Hall Effect SensorsOutlineOutlineReferences used:To Explore Further……..Major ApplicationsWhat is the hall effect?What is the Hall effectSlide 9How does this work???In other words….????A Typical use: Honeywell’s magnetic position Sensor:How Hall Effect sensors are classifiedMajor specificationsLimitationsWhat else do I need to knowTo Conclude……..Hall Effect Sensors Daniel FreiUtah State UniversityECE 5320March 5, 2004OutlineReferences usedTo Explore FurtherMajor ApplicationsWhat is the hall effect?How does this work?A Typical use: Honeywell’s magnetic position Sensor:Major specificationsOutlineLimitationsWhat else do I need to knowConclusionReferences used:http://www.eeel.nist.gov/812/hall.htmlhttp://www.micronas.com/products/overview/sensors/index.phphttp://content.honeywell.com/sensing/prodinfo/solidstate/ Mechatronics Handbook, chapter 7. John C. Brasunas,G. Mark Cushman ,Brook Lakew 1999, by CRC Press LLCThe Measurement Instrumentation and Sensors Handbook, chapter 16-18. M. Anjanappa, K. Datta, and T. Song, 2002 CRC Press LLC.To Explore Further……..http://www.eeel.nist.gov/812/hall.htmlhttp://www.micronas.com/products/overview/sensors/index.phphttp://www.pha.jhu.edu/~qiuym/qhe/qhe.htmlhttp://www.pha.jhu.edu/~qiuym/qhe/node2.htmlhttp://www.warwick.ac.uk/~phsbm/qhe.htmhttp://www.xs4all.nl/~skoric/quantum/http://www.sypris.com/stm/content.asp?page_id=678Major Applications Electromagnetic fieldProximity Velocity DirectionWhat is the hall effect?Just the basics: The change in magnetic field induces a current, the change in intensity and direction of the current can measure the velocity and direction object producing the magnetic field.What is the Hall effect“The basic physical principle underlying the Hall effect is the Lorentz force. When an electron moves along a direction perpendicular to an applied magnetic field, it experiences a force acting normal to both directions and moves in response to this force and the force effected by the internal electric field. For an n-type, bar-shaped semiconductor shown in Fig.1, the carriers are predominately electrons of bulk density n. We assume that a constant current I flows along the x-axis from left to right in the presence of a z-directed magnetic field. Electrons subject to the Lorentz force initially drift away from the current line toward the negative y-axis, resulting in an excess surface electrical charge on the side of the sample. This charge results in the Hall voltage, a potential drop across the two sides of the sample. “ (figure one to the left)From the website:http://www.eeel.nist.gov/812/effe.htm#loreWhat is the Hall effect“This transverse voltage is the Hall voltage VH and its magnitude is equal to IB/qnd, where I is the current, B is the magnetic field, d is the sample thickness, and q (1.602 x 10-19 C) is the elementary charge. In some cases, it is convenient to use layer or sheet density (ns = nd) instead of bulk density. One then obtains the equation ns = IB/q|VH|.(1)Thus, by measuring the Hall voltage VH and from the known values of I, B, and q, one can determine the sheet density ns of charge carriers in semiconductors. If the measurement apparatus is set up as described later in Section III, the Hall voltage is negative for n-type semiconductors and positive for p-type semiconductors. The sheet resistance RS of the semiconductor can be conveniently determined by use of the van der Pauw resistivity measurement technique. Since sheet resistance involves both sheet density and mobility, one can determine the Hall mobility from the equation µ = |VH|/RSIB = 1/(qnSRS).(2)If the conducting layer thickness d is known, one can determine the bulk resistivity (r = RSd) and the bulk density (n = nS/d). “From the website:http://www.eeel.nist.gov/812/effe.htm#loreHow does this work??? “This sensor measures the thickness of nonferrous materials with 1% accuracy by sandwiching the material being measured between a magnetic probe on one side and a small target steel ball on the other side [6]. It measures up to 10 mm. The Hall effect sensor is used to measure the magnetic field, as a dc measurement; ac Hall effect measurements can be made more precisely because they eliminate bias and are done with less noise”From the website:http://www.eeel.nist.gov/812/effe.htm#lore© 1999 by CRC Press LLCIn other words….????As the magnetic field between the sensor and a metal ball changes the sensor can measure it’s proximity and direction by measuring the direction and intensity of the current induced. Picture is from: http://www.micronas.com/products/overview/sensors/index.phpA Typical use: Honeywell’s magnetic position Sensor:“Position sensors are used in applications that require accurate, reliable outputs. They are found in brushless DC motors, utility meters, welding equipment, vending machines, home appliances, computers, and so on.”-http://content.honeywell.com/sensing/prodinfo/solidstate/Pictures: form http://content.honeywell.com/sensing/prodinfo/solidstate/ and http://www.micronas.com/products/overview/sensors/index.phpHow Hall Effect sensors are classifiedSwitchesSensors Absolute fieldDifferential fieldSpecial-PurposePicture From the website:http://www.eeel.nist.gov/812/effe.htm#loreMajor specificationsRange of about 6 mm (Mechatronics handbook )Works on about 5v-6v and about 4-10 mATemperature: from about -40°C to about 150°CCan work as sourse or sink depending on the typeWorks on proximity to other external magnet. Picture From the website:http://www.eeel.nist.gov/812/effe.htm#loreLimitationsSensor only deviseGood only in close proximityMust have a reference pointMagnetic field must be presentMust be calibratedWhat else do I need to knowNon-contact switching actionHigh resolution Can Produce a digital outputGreat motors Where can I buy these?-http://content.honeywell.com/sensing/prodinfo/solidstate/To Conclude……..Hall effect sensors are good for proximity, electromagnetic, and direction
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