Principles of Data Acquisition And Coversion.pdf

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1、®APPLICATIONBULLETINMailingAddress:POBox11400•Tucson,AZ85734•StreetAddress:6730S.TucsonBlvd.•Tucson,AZ85706Tel:(602)746-1111•Twx:910-952-111•Telex:066-6491•FAX(602)889-1510•ImmediateProductInfo:(800)548-6132PRINCIPLESOFDATAACQUISITIONANDCONVERSIONDataacquisitionandconversionsystemsareusedtoac

2、quireSYSTEMSAMPLINGRATE—analogsignalsfromoneormoresourcesandconverttheseErrorConsiderationssignalsintodigitalformforanalysisortransmissionbyendTheapplicationandultimateuseoftheconverteddatadevicessuchasdigitalcomputers,recorders,orcommunica-determinestherequiredsamplingandconversionrateofthet

3、ionsnetworks.Theanalogsignalinputstodataacquisitiondataacquisitionandconversionsystem.Systemsamplingsystemsaremostoftengeneratedfromsensorsandtransduc-rateisdetermined,asshowninFigure1,bythehighesterswhichconvertreal-worldparameterssuchaspressure,bandwidthchannel,thenumberofdatachannelsandthe

4、temperature,stressorstrain,flow,etc.,intoequivalentnumberofsamplespercycle.electricalsignals.Theelectricallyequivalentsignalsarethenconvertedbythedataacquisitionsystemandarethenuti-AliasingErrorlizedbytheenddevicesindigitalform.TheabilityoftheFromtheNyquistsamplingtheorem,aminimumoftwoelectro

5、nicsystemtopreservesignalaccuracyandintegrityissamplespercycleofthedatabandwidthisrequiredinanthemainmeasureofthequalityofthesystem.idealsampleddatasystemtoreproducesampleddatawithThebasiccomponentsrequiredfortheacquisitionandnolossofinformation.Thus,thefirstconsiderationforconversionofanalog

6、signalsintoequivalentdigitalformaredeterminingsystemsamplingrateisaliasingerror,i.e.,thefollowing:errorsduetoinformationbeinglostbynottakingasufficient1.AnalogMultiplexerandSignalConditioningnumberofsamplespercycleofsignalfrequency.2.Sample/HoldAmplifierFigure2illustratesaliasingerrorcausedfr

7、omaninsufficientnumberofsamplespercycleofdatabandwidth.3.Analog-to-DigitalConverter4.TimingorSequenceLogicHowManySamplesperCycle?Typically,today’sdataacquisitionsystemscontainalltheTheanswertothisquestiondependsontheallowableaver-elementsneed