Inductive sensor

About: Inductive sensor is a research topic. Over the lifetime, 2282 publications have been published within this topic receiving 21984 citations.

A sensor for imaging steel in reinforced concrete structures and visualisation of surface corrosion, incorporating real-time DSP

Abstract: A combined Q and heterodyne inductive sensor is described incorporating real-time digital signal processing (DSP) for the imaging of steel reinforcement together with surface corrosion within concrete. The sensor exploitsthe principle whereby a time- varying magnetic field is induced around a sensing coil carrying an alternating current. When a metal target is exposed to the sensing coil, eddy currents will be induced resulting in an EMF, which will oppose the change producing it. As a result the electrical properties and the impedance of the sensing coil will change due to the interaction with the field around the target. In general, conductive targets change the resistive part and non-conducting permeable targets change the reactive part. A change in voltage amplitude will occur for conductive targets and frequency change for non-conducting ferrous targets. These parameter changes are expressed as a voltage level and processed by a DSP system. The DSP system is acquiring hundreds of samples per second and filtering the data using moving averaging. It is possible to detect a steel bar to a depth of approximately 150 mm and to generate an image to a depth of approximately 30 to 60 mm, indicating the presence of surface corrosion.

Low Cost Binary Proximity Sensor For Automotive Applications

Abstract: A fiber optic binary position sensor has been fabricated simply and inexpensively. This sensor exploits the Faraday Effect to detect the presence of a piece of ferrrous metal The sensor is positioned inside a ring magnet, so that when a ferrous metal object passes close to the face of the magnet, it distorts the field, changing the output of the sensor from low optical power to high. The key component is a piece of bismuth doped iron garnet film with an extremely high Faraday Rotation per unit length and a low saturation magnetization. Material properties of this film will be discussed, along with sensor design and performance. This sensor has many potential applications in the automotive industry, such as monitoring door, hood and trunk positions.

Planar high-frequency contactless inductive position sensor

Abstract: This paper presents a low cost, precise and reliable inductive absolute position measurement system. It is suitable for rough industrial environments, offers a high inherent resolution (0.1 % to 0.01 % of antenna length), can measure target position over a wide measurement range and can potentially measure multiple target locations. The position resolution is improved by adding two additional finer pitched receive channels. The sensor works on principles similar to contactless resolvers. It consists of a rectangular antenna PCB and a passive LC resonance target. A mathematical model and the equivalent circuit of this kind of sensor is explained in detail. Such sensors suffer from transmitter to receiver coil capacitive crosstalk, which results in a phase sensitive offset. This crosstalk will be analyzed by a mathematical model and will be verified by measurements. Moreover, the mechanical transducer arrangement, the measurement setup and measured results will be presented.

Non contact inductive sensor for measuring rectilinear or angular displacements

Abstract: The inductive sensor has a magnetic circuit (2) with an airgap and excitation winding (1). A movable part (3) slides in the airgap and a measuring circuit (4,5,v), see Fig. 2a,2b, measures the reluctance of the magnetic circuit so as to deduce a position of an object mechanically linked to the moving part (3). the part (3) has a section, measured perpendicular to the sense of sliding which is variable along the slide direction. The excitation winding can include a series connected primary winding (7) see Fig. 5, and a secondary winding (8) mounted respectively on the first and second pole either side of the airgap. The measuring circuit includes an a.c. and d.c. current source connected in parallel with the winding. The circuit also includes: - a low and high pass circuits and a multiplier circuit; - an analogue - digital converter which has a reference input connected to the low pass circuit.

Breakerless electronic ignition system

Abstract: Ignition pulses are supplied to an internal combustion engine from a breakerless electronic ignition system wherein the ignition pulses are produced in response to the movement of teeth on an electrically conductive trigger wheel past an inductive sensor. The inductive sensor is part of a LC tank circuit of an oscillator normally producing an oscillatory output signal which is detected by a bistable demodulator, and as a tooth moves into close proximity with the inductive sensor energy from the tank circuit is lost through an inductive coupling with the trigger wheel until the oscillatory output signal is terminated. The bistable demodulator responds to the absence of an oscillatory output signal by producing a timing signal which causes an ignition pulse to be supplied to the engine. The trigger wheel rotates in synchronization with the engine, and the initial timing of the ignition system is determined by setting the relative positions of the sensor and the trigger wheel. To advance or retard the initial timing of the ignition system, a resistor is connected across the tank circuit by a controllable switch to control the energy level in the tank circuit and hence the time required to terminate the oscillatory output signal. The initial timing of the ignition system may be set with the resistor electrically connected across the tank circuit, and upon the occurrence of engine conditions may result in undesirable ignition knock the controllable switch may be rendered nonconductive so as to retard the timing of the ignition pulses. Alternatively, the initial timing of the ignition system may be set with the resistor electrically connected across the tank circuit so that under certain engine operating conditions the switch may be rendered conductive to advance the initial timing of the ignition system. The switch connecting the resistor across the tank circuit may be a transistor which is rendered fully conductive or nonconductive by control signals produced according to predetermined engine operating conditions, or alternatively the conduction of the transistor may be gradually varied from fully conductive to nonconductive so as to serve as a variable resistor gradually increasing or decreasing the resistance across the tank circuit and thereby gradually advancing or retarding the initial timing of the ignition system.