Inductive sensor

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

An integrated inductive proximity sensor

Abstract: Inductive proximity sensors are widely used for the contactless measurement of object or target displacement and position in numerous technical products and systems. They are found in various application domains such as transportation, robots, assembly lines, telecommunication or security. The inductive sensing principle is known for its robustness, high precision and low sensitivity to environmental conditions as well as to extreme working conditions like cryogenic temperatures. The typical measuring range of inductive proximity sensors is between 0.1 cm and 5 cm. The overall dimensions of the smallest inductive proximity sensors, including the sensing coil and the electronic circuit interface, is rarely under some cubic centimeters, due to the high number of components of which such sensors are composed. Although the electronic interface circuitry may be integrated in an "application specific integrated circuit" (ASIC), the traditional fabrication processes of the inductive primary transducer (the coil and the flux concentrator) set the limit to the scaling down. The introduction of the inductive principle for proximity sensors into new technical mechatronic systems requires a small size and ease of fabrication (i.e. a low cost). The challenge of this thesis work was to develop such a sensor by using new technologies for the integration of microsystems. In this work, we successfully demonstrate the integration of an inductive proximity sensor on a small-size chip, and its usefulness as a key component in new sensing and mechatronic applications. To the best of our knowledge, we have realized the first fully integrated inductive proximity sensor ever reported. This challenge has been taken up by first studying the effect of the miniaturization on the basic behavior of sensing coils, and then by determining the scaling down laws as well as the limitations due to the parasitics, especially the increase of the inductor series resistance. Considering these first results, we developed a new and simple electronic interface, namely the differential relaxation oscillator. This highly sensitive, self oscillating circuit has only few components and the output signal is digital compatible. This readout principle is well adapted for miniaturized coils with low Q factor. A comparator has been designed and integrated with the two relaxation branches, forming the oscillator, on an ASIC. The miniaturized flat coil has been integrated on top of this ASIC using photolithography and electrodeposition compatible with the standard processes. The connections between the coil and the electronic circuit interface is realized through vias. In its smaller version, the integrated sensor chip size is of 1.5 x 2 mm2 with a square coil of 1 x 1 mm2 on top. This miniaturized flat coil has an inductance of 75 nH, a serial resistance of 6.2 Ω and a resonance frequency of 315 MHz. Its excitation frequency is close to 10 MHz. No external component is needed for this microsensor basic functioning, and the connections with the external world are limited to power supply and output signal. This integrated sensor is fabricated using the 1 µm 3V CMOS technology and the standard and compatible gold bumping layer to form the coil. This new device has been successfully tested. In the measuring range from 50 µm up to 150 µm, it shows a high sensitivity (24 kHz/µm) and a submicrometric resolution. The temperature behavior of integrated coils, of the electronic circuit principle and of their combination as a integrated sensor, has been studied. A simple temperature compensation scheme using one NTC resistor, compatible with the sensor integration, has been developed and tested successfully. Using this method, a temperature independence better than ±100 ppm/°C between -20 °C and +80 °C has been achieved with the 3.8 mm side flat coil version of the integrated inductive proximity sensor. New application have been demonstrated, using the good performances of the developed inductive proximity sensor microsystems. Metallic profile and inductive coin imaging have been successfully recorded. The angular position control of a watch motor has been evidenced with an angular precision of 2 DEG (limited by the step motor). The angular speed and position sensing of a non-ferromagnetic toothed wheel has been sensed up to at least 7800 rpm (corresponding to an excitation of 13 kHz). The application and the promising perspective of our integrated inductive proximity sensor into active magnetic bearings for hard disk drives has been presented. This multidisciplinary thesis work has been realized with emphasis on using simple elements and on obtaining a simple overall behavior. The device has only one coil, it uses only one comparator, it is made of only one chip, and moreover it can be fabricated in only one wafer foundry using standard processes. By focusing on the optimization of the global sensor system, good performances have been achieved and the integration of an inductive proximity sensor has been proven.

Inductive proximity sensor

Abstract: PURPOSE: To prevent an inaccurate sensing result from being made due to inter nal loss of a resonance circuit. CONSTITUTION: An inductive proximity sensor includes a power supply and a coil 2. The power supply supplies a periodic current to the coil 2, and its conduction time interval is shorter than a feeding time interval. A response of an object to be detected is measured at a time interval, when the current flowing to the coil 2 is essentially zero.

Program an embedded system with inductive proximity sensor and RFID reader

Abstract: [ANGLES] This project consists on an embedded system with three parts; ALIX board, inductive proximity sensor and RFID reader. Using a program is possible to manage these three devices to make a control point of goods that can be used in an industry.

Drowsiness alert system

Abstract: Active safety in automobile vehicles can be improved by incorporating this system which detects situations of driver drowsiness or unconsciousness and alerts him or her or applies emergency measures. To keep a driving vehicle centred in a lane it is necessary to continuously use the steering wheel to make small trajectory corrections by means of slight turns with an angular amplitude of a few degrees. These movements are permanently monitored by means of a specific sensor which can take information concerning different parameters of the steering system such as for example changes in oil pressure or flow from the hydraulic system, voltage or current if the steering is electric or directly from the angular movement of the steering wheel and steering shaft. Absence of these trajectory corrections is interpreted as a lack of attention to driving caused by drowsiness or unconsciousness. The signals coming from the sensor are sent to an electronic unit which triggers appropriate action a few seconds after failure to receive signals from the sensor. In a first phase these are luminous and auditory signals intended to wake the driver and if there is no reaction, in the next phase there are accompanying orders to the electronic controllers for vehicle management so that they give warning of the danger and stop the vehicle. Figure A is a schematic representation of the components of this system. 1) Trajectory correction sensor. This case shows an inductive sensor fitted to the steering column. 2) Electronic unit 2a) Sensor device 2b) Microprocessor 2c) Warnings module 3) Speed information source 4) Emergency button 5) Light signal (flashing) 6) Low intensity acoustic signal 7) High intensity acoustic signal 8) Activation of vehicle indicators, fuel cut-off, braking etc. 9) Power supply 10) Encoder.

Method of operating open-end spinning device and magnetic bearing arrangement for making the same

Abstract: In the present invention, there is disclosed a method of operating an open-end spinning device (1) having a spinning rotor (3) supported by a rotor shaft (4) both radially and axially in a magnetic bearing arrangement (5) comprising spaced permanent magnet pairs and an electromagnetic central position control device (50) comprising a sensor (51) and at least one actor coil (32, 42) that can be supplied with current in a defined manner, the method comprising processing an output signal of the rotor position sensor (51) in the central position control device (50) by initiating a coil current by a PD controller (53) and initially regulating the coil current toward zero by negative feedback of an integrator (55), subsequently producing a positive feedback of the coil current by negating an input signal of the integrator (55), which positive feedback results in an at least intermittent increase of the coil current in the magnetic bearing arrangement (5) actor coil (32, 42) and thereby lifting the spinning rotor (3) from its axial catch bearing (45) and transferring the spinning rotor (3) into its operating position, and subsequently regulating the coil current in the magnetic bearing arrangement (5) actor coils (32, 42) back toward zero in the operating position of the spinning rotor (3) There is also disclosed a magnetic bearing arrangement (5) comprising a central position control device (50) having at least one rotor position sensor (51) for generating an output signal and performed as an inductive sensor, further comprising a PD controller (53) for initiating a coil current and an integrator (55) for negative feedback of the coil current