数量测量值-助理3 syllabus dcac信号源chapter measurement章电气.pptx

3. ELECTRICALQUANTITIES MEASUREMENTS -Syllabus

3. ELECTRICALQUANTITIESMEASUREMENTS-SyllabusDCandACsignalsources: DCpowersupply,FunctiongeneratorsVoltage,currentandresistancemeasurements: Useofanaloganddigitalmulti-metersandtheirlimitations,rangeandsensitivity,shuntandmultiplier,measurementsusingbridgeconfigurations.Phase,timeandfrequencymeasurements: Basicoscilloscopecontrolsandoperatingtechniques,connectors,probesandcompensation;measurementofwaveformvoltage,period,frequency,phaseshift,rise/fall-time;useofuniversalfrequencycounter/timerinfrequencyandtimingmeasurements.Singlephasepowermeasurements: Wattmeter

DCpowersourceBackground:Directcurrent(dc)powersupplyisnormallyusedforportabledevicessuchastorch,radio,mobilephoneandagreatvarietyofportableandmobileequipments.dcpowercanbeobtainedbychemicalreactionandphysicalconversion,theyare:Chemicalreactiontype:BatteryFuelcell

Physicalconversion:dcgeneratorbyelectro-mechanicalenergyconversionPhotocellbyphotovoltaicconversionHowever,inlaboratory,themostcommontypeofdcpowersupplyisbenchdcpowersupply:dcregulatedpowersupply.dcregulatedpowersupplyisaninstrumentwhichconverttheacpowerfromsocketoutlettovariableandstabledcvoltage.

Fig.3.1Benchd.c.powersupply

TypicalcharacteristicsofdcpowersupplyAbasicdcpowersupplyusesatransformertostepdowntheacinputtoanappropriatelevel,whichisthenrectifiedtogiveadcsupply.Avoltageregulatorcircuitisincorporatedtoproduceamorestabledcoutputvoltageandallowstheoutputvoltagetobeadjustable.dcpowersuppliesareusuallyavailableassingle-voltage,dual-voltageandtriple-voltageoutputunits.Eitheroutputoftheunitcanbegroundedtogiveaplusorminusvoltage.Metersareprovidedformonitoringoutputvoltageandcurrent.Forsomemodels,outputcurrentlimitscanbeset.

Shunt