基于單片機(jī)的超聲波測(cè)距系統(tǒng)的研究與設(shè)計(jì)外文翻譯

附錄附錄A外文翻譯theequivalentdcvalue.Intheanalysisofelectroniccircuitstobeconsideredinalatercourse,bothdcandacsourcesofvoltagewillbeappliedtothesamenetwork.Itwillthenbenecessarytoknowordeterminethedc(oraveragevalue)andaccomponentsofthevoltageorcurrentinvariouspartsofthesystem.EXAMPLE13.13DeterminetheaveragevalueofthewaveformsofFig.13.37.Example13.13.Solutions:a.Byinspection,theareaabovetheaxisequalstheareabelowoveronecycle,resultinginanaveragevalueofzerovolts.b.UsingEq.(13.26):asshowninFig.13.38.Inreality,thewaveformofFig.13.37(b)issimplythesquarewaveofFig.13.37(a)withadcshiftof4V;thatisv2=v1+4VEXAMPLE13.14Findtheaveragevaluesofthefollowingwaveformsoveronefullcycle:Fig.13.39.b.Fig.13.40.Solutions:Wefoundtheareasunderthecurvesintheprecedingexamplebyusingasimplegeometricformula.Ifweshouldencounterasinewaveoranyotherunusualshape,however,wemustfindtheareabysomeothermeans.Wecanobtainagoodapproximationoftheareabyattemptingtoreproducetheoriginalwaveshapeusinganumberofsmallrectanglesorotherfamiliarshapes,theareaofwhichwealreadyknowthroughsimplegeometricformulas.Forexample,theareaofthepositive(ornegative)pulseofasinewaveis2Am.Approximatingthiswaveformbytwotriangles(Fig.13.43),weobtain(usingarea1/2baseheightfortheareaofatriangle)aroughideaoftheactualarea:Acloserapproximationmightbearectanglewithtwosimilartriangles(Fig.13.44):whichiscertainlyclosetotheactualarea.Ifaninfinitenumberofformswereused,anexactanswerof2Amcouldbeobtained.Forirregularwaveforms,thismethodcanbeespeciallyusefulifdatasuchastheaveragevaluearedesired.Theprocedureofcalculusthatgivestheexactsolution2Amisknownasintegration.Integrationispresentedhereonlytomakethemethodrecognizabletothereader;itisnotnecessarytobeproficientinitsusetocontinuewiththistext.Itisausefulmathematicaltool,however,andshouldbelearned.Findingtheareaunderthepositivepulseofasinewaveusingintegration,wehavewhere∫isthesignofintegration,0andparethelimitsofintegration,Amsinaisthefunctiontobeintegrated,anddaindicatesthatweareintegratingwithrespecttoa.Integrating,weobtainSinceweknowtheareaunderthepositive(ornegative)pulse,wecaneasilydeterminetheaveragevalueofthepositive(ornegative)regionofasinewavepulsebyapplyingEq.(13.26):ForthewaveformofFig.13.45,EXAMPLE13.15DeterminetheaveragevalueofthesinusoidalwaveformofFig.13.46.Solution:Byinspectionitisfairlyobviousthattheaveragevalueofapuresinusoidalwaveformoveronefullcycleiszero.EXAMPLE13.16DeterminetheaveragevalueofthewaveformofFig.13.47.Solution:Thepeak-to-peakvalueofthesinusoidalfunctionis16mV+2mV=18mV.Thepeakamplitudeofthesinusoidalwaveformis,therefore,18mV/2=9mV.Countingdown9mVfrom2mV(or9mVupfrom-16mV)resultsinanaverageordclevelof-7mV,asnotedbythedashedlineofFig.13.47.EXAMPLE13.17DeterminetheaveragevalueofthewaveformofFig.13.48.Solution:EXAMPLE13.18ForthewaveformofFig.13.49,determinewhethertheaveragevalueispositiveornegative,anddetermineitsapproximatevalue.Solution:Fromtheappearanceofthewaveform,theaveragevalueispositiveandinthevicinityof2mV.Occasionally,judgmentsofthistypewillhavetobemade.InstrumentationThedcleveloraveragevalueofanywaveformcanbefoundusingadigitalmultimeter(DMM)oranoscilloscope.Forpurelydccircuits,simplysettheDMMondc,andreadthevoltageorcurrentlevels.Oscilloscopesarelimitedtovoltagelevelsusingthesequenceofstepslistedbelow:1.FirstchooseGNDfromtheDC-GND-ACoptionlistassociatedwitheachverticalchannel.TheGNDoptionblocksanysignaltowhichtheoscilloscopeprobemaybeconnectedfromenteringtheoscilloscopeandrespondswithjustahorizontalline.Settheresultinglineinthemiddleoftheverticalaxisonthehorizontalaxis,asshowninFig.13.50(a).2.Applytheoscilloscopeprobetothevoltagetobemeasured(ifnotalreadyconnected),andswitchtotheDCoption.Ifadcvoltageispresent,thehorizontallinewillshiftupordown,asdemonstratedinFig.13.50(b).Multiplyingtheshiftbytheverticalsensitivitywillresultinthedcvoltage.Anupwardshiftisapositivevoltage(higherpotentialattheredorpositiveleadoftheoscilloscope),whileadownwardshiftisanegativevoltage(lowerpotentialattheredorpositiveleadoftheoscilloscope).Ingeneral,1.UsingtheGNDoption,resetthehorizontallinetothemiddleofthescreen.2.SwitchtoAC(alldccomponentsofthesignaltowhichtheprobeisconnectedwillbeblockedfromenteringtheoscilloscope—onlythealternating,orchanging,componentswillbedisplayed).Notethelocationofsomedefinitivepointonthewaveform,suchasthebottomofthehalf-waverectifiedwaveformofFig.13.51(a);thatis,noteitspositionontheverticalscale.Forthefuture,wheneveryouusetheACoption,keepinmindthatthecomputerwilldistributethewaveformaboveandbelowthehorizontalaxissuchthattheaveragevalueiszero;thatis,theareaabovetheaxiswillequaltheareabelow.3.ThenswitchtoDC(topermitboththedcandtheaccomponentsofthewaveformtoentertheoscilloscope),andnotetheshiftinthechosenlevelofpart2,asshowninFig.13.51(b).Equation(13.29)canthenbeusedtodeterminethedcoraveragevalueofthewaveform.ForthewaveformofFig.13.51(b),theaveragevalueisaboutTheprocedureoutlinedabovecanbeappliedtoanyalternatingwaveformsuchastheoneinFig.13.49.InsomecasestheaveragevaluemayrequiremovingthestartingpositionofthewaveformundertheACoptiontoadifferentregionofthescreenorchoosingahighervoltagescale.DMMscanreadtheaverageordclevelofanywaveformbysimplychoosingtheappropriatescale.13.7EFFECTIVE(rms)VALUESThissectionwillbegintorelatedcandacquantitieswithrespecttothepowerdeliveredtoaload.Itwillhelpusdeterminetheamplitudeofasinusoidalaccurrentrequiredtodeliverthesamepowerasaparticulardccurrent.Thequestionfrequentlyarises,Howisitpossibleforasinusoidalacquantitytodeliveranetpowerif,overafullcycle,thenetcurrentinanyonedirectioniszero(averagevalue0)?Itwouldalmostappearthatthepowerdeliveredduringthepositiveportionofthesinusoidalwaveformiswithdrawnduringthenegativeportion,andsincethetwoareequalinmagnitude,thenetpowerdeliverediszero.However,understandthatirrespectiveofdirection,currentofanymagnitudethrougharesistorwilldeliverpowertothatresistor.Inotherwords,duringthepositiveornegativeportionsofasinusoidalaccurrent,powerisbeingdeliveredateachinstantoftimetotheresistor.Thepowerdeliveredateachinstantwill,ofcourse,varywiththemagnitudeofthesinusoidalaccurrent,buttherewillbeanetflowduringeitherthepositiveorthenegativepulseswithanetflowoverthefullcycle.Thenetpowerflowwillequaltwicethatdeliveredbyeitherthepositiveorthenegativeregionsofsinusoidalquantity.AfixedrelationshipbetweenacanddcvoltagesandcurrentscanbederivedfromtheexperimentalsetupshowninFig.13.52.Aresistorinawaterbathisconnectedbyswitchestoadcandanacsupply.Ifswitch1isclosed,adccurrentI,determinedbytheresistanceRandbatteryvoltageE,willbeestablishedthroughtheresistorR.Thetemperaturereachedbythewaterisdeterminedbythedcpowerdissipatedintheformofheatbytheresistor.Ifswitch2isclosedandswitch1leftopen,theaccurrentthroughtheresistorwillhaveapeakvalueofIm.Thetemperaturereachedbythewaterisnowdeterminedbytheacpowerdissipatedintheformofheatbytheresistor.Theacinputisvarieduntilthetemperatureisthesameasthatreachedwiththedcinput.Whenthisisaccomplished,theaverageelectricalpowerdeliveredtotheresistorRbytheacsourceisthesameasthatdeliveredbythedcsource.ThepowerdeliveredbytheacsupplyatanyinstantoftimeisTheaveragepowerdeliveredbytheacsourceisjustthefirstterm,sincetheaveragevalueofacosinewaveiszeroeventhoughthewavemayhavetwicethefrequencyoftheoriginalinputcurrentwaveform.Equatingtheaveragepowerdeliveredbytheacgeneratortothatdeliveredbythedcsource,which,inwords,statesthattheequivalentdcvalueofasinusoidalcurrentorvoltageis1/2or0.707ofitsmaximumvalue.Theequivalentdcvalueiscalledtheeffectivevalueofthesinusoidalquantity.Insummary,Asasimplenumericalexample,itwouldrequireanaccurrentwithapeakvalueof2(10)14.14AtodeliverthesamepowertotheresistorinFig.13.52asadccurrentof10A.Theeffectivevalueofanyquantityplottedasafunctionoftimecanbefoundbyusingthefollowingequationderivedfromtheexperimentjustdescribed:which,inwords,statesthattofindtheeffectivevalue,thefunctioni(t)mustfirstbesquared.Afteri(t)issquared,theareaunderthecurveisfoundbyintegration.ItisthendividedbyT,thelengthofthecycleortheperiodofthewaveform,toobtaintheaverageormeanvalueofthesquaredwaveform.Thefinalstepistotakethesquarerootofthemeanvalue.Thisproceduregivesusanotherdesignationfortheeffectivevalue,theroot-mean-square(rms)value.Infact,sincethermstermisthemostcommonlyusedintheeducationalandindustrialcommunities,itwillusedthroughoutthistext.EXAMPLE13.19FindthermsvaluesofthesinusoidalwaveformineachpartofFig.13.53.Solution:Forpart(a),Irms0.707(12103A)8.484mA.Forpart(b),againIrms8.484mA.Notethatfrequencydidnotchangetheeffectivevaluein(b)abovecomparedto(a).Forpart(c),Vrms0.707(169.73V)120V,thesameasavailablefromahomeoutlet.EXAMPLE13.20The120-VdcsourceofFig.13.54(a)delivers3.6Wtotheload.Determinethepeakvalueoftheappliedvoltage(Em)andthecurrent(Im)iftheacsource[Fig.13.54(b)]istodeliverthesamepowertotheload.Solution:EXAMPLE13.21FindtheeffectiveorrmsvalueofthewaveformofFig.13.55.Solution:EXAMPLE13.22CalculatethermsvalueofthevoltageofFig.13.57.Solution:EXAMPLE13.23DeterminetheaverageandrmsvaluesofthesquarewaveofFig.13.59.Solution:Byinspection,theaveragevalueiszero.Thewaveformsappearingintheseexamplesarethesameasthoseusedintheexamplesontheaveragevalue.Itmightproveinterestingtocomparethermsandaveragevaluesofthesewaveforms.ThermsvaluesofsinusoidalquantitiessuchasvoltageorcurrentwillberepresentedbyEandI.Thesesymbolsarethesameasthoseusedfordcvoltagesandcurrents.Toavoidconfusion,thepeakvalueofawaveformwillalwayshaveasubscriptmassociatedwithit:Imsinqt.Caution:Whenfindingthermsvalueofthepositivepulseofasinewave,notethatthesquaredareaisnotsimply(2Am)24A2m;itmustbefoundbyacompletelynewintegration.Thiswillalwaysbethecaseforanywaveformthatisnotrectangular.AuniquesituationarisesifawaveformhasbothadcandanaccomponentthatmaybeduetoasourcesuchastheoneinFig.13.61.Thecombinationappearsfrequentlyintheanalysisofelectronicnetworkswherebothdcandaclevelsarepresentinthesamesystem.Thequestionarises,WhatisthermsvalueofthevoltagevT?Onemightbetemptedtosimplyassumethatitisthesumofthermsvaluesofeachcomponentofthewaveform;thatis,VTrms0.7071(1.5V)6V1.06V6V7.06V.However,thermsvalueisactuallydeterminedbywhichfortheaboveexampleis直流值相等。在電子電路的分析要考慮在后來的過程中，既DC和AC電壓源會(huì)適用于同一個(gè)網(wǎng)絡(luò)。這將是必要的了解或確定直流〔或平均值〕和交流電壓或電流元件在系統(tǒng)的各個(gè)局部。例13.13確定的波形平均值圖。13.37。圖。13.37例如13.13。解決方案：字母a.通過檢查，上述地區(qū)的軸以下面積等于多一個(gè)周期，在一個(gè)零電壓的平均值結(jié)果。采用式。〔13.26〕：灣采用式?！?3.26〕：如下圖。13.38。在現(xiàn)實(shí)生活中，波形圖。13.37〔二〕僅僅是方波無花果。13.37〔1〕為4直流電壓轉(zhuǎn)變，也就是說，2版=V1的+4V的例13.14查找以下波形的平均值在一個(gè)完整周期：字母a.圖。13.39。灣圖。13.40。圖。13.38定義為波形的平均值無花果。13.37〔b〕項(xiàng)。圖。13.39例如13.14，第〔1〕。根據(jù)我們發(fā)現(xiàn)在前面的例子曲線地區(qū)的使用簡(jiǎn)單的幾何公式。如果我們遇到一個(gè)正弦波或任何其他不尋常的形狀，但是，我們必須找到一些地區(qū)其他手段。我們可以獲取該地區(qū)良好的逼近試圖重現(xiàn)原始波形使用了假設(shè)干小矩形或其他熟悉的形狀，面積，我們已經(jīng)知道通過簡(jiǎn)單的幾何公式。例如，積極的〔或負(fù)區(qū)〕的正弦波脈沖是凌晨2點(diǎn)。逼近的兩個(gè)三角形〔圖13.43〕這個(gè)波形，我們得到〔使用面積_二分之一基地_為三角形的面積高〕一個(gè)粗略的概念實(shí)際面積：保華阿更接近于可能有兩個(gè)類似三角形的矩形〔圖13.44〕：這肯定接近實(shí)際面積。如果無限人數(shù)形式使用，是凌晨2點(diǎn)確切的答案可以得到的。對(duì)于不規(guī)那么波形，這種方法可能是特別有用的資料，例如平均值是所期望的。該演算過程，給出了確切的解決方法是凌晨2點(diǎn)被稱為整合。整合是這里唯一令圖。13.41在直流米響應(yīng)波形圖。13.39。圖。13.42在直流米響應(yīng)波形圖。13.40。圖。13.43逼近的正脈沖形狀正弦波形的兩個(gè)權(quán)三角形。圖。13.44一種形狀的更好的近似正脈沖波形的正弦。識(shí)別方法給讀者，它是沒有必要精通它的使用繼續(xù)這個(gè)文本。這是一個(gè)有用的數(shù)學(xué)工具，但是，并應(yīng)教訓(xùn)。在積極尋找該地區(qū)的脈沖正弦波使用一體化，我們已是集成，0和p簽署的一體化的限制，其中∫我罪一是要集成的功能，達(dá)表示，我們結(jié)合方面答：整合，我們得到因?yàn)槲覀冎涝谡妗不蜇?fù)地區(qū)〕的脈搏，我們可以很容易地確定正〔或負(fù)平均值〕一個(gè)正弦波脈沖地區(qū)運(yùn)用方程?！?3.26〕：為了圖波形。13.45，〔平均相同作為一個(gè)完整脈沖〕例13.15確定的正弦平均值波形圖。13.46。解決方案：通過檢查相當(dāng)明顯一個(gè)純粹弦波形超過一個(gè)完整周期的平均價(jià)值為零。例13.16確定波形的平均價(jià)值圖。13.47。解答：峰值正弦函數(shù)的峰值16壓_為2mV_18壓。正弦的波形峰值振幅因此，18毫伏/2_9壓。倒數(shù)第2至9壓壓〔或9壓從_16機(jī)動(dòng)車輛〕在一個(gè)_7壓或DC平均水平的成果，正如由圖虛線。13.47。圖。13.45找到的一個(gè)平均值的一半正脈沖波形的正弦。圖。13.46例如13.15。圖。13.47例如13.16。例13.17確定波形的平均價(jià)值圖。13.48。解決方案：例13.18為了圖波形。13.49，確定是否平均價(jià)值是正面還是負(fù)面，并確定其近似值。解決方案：從波形的出現(xiàn)，平均價(jià)值是積極的，在2壓附近。有時(shí)候，這個(gè)判決類型將要作出。儀表直流水平或任何波形的平均值，可以發(fā)現(xiàn)使用一數(shù)字萬用表〔DMM〕或示波器。對(duì)于純粹的直流電路，簡(jiǎn)單地設(shè)置的直流數(shù)字多用表，并讀取電壓或電流的水平。示波器僅限于電壓等級(jí)使用的一系列步驟列舉如下：1。首先選擇從直流接地，接地，交流相關(guān)的選項(xiàng)列表每個(gè)垂直通道。接地模塊選擇的任何信號(hào)其中示波器探頭可能會(huì)連接進(jìn)入示波器，只需水平線響應(yīng)。設(shè)置結(jié)果在垂直軸中間的水平線軸，如下圖。13.50〔1〕。圖。13.49例如13.18?！捕炒怪膘`敏度=50mV/div時(shí)。移=2.5股利。〔一〕圖。13.50使用示波器測(cè)量直流電壓：〔一〕設(shè)置接地的條件;〔二〕的垂直轉(zhuǎn)移時(shí)轉(zhuǎn)移到區(qū)選擇一個(gè)直流電壓產(chǎn)生的。2。應(yīng)聘示波器探頭的電壓進(jìn)行測(cè)量〔如尚未連接〕，并切換到DC的選擇。如果直流電壓是目前，水平線將轉(zhuǎn)向上漲或下跌，因?yàn)轱@示了圖。13.50〔b〕項(xiàng)。乘以垂直移位敏感性將導(dǎo)致直流電壓。一個(gè)上移是一個(gè)正電壓〔高潛力在紅色或積極的主導(dǎo)作用示波器〕，而向下轉(zhuǎn)移是負(fù)電壓〔較低的潛能示波器的紅色或積極牽頭〕。一般來說，伏_〔垂直轉(zhuǎn)移組?！砡〔垂直靈敏度在V/分區(qū)。〕〔13.29〕為了圖波形。13.50〔b〕項(xiàng)，伏_〔2.5分區(qū)。〕〔50毫伏/分區(qū)。〕_125壓示波器也可用于測(cè)量DC或平均水平波形的任何使用以下順序：1。使用接地選項(xiàng)，重置水平線中間在屏幕上。2。切換到交流〔信號(hào)的所有組成局部的直流探頭連接將被阻止進(jìn)入示波器只有交替，或改變，局部將顯示〕。請(qǐng)注意一些明確的點(diǎn)的位置上的波形，例如作為下半波整流無花果波形。13.51〔1〕，即說明其對(duì)縱坐標(biāo)位置。對(duì)于今后，只要您使用AC選項(xiàng)時(shí)，請(qǐng)記住，計(jì)算機(jī)將派發(fā)上述波形及以下水平軸這樣的平均值為零，也就是說，面積上述軸將等于下面的區(qū)域。3。然后切換到DC〔允許同時(shí)直流和交流組件對(duì)進(jìn)入波形示波器〕，并注意轉(zhuǎn)移第2局部選擇的水平，如下圖。13.51〔b〕項(xiàng)。方程〔13.29〕，然后可以用于確定DC或平均值波形。為了圖波形。13.51〔二〕，平均價(jià)值約變風(fēng)量_伏_〔0.9分區(qū)?！场?伏/分區(qū)?！砡4.5V圖。13.51確定非正弦波形的平均值使用示波器：〔1〕垂直渠道的交流方式;〔二〕在垂直通道DC模式。上述的程序可以適用于任何交流如波形圖之一。13.49。在某些情況下的平均值可能需要?jiǎng)幼h下波形的起始位置交流選擇屏幕的一個(gè)不同地區(qū)或選擇更高電壓規(guī)模。數(shù)字萬用表可以讀取任何波形或DC平均水平只需選擇適當(dāng)?shù)囊?guī)模。13.7有效〔均方根〕值本節(jié)將開始與有關(guān)直流和交流的數(shù)量權(quán)力交付給負(fù)載。這將幫助我們確定的振幅一個(gè)正弦交流電流必須將它作為一種同樣的權(quán)力特別是直流電流。經(jīng)常發(fā)生的問題，怎么可能正弦交流的數(shù)量，以提供凈功率的是，經(jīng)過一個(gè)完整周期，凈在任何一個(gè)方向的電流為零〔平均價(jià)值0〕？它幾乎看來，動(dòng)力，積極發(fā)表波形的正弦局部撤回在負(fù)局部，而且由于兩個(gè)幅度相等，凈功率傳送是零。然而，理解，不管方向，電流通過電阻器將提供任何規(guī)模權(quán)力的電阻。換句話說，在正面還是負(fù)面局部的正弦交流電流，功率，正在每個(gè)交付時(shí)間瞬間的電阻。交付的權(quán)力在每個(gè)瞬間當(dāng)然會(huì)，而改變正弦交流電流的大小，但將在凈流量無論是正面還是負(fù)面一觸即發(fā)的