SectionTwo

Unit4：ToolsandEquipmentUnit5：ThermometersUnit6：ElectricalInstrumentUnit6：ElectricalInstrumentNewWords&ExpressionsTextNotestothe

TextExerciseNewWords&ExpressionsServiceperson

n.維修員short

【電子學(xué)】短路；短路引起的故障malfunctions

n.故障，機(jī)能障礙，失靈ammeter

n.【電學(xué)】安培計(jì)D’Arsonval達(dá)松法電流計(jì)AC（AlternatingCurrent）

交流電diode

n.【電子學(xué)】二極管DC（directcurrent）直流電multipliers

n.倍數(shù)，乘子whereas

conj.既然;然而，卻；反之eventual

adj.最后的，最終的，結(jié)局的，結(jié)果的burnout

n.

燒壞；燒毀NewWords&Expressions銘記；標(biāo)出stampvt.微妙的；精美的，易碎的

nameplate

n.銘牌；標(biāo)示牌Ohmmeter

n.[電]歐姆計(jì)；[電]電阻表energize

vt.激勵(lì)；使活躍；供給…能量

vibration

n.振動(dòng)wattmeter

n.[電]瓦特計(jì)；電力計(jì)volt-amperes

n.伏安；伏特安培truepower[電]有效功率appar-entpower[電]視在功率；[電]表觀功率cosine

n.[數(shù)]余弦phaseangle[數(shù)][物]相位角delicateadj.Text

空調(diào)維修人員用一些電氣儀表來判斷設(shè)備是否運(yùn)行正常。研究顯示加熱和冷卻設(shè)備的大多數(shù)故障本質(zhì)上是電的問題。最常見的測量值有伏特、安倍、和歐姆。有些情況下，也測量瓦特來檢查短路和其他故障。電氣儀表可以檢測許多影響因素。例如，電氣儀表可以測量離心式水泵的流量，電容器的狀況，或者一個(gè)電動(dòng)機(jī)線圈的狀況。Severalelectricalinstrumentsareusedbytheair-conditioningservicepersontoseeiftheequipmentisworkingproperly.Studiesshowthatthemosttroublecallsonheatingandcoolingequipmentareelectricalinnature.1Themostfrequentlymeasuredquantitiesarevolts,amperes,andohms.Insomecases,wattageismeasuredtocheckforshortsandothermalfunctions.2Anumberoffactorscanbecheckedwithelectricalinstruments.Forexample,electricalinstrumentscanbeusedtochecktheflowratefromacentrifugalwaterpump,theconditionofacapacitor,orthecharacterofawindingofanelectricmotor.Text

電流計(jì)電流計(jì)用來測量電流?？梢詼y量電路中電流量。最常用的儀表測量機(jī)構(gòu)是檢流計(jì)。如圖6-1所示。當(dāng)一個(gè)二極管與移動(dòng)的線圈組相連接的時(shí)，檢流計(jì)也可以用于交流電。二極管將交流電變成直流電，儀表在直流電下工作。如圖6-2所示。還有其他類型的電流計(jì)，雖然有時(shí)不如檢流計(jì)精確，但也是有效的。如圖6-3所示。。AmmeterTheammeterisusedtomeasurecurrent.Itcanmea-suretheamountofcurrentflowinginacircuit.ThemostfrequentlyusedofthemetermovementsistheD’Arsonvaltype.SeeFig.6-1.TheD’ArsonvalmetermovementmayalsobeusedonACwhenadiodeisplacedinserieswiththemovingcoilwinding.3ThediodechangestheACtoDCandthemeterworksasonDC.SeeFig.6-2.ThereareothertypesofACammeters.TheyarenotalwaysasaccurateastheD’Arsonval，buttheyareeffective.Text

檢查運(yùn)轉(zhuǎn)中的電流計(jì)可以看出運(yùn)行中的電動(dòng)機(jī)是否過載或短路。通過電動(dòng)機(jī)引起的電流讀數(shù)可以決定機(jī)泵的流量。整個(gè)線路上的載荷可以通過線上安裝的電流計(jì)來檢查。電流計(jì)讀數(shù)應(yīng)該接近儀表刻度的中心一伙的較精確的讀數(shù)。在安裝電流表之前，確信你對(duì)電路中的電流量心中有數(shù)。這樣才能選擇合適的電流計(jì)。Runningamperesmaybecheckedtoseeifthemotorisoperatingwithtoomuchloadoritisshorted.4Theflowrateofsomepumpscanbedeterminedbyreadingthecurrentthemotorpulls.5Theloadontheentirelinecanbecheckedbyinsertingtheammeterintheline.Theread-ingoftheammetershouldbenearthecenterofthemeterscaleforamoreaccuratereading.Makesureyouhavesomeideawhatthecurrentinthecircuitshouldbebeforein-sertingthemeter.6Thus,thecorrectmetercanbeselected.Text

電壓計(jì)

電壓計(jì)用于測量電壓。電壓是電流流動(dòng)的壓力。電壓計(jì)跨接于線路中或電動(dòng)機(jī)或是用于消費(fèi)設(shè)備。電壓計(jì)也只不過是安倍表，校準(zhǔn)用于電壓。但有一個(gè)重要的區(qū)別，電壓計(jì)有非常高的內(nèi)電阻。意味著很小的電路通過線圈。如圖6-3所示。高電阻是由倍增器產(chǎn)生的。電壓計(jì)跨接于線路中，反之電流表串聯(lián)在線路中。VoltmeterThevoltmeterisusedtomeasurevoltage.Voltageistheelectricalpressureneededtocausecurrenttoflow.Thevoltmeterisusedacrossthelineoracrossamotororwhateverisbeingusedasaconsumingdevice.Voltmetersarenothingmorethanammetersthatarecalibratedtoreadvolts.7Thereis,however,anim-portantdifference.Thevoltmeterhasaveryhighinter-nalresistance.Thatmeansverysmallamountsofcurrentflowthroughitscoil.SeeFig.6-3.Thishighresistanceisproducedbymultipliers.Thevoltmeterisplacedacrosstheline,whereastheammeterisplacedinseries.Text

Normallinevoltageinmostlocationsis120V.Whenthelinevoltageislowerthannormal,itispossiblefortheequipmenttodrawexcessivecurrent.Thiswillcauseoverheatingandeventualfailureorburnout.Thecorrectvoltageisneededfortheequipmenttooper-ateaccordingtoitsdesignedspecifications.8Thevoltagerangeisusuallystampedonthenameplateofthedevice.大多數(shù)場合線路中正常電壓為120V。當(dāng)線路電壓低于正常值，設(shè)備可能承受過載電流，這會(huì)導(dǎo)致過熱和故障或燒壞設(shè)備。設(shè)備運(yùn)轉(zhuǎn)所需要的正確電壓值應(yīng)按照設(shè)計(jì)規(guī)范確定。電壓值通常標(biāo)在設(shè)備的銘牌上。Text

OhmmeterTheohmmetermeasuresresistance.Thebasicunitofresistanceistheohm.Everydevicehasresistance.Itisnecessarytoknowtheproperresis-tancebeforetryingtotroubleshootadevicebyusinganohmmeter.9

Theohmmeterhasitsownpowersupply.SeeFig.6-4.Donotuseanohmmeteronalinethatisenergizedorconnectedtoapowersourceofanyvoltage.電阻表電阻表測量電阻。電阻的單位是歐姆。每個(gè)電氣裝置都有電阻。在用電阻表檢查設(shè)備故障時(shí)必須知道其自身電阻。電阻表自身帶有電源。如圖6-4所示。不要將電阻表用在帶電線路上或連接在有電壓的電源上。Text

Anohmmetercanreadtheresistanceofthewind-ingsofamotor.Ifthecorrectreadinghasbeengivenbythemanufacturer,itisthenpossibletoseeiftheread-inghaschanged.Ifthereadingismuchlower,itmayindicateashortedwinding.Ifthereadingisinfinite,itmaymeanthereisalooseconnectionoranopencircuit.Rememberthatthepowermustbeofftousetheohmmeter.Itshouldbeprotectedfromshockandvibrationjustasanyothersensi-tiveinstrument.電阻表可以讀出電動(dòng)機(jī)線圈的電阻。如果制造商給出了標(biāo)準(zhǔn)讀數(shù)，那么可以判斷讀數(shù)是否發(fā)生變化。如果讀數(shù)過低，表明線圈也許短路了。如果讀數(shù)無窮大，表明接頭松動(dòng)了或斷路了。記住用電阻表的時(shí)候電源必須斷開。正如其它精密儀表一樣，電阻表不能收到?jīng)_擊和振動(dòng)。Text

WattmeterThewattmeterisusedtomeasurewatts.However,whenusedonanAClineitmeasuresvolt-amperes.Ifwattsaretobemeasured,thereadingmustbecon-vertedtowattsmathematically.Itisconvertedtowattsbymultiplyingtheread-ingbythepowerfactor.功率表功率表測量瓦特。如果用在交流電路上測量伏安。如果測量功率，讀數(shù)必須數(shù)學(xué)轉(zhuǎn)變?yōu)橥咛?。將讀數(shù)乘以功率因數(shù)轉(zhuǎn)化為功率。Text

Thepowerfactoristheratiooftruepowertoappar-entpower.ApparentpoweriswhatisreadonawattmeteronanACline.Truepoweristhewattageread-ingofDC.Thetwocanbeusedtofindthepowerfactor.Thepowerfactoristhecosineofthephaseangle.Thepowerfactorcanbefoundbyusingamathematicalcom-putationoraverydelicatemeterdesignedforthepur-pose.However,thepowerfactorofequipmentusingalternatingcurrentisusuallystampedonthenameplateofthecompressor,themotor,etc.Wattmetersarealsousedtotestcapacitors.Thewattmetercantesttheactualconnectionofthecapacitor.Theohmmetertellsifthecapacitorisgoodorbad.功率因數(shù)是有效功率與視在功率的比值。視在功率是交流線路上功率表的讀數(shù)。有效功率是直流電路上的讀數(shù)。用這兩者可以找到功率因數(shù)。功率因數(shù)是相位角的余弦。功率因數(shù)可以有數(shù)學(xué)計(jì)算或?qū)Ｓ械木軆x器得到。然而，用交流電的設(shè)備其功率因數(shù)通常標(biāo)在銘牌上，如壓縮機(jī)，電動(dòng)機(jī)等。功率計(jì)也可用來測試電容。功率表可以測試電容器真實(shí)的連接狀態(tài)。功率表可以分辨電容器是好的還是壞的NotestotheTextUnit6NotestotheText1、Studiesshowthatthemosttroublecallsonheatingandcoolingequipmentareelectricalinnature.句中省略主語，that引導(dǎo)賓語從句themosttroublecallsonheatingandcoolingequipmentareelectricalinnature。troublecalls在句中意為“故障投訴”。例如：troublecallsystems

事故呼叫系統(tǒng)Unit6NotestotheText句中不定式短語tocheckforshortsandothermalfunctions作目的狀語。Short有多重意義。如：“短；缺乏；短路；不足；突然；唐突地”。在句中做“短路”解釋。2、Insomecases,wattageismeasuredtocheckforshortsandothermalfunctions.

Unit6NotestotheText句中when引導(dǎo)時(shí)間狀語從句adiodeisplacedinserieswiththemovingcoilwinding。Movement通常譯為“運(yùn)動(dòng)”，在句中作“機(jī)件；機(jī)械裝置”解釋。對(duì)于多義詞，翻譯時(shí)要根據(jù)上下文選擇適當(dāng)?shù)脑~義。3、TheD’ArsonvalmetermovementmayalsobeusedonACwhenadiodeisplacedinserieswiththemovingcoilwinding.Unit6NotestotheText句中，主語為“Runningamperes”，不定式“tosee。。?！弊鰻钫Z，if從句themotorisoperatingwithtoomuchloadoritisshorted不定式tosee的賓語。Check意為“檢查，核對(duì)”。例如：Checktheaccuracyofeverythinginyourrésumé.核查你簡歷中每一項(xiàng)的準(zhǔn)確性。4、Runningamperesmaybecheckedtoseeifthemotorisoperatingwithtoomuchloadoritisshorted.Unit6NotestotheText句中byreadingthecurrentthemotorpulls作狀語?！皌hemotorpulls”為定語從句修飾current。pull是多義詞，句中意為：“操縱(某物)”。例如：Hepulledthevantotherighttoavoidthedog.他把客貨車向右一閃以免壓著狗。5、Theflowrateofsomepumpscanbedeterminedbyreadingthecurrentthemotorpulls.Unit6NotestotheText句中，省略主語youhavesomeidea為賓語從句，省略了引導(dǎo)詞that。what引導(dǎo)從句thecurrentinthecircuitshouldbebeforein-sertingthemeter修飾someidea。Makesure意為確信；證實(shí)。例如：Wewantto

make

surethateveryhumanbeinghasadignifiedlife.

我們想確保每個(gè)人都過上有尊嚴(yán)的生活。6、Makesureyouhavesomeideawhatthecurrentinthecircuitshouldbebeforein-sertingthemeter.Unit6NotestotheText電壓計(jì)也只不過是安倍表，校準(zhǔn)用于電壓。句中that引導(dǎo)定語從句修飾ammeters。nothingmorethan

意為

“不過是；無非是”。例如：He

is

nothing

more

than

a

dreamer.

他只

不過是一個(gè)做白日夢(mèng)者7、Voltmetersarenothingmorethanammetersthatarecalibratedtoreadvolts.Unit6NotestotheText設(shè)備運(yùn)轉(zhuǎn)所需要的正確電壓值應(yīng)按照設(shè)計(jì)規(guī)范確定。句中，現(xiàn)在分詞短語accordingtoitsdesignedspecifications作狀語。accordingto

意為“按照；取決于”。例如：They

doeverything

according

to

Hoyle.他們一切都按照規(guī)定辦理8、Thecorrectvoltageisneededfortheequipmenttooper-ateaccordingtoitsdesignedspecifications.Unit6No