电子与通信技术专业英语(第4版)Unit-2--lesson-7课件.ppt

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1、UnitElectronicInstrumentandProducts 本单元重点介绍常用的电子仪器和电子设备及其应用，主要包括万用表、数字电压表、示波器、触摸屏、液晶显示器、智能手机、无线电接收机、电视、家庭影院、录像机和数字音响等。通过本单元的学习，学生可以学到较为系统的关于电子技术应用的英语表达，为能在真实电子技术应用专业环境中应用英语进行工作打下基础。ExercisesUnit2PART1Multimetersareveryusefultestinstruments.Byoperatingamulti-positionswitchonthemetertheycanbequicklyan

2、deasilysettobeavoltmeter,anammeteroranohmmeter.Theyhaveseveralsettings(calledranges)foreachtypeofmeterandthechoiceofACorDC.Somemultimetershaveadditionalfeaturessuchastransistortestingandrangesformeasuringcapacitanceandfrequency.Therearetwobasictypesofmultimeters,digitalandanalog.Analogmultimetershav

3、eaneedleandthedigitalhasaLEDdisplay.Alldigitalmeterscontainabatterytopowerthedisplaysotheyusevirtuallynopowerfromthecircuitundertest.ThismeansthatontheirDCvoltagerangestheyhaveaveryhighresistance(usuallycalledinputimpedance)of1Mormore,usually10M,andtheyareveryunlikelytoaffectthecircuitundertest.Meas

4、uringvoltageandcurrentwithamultimeterLesson7MultimetersandItsUsageExercisesPART2Lesson7MultimetersandItsUsage1.Selectarangewithamaximumgreaterthanyouexpectthereadingtobe.2.Connectthemeter,makingsuretheleadsarethecorrectwayround.Digitalmeterscanbesafelyconnectedinreverse,butananaloguemetermaybedamage

5、d.3.Ifthereadinggoesoffthescale:immediatelydisconnectandselectahigherrange.ExercisesFig.7-1MeasuringVoltageataPointPART3Lesson7MultimetersandItsUsageExercisesMultimetersareeasilydamagedbycarelessuse,sopleasetaketheseprecautions:1Alwaysdisconnectthemultimeterbeforeadjustingtherangeswitch.2Alwayscheck

6、thesettingoftherangeswitchbeforeyouconnecttoacircuit.3Neverleaveamultimetersettoacurrentrange(exceptwhenactuallytakingareading).Thegreatestriskofdamageisonthecurrentrangesbecausethemeterhasalowresistance.MeasuringvoltageatapointWhentestingcircuits,youoftenneedtofindthevoltagesatvariouspoints,forexam

7、plethevoltageatpin2ofa555timerchip(asshowninFig.7-1).Thiscanseemconfusingwhereshouldyouconnectthesecondmultimeterlead?1Connecttheblack(negative-)leadto0V,normallythenegativeterminalofthebatteryorpowersupply.PART5Newwordsandphrases:multimetermltimitn.万用表instrumentinstrumntn.工具，仪器，器械ammetermitn.安培表ohm

8、meterum,mi:tn.欧姆表needleni:dln.指针display,displein.显示，表现disconnect,disknektv.断开confusingknfju:ziadj.使人困惑的，令人费解的infiniteinfintadj.无限的，无穷的reverseriv:sadj.相反的pinpinn.大头针，针，拴precautionprik:nn.预防，留心，警戒riskriskn.风险，危险ExercisesPART6PhrasesandExpressionstakeprecautions采取预防措施voltageranges电压范围inputimpedance输入阻抗

9、Newwordsandphrases:ExercisesPART7Notes:1.Byoperatingamulti-positionswitchonthemetertheycanbequicklyandeasilysettobeavoltmeter,anammeteroranohmmeter.译文：通过操控万用表上的切换开关，可将万用表调定到电压表、电压表和电阻表。“By”是介词，因此by后面要跟名词、动名词或动词现在分词。2.andtheyareveryunlikelytoaffectthecircuitundertest.译文：数字式万用表不大会影响测试中的电路。“beunlikelyt

10、o”意为“不太可能、不大会”。3.Selectarangewithamaximumgreaterthanyouexpectthereadingtobe.译文：根据预期的读数范围选择大一级的量程。“reading”意为“读数”。ExercisesPART9Exercises:1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.a.AnalogmultimetershaveaLEDdisplayandthedigitalhasaneedle.b.Alldigitalmeterscontainaelectricalmoto

11、rtopowerthedisplaysotheyusevirtuallynopowerfromthecircuitundertest.c.ThismeansthatontheirDCvoltagerangestheyhaveaveryhighresistanceof10Mormore,usually100M,andtheyareveryunlikelytoaffectthecircuitundertest.d.Ananaloguemetercanbesafelyconnectedinreverse,butthedigitalmetersmaybedamaged.e.Connectthemete

12、r,makingsuretheleadsarethecorrectwayround.f.Alwaysdisconnectthemultimeterbeforeadjustingtherangeswitch.2.Fillinthemissingwordsaccordingtothetext.a.Byoperatingamulti-positionswitchonthemetertheycanbequicklyandeasilysettobea,anoran.b.Theyhaveseveralsettings(called)foreachtypeofmeterandthechoiceofor.Ex

13、ercisesExercises:c.Somemultimetershaveadditionalfeaturessuchasandrangesformeasuringcapacitanceand.d.Therearetwobasictypesofmultimeters,and.e.Selectarangewithathanyouexpectthereadingtobe.f.Multimetersareeasilydamagedbycarelessuse,sopleasetakethe.3.TranslatethefollowingparagraphintoChinese.MeasuringRe

14、sistancewithamultimeter:AnotherusefulfunctionoftheDMMistheohmmeter.Anohmmetermeasurestheelectricalresistanceofacircuit.Ifyouhavenoresistanceinacircuit,theohmmeterwillread0.Ifyouhaveanopeninacircuit,itwillreadinfinite.ExercisesPART10在调节量程前，保持万用表处于断开状态；在测量前检查量程设置；绝不把万用表设置在电流挡（除非实际要测电流）。因为万用表的电阻较小，所以在电流档时最容易损坏。测量某一点的电压当我们进行电路测量时，常常需要知道某一点的电压，例如，图7-1中555定时器芯片2脚的电压。这似乎有点令人迷惑，应该把万用表的表笔连在哪里呢？将黑表笔接在0V，通常是电池或电源的负端。将红表笔接在需要测量电压的点上。可以把黑表笔固定在0V位置，同时用红表笔依次点在各个测量点测量电压。用万用表测量电阻数字万用表的另一个有用的功能是欧姆表。欧姆表是测量电阻的仪表，如果电路没有电阻，则欧姆表读数为0，如果电路断开，则欧姆表读数为无穷大。ExercisesPART12