《传感器与检测基础》超声波流量计.pptx

传感器与检测基础FundamentalsofSensorsandDetection

FlowMeasurement流量测量05

UltrasonicFlowmeters 超声波流量计1.测量原理2.传播速度法（time-of-flightmethod）3.多普勒法（Dopplermethod）4.特点

UltrasonicFlowmeters 超声波流量计1.测量原理传播速度法（time-of-flightmethod）多普勒法（Dopplermethod）Ultrasonicflowmeters,suitableforbothliquidsandgases,havebeenavailableformorethantwentyyearsandarecurrentlytheonlytrulyviablenon-intrusivemeasuringalternativetotheelectromagneticflowmeter.Unfortunately,althoughoriginallyhailedasageneralpanaceafortheflowmeasurementindustry,lackofknowledgeandpoorunderstandingofthelimitationsofearlyinstruments(especiallytheDopplermethod)oftenleadtoitsuseinunsuitableapplications.Nonetheless,theultrasonicmeterisprobablytheonlymetercapableofbeingusedonlargediameterpipes(above3mbore)atareasonablecostandperformance(around1%).Inessencetherearethreebasicprinciplesusedinultrasonicmetering:theDopplermethod;thetime-of-flightmethod;andthefrequencydifferencemethod.

UltrasonicFlowmeters 超声波流量计2.传播速度法（time-of-flightmethod）Inthetransittimemetertwotransducers(AandB)eachactalternatelyasthereceiverandtransmitterT1→R1声波被流体加速T2→R2声波被流体减速由于c2u2(1)时差法

UltrasonicFlowmeters 超声波流量计2.传播速度法（time-of-flightmethod）Inthetransittimemetertwotransducers(AandB)eachactalternatelyasthereceiverandtransmitter数量级10-5s，灵敏度低ω—超声波的角频率避免微小时差的测量，提高了灵敏度和测量精度，需校正声速

UltrasonicFlowmeters 超声波流量计2.传播速度法（time-of-flightmethod）Increasingthepathlengthusingadoubletraverse,single‘V’pathonthecentreline.Thesearrangementsarefrequentlyusedforgasmeasurementinlinesandgasflowmeasurement.Thedoubletraverse,singlepathflowmeterisfrequentlyusedforlow-costliquidmeasurementanaccuratereal-timemeasurementofhazardousandnon-hazardousgasflowsinlinesfrom100to900mmDN.

UltrasonicFlowmeters 超声波流量计2.传播速度法（time-of-flightmethod）TheU-formmetercanbeused