Showing papers on "Inductive sensor published in 1997"

Self-verifying temperature sensor

Abstract: A self-verifying temperature sensor and method for measuring and verifying the true thermodynamic temperature of a system. The sensor is constructed of various combinations of the following temperature-dependent elements: thermoelements, resistive elements, capacitive elements and other inductive elements. In the preferred embodiment, the sensor is constructed of resistive element connected between four thermoelement wires. A fifth thermoelement wire is connected to the resistive element. The sensor produces a data signature from various voltage, resistance, inductance, and capacitance measurements. Measurement electronics collect and condition the data signature. A computer analyzes the data signature and provides the system operator with a verified sensor temperature, thus, allowing the system operator to recognize and account for drift or decalibration of the sensor. The self-verifying temperature sensor can also be recalibrated in situ, thereby eliminating the necessity of sensor removal to verify recalibration.

Optical liquid level sensor including built-in test circuitry

Abstract: A liquid sensing apparatus for a fuel tank comprises a first optical sensor for producing an output having a first state that corresponds to the first optical sensor being exposed to air and a second state that corresponds to the first optical sensor being exposed to fuel; and a circuit for detecting the first and second optical sensor output states. The sensor circuit also has self test capability for testing both active and passive components. The sensor circuits can be accessed using a two wire only interface, and thermal stability can be achieved with the electronic circuit as shown.

Method for the non-invasive sensing of physical matter on the detection surface of a capacitive sensor

Abstract: A capacitance sensor detects the absence/presence of physical matter on a sensing surface of the sensor. The capacitive sensor is a multi-cell sensor wherein each cell has one or more buried, protected, and physically inaccessible capacitor plates. The sensor is physically placed in an environment that is to be monitored for deposition of a particle, vapor, and/or drop of a foreign material on the sensing surface. All cells are initially placed in a startup condition or state. Thereafter, the cells are interrogated or readout, looking for a change in the equivalent feedback capacitance that results from an electrical field shape modification that is caused by the presence of physical matter on the sensing surface. When no such change is detected, the method is repeated for another cell. When a change is detected for a cell, a particle/vapor/drop output is provided. As an optional step, the sensor is provided with a layer of a material that is selectively reactive to or reactive with, a particle/vapor/drop of a known type of foreign material.

Inductive proximity sensor with a flat coil and a new differential relaxation oscillator

Abstract: A high-sensitivity flat-coil inductive proximity sensor microsystem has been realized and successfully tested. The flat coil, made with CMOS-compatible post processes, is connected to a versatile differential relaxation oscillator electronic interface. In this new and simple interface, the excitation, the signal extraction and amplification are assured by only one operational amplifier. Experimental results on the microsystem confirm that large output frequency variations occur when a metallic target approaches the sensor.

A differential relaxation oscillator as a versatile electronic interface for sensors

Abstract: A simple and versatile electronic interface circuit for sensors is presented. The novel interface circuit is based on a relaxation oscillator in differential configuration. In such a configuration, the sensitivity is strongly increased and compensations are made possible. It can be applied to resistive, capacitive and inductive sensors or detectors. Experimental and simulation results confirm the theory built up. High sensitivity is measured. Non-idealities of electronic components set the limit of attainable sensitivity.

System for adjusting a magnetic sensor to detect the presence of ferrous objects

Abstract: A proximity detector that employs a Hall-effect flux sensor disposed between the like poles of two magnets. The opposing fields of the magnets define a null flux field at a sensing plane of the Hall-effect sensor. A proximate ferrous object will deflect the null point and will therefore apply flux to the sensor. The sensor generates a signal indicative of the presence or absence of the ferrous object. In manufacturing a preferred spatial position of the null point with respect to the Hall-effect sensor is defined by adjusting the field strength of at least one of the opposed magnets.

Proximity sensor circuit with frequency changing capability having a plurality of sensors and a multiplexer with a single filter

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.

Exterior temperature sensor on antenna finial

Abstract: A temperature sensing system for sensing ambient temperature around a vehicle. The sensing system includes a temperature sensor, such as a thermistor or thermocouple, positioned within the antenna finial of a fixed-mast antenna of the vehicle. A sensor signal from the sensor is applied to a sensor circuit that includes suitable filtering components. The filtered sensor signal is then applied to a microcontroller where the signal is processed to display the exterior temperature on display within the vehicle passenger compartment. A sensor lead and a return lead are wrapped around the mast antenna to transfer the sensor signal from the sensor to the sensor circuit. The mast antenna is wrapped with a shrink-type tubing or covered with an epoxy-type coating to cover the sensor lead and return lead. The presence of the wires provides the added benefit of reducing wind noise traditionally associated with the antenna mast.

Inductive proximity sensor comprising a resonant oscillatory circuit responding to changes in inductive reaction

Abstract: An inductive proximity sensor that uses a resonant oscillatory circuit to detect a target by changes to inductive reaction. The oscillating circuit has primary and secondary windings where a capacitor and load resistance are connected in parallel with the primary winding, the value of the load resistance is selected so that in a state of oscillation the ohmic losses in the load resistance are substantially higher than the ohmic losses in the primary winding, and the primary and secondary windings are disposed so that the mutual flux between the primary and secondary windings is substantially less than the particular flux of each winding.

Temperature-compensated object sensing device and method therefor

Abstract: A device and method is provided for sensing an object or vehicle in proximity to a sensing zone, wherein the device is exposed to an environment temperature. The object sensing device comprises a sensor, such as an inductive loop having a characteristic, such as the inductance of the inductive loop, responsive to the proximity of the object is to the sensor; a signal generator, such as an oscillator, coupled to the sensor for producing a first periodical signal cycling at a first frequency dependent on the sensor characteristic and the environment temperature. A de-coupling mechanism for de-coupling or isolating the sensor from the signal generator so that the signal generator produces a second periodical signal cycling at a second frequency dependent on the environment temperature, but not substantially dependent on the characteristic of the sensor; and a device for producing a temperature-compensated response indicative of whether the object is in the sensing zone from the first and second periodical signals or their respective frequencies. Using the temperature-compensated object or vehicle sensing device, a gate operating system and a vehicle driver stimulus device is also provided herein.

Self testing optical liquid level sensor

Abstract: A liquid sensing apparatus for a fuel tank comprises a first optical sensor (24,26,28,30) for producing an output having a first state that corresponds to the first optical sensor being exposed to air and a second state that corresponds to the first optical sensor being exposed to fuel; and a circuit for detecting the first and second optical sensor output states. The sensor circuit also has self test capability for testing both active and passive components. The sensor circuits can be accessed using a two wire only interface, and thermal stability can be achieved with the electronic circuit.

Device for detecting electromagnetic stray effects in systems with at least two inductive sensors providing periodic output signal

Abstract: A device for detecting electromagnetic stray effects in systems with at least two inductive sensors which provide an essentially periodic output signal, performs a signal evaluation for evaluating signals of the sensors, a test for detecting an electromagnetic stray effect, whether periods of the signals to be evaluated lie within a period length of expected stray effects, a test, if applicable, whether detected signal progressions have at least a progression typical for stray pick-up, plausibility tests by means of at least one further detected signal in which a signal to be checked is compared with parallel measured other signals, and detecting a stray effect only if all tested conditions provide a result which is typical for stray effects.

Application of high temperature superconducting quantum interference devices in transient electromagnetic method for magnetotelluric soundings

Abstract: We have explored the application of high temperature superconducting interference devices (SQUIDs) in the artificial source magnetotelluric sounding. Field experiments were performed to test the high T c SQUID in transient electromagnetic source. It showed that the SQUID sensor has some advantages over the conventional inductive sensor, and also revealed some problems. Theoretical studies have been carried out to investigate the prospects and limitations of the SQUID sensor.

Axis counting arrangement for rail-bound vehicle

Abstract: The arrangement distinguishes between frequency-modulated inductive sensor signals generated at a remote place and transmitted over signal conductors to an evaluation arrangement. The sensor signals are caused by eventual wheel influences, and are supplied to an input filter, by which they are prepared for the evaluation. A frequency-to-voltage converter (FSU1, FSU2) with at least one coupled trigger (T12, T22) is connected to the signal conductors (SK). The threshold of the trigger lies below or above a signal level which settles in when the sensor is not influenced and when no noise is present. The trigger responds to an under- or overstepping of the threshold value. The output signal of the trigger is combined by an AND function with the output signal of a further trigger (T13, T23) which is connected at least indirectly to the output of the input filter, and which responds when the value falls below its predetermined threshold.

Ground loop detector circuit and method

Abstract: A ground loop detector circuit and method for an instrument that is used with either a pH sensor or a conductivity sensor. In the instrument used with a pH sensor, an AC diagnostic signal is provided to the sensor. A high input impedance diagnostic signal monitor monitors the voltage at a node adjacent the output of the diagnostic signal source. The occurrence of a ground loop causes the voltage at the node to drop. The instrument used with the conductivity sensor, not only monitors current returning to the diagnostic circuitry from the sensor but also uses a high input impedance monitor to monitor the current leaving the diagnostic circuit to the sensor. The relationship between the current from the sensor and the current to the sensor can be used to determine if a ground loop has occurred as such a loop will cause the current from the sensor to be less than the current to the sensor.

Sensor for a position measuring device

Abstract: There is provided a sensing element for a position measuring device, which serves to generate position-dependent output signals in the inductive scanning of at least one division track which is arranged from alternating electrically conductive and non-conductive areas. The sensing element comprises a carrier element on which a plurality of exciting elements for generating a uniform electromagnetic excitation field as well as one or more flat sensor windings are arranged. Here, at least two adjacent scanning tracks are arranged sensor coils of different periodicity of each laterally adjacent energizing elements, so that each forms a homogeneous electro-magnetic excitation field in the region of the scanning on the carrier element.

Sensor circuit with diagnostic 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.

New Contactless Inductive Sensor for the Measurement of Concentration of an Electrolytic Solution

Abstract: In this paper an inductive sensor with a new and simple contactless structure to determine the concentration of an electrolytic solution is presented. The authors propose a novel idea of designing the sensing coil of the sensor so that the magnetic field is focused inside the conducting liquid, thereby increasing the sensitivity of the sensing coil. By detecting the change in inductance of the sensing coil due to a solution of known concentrations of a particular electrolyte, a database is created. With the help of this database it is possible to estimate the unknown concentration of an electrolytic solution. It was tested for various concentrations of NaCl and it shows a distinct response for each concentration.

Rotational speed or direction detector especially of induction motor

Abstract: The device is installed in a motor having a fan (1) fitted to the rotor shaft under a cover (2). A pulse source (13) on the outside of the cover co-operates with vanes (9) co-rotating on the inside within the fan space (14). The pulses are produced by an inductive proximity sensor influenced by the passage of vanes of electrically conductive material (e.g. steel or Al) uniformly distributed around a disc (6) attached to the fan on the side facing the motor.

Coin recognition using an inductive proximity sensor microsystem

Abstract: We have realized metallic profile imagery of coins using a miniaturized inductive proximity sensor. The sensor is a microsystem composed of a 1 mm diameter coil and a new ASIC interface based on the principle of a differential relaxation oscillator. This imagery is appropriate for coin pattern recognition. We successfully acquired well recognizable images of various coins with similar and different geometrical, electrical and magnetic properties.

Steering angle sensor for automobile

Abstract: The sensor has at least one inductive sensor element (4) cooperating with a soft magnetic ring (1) with a varying cross-section around its periphery, secured to the steering spindle. The ring is displaced within an air-gap provided by the inductive sensor element during the rotation of the steering spindle, for varying the sensor inductance, to provide a signal representing the angular position of the spindle. The radial thickness of the soft magnetic ring may vary around its periphery between maximum and minimum values.

Inductive proximity sensor comprising oscillatory circuit with inductive reaction

Abstract: The invention concerns a proximity sensor comprising an oscillatory circuit with reactive induction with load resistance, the primary and secondary windings being arranged such that the mutual flux between the 2 windings is substantially weaker than the particular flux of each winding.

Electric switch with movable switch lever e.g. automobile light- and windscreen wiper switch

Abstract: The switch has a switch lever (30) which is moved between at least two switch positions, for selecting respective switch functions, with a magnetic flux amplifying element (35) at the end of the switch lever cooperating with inductive sensors (21,22,3) in each switch position. The inductive sensors can be provided by secondary coils cooperating with a common primary coil, with the signals from the inductive sensors fed to an evaluation circuit (34) for determining the switch lever position.

Output-signal generating circuit

Abstract: PROBLEM TO BE SOLVED: To provide a sensor circuit generating an output signal proportional to the liquid level in a tank or the angular displacement of a sensor independently from the temperature or electrical characteristics of a sensor of a medium to be detected. SOLUTION: A feedback circuit generating an output signal from a sensor produces an output regardless of the temperature or electrical characteristics of a sensor or a medium to be detected. A sensor 14 is set in the feedforward loop of a circuit 10 and produces an output dependent on a region of parallel plates but not dependent on the temperature or electrical characteristics of sensor or a medium to be detected. The sensor 14 comprising parallel conductive plates and filled with a liquid has one complete plate 28 and the other divided differential plates 24, 26 and used as a liquid level sensor or a clinometer in the feedforward loop. Other sensor, e.g. an inductive sensor, may also be used.

Inductive sensor for slow varying magnetic fields

Abstract: The usual inductive sensors can not be used in slowly varying (variation rate almost zero) magnetic fields due to their lack of sensitivity. We describe an inductive sensor capable of detecting slow variations of the magnetic filed. The device is based on the magnetic domains reordering due to external variations of the applied magnetic field. The sensor contains a coil with ferromagnetic core. A continuous variation of the applied field determines the sequential reordering of the magnetic domains in the core and, consequently, the variation in steps of the magnetic induction, therefore, the coil will generate a pulse train. The number and amplitude of pulses are not influenced by the speed of the variation. To obtain larger amplitude pulses the magnetic core of the sensor is ferromagnetic, relatively thin layer, (10–50 μm), with high permeability and moderate coercitive field. Such layers may be amorphous ribbons or laminated ribbons thermally and mechanically treated. Along with an electronic amplifier and analyser of the generated pulses, the described sensor may be used in a variety of applications featured by a slow variation of a magnetic field.

Lithium Niobate Integrated-Optic Voltage Sensor with Variable Sensing Ranges

Abstract: Integrated optical sensors for voltage and field measurement have intrinsic advantages over electronic sensors in terms of isolation from electronic instrumentations, large bandwidth, and immunity to electromagnetic interferences.

Detector with variable resistance sensor

Abstract: An ambient condition sensor exhibits a resistance change as a function of the sensed condition. This change varies over several orders of magnitude. The sensor can be coupled to a circuit with a dynamically changing impedance to facilitate an accurate measurement of the variable sensor resistance. This circuit can include a ladder network of resistors which can be controllably coupled to the sensor as a function of sensor output resistance. The output signal from the sensor can be processed using analog or digital techniques to minimize noise induced variations. The sensor output resistance value can be converted to time for purposes of measurement and subsequent processing.

Inductive coin validation system

Abstract: A coin validation arrangement, usable for example in pay telephones, uses one or more inductive sensors 17 having a small effective magnetic field so that the inductive sensor 17 responds only to the material of a strip across the coin Preferably a plurality of inductive sensors 17 are used, mounted at different heights above the floor of the coin guide, at different positions along the coin path At each position along the coin path there may be either one or a plurality of inductive sensors 17 Such arrangements are particularly useful for recognising coins having a central hole or an outer ring made of a different material from the central disc, and for distinguishing such coins from uniform composition coins The inductive sensor(s) may be mounted on a circuit board in the side wall of the coin guide A capacitive sensor may also be provided to interact with the coin

Sensor circuit with frequency changing capability

Abstract: A proximity sensing circuit is provided with various attributes, including the connection of a proximity sensor coil (10) in a feedback loop of an amplifier (14), 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.

Non contact piezo-inductive sensor for automobile door locking purposes.

Abstract: Uses a winding on a piezo-electric chip which causes vibration of a part of the chip. The sensor (1) detects, without contact, the presence of a metallic piece. It consists of a support (2), a piezo-electric transducer chip (3) with two electrodes (6,9). The chip (3) is fixed to one of the faces of the support (2). An induction winding (4) is fixed onto the chip in a zone where the chip (3) is designed to vibrate under the action of micro-vibrations of the winding (4) generated by the magnetic field produced by it, when fed with current. A metal piece is positioned opposite the winding (4) at a sufficient from it.