ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Linear Position Sensors (LPS)OutlineReference ListTo Explore FurtherMajor ApplicationsResistive Linear Position Sensor: Basic Working PrincipleResistive Linear Position Sensor: Typical Sample ConfigurationResistive Linear Position Sensor: Advantages/DisadvantagesCapacitive LPS: Basic Working PrincipleCapacitive LPS: Typical Sample ConfigurationCapacitive LPS: Advantages/DisadvantagesInductive LPS: Basic Working PrincipleInductive LPS: Typical Sample ConfigurationInductive LPS: Advantages/DisadvantagesLVDT LPS: Basic Working PrincipleLVDT LPS: Typical Sample ConfigurationLVDT LPS: Advantages/DisadvantagesMagnetoresistive LPS: Basic Working PrincipleMagnetoresistive LPS: Typical Sample ConfigurationMagnetoresistive LPS: Advantages/DisadvantagesLaser Interferometry LPS: Basic Working PrincipleLaser Inteferometry LPS: Typical Sample ConfigurationLaser Interferometry LPS: Advantages/DisadvantagesMajor SpecificationsCost vs Accuracy in Different TechnologiesECE5320 MechatronicsAssignment#01: Literature Survey on Assignment#01: Literature Survey on Sensors and Actuators Sensors and Actuators Topic: Linear Position Sensors (LPS)Okan GurdilEmail: [email protected]: (435)797-6203Outlinei. Reference Listii. To Explore Further …iii. Major Applicationsiv. Resistivev. Capacitivevi. Inductivevii. Linear Variable Differential Transformers (LVDTs)viii. Magnetoresistiveix. Laser Interferometryx. Major Specificationsxi. Cost vs AccuracyReference List 1) Nyce, David S. (2003). Linear Position Sensors – Theory and Application. New Jersey: Wiley-Interscience2) http://www.mtssensors.com/Linear.htm3) http://www.beiduncan.com/html/products/linear/linear.htm4) http://www.sensorsmag.com/articles/1199/38_1199/main.shtml5) http://www.sensorland.com/HowPage006.html6) http://www.ee.polyu.edu.hk/staff/eencheun/WebSubject2/chapter1.htm7) http://zone.ni.com/devzone/conceptd.nsf/webmain/8) http://www.daytronic.com/products/trans/lvdt/default.htm9) http://www.ssec.honeywell.com/magnetic/datasheets/linearpositionsensing.pdf10) http://www.feanor.com/laser_principles.pdfTo Explore Furtherhttp://www.novotechnik.com/ This website produces linear position sensors and you can pick what specifications you would like.http://www.engineeringtalk.com Provides more specific discussion of various sensor technologies.http://zone.ni.com/devzone/ Explanations and usage guides for various linear position sensor technologiesMajor ApplicationsResistive – Volume, tone, and similar controlsCapacitive – Detection of a moving metal targetInductive – Valve positionersLVDTs – Mission critical military applicationsMagnetoresistive – Motion detection in industrial machinery, automotive, aviation, elevatorsLaser Interferometry – Machining, surveying, surface profilingResistive Linear Position Sensor:Basic Working PrincipleMeasures a physical variableA voltage potential is applied across a resistive elementA slide, or brush, contacts the resistive element and is wiped across itCreates a voltage divider, where V is the measured dataResistive Linear Position Sensor:Typical Sample Configuration(6)Resistive Linear Position Sensor:Advantages/DisadvantagesAdvantagesLow CostLow TechEase of useDisadvantagesMoving partsLimited lifetime due to wear of brushesLimited frequency responseCapacitive LPS:Basic Working PrincipleConsists of a target, a capacitive sensing element, and support electronics and mechanics “[An] electronic circuit drives the sensing element with an alternating current, the sensing element changes capacitance due to changes in the measurand, and the resultant signal is demodulated by the electronic circuit.” (1)Capacitive LPS:Typical Sample Configuration(6)Capacitive LPS:Advantages/DisadvantagesAdvantagesCan be used to measure moving partsNo wear on parts, low maintenanceLow costDisadvantagesMust be close to the measurand targetNot a directly measurable outputMeasurement accuracy is effected by the environment the sensor is installed inInductive LPS:Basic Working PrincipleUses the property of inductance in electrical conductorsConsists of a coil within an appropriate housing, a movable core piece and pushrod, and support electronics to condition the output(7)Inductive LPS:Typical Sample ConfigurationCourtesy http://www.balluff.com/Inductive LPS:Advantages/DisadvantagesAdvantagesSmall sizeSimplistic designLow costCan be made with no moving parts, thus eliminating maintenance needsDisadvantagesShorter rangeContact with measurand must be madeLower precisionLVDT LPS:Basic Working PrincipleLinear Variable Differential TransformersVery similar to the Inductive linear position sensorConsists of a tube with a primary coil in the middle, and two secondary coils, one on either end of the primaryA core moves in the middle of the coils“If the core is displaced from "null" position, in either direction, one secondary voltage will increase, while the other decreases. Since the two voltages no longer cancel, a net output voltage will now result.” (8)LVDT LPS:Typical Sample Configuration(8)LVDT LPS:Advantages/DisadvantagesAdvantagesVery AccurateCan be sealed and used in hostile environmentsRobust application rangeDisadvantagesMust be calibrated more frequentlyContact with measurand must be madeMagnetoresistive LPS:Basic Working PrincipleUses three elements: an array of sensors, a magnet attached to the measurand and associated electronicsOperates by detecting the change in resistance when a magnetic field is applied to a current-carrying conductorThe longer the array of sensors, the longer the measured displacement can beMagnetoresistive LPS:Typical Sample Configuration(9)Magnetoresistive LPS:Advantages/DisadvantagesAdvantagesRange can be extended almost infinitelyCan operate in a broad temperature rangeNon-contactDisadvantagesAs range is extended, cost goes upNot as accurate as other methodsSensitive to interfering magnetic fieldsLaser Interferometry LPS:Basic Working PrincipleConsists of a laser and a beam splitterOne beam is sent to a fixed mirror for reference purposesThe other beam targets a mirror fixed to the moving objectThe position change of the object is calculated from the resulting interference of the beams
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