Showing papers on "Inductive sensor published in 2008"

Medical training simulator including contact-less sensors

Abstract: A medical training simulator includes contact-less sensors and corresponding detection objects, configured to enable sensor data collected during a training exercise to be used to evaluate the performance of the training exercise. The simulator includes a simulated anatomical structure, at least one contact-less sensor, and at least one detection object. During a training exercise, a spatial relationship between the contact-less sensor and the detection object produces data for evaluating performance of the training exercise. Either the contact-less sensor or the detection object is embedded in the simulated physiological structure, while the other is included in either a support for the simulated physiological structure, or as part of a tool used during the training exercise. Many types of contact-less sensors can be employed, including capacitance sensors, impedance sensors, inductive sensors, and magnetic sensors.

A Magneto-Inductive Sensor Based Wireless Tongue-Computer Interface

Abstract: We have developed a noninvasive, unobtrusive magnetic wireless tongue-computer interface, called ldquoTongue Drive,rdquo to provide people with severe disabilities with flexible and effective computer access and environment control. A small permanent magnet secured on the tongue by implantation, piercing, or tissue adhesives, is utilized as a tracer to track the tongue movements. The magnetic field variations inside and around the mouth due to the tongue movements are detected by a pair of three-axial linear magneto-inductive sensor modules mounted bilaterally on a headset near the user's cheeks. After being wirelessly transmitted to a portable computer, the sensor output signals are processed by a differential field cancellation algorithm to eliminate the external magnetic field interference, and translated into user control commands, which could then be used to access a desktop computer, maneuver a powered wheelchair, or control other devices in the user's environment. The system has been successfully tested on six able-bodied subjects for computer access by defining six individual commands to resemble mouse functions. Results show that the Tongue Drive system response time for 87% correctly completed commands is 0.8 s, which yields to an information transfer rate of ~ 130 b/min.

Simultaneous Noncontact Measurement of Water Level and Conductivity

Abstract: Measurement of water level and conductivity is important in many applications, including geophysics, ocean engineering, and the oil industry, with one example being gas/oil/water separation. Noncontact measurement is ideal for those applications. Capacitance, radar, ultrasonic, and laser techniques have been used in measuring the level, but simultaneous measurements of level and conductivity have not been reported. In this paper, we developed a novel inductive sensor, which uses two coils of different sizes to simultaneously infer conductivity and level based on a simplified model deduced from an analytical solution. The simplified model is verified with both simulation and experimental data. The experimental results have shown that the measurement accuracy for both level and conductivity is within 3%.

Sensor Fusion for Improved Control of Piezoelectric Tube Scanners

Abstract: In nanopositioning applications, capacitive or inductive sensors are used to measure displacement and provide feedback to eliminate actuator nonlinearity, dynamics, cross-coupling between axes, and thermal drift. Due to their noise density, typically 20 pm/radicHz for 100-mum range transducers, feedback loops are restricted to a few tens of Hertz if nanometer precision is required. In this study, a capacitive displacement sensor is used with a piezoelectric strain voltage measurement to reduce sensor noise at frequencies above 1 Hz. The piezoelectric strain voltage is derived from an open-circuit electrode on a four-quadrant piezoelectric tube actuator and requires no additional hardware. The noise density of the piezoelectric strain voltage is measured to be three orders of magnitude lower than the capacitive sensor. This allows a large increase in closed-loop bandwidth with no penalty on sensor-induced noise. The advantageous properties of the capacitive sensor and piezoelectric strain voltage are discussed and utilized to design a Kalman filter that combines the two signals in a statistically optimal way. A receding horizon control strategy is then introduced as a technique for controlling the tube scanner. A wide-bandwidth controller is implemented that provides reference tracking and damping of the actuator resonance, with root-mean-square displacement noise below 0.4 nm.

Simultaneous sensing and actuation with a piezoelectric tube scanner

Abstract: Piezoelectric tube scanners with quartered external electrodes are the most widely used nanopositioning technology in modern scanning probe microscopes. There has been increasing interest in utilizing feedback control techniques to improve bandwidth and accuracy of these nanopositioners. The use of feedback requires a sensor to be incorporated into the nanopositioning device. Noncontact displacement sensors, e.g., capacitive and inductive sensors, have been used for this purpose. However, their measurements contain a significant noise component if operated over large bandwidths. The piezoelectric voltage induced in a tube nanopositioner has been proposed recently as an alternative measure of displacement with a much improved noise figure, up to three orders of magnitude better than capacitive sensors. In this arrangement, an electrode is used to actuate the tube, while the opposite electrode is used as a sensor. This approach has two drawbacks: (i) the operating range of the tube is reduced to half and (ii) the tube is not driven symmetrically, thus the opposite sides of the tube experience asymmetric stresses, i.e., in this mode of operation, the scanner is not a perfectly collocated system. In this paper, we present a new electrode pattern for piezoelectric tube scanners which addresses the above problems and allows simultaneous sensing and actuation of the tube in an efficient way.

Low-Cost IR Reflective Sensors for Submicrolevel Position Measurement and Control

Abstract: This paper investigates the feasibility of using commercially available, low-cost IR reflective sensors for micro- to sub- microscale position measurement and control. These sensors are typically used as optical switches; however, their application for detecting fine motion, such as the movement of a piezoactuator, has not been investigated. Five IR sensors were evaluated to determine their range, resolution, linear distortion, noise characteristics, and bandwidth. Experimental results show that the performance of the IR sensors compares well with a commercial inductive sensor that costs significantly more. For example, the measured resolution was within several hundred nanometers over a plusmn200 mum range and the linear distortion was significantly lower than the inductive sensor. A selected IR sensor was used in the design of a state-feedback control system to compensate for hysteresis and creep in an experimental piezopositioner. Compared to the open-loop system, by using the IR sensor in feedback, the output hysteresis was reduced by over 95 %. These results show the potential of such sensors in the design of low-cost microprecision mechatronic positioning systems.

Inductive proximity sensor

Abstract: The invention relates to an inductive proximity sensor with a sensor element which includes a resonant circuit which provides an output signal which depends on the damping by an electrically conductive object. In accordance with the invention, the inductive proximity sensor has a ΣΔ modulator for the evaluation of an output signal of the resonant circuit. The invention furthermore relates to a method for the determination of the presence and/or of the spacing of a metallic object with the help of an inductive proximity sensor.

Inductive Probe for Flaw Detection in non-Magnetic Metallic Plates Using Eddy Currents

Abstract: This paper describes the design of an inductive sensor and its application to detect the presence of structural flaws inside electrically conducting nonmagnetic plates. The principle of operation is based on the measurement of the induced voltages in two sensing coils. These voltages are related to the eddy currents that are generated inside the plates with perturbations due to the electrical conductivity inhomogeneities. The modeling work aims at determining the optimum operating frequencies and the resulting signal magnitudes.

Wireless corrosion sensor

Abstract: A passive sensor that is located on or adjacent to a structure that can be used to monitor the affect of environment on a structure or coating that is used to protect the structure. The sensor includes a parasitic element that interacts with the environment and influences the intensity of the electromagnetic response between the inductive element of the sensor and the antenna of the interrogation reader device. The condition of the parasitic element is determined by the radio frequency interaction of the reader antenna and the inductive element of the sensor. The parasitic element condition correlates to the environmental severity, or corrosivity of the environment and damage to metallic structures or protective coatings. An integrated circuit within the sensor is capable of storing identification, time, material, and measurement information. The sensor and system of the present invention is useful for tracking and monitoring cumulate environmental damage to a structure.

Design of inductive sensors for tongue control system for computers and assistive devices

Abstract: Design of air-core inductive sensors in printed circuit board technology is presented. Comparative analysis with existing hand made inductive sensors is performed with respect to inductance, resistance, and sensitivity to activation when a soft ferromagnetic material is placed in the center of the sensor. Optimization is performed in a finite element model. This technology allows flexibility in design, automation of production and ease of possible integration with supplying electronics. The basic switch function of the inductive sensor can be extended to two-dimensional movement detection for pointing devices.

A Novel Approach to Extending the Linearity Range of Displacement Inductive Sensor

Abstract: This paper presents a meander-type displacement inductive sensor, usable for the detection of small displacements (less than 0.5 mm) in the plane. It also describes design, realization, and the input inductance measurement of sensor. A displacement in two directions can be detected by using two sensor elements, each having a pair of meander coils. In each pair, one of the coils is fixed and between its terminals the input inductance was measured, while the other coil is short-circuited. If one coil is moved above the other, in directions of x - and z -axes, coupling between the coils will change, as well as the input inductance, which serves as a measure of displacement. In order to achieve better linearity of the sensor, longitudinal gaps are inserted in the middle of each conductive segment of one fixed coil. Four sets of inductive sensors were realized: without gap and with three different gaps. Planar, low-cost PCB technology was chosen for our prototype. In addition, an improved model of the inductive sensor is proposed. The input inductance of displacement sensor was calculated and compared with measured values. A good agreement was found.

Capacitive proximity sensor and proximity sensing method

Abstract: A capacitive proximity sensor ( 100 ) comprises a sensor unit ( 10 ) and a sense circuit unit ( 20 ). The sensor unit ( 10 ) includes a sensor electrode ( 11 ), a shield electrode ( 12 ) and an auxiliary electrode ( 13 ). The sensor electrode ( 11 ) is connected to a C-V conversion circuit ( 21 ) and the shield electrode ( 12 ) is connected to a shield drive circuit ( 24 ). The auxiliary electrode ( 13 ) is connected via a change-over switch ( 30 ) to the C-V conversion circuit ( 21 ) or the shield drive circuit ( 24 ). The capacitance values (C 1 , C 2 ) switched by the change-over switch ( 30 ) and detected at the C-V conversion circuit ( 21 ) are compared to arbitrarily set a range of a sense region on the sensor electrode ( 11 ).

Analog to interval encoder with active use of gate leakage for an implanted blood-sugar sensor

Abstract: We have developed an ultra low power integrated circuit control module that will be incorporated into a micro machined pill-sized medical implant that continuously monitors blood-sugar levels for patients with Diabetes mellitus. The circuit converts a piezoresistive sensor signal to an inter-pulse interval suited for digital transmission through a wire-less inductive link. Instead of a full analog-to-digital conversion, this analog-to-analog conversion is much simpler and more power conservative. The circuit is entirely asynchronous, requiring no energy consuming clock and operates on sub-threshold currents. A first prototype, produced with the STM 90 nm CMOS process, consumes 1.7muW. A compact on-chip resistive element is employed in a feedback loop to cancel 1/f-noise and offsets in both the sensor and the initial amplification stage. The resistive element is implemented using the quantum effect of gate-leakage, achieving an equivalent resistance of several GOmega with minimal consumption of layout space. The effectiveness of this noise reduction has been asserted in a 62 hour recording with fixed input. The measured noise spectrum appears completely white down to the minimal frequency of the recording, i.e. 4.5muHz. The standard deviation of single pulse intervals (dynamic range from 4.3ms to 15.4 ms) restricts the reconstruction of the sensor value to an accuracy equivalent to 4.41 bits. Averaging over the samples during 1 second increases this accuracy to 7.84 bits. Longer averaging will further improve that figure at the cost of longer periods of active power consumption of the implant, which will be woken up only once every 5 minutes.

Planar inductive sensor for small displacement

Abstract: This paper presents a meander type displacement inductive sensor, developed in printed circuit board (PCB) technology. It also describes design, realization and the input inductance measurement of sensor. The displacement in two directions (less than 0.5 mm) can be detected by using two sensor's elements (i.e. two pairs of meander coils). In each pair, one of the coils is fixed, and between its terminals the input inductance was measured, while other coil is short-circuited. If one coil is moved above the other in directions of x- and z-axes, coupling between coils will change, as well as input inductance, which serves as a measure of displacement. In order to achieve better linearity of the sensor, gap is inserted in the middle of each conductive segment of fixed coils. Four sets of inductive sensors were realized: without gap and with three different gaps: 0.25 mm, 0.51 mm and 0.76 mm. In addition, a simple model of the inductive sensor is proposed. Using this model, the input inductance of displacement sensor was calculated and compared with measured values. A good agreement was found.

Piston and cylinder combination driven by linear motor with cylinder position recognition system and linear motor compressor, and an inductive sensor

Abstract: The present invention discloses a piston and cylinder combination driven by linear motor with cylinder position recognition system, comprising a support structure (4) forming an air gap (12); a motor winding (6) generating a variable magnetic flow at least along part of the air gap (12); a cylinder (2) having a head at one of its ends; a piston (1 ) connected to a magnet (5), the magnet being driven by the magnetic flow of the motor winding (6) to move inside a displacement path including at least partially the air gap (12); the displacement of the magnet making the piston (1 ) reciprocatingly move inside the cylinder (2); and an inductive sensor (8) disposed at a point of the displacement path of the magnet (5), such that when the piston (1 ) reaches a position of closest approach to the cylinder head, the inductive sensor detects a variation in the magnetic field resulting from the corresponding position of the magnet, and generates a voltage signal arising from this magnetic field variation. The invention also discloses a linear motor compressor, which comprises a piston and cylinder combination of the kind of the present invention, and is capable of recognizing the position of the cylinder.

Capacitive sensor and proximity detector using it

Abstract: A capacitive sensor may be used as a proximity detector in an obstruction warning system for road vehicles, e.g. for use when the vehicle is reversing. A digital signal processor 11 sends a sine wave through a sensor RC circuit 1, 7. A sensor plate 3 acts as one plate of a sensor capacitor 1 and the obstruction 45 acts as the other plate 5. Changes in the distance between the car 43 and the obstruction 45 result in changes in the capacitance of the sensor capacitor 1, changing the amplitude and phase of the sine wave output by the sensor RC circuit 1, 7. A reference sine wave, generated by a reference signal circuit 17, 19, 21 is subtracted from the sensor output signal in a subtractor 15. The reference signal has a phase offset from the sensor signal so that the amplitude of the difference signal is highly sensitive to changes in phase of the sensor signal. An additional signal, substantially identical to the sensor signal, is coupled to the output of the sensor RC circuit by a coupling capacitor 41. This provides a path to ground for high frequency noise without disrupting the sensor signal.

Magneto-resistance based nano-scale position sensor

Abstract: A position sensor and method include a magnetic component, a first magneto-resistive sensor disposed in proximity to the magnet/coil; and a second magneto-resistive sensor disposed in proximity to the magnetic component and the first magneto-resistive sensor. The first magneto-resistive sensor and second magneto-resistive sensor are configured to sense changes in a stray magnetic field created by the magnetic component in accordance with a relative positional change between the magnetic component and the first and second magneto-resistive sensors.

Capacitive force sensor

Abstract: A force sensor is provided which has a capacitive sensor circuit incorporating a sensor capacitor having variable capacitance C sen arranged so that an output of the capacitive sensor circuit is proportional to 1/C sen .

Detection apparatus for a capacitive proximity sensor

Abstract: A switched capacitance detection circuit is responsive to changes in the fringing capacitance of a capacitive proximity sensor having at least one capacitive sensor element. In cases where the sensor has a single sensor element, the switching frequency of the detection circuit is controlled to maintain measurement accuracy in the presence of sensor moisture while minimizing power consumption and electromagnetic radiation. In cases where the sensor has multiple sensor elements, the capacitance values for each sensor element are differenced, absolute-valued and summed to form an output in which common-mode effects due to sensor moisture, temperature and sensor aging are canceled out.

Metal face inductive proximity sensor

Abstract: Metal face inductive proximity sensors and methods are presented for sensing the presence or absence of a target object in a target sensing area in which a coil system is operated to generate a magnetic field extending outward from the sensing face at a frequency in a range that maximizes a relative target effect for the sensing face area, material, and thickness, and a target material from which the target object is made to allow the protective advantages of metal sensing face materials while enhancing sensing distance by optimizing the ratio of the target energy loss to the energy loss in the metal face.

Lens positioning system

Abstract: Systems and methods to position most precisely a lens system of an optical device are disclosed. Embodiments of these electrical sensors comprise capacitive sensors, inductive sensors and resistive sensors to measure the actual position of a lens system with a precision of at least 1 μm. Read-out circuits using double-correlated sampling structures are providing the position signals from the electrical sensors to a controller. The controller compares the actual position signals with a set-signal representing a target position of the lens signal and issues a signal to a motor to get the lens system moved to the target position. A variety of motors/actuators can be used to move a slider carrying the lens system to the position desired.

Measuring power system voltage remotely using micromachined electric field sensor

Abstract: This paper describes a new type of miniature electric field sensor that can be used to measure power system voltages remotely. The ability to measure both ac and dc voltage is a significant advantage of this sensor in comparison to other sensors, which can only measure either ac or dc voltage. Micromachining technology was used to fabricate the sensor. The sensing area of this sensor is only 1 mm2 and it requires only 75 mV and 70 muW to drive its shutter. The use of a miniature sensor also helps to measure local electric field accurately since the field distortion caused by the sensor is minimum.

Large-sized precision bearing radial play multifunctional automatic measurement method and measuring apparatus

Abstract: A multifunctional automatic measurement method for radial clearance of large-scaled precision bearing adopts static measurement, dynamic measurement and three-point measurement and is capable of automatically loading and automatically measuring. The three measurement manners can be implemented on one measuring apparatus at the same time. The measuring apparatus mainly comprises an electrical system (1), a measurement pedestal (2), a sensor support (3), a sensor adjusting nut (4), an inductive sensor (5), an upper cylinder support (6), an upper loading cylinder (7), a measurement shaft centre (9), a measurement main shaft (10), a lower loading cylinder (11), a lower cylinder support (12), a measurement support (13), a synchronous motor (14), a Hall element (15), a belt wheel and cog belt (16), a precise pressure regulating valve (17), and a precise pressure gauge (18). The measuring apparatus can provide reliable detection and analysis data for high-precise measurement of radial clearance of large-scaled precision bearings (8).

Position sensor system

Abstract: A sensing mechanism includes a magnetic source, a magnetic flux sensor, a sensor backing on which the magnetic source and flux sensor are mounted, and a ferromagnetic target, where the magnetic source, magnetic flux sensor, and ferromagnetic target are positioned to form a magnetic circuit from the magnetic source to the target, from the target to the sensor, and returning to the magnetic source through the sensor backing.

Device and method for detecting lightning strikes on a structure made of electrically insulating material

Abstract: A device for detecting lightning strikes ( 9 ) on an electrically insulating structure ( 11 ) likely to be subjected to a lightning strike, for example an aircraft radome, includes on an external surface ( 12 ) one or more lightning arrester strips ( 10 ), made of an electrically conductive material and electrically linked to an electrically conductive structure. At least one inductive sensor ( 3 ) is positioned near the internal surface ( 13 ) of the electrically insulating structure so that the inductive sensor delivers a signal when a lightning arrester strip is passed through by a lightning current I. The signals from the inductive sensor, for example a flat coil or two flat coils mounted in opposition, are received and processed by acquisition means.

Wireless surface acoustic wave-based proximity sensor, sensing system and method

Abstract: The subject invention is related to wireless proximity sensor and sensing system for detecting the position of an object. The system includes a transceiver for providing wireless communication with a passive wireless surface acoustic wave (SAW) proximity sensor. The wireless proximity sensor receives a wireless signal from the transceiver, which powers the SAW device and in turn transmits a signal back to the transceiver that includes information about the position of an object. The wireless proximity sensor uses one or more SAW devices with a sensing element made of magnetostrictive material, in conjunction with one or more magnets and one or more targets that are positioned relative to an object. The movement of the target(s) in relation to the proximity sensor operatively produces a mechanical response due to the shift in the magnetic field of the sensing element. The sensing element in turn enhances the magnetic field of the SAW device to which it is attached, and this information is transmitted to the transceiver as information about the position of an object.

Inductive edge sensors: an innovative solution for ELT segmented mirror alignment monitoring

Abstract: The largest telescopes (ELT) involve a highly segmented primary mirror. The monitoring of the mirror shape use thousands of sensors, located on segment edges, which measure the relative piston, tip and tilt of all segments. Today, telescopes with segmented primary mirrors use capacitance-based edge sensors. Although this technology offers excellent metrological performances, its practical use is limited by the intrinsic sensitivity to humidity, dust and condensation, whose effect exceeds the requirements for future ELTs. Being specialized in both capacitive and inductive metrology, Fogale nanotech has developed a novel concept of edge sensors using the inductive technology, which does not suffer from humidity, condensation, and dust effects. Cost effective sensor with specific layout, associated electronics, demonstrated metrological performance (sub-nanometer resolution and nanometer stability) that outperforms the capacitive concept.

SALT segmented primary mirror: commissioning capacitive edge sensing system and performance comparison with inductive sensor

Abstract: The SAMS (Segment Alignment Measurement System) is a capacitance-based edge sensing solution for the active alignment of the 10m SALT segmented primary mirror. Commissioning and calibrating the system has been an ongoing task in an attempt to counteract the unfavourable response of the sensors to high humidity conditions and high dust levels. Several solutions were implemented and tested including real-time feedback systems and the application of corrective functions. In parallel with the continuing efforts to improve the performance of the capacitive sensors, we have also been testing a prototype inductive sensor developed by Fogale Nanotech that is of a very similar flexible plate construction. In this paper we present the results obtained and performance gains achieved thus far with the capacitive edge-sensing system as well as a performance comparison of the Fogale inductive sensor to the capacitive edge sensor.

Capacitance sensor and position sensor

Abstract: A capacitance sensor of the present invention comprises arrayed sensor electrodes, a switch unit for selecting a part of the sensor electrodes, and a capacitance detection unit for detecting the capacitances between the selected sensor electrodes and the earth. A position sensor of the present invention comprises such a capacitance sensor for changing the sensor electrodes selected every predetermined time by the switch unit and a data processing unit. The data processing unit can calculate the position of a conductor that has approached by weighting information indicating the capacitance with information indicating the position and calculating an average (weighted average).

Inductive proximity sensors and housings for inductive proximity sensors

Abstract: An inductive proximity sensor includes a sensor housing, a sensing coil and an evaluation circuit. The sensor housing may generally include a sensing portion and a body portion. The evaluation circuit may be electrically coupled to the sensing coil and disposed in the body portion. The sensing coil may be positioned in the sensing portion such that the sensing coil is recessed from an outer edge of the sensor housing by a protective annulus disposed between the sensing coil and the outer edge. The sensing coil may be spaced from the sensor housing by a zone having low magnetic permeability relative to the sensor housing disposed between the sensing coil and the sensor housing. The zone may extend circumferentially around the sensing coil. A protective plate may be disposed between the outer edge of the sensor housing and the sensing coil and recessed from the outer edge of the housing.