Showing papers on "Inductive sensor published in 2011"

A Wireless Sensor Readout System—Circuit Concept, Simulation, and Accuracy

Abstract: In this paper, we present an electronic readout system for wireless passive sensors based on inductively coupled LC resonant circuits. The proposed system consists of a reader coil inductively coupled to the sensor circuit, an analog frontend circuit, and a digital signal processing unit. The analog frontend circuit generates a dc voltage representing the sensor resonance curve. The frequency of the reader coil driving signal is continuously readjusted by the digital signal processing unit. Based on analytical calculation and system simulation, we derive a model for the achievable accuracy of the overall sensor and readout system. The accuracy is limited by noise and systematic errors due to the measurement principle. We show how to design the digital signal processing system for optimal insensitivity to voltage noise. The noise sensitivity of the measurement system is inversely proportional to the square of the quality factor of the LC sensor. This means that minimizing the losses of the sensor is of crucial importance to obtain a wireless measurement system with a high range and a good insensitivity to noise. Subsequently, we outline an approach to calculate the sensor resonance frequency, quality factor, and inductive coupling factor from the available voltage signals in the signal processing unit using linear fitting functions. The accuracy of our approach is exemplified by a system simulation for typical sensor parameters. For the system studied, we show that the relative linearization error of the sensor resonance frequency measurement is below 0.02%. Taking the general models presented for both the noise sensitivity and linearization error into account, it is possible to estimate the maximum distance and accuracy for any wireless sensor system based on an inductively coupled LC resonator.

Proximity sensing for capacitive touch sensors

Abstract: A method and apparatus for operating an input device having an array of capacitive sensor electrodes and a proximity sensor electrode are disclosed herein The input device includes a processing system communicatively coupled to the array of capacitive sensor electrodes and the proximity sensor electrode and configured to operate in an input mode and a proximity mode When operating in the input mode, the processing system scans the array of capacitive sensor electrodes to detect input from an object in an active region of the input device When operating in the proximity mode, the processing system drives a sensing signal on at least one sensor electrode of the array of capacitive sensor electrodes and receives a resulting signal from the proximity sensor electrode Based on the resulting signal, the processing system generates an indication of an object presence in a second sensing region from the resulting signal

Optical High-Voltage Sensor Based on Fiber Bragg Grating and PZT Piezoelectric Ceramics

Abstract: Electric power facilities, such as substations, rely on voltage transformers (VTs) for measurement and protection. These pieces of equipment are bulky and heavy and tend to explode, destroying nearby equipment and posing a threat to substation personnel. Optical voltage transducers offer many improvements on traditional inductive and capacitive VTs, such as linear performance, wider dynamic range, lighter weight, smaller size, and improved safety. This paper relates to the development of a high-voltage sensor system using a PZT piezoelectric crystal as a transducer and a fiber Bragg grating as a sensor for an optical VT for a 13.8-kV class. The results show that the developed sensor is capable of attaining the International Electrotechnical Commission 0.2%-accuracy class for the revenue metering system.

Circuits and methods for self-calibrating or self-testing a magnetic field sensor

Abstract: A magnetic field sensor includes a reference-field-sensing circuit channel that allows a calibration or a self-test of the circuitry of the magnetic field sensor. The magnetic field sensor can generate a reference magnetic field to which the magnetic field sensor is responsive.

High-Sensitivity Inductive Pressure Sensor

Abstract: A new type of pressure sensors with extremely high sensitivity is introduced. Unlike piezoresistive, capacitive, and linear-variable-differential-transformer-based pressure sensors, the new sensor is based on a technique for substantially changing the inductance of a coil. The prototype device has demonstrated a change in inductance of approximately 34.5 mH over a pressure range of 10 kPa. The sensor offers a number of desirable features, including linearity, low temperature, and pressure hysteresis, in addition to small size.

Intermodulation Read-Out Principle for Passive Wireless Sensors

Abstract: This paper presents a general intermodulation read-out principle for passive wireless sensors. A sensor utilizes a mixing element, such as a varactor, and it can be equipped with a capacitive, inductive, or resistive sensor element. When the sensor is illuminated with signals with two frequencies, it replies the sensor data at an intermodulation frequency. An analytical expression for the intermodulation response of the sensor is derived and verified by simulations. The concept is demonstrated at 1.2 GHz.

System And Method To Integrate Ambient Light Sensor Data Into Infrared Proximity Detector Settings

Abstract: A device is provided that includes an ambient light level sensor, a proximity sensing system, and a processor. The ambient light level sensor generates a signal as a function of an ambient light level at the device. The proximity sensing system comprises an emitter component. The processor is configured to receive the signal from the ambient light level sensor and to adjust an electrical current through the emitter component based on the signal.

Vehicle Keyless Entry Assembly Having Capacitance Sensor Operative for Detecting Objects

Abstract: A keyless entry assembly for a vehicle includes a sensor carrier, a sensor in the form of an electrically conductive pad, and a controller. The sensor is mounted to the sensor carrier and the sensor carrier is positioned adjacent a panel such that the sensor is adjacent the panel. The sensor capacitively couples to an electrically conductive object proximal to the panel while the sensor is driven with electrical charge such that capacitance of the sensor changes due to the sensor capacitively coupling with the object. The controller is operable for driving the sensor with the electrical charge and controlling a vehicle operation as a function of the capacitance of the sensor.

A multiple loop vehicle detection system for heterogeneous and lane-less traffic

Abstract: This paper presents a novel inductive loop sensor which detects large (e.g., bus) as well as small (e.g., bicycle) vehicles and help a traffic control management system in optimizing the best use of existing roads. To accomplish the sensing of large as well as a small vehicle, a multiple loop inductive sensor system is proposed. The proposed sensor structure not only senses and segregates the vehicle type as bicycle or motor cycle or car or bus but also enables accurate counting of the number of vehicles that too in a mixed traffic flow condition. A prototype of the multiple loop sensing system has been developed using a virtual instrumentation scheme and tested. Field tests indicate that the prototype successfully detected all types of vehicles and counted, correctly, the number of each type of vehicles. Thus the suitability of the proposed multi loop sensor system for any type of traffic has been established.

Wireless magnetic position sensor

Abstract: In one example, a position sensor is provided. The position sensor comprises an integrated circuit, and a magnetic field sensor that provides a detected signal indicative of a position of a magnetic field source to the integrated circuit. The magnetic field sensor comprises a tunneling magnetoresistance (TMR) sensor. The position sensor further comprises a wireless circuit coupled to the integrated circuit, wherein the wireless circuit comprises an antenna configured to radiate a position signal based on the detected signal.

Self-powered wireless induction sensor

Abstract: An induction sensor generates speed data based on a frequency of the change in magnetic flux within the sensor and powers sensor circuitry by recharging a power source using at least a portion of the electrical voltage induced by the change in magnetic flux. In this manner, the induction sensor may generate its own power to sense and transmit data. To optimize the recharging power available from the induced electrical voltage, the sensor may also include a variable load. This variable load may be automatically controlled by the sensor based on the induced voltage and/or current. The induction sensor may also wirelessly transmit generated data. In addition, the sensor may, after shutting down, automatically power up in response to the change in magnetic flux exceeding a start-up threshold.

Study of an Inductive Sensor for Measuring High Frequency Current Pulses

Abstract: The objective of this paper is to present a simple sensor based on Faraday's Law together with an integration and amplifying stage and used this for measuring fast current pulses. Its behavior in time and frequency is tested by measuring Partial Discharges (PD) in electric insulation systems following the guidelines given in the standard IEC 60270. The measurements are also taken with two other sensors, a commercial high frequency current transformer and a resistive transducer, with the aim of comparing the results obtained with the proposed probe and obtaining an estimation of its sensitivity. An estimation of the uncertainty of the measurements is also calculated obtaining an error similar to other commercial devices.

Inductive Sensor for Lightning Current Measurement, Fitted in Aircraft Windows—Part I: Analysis for a Circular Window

Abstract: A novel sensor is described for the detection of the lightning current through the fuselage of an aircraft. The sensor relies on the penetration of the magnetic field through fuselage openings and can be embedded in a window inside the aircraft. The sensor combines good sensitivity with sufficient bandwidth to record the lightning transient current. Guidelines for the position are derived from a mathematical analysis for a circular window.

Sensor apparatus, in particular metal sensor, with a field-compensated magnetic field sensor

Abstract: The invention relates to a sensor apparatus, in particular a metal sensor, having at least two coils and a magnetic field sensor, in which the arrangement of coils and magnetic sensor with respect to one another and/or the number of coil turns and/or the winding sense of the coils and/or the coil current is/are selected in such a manner that the magnetic field generated by the coils approximately disappears at the location of the magnetic field sensor. The invention also relates to a method for detecting objects, in particular a method for finding metal objects, using at least two coils and a magnetic field sensor, in particular an AMR, GMR or Hall sensor, in which the arrangement of the coils and the magnetic sensor with respect to one another and/or the number of coil turns and/or the winding sense of the coils and/or the coil current is/are selected in such a manner that the magnetic field generated by the coils approximately disappears at the location of the magnetic field sensor.

The key points of inductive wear debris sensor

Abstract: This review paper has presented several examples of inductive wear debris sensor. Many of these have important applications in industry. Thus, when monitoring the oil system which operates under extremely severe conditions and various features (size and type) need to detect, it is worth considering the use of inductive wear debris sensor. Based on the electromagnetic field analysis for the coil and particles, three structures of such sensors, classified by the number of coils, are available, and they all can detect, count or classify wear debris. However, the detectable particle size is mainly limited by the background noise. Accordingly, to enhance the sensor performance, the signal processing methods are necessary.

Device for detecting the twist angle of a shaft and/or a torque occurring on the shaft and methods for operating the device

Abstract: A device for detecting a twist angle and/or a torque of a shaft occurring on the shaft and methods for operating the device uses at least one first encoder and at least one second encoder at a predefined spacing therefrom. Each encoder influences at least one coil parameter, is associated with at least a part of the circumference of the shaft, and has at least one track having at least one period per revolution of the shaft. At least first and second inductive sensors scan the first and second encoders, respectively. Each inductive sensor provides a respective sensor signal reflecting at least one measure for the rotational angle of the shaft within the period, and a difference ascertainment unit ascertains and provides the twist angle of the shaft as an angle difference of the two rotational angles detected by the inductive sensors.

Method for e.g. determining degree of wear i.e. blunting, of rotary blade in field chopper in agricultural field, involves determining reduction of width of blade back side and distance from blade to counter blade from parameters of curve

Abstract: The method involves transmitting sensor values to an evaluation unit during transit of a blade through a measuring field (4) of an analog inductive sensor (3). Signals e.g. voltage signal and current signal, of the inductive sensor are converted into a curve i.e. u-shaped voltage-time-curve. Reduction of width of blade back side and distance from a blade (11) to a counter blade (2) are determined from two characterizing parameters e.g. sensor voltage, of the curve. Sharpness of the blade is determined from the characterizing parameters of transit time and change of minimum voltage. An independent claim is also included for a device for determining degree of wear of a rotary blade and/or change of distance from the blade to a counter blade of a straw cutter.

A simple multiple loop sensor configuration for vehicle detection in an undisciplined traffic

Abstract: This paper presents an inductive loop vehicle detection system suitable for heterogeneous and less-lane disciplined traffic. Vehicle detection system based on conventional inductive loop principle has been in use but works well only for lane based and homogeneous traffic. A multiple loop system that is suitable for sensing vehicles in a heterogeneous and less-lane disciplined condition has been reported recently. This paper proposes a new measurement scheme for the multiple loop system. According to the new scheme, all the inductive loops are connected in series and only two cables are required, instead of two per each loop, between the measurement unit and multiple loop system, there by reduces the system complexity. Each loop has a unique resonance frequency and the excitation given to the loops connected in series is programmed to have frequency components covering all the resonance frequencies of the loops. When a vehicle goes over a loop the corresponding inductance and resonance frequency will change. The shift in frequency or its effect for individual loops can be monitored simultaneously and the vehicles can be sensed and identified as bicycle, motor-cycle, Car, Bus, etc. A prototype multiple loop system has been built and tested based on the proposed measurement scheme. The system developed sensed, classified and counted the vehicles accurately.

Working Distance Comparison of Inductive and Electromagnetic Couplings for Wireless and Passive Underwater Monitoring System of Rinsing Process in Semiconductor Facilities

Abstract: This paper reports a side-by-side comparison of two wireless and passive sensing systems: inductive and electromagnetic (EM) couplings for an application of in-situ and real-time monitoring of wafer cleanliness in the rinsing process at semiconductor/microelectromechanical system (MEMS) manufacturing facilities. A MEMS sensor is designed to measure the resistivity of water, corresponding to the ionic concentration, to evaluate the rinsing process inside the micro-features. The transponder, containing the MEMS sensor, receives power from an external interrogator, modulates the resistivity data, and emits back the modulated signal to the interrogator, in all wireless and battery-free operation. Two wireless systems based on inductive and EM couplings have been implemented on 4-inch glass wafers, maintaining the wafer form factor. Inductive coupling system has parasitic electric field coupling. The working distance of the inductive coupling system is attenuated in water and is likely limited by signal-to-noise ratio (SNR), while that of the EM coupling is primarily limited by the coupled power. Hence, inductive coupling is suitable for a short distance measurement that allows more sophisticated functionality with sufficient power, whereas EM coupling could be optimized for long distance detection but has a tight power budget. The implemented on-wafer wireless monitoring units achieve a working distance of 6 and 25 cm with a concentration resolution of less than 2% (4 ppb for a 200 ppb solution) for inductive and EM couplings, respectively.

Inductive Sensor for Lightning Current Measurement, Fitted in Aircraft Windows—Part II: Measurements on an A320 Aircraft

Abstract: A novel sensor for the detection of the lightning current through the fuselage of an aircraft has been tested on an A320 aircraft. An accurate method-of-moment model of the window edge provided reliable calibration of the sensor for external fields. The data have been analyzed and the good performance of the sensor in sensitivity and bandwidth is demonstrated.

A New Method of Inductive Sensor Impedance Measurement Applied to the Identification of Vehicle Parameters

Abstract: Inductive loop sensors are widely used f or detection of presence, measurement of parameters as well as classification of vehicles. Vehicle classification may be performed based on their magnetic profiles. The magnetic profile is a signal which is proportional to the resultant of an impedance cha nge of the sensor, caused by the measured object (the changes are minor - of the order of 1%). Generator and bridge circuits are most commonly used as conditioning circuits for such sen sors. As a result we can obtain one output signal proportional to total changes of sensor parameters (R and L). In this pa per, a modified bridge circuit that allows independent measurement of the components (R and L) of the sensor’s impedance, has been proposed. With that provided, it is possible to receive broader informa tio n on the object, which allows higher classification resolution. This paper provides the concept of a ci rcuit, model testing results, processing algorithms used and the test results of a real circuit.

Angle measurement device and method

Abstract: The present invention relates to a sensor device for determining an absolute angle of a prosthetic joint, and which is resistant to environmental elements and has a reduced power draw. The sensor device includes an inductive sensor and a rotatable member including a metal material. The metal material can include a non-ferrous metal material. The inductive sensor detects an amount of the metal material in a proximate location to the inductive sensor. Rotation of the rotatable member increases or decreases an amount of metal material in the proximate location of the inductive sensor. The amount of metal material in the proximate location corresponds to an angle of the rotatable member and the prosthetic joint based on a monotonic function. Thus, the inductive sensor detects the amount of metal material in the proximate location to determine the angle of the rotatable member and subsequently the angle of the prosthetic device.

Implementation of inductive proximity sensor using nanoporous anodic aluminum oxide layer

Abstract: This study presents an inductive proximity sensor implemented through the integration of nano-texture metal-spiral and np-AAO (anodic aluminum oxide (AAO) with nanopores) insulation layer on Si-substrate. The advantages of such nano-structure inductive proximity sensor are as follows, (1) The surface area of nano-texture metal-spiral is increased. Thus, the performance of inductive sensor is increased; and (2) The nano-texture metal-spiral consists of nanopores transferred from the AAO template. Thus, the eddy current on metal-spiral induced by lower electrode can be reduced by the nanoporous film. In applications, inductive proximity sensor consisted of nano-texture Au-spiral on np-AAO is implemented. Measurements demonstrate the performance of the nano-texture proximity sensor is significantly improved.

Current sensor and battery with current sensor

Abstract: A current sensor includes a magnetic detection element having a resistance value changed by applying inductive magnetic field from measurement target current, a magnetic core provided in the vicinity of the magnetic detection element, and a coil generating magnetic field attenuating the inductive magnetic field. A constant level current in a predetermined range of output voltage of the magnetic detection element flows in the coil, and the measurement target current is detected on the basis of the output voltage of the magnetic detection element.

Measurement of Material Flow in Series Production

Abstract: This paper provides first results of a contact-free measurement system for monitoring the material flow in series production which has been under investigation for more than one year. An inductive proximity sensor with analog output was used to measure its own sheet metal coverage. Multiple sensors were integrated in the blank holder without affecting the deep drawing process. The robustness of the monitoring principle was assessed under series production conditions by using optical measurement equipment. This paper describes the basic information of the inductive measurement, the comparison of the inductive and optical measurement results and analyses correlations between the sensors.

Fuzzy inference system for analog joystick emulation with an inductive tongue-computer interface

Abstract: This paper describes the development of a fuzzy inference system (FIS) for emulating an analog joystick using an inductive tongue-computer interface. The principle of operation of the interface and the inductive sensors signals are described. The FIS receives sensor signals and output the Cartesian position of the virtual joystick, which can be used to control the mouse pointer in a personal computer, wheelchairs or other joystick enabled applications at varying magnitude and directions proportional to the tongue position over the palatal plate. This provides a significant advantage to individuals with tetraplegia using this computer interface.

A method for reducing piezoelectric non-linearity in scanning probe microscope images

Abstract: This paper describes a new technique for reducing the piezoelectric hysteresis in SPM images. Imaging modes such as constant-force AFM require a piezoelectric actuator to vary the probe-sample distance. In such modes, the topography of the sample is reconstructed from the voltage applied to the vertical piezoelectric actuator. However, piezoelectric actuators exhibit significant hysteresis which can produce up to 14% uncertainty in the reproduced topography. To combat this problem, the recent generation of commercial AFM's use capacitive or inductive position sensors to eliminate hysteresis; however, these sensors can be difficult to incorporate into the scanning head and also increase the imaging noise. In this work, an alternative technique is proposed that avoids the use of a vertical position sensor. Instead, a charge amplifier is utilized to linearize the vertical piezoelectric actuator and eliminate imaging hysteresis. Experimental results demonstrate a reduction in non-linearity from from 14% to 0.65%, which is visibly undetectable.

Self-integrating inductive loop for measuring high frequency pulses

Abstract: High frequency pulses can be measured by means of inductive sensors. The main advantage of these sensors consists of non-contact measurements that isolate and protect measuring equipment. The objective of this paper is to present the implementation of an inductive sensor for measuring rapidly varying currents. It consists of a rectangular loop with a resistor at its terminals. The inductive loop gives the derivative of the current according to Faraday's law and the resistor connected to the loop modifies the sensor's frequency response to obtain an output proportional to the current pulse. The self-integrating inductive sensor was validated with two sensors, a non-inductive resistor and a commercial high frequency current transformer. The results were compared to determine the advantages and drawbacks of the probe as an adequate inductive transducer.

Signal processing and pattern recognition for eddy current sensors, used for effective land-mine detection

Abstract: Magnetic and inductive sensors are widely used in research and industry for a variety of applications, e.g. for geophysical prospecting, nondestructive testing (NDT) of materials, in the food industries, for distance and proximity sensing, security systems as well as for landmine detection. Metal detectors (MD), based on the eddy current principle, are the most used systems in humanitarian demining. Their main disadvantage is the high false alarm rate, caused by harmless metal objects and "uncooperative" soils with magnetic properties. The sensor signal (i.e. the induced complex coil voltage) is influenced by the object properties (material, shape). This paper describes an object recognition based on multi-parameter MD signals, which are classified by the fuzzy method. The ability to identify mines by their characteristic signature was demonstrated in test lanes for mine detection provided by the University of Rostock (Germany), JRC-Ispra (Italy) and the CTRO-Benkovac (Croatia).