Showing papers on "Inductive sensor published in 2003"

Micro-mechanical capacitive inductive sensor for wireless detection of relative or absolute pressure

Abstract: A micro-mechanical pressure transducer is disclosed in which a capacitive transducer structure is integrated with an inductor coil to form a LC tank circuit, resonance frequency of which may be detected remotely by imposing an electromagnetic field on the transducer. The capacitive transducer structure comprises a conductive movable diaphragm, a fixed counter electrode, and a predetermined air gap between said diaphragm and electrode. The diaphragm deflects in response to an applied pressure differential, leading to a change of capacitance in the structure and hence a shift of resonance frequency of the LC tank circuit. The resonance frequency of the LC circuit can be remotely detected by measuring and determining the corresponding peak in electromagnetic impedance of the transducer.

Welding machine with automatic parameter setting

Abstract: A method and apparatus for welding that includes a power source and a wire feeder is disclosed. One or more sensors sense one or more welding conditions before the weld is initiated. A set up circuit is coupled to sensor, the power source, and the wire feeder. The set up circuit automatically sets up the welding machine in response to what the sensor senses. The sensor may be a wire sensor, including a diameter sensor and a material sensor, a gas sensor (if a source of gas is included) such as a cyclic voltametry gas microsensor, a workpiece thickness sensor such as a strain gauge or displacement sensor. Alternatively the sensor includes a bar code reader that reads a code on, for example, the spool of wire, an analog proximity detector, a plurality of proximity detectors, and a displacement sensor.

Material condition assessment with spatially periodic field sensors

Abstract: Inductive sensors measure the near surface properties of conducting magnetic materials. The sensors generally include parallel winding segments to induce a spatially periodic magnetic field in a material under test. The sensors may provide a directionally dependent measure with measurements made in varying orientations of the sensor with respect to the material property variation directions. The sensors may be thin, conformable sensors that can be mounted on a test material and, for example, monitor crack initiation under the sensor. A second sensor may be left in air to provide a reference measurement, or the temperature of the material under test can be varied to verify the response of the individual sensing elements. Sensors can be mounted to materials under test in order to not modify the environment that is causing the stress being monitored. A sensor may be flexible to conform to the shape of the surface of the material under test and may be mounted in difficult to access locations such as around fasteners of an aircraft. Spatially periodic field eddy current sensors may be scanned across a material to create images of the absolute material property beneath the sensor.

Sensor module for measuring surfaces

Abstract: This invention relates to a sensor module for measuring structures in a surface, especially in a finger surface being moved over the sensor module, comprising a number of sensor elements, and an outer electrode located aside the sensor elements, the sensor elements being coupled to at least one AC drive circuit providing a varying current or voltage, thus coupling a signal through the sensor elements to the outer electrode. The sensor elements are also coupled to an electronic circuit positioned on a substrate, said substrate comprising conductor leads coupling the sensor elements to the electronic circuit, and said electronic circuit being adapted to measure the magnitude of said capacitance or AC impedance.

Sensor arrangement and method for operating a sensor arrangement

Abstract: The invention relates to a sensor arrangement (800) and a method for operating a sensor arrangement. The sensor arrangement contains a plurality of sensor devices (600) embodied on and/or in a substrate. Each of the sensor devices comprises an electric signal converter (601) and a sensor element (602) coupled to the signal converter in order to characteristically influence the electrical conductivity of the signal converter as a result of a sensor event on the sensor element. Each sensor device comprises a device (603) for keeping an electric voltage, which is applied to the signal converter, constant and a device (603) for detecting the value of the electric current flowing through the signal converter in the form of a sensor signal.

Low noise proximity sensing system

Abstract: An electronic proximity sensing apparatus has at least one signal pad. The signal pads are each connected to receive an electric voltage signal. At least two sensing conductors are routed in proximity to the signal pads, and a sensor is operable to detect the difference in voltage between two of the at least two sensing conductors. Differential sensing is further applied to other capacitive proximity sensing circuits to reduce common-mode interference.

High resolution inductive sensor arrays for UXO

Abstract: For the inspection of materials and the detection and characterization of hidden objects, features, or flaws sensors and sensor arrays are used to image form two-dimensional images suitable for characterizing the hidden features. Magnetic field or eddy current based inductive and giant magnetoresistive sensors may be used on magnetizable and conducting materials, while capacitive sensors can be used for dielectric materials. Enhanced drive windings and electrode structures permit nulling or cancellation of local fields in the vicinity of the sense elements to increase sensor sensitivity. The addition of calibration windings, which are not energized during measurements, allows absolute impedance and material property measurements with nulled sensors. Sensors, sensor arrays, and support fixtures are described which permit relative motion between the drive and sense elements. This facilitates the volumetric reconstruction of hidden features and objects.

Sensors for on-line PD detection in MV power cables and their locations in substations

Abstract: For developing a system capable of on-line detecting and localizing PDs in MV power cables, the choice of the sensor type is crucial. Sensors for detecting PDs can be divided into two main groups: capacitive and inductive sensors. In this paper, the advantages and disadvantages of these two types of sensors are discussed for on-line application. In multi-conductor cables, e.g. a three-phase belted cable, it is essential to distinguish the different propagation channels. When the cable is under normal operating conditions, all three the phases are energized simultaneously, implying that the PD pulses are propagating through two distinctive propagation channels: the Phase-to-Phase (PP) channel and the Shield-to-Phase (SP) channel. Measuring sensors can therefore also be subdivided with respect to the detected channel. If sensors can detect signals in all three conductors separately, both SP and PP channels are obtained. In this paper different positions in a substation for placing sensors are evaluated, with respect to the measured propagation channels, signal-and interference sensitivity, safety and practical applicability.

Detection and imaging of surface corrosion on steel reinforcing bars using a phase-sensitive inductive sensor intended for use with concrete

Abstract: A new inductive sensor is described that exploits the principle of frequency shift and phase sensitive detection to identify and image corrosion on the surface of steel reinforcing bars intended for embedment within concrete. A search coil radiating a time-varying magnetic field experiences impedance changes when conductive and/or permeable targets are brought within its vicinity. Depending on the electrical properties of the target, the impedance changes are manifest predominantly as a shift in the Q-factor of the coil, or as a change in its inductance. It is the latter condition that is the primary effect with corrosion product. Under normal circumstances the change in inductance L is very small, but can be detected by configuring the coil as part of a free-running tuned oscillator, whose resonant frequency is governed by L. A shift in the sensor signal frequency is detected by comparing its phase to that of a signal produced by a stable reference oscillator (heterodyning), and producing a voltage proportional to the difference. Such phase sensitive detection is widely employed in metal detector instrumentation, but in this case the signal is used to produce images of corrosion. Significantly, experiments also show that the system is capable of detecting varying amounts of corrosion product, something that is beyond the capabilities of ultrasonic, X-ray or microwave sensing systems. At the present time, the sensor is capable of detecting and imaging a 2 mm thick layer of corrosion on a 20 mm diameter steel bar, located 30 mm below the surface of ceramic material whose conductivity and relative permeability is almost identical to that of concrete.

Device for contact-less measurement of distances in multiple directions

Abstract: A device for contact-less measurement of distances (10, 20) in multiple directions of an electrically conductive body (2, 22) comprises a plurality of inductive elements (1, 4, 7). At least one (1) of the plurality of inductive elements (1, 4, 7) is placed essentially around the body (2). The other inductive ele­ments or other magnetic field sensors (4, 7) are provided in the vicinity of said one inductive element (1). The device with these features allows integrating a multi axis inductive sensor on a single circuit board.

Turbine blade proximity sensor and control system

Abstract: A proximity sensor system uses a sensor coil as the frequency determining element of an oscillator circuit. The frequency of the oscillator circuit is thus modulated based on the proximity of the sensor coil to a conductive element, thereby supplying a frequency modulated sensor signal. A frequency modulation (FM) detector circuit demodulates the sensor signal, and supplies a signal having an amplitude that varies with, and is representative of, the proximity of the sensor coil to the conductive element.

Multiplexed dual-purpose magnetoresistive sensor and method of measuring current and temperature

Abstract: The present invention determines temperature and current from resistance measurements of a single magnetoresistive sensor. A dual-purpose sensor includes the magnetoresistive sensor having a single pair of terminals. The sensor is multiplexed under separate current conditions to produce both a temperature measurement and a current measurement in a vicinity of the sensor. A sensor system includes the dual-purpose sensor, a resistance sensing subsystem and a controller that controls the current conditions. A method of measuring temperature and current includes measuring a first resistance of the dual-purpose sensor while a first current is flowing in a conductor adjacent to the sensor, and measuring a second resistance of the sensor while a second current is flowing in the conductor. The first current has a known value while the second current has an unknown value. The temperature and current are determined respectively from the first and second resistance measurements.

New practices for partial discharge detection and localization in large rotating machines

Abstract: This paper presents a new technique for detection and localization of partial discharges (PD) in large rotating machines. In this technique, denoted "InTech", a stator winding with (n) coils is equipped with (n + 1) inductive sensors; as a result, every stator coil is situated between two sensors. The measurement is then focused on the individual stator coils. In this way common difficulties facing partial discharge measurements in rotating machines such as attenuation and distortion of the signals in the stator winding, noise reduction, and the calibration accuracy are reduced considerably. The treatment of the sensor signals, using a special method, results in a measurement of PD in each respective stator coil. In addition, the stator coil from which the PD originates is identified. Results from field measurements on both hydro and turbo machines are presented and discussed.

Method for measuring the temperature of a metal saucepan

Abstract: A method for measuring the temperature of a cooking vessel or saucepan by means of a radiant heater is described The radiant heater has a heating coil with a corresponding control and an induction coil as an inductive sensor and which is located in a metal tray With the inductive sensor, measurement takes place of the frequency of the inductive resonant circuit comprising saucepan, heating coil, induction coil and metal tray, which is dependent on the temperature of the components In the control is stored known slopes or paths of the temperature and therefore the frequency of the metal tray over the time From this the control means gathers correction values in order to produce from the measured curve a compensated curve At characteristic points, such as the start of a cooking or boiling process or an empty cooking or boiling of the saucepan, it is possible to detect said temperatures

Three-dimensional image rendering of steel reinforcing bars using curvilinear models applied to orthogonal line scans taken by an inductive sensor

Abstract: A technique is described that enables virtual reconstruction of three-dimensional images of steel reinforcing bars embedded within concrete. The method is based on the systematic characterization of an inductive sensor response, using appropriate curvilinear models; this characterization is then applied to real, two-dimensional scan data. The first phase involves formulating a mathematical description of the line scan response for a single bar, taken at several depths, using a Pearson VII model. The data in this case are termed the depth response image, with the critical properties of interest being the peak position, peak intensity, and full width at half height. The next phase requires application of this model to actual scan data, and a description of the sensor's depth response using a Bleasdale power-law regression model. In the final phase, different bar layers are isolated using a polynomial-based layer separation technique. Data provided by these means enable a three-dimensional image of the bar mesh to be constructed and visualized. Given a known bar size, the scan depth can be calculated to an accuracy of ±2 mm or ±5%, whichever is greater. When neither the depth nor the size is available, the method allows estimates to be made with accuracies of ±1 bar size (DIN 488) and ±10% cover depth (BS1881).

Fluid pump, a fluid-transfer plate and an inductive sensor for a fluid pump

Abstract: The present invention relates to a fluid pump and a fluid-transfer plate and a sensor for a fluid pump, particularly applicable to linear compressors, for detecting the position of the respective piston and preventing the latter from colliding with the fluid-transfer plate upon variations in the compressor operation conditions, or even variations in the feed voltage. The objectives of the present invention are achieved by means of a fluid pump ( 1 ) comprising a piston ( 2 ) that is axially displaceable within a cylinder ( 3 ), the cylinder ( 3 ) comprising a cylinder closing fluid-transfer plate ( 40 ), the piston ( 2 ) being displaced toward the fluid-transfer plate ( 40 ) and capturing a gas or fluid from a low-pressure environment ( 11 ), and the fluid pump ( 11 ) comprising a sensor assembly ( 98 ), which includes an inductive sensor ( 8 ) associated with the fluid-transfer plate ( 40 ). The objectives of the present invention are also achieved by means of a fluid-transfer plate ( 40 ) particularly applicable to a fluid pump ( 1 ) and that comprises a valve plate ( 4 ) provided with a though-bore ( 10 ) for associating a protector ( 9 ) that cooperates with the cavity ( 10 ), the protector ( 9 ) comprising at least one sensor cavity ( 8 ′) for associating an inductive sensor ( 8 ). An inductive sensor ( 8 ) is also foreseen, which is applicable to the fluid pump ( 1 ).

Method and device for triggering power supply switch of a cordless electric-apparatus

Abstract: A method for triggering power supply module switch of a cordless electric-apparatus which includes a metal inductive area and an electrostatic inductive element comprising the following steps: when user body approaches the device to a predetermine distance which is less than the electrostatic induction distance, the electrostatic inductive element detecting electrostatic charge from user body so as to turn a switch within the electrostatic inductive element on; according to the switch turned on, a power supply module supplying power for the cordless electric-apparatus; when user body leaving away from the cordless electric-apparatus exceed the electrostatic induction, the switch within the electrostatic inductive element being turn off; and according to the switch within the electrostatic inductive element turned off, the power supply module supplying a part power for the cordless electric-apparatus. A device for triggering power supply module switch of a cordless electric-apparatus comprising: a metal inductive area placed on the shell of the cordless electric-apparatus; an electrostatic inductive element having an inductive electrode connected to the metal inductive area, so as to detect whether the distance between user body and the metal inductive area less than the electrostatic induction distance; and a power supply module connecting to the electrostatic inductive element.

Capacitance detecting proximity sensor

Abstract: A capacitance detecting proximity sensor forms a proximity detection range in a spatially open region, avoids the effects resulting from peripheral objects outside the detection target, and enables proximity detection with few malfunctions. The proximity sensor includes: a first detection electrode and a second detection electrode that are disposed to have a predetermined range difference h with respect to a detection direction Y in which a detection subject comes into proximity to the proximity sensor and are independent from a ground potential; and a proximity detection circuit that outputs, as a proximity detection output, the difference between a capacitance to ground Ca formed by the first detection electrode and a capacitance to ground Cb formed by the second detection electrode.

Hybrid inductive sensor

Abstract: A hybrid speed and or proximity sensor may include a variable reluctance sensor with an added excitation circuit. Similarly, a hybrid speed and or proximity sensor may include a variable inductance proximity sensor having a magnet and a magnetically permeable pole piece added in the sensor. It is emphasized that this abstract is provided to comply with the rules requiring an abstract, which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Inductive derailment sensor

Abstract: The detection method uses at least one inductive sensor (SEN) positioned at a given vertical distance above the track rail (SCH) adjacent the rail vehicle wheel (RAD) and monitoring the relative spacing from the track rail, for indicating de-railing or wheel wear when this spacing is above or below a defined limit range, with provision of a corresponding signal and/or activation of emergency braking. An Independent claim for a device for detection of de-railing or wheel wear for a rail vehicle wheel is also included.

Optical sensor unit for measuring current and voltage of high frequency

Abstract: An optical sensor unit, free from electrical noise, includes a sensor case which has both lateral sides having high frequency connectors mounted thereon, and a metallic plate mounted inside the case The metallic plate has both ends connected to inner conductors of the high frequency connectors, and its upper surface having a current and a voltage sensor unit mounted thereon for measuring the high frequency current and voltage, respectively The current sensor unit includes total-reflection mirrors and a current sensor, and the voltage sensor unit includes further total-reflection mirrors and a voltage sensor The voltage sensor has its upper surface having an electrode provided thereon to be connected to the sensor case The laser light from outside is input to the current and voltage sensor units over optical fibers The signal light output from the current and voltage sensor units is taken outside on output optical fibers

Lithographic projection apparatus with positioning system for use with reflectors

Abstract: In a lithographic projection apparatus the positions and/or orientations of reflective optical elements is dynamically controlled. The position of a reflective optical element such as a mirror in an illumination or projection system is first measured using an absolute position sensor mounted on a reference frame and thereafter measured by a relative position sensor also mounted on said reference frame. The position of the element is controlled in accordance with the measured position, e.g. to maintain it stationary in spite of vibrations that might otherwise disturb it. The absolute sensor may be a capacitive or inductive sensor and the relative sensor may be an interferometer.

Inductive sensor for producing switching signal when electromagnetic radiation damping material approaches has flat circuit board with at least one through opening through which coil core is passed

Abstract: The inductive sensor has at least one conducting track (14) on a circuit carrier (16) that forms at least one coil (12) and a coil core (18) associated with the coil. The circuit carrier is a flat circuit board and has at least one through opening (28) through which the coil core is passed. The coil core is U-shaped or semi-toroidal in shape. An independent claim is also included for a method of manufacturing an inventive device.

Evaluation of different types of sensors and their positioning for on-line PD detection and localisation in distribution cables

Abstract: Different types of sensors can be used for on-line detection and localisation of PDs in medium voltage cables. These sensors can be placed on different locations in the substa-tions where the cable under test is terminated. Both aspects have a significant influence on the measured signals. In this paper both capacitive and inductive sensors are briefly evaluated, especially concerning their applicability for on-line measurements. Further-more, when the sensors are applied on-line, it is essential to realize which signals are being measured. Especially when three-phase belted cables are being measured, the situation differs considerably from off-line situations. When the cable is on-line, i.e. powered by the network itself, all three the phases are energized simultaneously. This means the PD pulses are propagating through two distinctive propagation modes: the Phase-to-Phase (PP) mode and the Shield-to-Phase (SP) mode. In this paper the differ-ent possible locations in a substation for placing sensors are discussed, with respect to the measured propagation modes, signal- and interference sensitivity, safety and practi-cal applicability. Field measurements confirm the findings.

Sensor circuit and method of producing it

Abstract: A sensor circuit includes a sensor element, a current source for supplying an operating current for the sensor element and an amplifier circuit for amplifying a sensor voltage produced by the sensor element when applying the operating current, wherein the amplifier circuit has a resistor influencing the amplification of it. The resistor of the amplifier current and the sensor element are formed equally as regards technology so that variations, due to technology, of the sensor sensitivity of the sensor element are counteracted by an amplification factor of the amplifier circuit changing in the opposite way.

High-response inductive electromagnetic sensor

Abstract: A high-response inductive electromagnetic sensor can be made by arranging a conductive and/or magnetic material between the primary coil and the secondary coil. Compared with the conventional inductive electromagnetic sensor, the new sensor has a larger responsivity index (used here to evaluate its characteristics), though it also has a smaller induced voltage at the secondary coil.

Proximity sensor circuit with programmable logic device controller

Abstract: An improved proximity sensing circuit and method is provided. In particular, the proximity sensing system includes an improved controller comprising a programmable logic device ('PLD') [412]. In one particular aspect of the invention, the controller includes a field programmable gate array ('FPGA') controller. In general, the proximity sensing system measures the AC and DC resistances of a proximity sensor [402] and a precision resistor [404] and, from these measured values, calculates a compensated resistance. The compensated resistance may be used to determine the gap. The measured AC and DC resistances of the proximity sensor may be used to perform a self diagnostic on the sensing system and to aid in determining a system fault.

Remote temperature and stress monitoring using low-frequency inductive sensing

Abstract: The use of giant magnetoresistive (GMR) sensing elements in inductive sensors permits low frequency operation for materials characterization and defect detection in aerospace and engineering materials. This offers a substantially increased depth of sensitivity over conventional eddy-current sensing coils and also allows new measurement capabilities, such as the non-contact remote monitoring of temperature and stress variations through material layers. This paper provides an overview of the Meandering Winding Magnetometer (MWM) drive winding constructs that incorporate GMR based sensing elements. The sensors are designed so that the magnetic field distribution created by the primary winding and the resulting response of sensing elements can be accurately modeled. Representative applications to be described include (1) detection and imaging of 3% material loss in a 6.4-mm (0.25-in.) thick aluminum plate, (2) monitoring of temperature variations of an aluminum plate located behind another 6.4-mm thick aluminum plate with an air gap between the plates, and (3) independent measurements of stress (through magnetic permeability measurements) in a steel plate located behind an aluminum plate with an air gap between the plates.

Method and circuit employing current sensing to read a sensor

Abstract: A current sensing method and circuit for reading out a sensor cell, and a sensing apparatus comprising an array of sensor cells arranged along column lines and a current sensing readout circuit coupled to each column line. The sensor cell is configured to assert a sensor current indicative of a sensed value. In operation, an input node of the readout circuit is coupled to the sensor cell, typically by a column line of a sensor array that includes the sensor cell. Preferably, to read out the sensor cell, the sensor current flows from the sensor cell to the input node and in response, the readout circuit charges a capacitor to a voltage indicative of the sensed value while clamping the input node at a potential that is at least substantially fixed.

Inductive sensor for rotational speed determination with integrated temperature measurement

Abstract: The invention relates to the use of an inductive signal generator (1), for recording the position, path, angular position, or rotational speed of a moving element, for also generating a signal for the temperature of one or more components (16, 26) arranged near the signal generator An economical functional rationalisation in a single component is thus achieved The sensor can display the temperature of a wheel bearing and/or the brakes Brake overheating or bearing damage can be determined, by means of comparing the temperature on differing wheels