脉冲输出型数字涡街流量计的研究 毕业论文外文翻译

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1、附录AResearchonpulseoutputmodeldigitalvortexflowmetersThevortexflowmeteriswidelyusedindifferentfieldsduetoitsflexibilitytovariousmedia,non-mobileparts,simplestructureandlonglifeetc.However,ithaspoorperformancewhenoperatingatlowflowratewheretheSignal-to-Noiseratioisverysmal

2、loreventhesignalissubmergedbythenoise.Thetraditionalanalogvortexflowmeterhasbenefitsofsteadysignal,highaccuracyandgoodrealtimeintheregularflowrange,whileitalsohasadisadvantageofweaksignaldifficulttodetectatlowflowrate,whichleadstounsatisfyinglowerlimitandasmallerrangerat

3、ioof10:1.Basedonthepreviouseffortsapulseoutputmodeldigitalvortexflowmeterisdevelopedsuccessfully,whichinheritstheadvantagesoftheanalogoneandmakeupitsshortagementionedabove.Thedigitalvortexflowmeterwithitsdouble-corestructurethatmeansacoupleofCPUsmadeupofDSPandMSP430ident

4、ifiesthevortexsignalsfromnoisesbythefrequencyspectrumanalyzingalgorithminDSPatlowflowratewheretheanalogoneisnotaccurate,orevencan’twork.MeanwhileitworksoutbyitsmicrocontrollerMSP430thefrequencyofthevortexsignalthatissquarewavesoutputfrompre-amplifierforthevortexsignalsin

5、theregularflowrangewheretheSignal-to-Noiseratioisn’ttoomuchsmallandtheanalogoneisaccurateandrealtime.Thisdissertationconsistsoftheory,hardware/softwaredesignandexperiment.Themainpointincludes:1.Theschemecalleddouble-channelworkmodelofthepulseoutputmodeldigitalvortexflowm

6、eterisdesigned.Theprincipleisaswitchoftwodifferentmethodstodetectthevortexsignal.Thatisusingspectrumanalysisofdigitalsignalatlowflowrateandfrequencycountinglikeanalogvortexflowmetersintheregularflowrange.Thecriticalcriterionoftheswitchpointistheuncertaintyofthefrequency.

7、2.Apulseoutputmodeldigitalvortexflowmeterisdevelopedsuccessfully.TheflowmeterisstudiedrespectivelyatDN25andDN50pipelinesofthewaterflowexperimentfacilityandDN50andDN100pipelinesofthegasflowexperimentfacilitythatlocateatProcessDetect&ControlLaboratoryinTianjinUniversity.An

8、dthedatashowsthatthedigitalflowmeterhasthepropertyofabetterlowerlimitthantheanalogoneandabiggerrangerat