectronic devices: the role of chemistry in signal generation The physiological role of the ac photoelectric signal: the reverse engineering visual sensory transduction process Bacteriorhodopsin as an advanced bioelectronic material: a biunctional sensor Bioelectronic interfaces Immobilization of protein: the importance of membrane fluidity The concept of intelligent materials SENSOR AND SENSOR ARRAY CALIBRATION by W.P. Carey and B.R. Kowalski Zero-order sensor calibration (individual sensors) First-order sensors (sensor arrays) Second-order calibration MICROFLUIDICS by J.N. Zemel and R. Furlan Fabrication of small structures Sensors for use in microchannels Flow actuation and control Fluid flow phenomena PRACTICAL EXAMPLES OF POLYMER-BASED CHEMICAL SENSORS by M.J. Tierney Roles of polymers in chemical, gas, and biosensors Property/function-based selection of polymers for sensors Polymer membrane deposition techniques Examples: polymers in fast-response gas sensors SOLID-STATE, RESISTIVE GAS SENSORS by B. Hoffheins Materials Enhancing selectivity Fabrication Specific sensor examples OPTICAL SENSORS FOR BIOMEDICAL APPLICATIONS by G.G. Vurek Why blood gas monitoring? Oximetry Intra-arterial blood gas sensors Sensor attributes affecting performance Accuracy compared to what? Tools for sensor development Examples of sensor fabrication techniques In vivo issues ELECTROCHEMICAL SENSORS: MICROFABRICATION TECHNIQUES by C-C Liu General design approaches for microfabricated electrochemical sensors Metallization processes in the microfabrication of electrochemical sensors Packaging Practical applications Examples ELECTROCHEMICAL SENSORS: ENZYME ELECTRODES AND FIELD EFFECT TRANSISTORS by D. Pfieffer, F. Schubert, U. Wollenberger, and F.W. Scheller Overview of design and function Description of development steps Transfer to manufacturing and production Practical use and performance ELECTROCHEMICAL SENSORS: CAPACITANCE by T.M. Fare, J.C. Silvia, J.L. Schwartz, M.D. Cabelli, C.D.T. Dahlin, S.M. Dallas, C.L. Kichula, V. Narayanswamy, P.H. Thompson, and L.J. Van Houten Contributions to conductance and capacitance in device response Mechanisms of sensor response: kinetics, equilibrium, and mass transport Practical example: fabrication and testing of SmartSense immunosensors PIEZOELECTRIC AND SURFACE ACOUSTIC WAVE SENSORS by A.A. Suleiman and G.G. Guilbault Fundamentals Commercial devices Emerging technology THERMISTOR-BASED BIOSENSORS by B. Danielsson and B. Mattiasson Instrumentation Applications ON-LINE AND FLOW INJECTION ANALYSIS: PHYSICAL AND CHEMICAL SENSORS by G.E. Pacey Definitions and descriptions of on-line and flow injection Selectivity enhancements, matrix modification, and conversion Sensor cell design in FIA Measurements FLOW INJECTION ANALYSIS IN COMBINATION WITH BIOSENSORS by B. Mattiasson and B. Danielsson Flow injection analysis CHEMICAL AND BIOLOGICAL SENSORS: MARKETS AND COMMERCIALIZATION by R.F. Taylor Development and commercialization Current and future applications Current and future markets Development and commercialization of a chemical sensor or biosensor

Monitoring of internal partial discharges on a power transformer

Abstract: In a method for monitoring of partial discharges in an electric power transformer (1) under normal operating conditions, the magnetic field at a high-voltage bushing (2) on the power transformer is sensed with an inductive sensor (6) comprising at least one coil (6a, 6b) arranged at the bushing, and the electric field at the bushing is sensed with a capacitive sensor (5). The output signals from said sensors are supplied to a signal processing unit (3) in which each one of the output signals is filtered in a separate bandpass filter (101, 102), whereupon the filtered output signals from said sensors are multiplied by each other. An output signal (PDI) from the signal processing unit is formed in dependence on the result of said multiplication for the purpose of detecting internal partial discharges in the transformer.

Radio-interrogated surface-wave technology sensor

Abstract: Radio-interrogated surface-wave technology sensor, in which the sensitive element (12) is an impedance which is electrically connected as termination to a surface-wave structure (26) of the sensor.

Security system with variable inductance sensor

Abstract: A security system that includes an inductive sensor commonly known as a "proximity sensor" or "variable reluctance sensor", an alarm unit, and a controller that allows a user to position the movable structure on which the sensor is mounted, e.g., a door or window, at a selected position and then arm the security system with the structure in that position to detect movement of the structure away from the selected position. For example, the user may open a window on which the sensor is mounted and then arm the alarm to trigger upon detection of movement of the window from that position or, alternatively, only upon detection of further opening of the window or, alternatively, only upon detection of closing of the window. A user could thus open a window a small, selected amount to admit fresh air without triggering the security system or open a door a small, selected amount to receive a caller or allow pets to enter or leave the premises without triggering the security system.

Method and device for detecting displacement of valve rod movement in an electropneumatic position regulator with at least one proximity sensor

Abstract: A method and apparatus for detecting displacement of valve rod movement in electropneumatic position regulators, by generating a high-frequency electromagnetic alternating field by exciting a high-frequency oscillation within an LC oscillating circuit in an inductive sensor, damping the high-frequency oscillation as a function of displacement via an electrically conductive body moved along by the valve rod, demodulating the oscillator signal and feeding the demodulated signal to a microcomputer without amplification for evaluation of the displacement-dependent damping of the oscillation amplitude, measuring the temperature within the inductive sensor, correlating the temperature with the measured oscillation amplitude in the microcomputer, and determining a corrected displacement signal from the correlation.

Inductive sensor for monitoring fluid level and displacememt

Abstract: A sensor system for measuring the level of a fluid includes a tube having a primary coil and a pair of secondary coils wound thereabout. The secondary coils have a periodically varying winding density distribution. The winding density distribution of one secondary coil is shifted relative to the winding density distribution of the other secondary coil. A float positioned adjacent the tube modifies an electromagnetic field produced by the primary coil. In response to the modified electromagnetic field, the first and second secondary coils produce first and second signals having amplitudes that vary periodically in response to the movement of the float between the ends of the tube.

Inductive proximity sensor for detecting magnetic and non-magnetic metallic objects

Abstract: A universal inductive proximity detector including an oscillator, whose oscillating circuit is powered by a current source A fixed frequency master oscillator 16, which controls the current source 18, is coupled to the oscillator 10 so that the current source excites the oscillating circuit with a pulsed direct current

Method and apparatus for proximity sensing in the presence of an external field

Abstract: An inductive proximity sensor and a method of proximity sensing are described that permit targets of interest to be detected despite the presence of external magnetic fields due to AC or DC sources, such as resistive welding machines. The sensor has a pair of matched coils positioned adjacent to one another along a common central axis. The coils are coupled in series with oscillator and detecting circuitry, that also serves to drive a switching device. The coils are wound for current flow in opposite directions and produce oscillating electro-magnetic fields for detecting the targets in response to signals from the oscillator and detecting circuitry. Currents in the coils induced by strong external magnetic fields produces an additional components of the coil field which essentially cancel one another. The sensing field of the coil assembly may be shaped and directed by cooperation of the fields of the two coils and by appropriate shielding around one or both coils.

Means for reducing minimum sensing distance of an ultrasonic proximity sensor

Abstract: A rugged ultrasonic sensor is provided which is capable of detecting objects in very close proximity to the sensor. This close proximity detection includes the detection of objects which are immediately adjacent the sensor housing. Such close range operation is achieved by tailoring the transducer to operate at previously undesirable conditions, including low Q and high frequency. Such operating conditions allow the resonating characteristics of the transducer not to interfere with close range operation.

Inductive sensor and method for detecting displacement of a body

Abstract: A sensor for measuring angular displacement of a small body comprising a sealed housing containing a differential transformer having at least two primary coils (17, 18), one primary (67) and two secondary coils (65, 66), or two primary (27, 28) and two secondary coils (25, 29), said coils being partially submerged in a ferromagnetic fluid. The level of fluid relative to the coils will vary as the sensor is tilted. When AC current is applied to at least the primary coils of the transformer, the voltage across the circuit defined by the two primary coils or the two secondary coils is indicative of the angle of tilt of the sensor and the body to which it is attached.

An original approach to eddy current problems through a complex electrical image concept

Abstract: In this paper, we propose an original method for the physical analysis of electromagnetic interactions between an inductive sensor and any homogeneous conducting plane target. In the first part of this paper, the basic principles of inductive sensors are recalled. Then, we solve Maxwell's equations in order to obtain an analytical model for the relationship between the target properties and the electrical signals for a U-shaped sensor. Next, we emphasize the fact that our analytical relations can be interpreted as an extension of the electrical image method, even in the most difficult case of conducting and magnetic targets. In the last part, we present some measurements illustrating this new electrical image concept.

Monitoring method for sensor, e.g. inductive sensors used in car control systems

Abstract: The appliance monitors at least one sensor (103) and includes a first switching circuit (303) for connecting one terminal of the sensor to a power supply and an evaluator circuit (201) for assessing the resultant signal potential at the sensor terminals. The current supplied to the second sensor terminal is adjusted by operation of a second switchable circuit (304). The evaluator circuit can contain at least a first and a second group of circuits connected to the first or the second sensor terminal and also a microprocessor for processing the signals provided by the two circuit groups or for operating the first switching or the second switch able circuit

Inductive sensor measuring angular displacement or rotation from e.g. ferromagnetic sectored disc

Abstract: The unit measures rotation or angular displacement, producing a representative electrical signal. It comprises two principal parts. A measurement signal inducer (e.g. a sectored ferromagnetic disc) turning with the rotating body, and a stationary measurement sensor. This comprises a casing enclosing the components producing the signal, and a connecting cable led out from it. In the new design, the casing is assembled from two plastic shells (7, 7'). Once the components (5, 8, 9) have been fitted in, and the cable has been inserted, the shells are joined by adhering, ultrasonic welding or hot seal welding. Finally, a casting compound or hot melt adhesive is injected, to fill the casing. Also claimed is the corresponding method of making the measurement sensor.

Scaling down an inductive proximity sensor

Abstract: We analyse the problem of scaling down an inductive proximity sensor made of superposed multiple-turn flat coils. We scale down linearly all the geometrical dimensions. Then the nominal inductance is scaled down proportionally to the scale factor. The coupling factor of the superposed coils remains constant. However, for both ferromagnetic and non-ferromagnetic targets, the sensitivity remains constant when the frequency is scaled by the inverse square of the reduction factor. But the parasitic effects in the sensor coil become more important for small device dimensions. Therefore these effects are expected to set the ultimate limit in the miniaturization of the integrated inductive proximity sensors.

Method and system for testing a wheel speed sensor input circuit in an ABS and/or TC system

Abstract: Test signals are generated by a microcontroller (i.e., micro) and coupled to a transistor which is in series with an inductive sensor of a wheel speed sensor input circuit to test the input circuit. In one test, a test signal from the micro sweeps through a range of predetermined frequencies to turn the transistor off and on to provide a simulated wheel speed signal which is used to compute a corresponding number of simulated wheel speeds. The programmed micro compares the simulated wheel speeds with the predetermined frequencies to determine if the various components of the circuit are operating properly and also to determine if the wheel speed arithmetic of the programmed micro is operating properly since actual wheel speed routines within the micro are used to compute the simulated wheel speeds. In another test, a low pass filter circuit coupled to an A to D input port of the micro are both tested by having the micro read the input port at various times before and after a second test signal from the micro is coupled to the transistor.

A simple, non-invasive and inexpensive method for evaluating the displacement of local tissue surfaces: from vascular changes to muscle contraction.

Abstract: This paper describes a non-invasive, very inexpensive method of estimating tissue displacements of various origin that is easy and fast to set up. This technique utilizes an inductive proximity sensor (IPS), which is a non-contact length transducer measuring the distance between its probe and a metal target. Its working principle is based on the electromagnetic coupling originating between the sensor probe, a source of high-frequency magnetic field, and the metal target where parasitic currents take place. The linear working range of the IPS model used here is 0.1 to 6 mm probe-target distance, its resolution is about 2 microns. The IPS has been employed on rabbits and humans to measure the displacement of a target glued to the skin of various body areas with respect to the fixed probe of the sensor. Its high resolution, together with an extensive working range, allows the evaluation of numerous physiological events which produce displacements ranging from 2 microns -- to 9 mm, reflecting either tissue volume changes or movements. In particular, an interesting application is to monitor, through volume variations, the extent and the time course of local vascular modifications induced by manoeuvres which elicit changes in vasomotor tone; vascular filling, tissue swelling etc. Therefore, this measure may be considered a 'surface plethysmography' record. In addition, the contractions of skeletal muscles, under either isotonic or isometric conditions, can be estimated through this sensor. This system may therefore find applications for research purposes and practical demonstrations to students.

Proximity sensor circuit with frequency changing capability

Abstract: A proximity sensing circuit is provided with various attributes, including the connection of a proximity sensor coil in a feedback loop of an amplifier, the frequency hopping technique that periodically changes the two frequencies used by its proximity sensor circuit to avoid deleterious interference by constant frequency EMI sources and the provision of a self diagnosis technique. The connection of the proximity sensor coil in the feedback loop of an amplifier results in several advantages including the connection of the coil to a virtually infinite impedance, the reduction of the number of components needed in the proximity sensing circuit and decreased temperature sensitivity of the overall circuit. The frequency hopping technique that periodically changes the two frequencies used by the proximity sensor significantly decreases the likelihood that a constant frequency EMI source in the vicinity of the circuit will have a continually adverse affect on its accuracy and reliability. In applications that require a large number of sensors, the circuit uses a multiplexer with a plurality of sensors and a single filtering network to decrease the necessary number of components in the proximity sensing circuit. Self diagnosis can be performed by using precision resistors or by intelligently monitoring the changing values of the AC impedance, the DC resistance and the compensated resistance, either individually or in combination with each other, to predict certain potential malfunctions.

Inductive current sensor with reduced influence of spurious gaps and electrical apparatus including it

Abstract: Inductive current sensor and electrical apparatus incorporating this sensor. The magnetic circuit of the sensor comprises a separable part carrying the detector element and is made of a material having a permeability lying between 5 and 100. The circuit reduces the influence of spurious gaps and external interference on the current sensor for the electrical apparatus.

Monostructure touch sensor with multifunction for discrimination of material properties

Abstract: This paper describes the development of a mono-structure touch sensor that has three kinds of sensing functions for discriminating materials. The sensor consists of two spiral metallic lines on a thin insulating substrate and has four terminals. When the two lines are used as two coils, the sensor has the property of inductance. When the two lines are used as two parallel electrodes, the sensor has the property of capacitance. When one spiral metallic line is used as a heater and another is used as a resistor, the sensor has the property of a temperature sensor. The proposed sensor is used to discriminate typical materials such as iron, aluminum, copper, bronze, gum, wood, acrylic resin, styrene foam, etc. The experiments show that the sensor has considerably high potential in discriminating materials, indicating that the sensor would be a promising candidate for developing an artificial skin tactile sensing system in the future.

A position measurement apparatus

Abstract: A precision measurement apparatus detects the point at which a measurement probe contacts the surface of an object 37 to be measured by detecting the formation of a magnetic circuit as the probe approaches the object. This is achieved by making the probe of an electroconductive material and locating the probe and the object (which must also be metal or similar electroconductive material) as part of a magnetic circuit. The circuit includes an inductive sensor 1 responsive to ambient or externally induced electromagnetic fields and which produces an output signal which changes in response to the circuit being formed. Because the circuit is formed before actual contact is made the apparatus can sense when the probe approaches the object and adjust its speed accordingly. In a preferred arrangement the probe may in fact be the cutting tool 36 of a CNC machine tool, in which case the apparatus may also be used to detect breakage of the cutting tool.

Proximity switch for operation in the presence of interference fields

Abstract: In order to make the commonly used approximation switch insensitive to intermittently occurring magnetic interference fields, such switch consisting of a magnetic field sensor (1) acting via an amplifier stage (2) on a switching stage (3), provision is made for a second sensor (4) reacting to such interference fields, said sensor, in its activated state, returning the given output signal of the switching stage (3) to the input of the amplifier stage (2) for maintaining the given lead signal of the sensor stage (magnetic field sensor 1), and thus preserving the functional state of the approximation switch present in the event of interference.

Detection of sub-surface objects by electrical impedance tomography

Abstract: A technique called INSEIT (Imaging Near the Surface by Electrical Impedance Tomography) has been developed for potential applications in the field of medical imaging. The technique allows changes in electrical impedance to be imaged in sub-surface planes below an array of surface electrodes. Although the adaptation of this approach to the task of detecting buried land mines involves some obvious practical difficulties with electrode contact, the method might find application in situations where large electrical impedance contrasts are present. The image reconstruction mathematics used for INSEIT and for general cross-sectional electrical impedance tomography has been shown to be suitable for industrial imaging using capacitive and inductive sensors, so alternative sensing methods based on the same image reconstruction strategy are a possibility. The viability of INSEIT in the practical situation of unknown sub-surface features and an imperfectly flat surface, and the overall performance of the approach in locating buried objects is examined using software simulations and experimental data sets.

Device for vibration isolation of object wrt. a base

Abstract: The device has an air spring (2) and a sensor for determining the distance between the object (1) and the base (3). A contactless distance sensor (4) generates an electrical output signal which is fed into an electronic controller (5). The controller output signal drives an electrically controllable throughput valve (6) which is mounted in the compressed air line (7) feeding the air spring to form the control loop. The sensor can be an optoelectronic, capacitive or inductive sensor.

Circuit for operating a resistive, capacitive or inductive sensor

Abstract: The arrangement has a two-pole capacitive, inductive or resistive element (C1,C2,L2,R1,2,3) acting as a sensor. The sensor acts to detect when a predetermined threshold of the two pole element is exceeded or not reached. The circuit has an output (A). The circuit includes a first circuit part (R1,C1) defining a first time constant. It also has a second circuit part (R2,R3,C2,L2) defining a second time constant. It further has a third circuit part (2) which is fed by a voltage source relative to a reference potential. The two-pole element is either a component of the first or the second circuit part. The parameters of the other components of the first and second circuit part determine the threshold value. The time constants determine the fluctuation of the circuit so that the voltage at the output changes from an alternating to a constant form when the threshold is exceeded or not reached, or vice versa.

Extremely rugged inductive or optical sensor unit resisting vibration and shock

Abstract: A novel sensor has a closed, fluid-tight casing (2) with an optical or inductive sensor element inside. Its sensor chamber (3) is at least partly filled, preferably with a dry filling (6) of granular consistency.

Method and apparatus for sensing proximity or position of an object using near-field or magnetic effects

Abstract: A method and apparatus for sensing proximity of an object using near-field effects or magnetic effects. The sensor chips are designed to accommodate numerous sensing elements. In the electromagnetic sensor, radio frequency energy is fed to an antenna. The antenna radiates this radio frequency energy to charge the surface of an object. When the position of the object changes, the impedance of the antenna due to near-field effects changes. This impedance change is detected to provide an indication of the object's movement. In the magnetic sensor, the sensing element is placed at a right angle to the sensor electronics to provide a smaller surface area across the diameter of the sensor. The magnet that charges the object to be detected is manufactured as a part of the sensor encapsulant. The sensing device may be packaged to be inserted into a wall to provide a sensor having a leakfree seal.

Test method for hologram dynamic characteristics of magnetic induction sensor

Abstract: The dynamic characteristics test method for magnetically inductive sensor features that the probes of sensor to be tested and standard magnetic field detector are put in uniformly alternative magnetic field and their electric signals are compared with each other in amplitude-phase measure (0-100 KHz) to obtain their differences in amplitude and phase, that is, the amplitude and phase characteristics in 0-100 KHz range of the sensor are obtained. Their curves are also drawn correctly.

Continuous on-line partial discharge monitoring of power generators

Abstract: Partial Discharge (PD) detection as a measure of defects and weakness in the insulation system of high voltage equipment has always been a matter of importance and interest in high voltage studies. On-line PD monitoring of rotating machines has not been easy because of the large disturbances coupled to the windings and measurement system by different sources such as the power network, slip ring brushes and excitation system thyristors. Since 1989, the High Voltage Engineering Department of ABB Corporate Research in Sweden has been involved in development of a new technique, called INTECH, for on-line detection and localization of partial discharges. The technique is based on the decoupling of the partial discharges by a pair or group of inductive sensors and treatment of the detected signals. This paper especially considers the aspects of application of INTECH to power generators.

Schaltungsanordnung zur Aufbereitung eines Induktivgebersignals

Abstract: The invention concerns a circuit for processing an inductive sensor signal. The interference insensitivity, evaluation of small signal amplitudes and chronological accuracy of signal detection are improved in that earth is selected as the reference potential, a fixed basic trigger threshold is established in the zero-crossing of the inductive sensor signal, and the return trigger threshold is adjusted by the adjusting device in the region of only one half-wave.