測(cè)控技術(shù)與儀器專業(yè)英語(yǔ)unit-6

Unit6SignalConditioningUnit6SignalConditioning

Ameasuringtransmitterconsistsoftwoparts:aprimaryelement(orsensor)andasignalconditioner.Theprimaryelementusessomecharacteristicofitsmaterialandconstructiontoconvertthevalueofameasuredvariableintoanelectrical,mechanical,orfluidicsignal.

譯為：一個(gè)測(cè)量傳感器由兩部分組成：一個(gè)基本元件（傳感器）和一個(gè)信號(hào)調(diào)制器?；驹闷洳馁|(zhì)的特性和結(jié)構(gòu)將被測(cè)量轉(zhuǎn)化為電的、機(jī)械的或者流體的信號(hào)。

Theoutputoftheprimaryelementmaybeasmallvoltageoranelectricalresistance.Itmaybeaforce,adisplacement,apressure,orsomeotherphenomenon.Nomatterwhatformittakes,theprimaryelementoutputdependsonthevalueofthemeasuredvariable.

譯為：基本元件的輸出可能是一個(gè)小的電壓或電阻。也可能是一個(gè)力、一個(gè)位移、一個(gè)壓力或其他一些現(xiàn)象。不論它采取何種形式，基本元件的輸出依賴于測(cè)得量的數(shù)值。

Theoutputoftheprimaryelementisameasureofthevariableitissensing,butitisseldominaformsuitablefortransmissionandusebyothercomponentsinasystem.

譯為：基本元件的輸出是對(duì)它測(cè)量的變量的度量。但是它很少采用一種便于傳輸或被系統(tǒng)中其他部分使用的形式。

Usually,asignalconditionerisrequiredtoconverttheprimaryelementoutputintoanelectrical(orpneumatic)signalsuitableforusebyacontrollerordisplaydevice.Asignalconditionerpreparesasignalforusebyanothercomponent.Theinputtoasignalconditionerisusuallytheoutputfromasensor(orprimaryelement).譯為：通常，一個(gè)信號(hào)調(diào)制器被用來(lái)將基本元件的輸出變換為一個(gè)便于被處理器或顯示設(shè)備使用的電（或氣）信號(hào)。一個(gè)信號(hào)調(diào)節(jié)器將信號(hào)準(zhǔn)備好以備其他設(shè)備使用，信號(hào)調(diào)制器的輸入通常是傳感器的輸出（或基本元件）。

Thefull-scaleoutputsofmostsensors(passiveoractive)arerelativelysmallvoltages,currents,resistancesandcapacitances.Beforefurtheranalogordigitalprocessingcantakeplace,theseoutputsmustbescaledorconvertedtousefulranges.句中full-scale意為“滿量程”，passivesensor意為“被動(dòng)型傳感器”，activesensor意為“主動(dòng)型傳感器”，scale在這里指“換算縮放，改變值的大小”。譯為：絕大多數(shù)傳感器（被動(dòng)型或主動(dòng)型）的滿量程輸出都是比較小的電壓、電流、電阻和電容。在進(jìn)行進(jìn)一步模擬或數(shù)字信號(hào)處理之前，這些輸出必須要換算縮放或轉(zhuǎn)換到可用的范圍。

Thestandardtransmissionsignalsarea4to20mAelectriccurrentora3to15psipneumaticpressure.Forexample,athermocouple（熱電偶）(T/C)isaprimaryelementthatconvertstemperatureintoasmallvoltage.Asignalconditionerconvertsthemillivoltoutputofthethermocoupleintoa4to20mAelectriccurrent.AT/Ctemperaturetransmitterincludesboththethermocoupleandthesignalconditioner.

psi為壓力的單位，poundspersquareinch，磅/平方英寸。pneumaticpressure意為“氣壓”.譯為：標(biāo)準(zhǔn)的傳輸信號(hào)是一個(gè)4至20毫安電流或一個(gè)一個(gè)3至15磅/平方英寸氣壓。例如，熱電偶是一種將溫度轉(zhuǎn)化為小電壓的基本元件。一個(gè)信號(hào)調(diào)制器將熱電偶的毫伏輸出轉(zhuǎn)化為4至20毫安的電流，一個(gè)熱電偶溫度變送器同時(shí)包含熱電偶和信號(hào)調(diào)制器。

Signalconditioningcircuitsperformthenecessaryamplification,leveltranslation,impedancetransformation,linearizationandfiltering.Thecharacteristicsofanderrorinthesensoroutputdeterminethetypeofsignalconditioningcircuitsneeded.

譯為：信號(hào)處理電路實(shí)現(xiàn)必要的信號(hào)放大、電平變換、阻抗變換、線性化和濾波。傳感器輸出的特征及其誤差決定需要哪種信號(hào)調(diào)制回路。Ifthesensoroutputisnotconditionedproperly,factorssuchassensitivity,voltageandcurrentlevels,linearity（線性度，線性）,impedances,gain,offset,drift,timeconstants,maximumelectricalratings（最大額定電功率）,strayimpedances（雜散阻抗，寄生阻抗）andotherimportantconsiderationscanimpacttheoverallperformanceofthesensor.Asaresult,theoverallsystemwillsuffer,particularlywhenhighresolution,precisionorverylowlevelmeasurementsareinvolved.譯為：如果傳感器的輸出沒(méi)有被正確的調(diào)制，諸如靈敏度、電壓和電流電平、線性度、阻抗、增益、補(bǔ)償、漂移、時(shí)間常數(shù)、最大額定電功率、寄生阻抗和其他重要的因素能夠影響傳感器的整體表現(xiàn)。其結(jié)果是整個(gè)系統(tǒng)將受到影響，特別是當(dāng)涉及高清晰度，準(zhǔn)確度或很差水平的測(cè)量時(shí)。Caremustbetakenwhendesigningsignalgenerationandconditioningcircuitstoensurethatthesensoristheleastaccuratecomponentofthesystem.Ifsurroundingcircuitryaddsnoiseordegradesaccuracy,theaccuracyofthesensoroutputiscompromised.譯為：設(shè)計(jì)信號(hào)發(fā)生器和調(diào)制回路時(shí)一定要警惕以保證傳感器是系統(tǒng)中準(zhǔn)確度最低的部件，如果周圍回路有附加噪聲或降低了準(zhǔn)確度，傳感器輸出的準(zhǔn)確度將受影響。

Thefollowingaresomeofthetasksperformedbyasignalconditioner:以下是一個(gè)信號(hào)調(diào)制器執(zhí)行的操作：（1）Isolationandimpedanceconversion;隔離和阻抗變換（2）Amplificationandanalog-to-analogconversion;放大和模-模轉(zhuǎn)換（3）Noisereduction(filtering);降噪（濾波）（4）Linearization;線性化（5）Datasampling;數(shù)據(jù)采樣（6）Digital-to-Analogconversion;數(shù)-模轉(zhuǎn)換（7）Analog-to-Digitalconversion.模-數(shù)轉(zhuǎn)換Voltageoutput

Threetypesofinputtopologiesexistforthesignalconditioningofvoltageoutputsensors:differential,single-endedandpseudo-differential.Thetypeofsignalconditioninginputistypicallymatchedtotheoutputstructureandprecisionrequirementsofthesensor.句中differential有“微分”和“差分”之意，這里指信號(hào)處理的方式，意為“差動(dòng)”。譯為：電壓輸出傳感器的信號(hào)處理有3種輸入拓?fù)浞绞剑翰顒?dòng)方式、單端方式和偽差分方式。信號(hào)調(diào)制輸入的類型要符合特定的輸出結(jié)構(gòu)和傳感器的準(zhǔn)確性要求。

Adifferentialdevicerejectsinputsignalscommontothebalancedinputpair(+and-)whileacceptingthedifferencebetweentheinputsignals,specifiedastheCommon-ModeRejectionRatio(CMRR).Thedeviceisdesignedsothatthenoisecommontobothinputsisrejectedwhilethesignalofinterestisnot.句中balancedinput意為“對(duì)稱輸入”，Common-ModeRejectionRatio(CMRR)意為“共模抑制比”。譯為：差動(dòng)裝置在接收兩輸入端口的差分信號(hào)時(shí)，抑制這兩個(gè)對(duì)稱輸入端口（+和-）的共模輸入信號(hào)，這稱為共模抑制比CMRR。這個(gè)裝置被這樣設(shè)計(jì)兩個(gè)輸入共有的噪聲被抑制而所需要的信號(hào)不被抑制。

MuchlikedigitaldifferentialinputsignalssuchasLVDS,theanalogsignalsmaybeinvertedtoadoubledynamicrangeasiscommonwithdifferentialoutputdevices.

譯為：和數(shù)字差分輸入信號(hào)如低壓差分信號(hào)很類似，模擬信號(hào)可以倒置成一個(gè)雙重動(dòng)態(tài)范圍和差分輸出設(shè)備的輸出一樣。Thistypeofinputtopology（拓?fù)?，拓?fù)浣Y(jié)構(gòu)，布局，拓?fù)鋵W(xué)）isusedwhenmaximumnoiserejectionisrequiredandthesensormeasurementisnottiedtoground,aswiththeWheatstonebridge（惠斯頓電橋）configuration.Forremotesensorapplications,shieldedtwistedpaircablesshouldbeusedinordertomaintainsignalbalanceandshareacommongroundreference.句中twistedpaircables意為“雙絞線”。譯為：這種輸入拓?fù)湫问皆谛枰畲笤肼曇种坪蛡鞲衅鳒y(cè)量裝置沒(méi)有接地時(shí)使用，后者和惠斯頓電橋的結(jié)構(gòu)相類似。對(duì)遠(yuǎn)程傳感器應(yīng)用，應(yīng)該使用屏蔽雙絞線以保持信號(hào)的平衡和共地。Incontrast,asingle-ended(SE)devicehasasinglesignalinput.Theboarddesignermustensureacommongroundbetweenthedeviceanditsinput,whichisthesensorcircuitryinthiscase.Therefore,SEdevicesaregenerallyplacedincloseproximitytooneanothertomitigate（減輕，緩和）thepossibilityofreferencedifferencesbetweenthedevices.

譯為：相反地，一個(gè)單端設(shè)備只有一個(gè)信號(hào)輸入端。面板設(shè)計(jì)員必須保證設(shè)備和其輸入之間有共同之處，傳感器回路就是這種情況。因此，單端設(shè)備通常彼此緊密排列以減少設(shè)備間相互參照引起的不同的可能。

Ingeneral,SEdevicesareusedforconditioninglargersignalsandarenottieddirectlytosmallsignalsensors.AlthoughSEdeviceshavelowerCMRRsandintroducegreaterDCoffsets（偏移，偏置）,theyarelesscostly.Forremotesensorapplications,coaxial（同軸的，共軸的）cablesaresufficientforshieldingthesignalconductorandsharingcommongroundreferences.譯為：通常情況下，單端設(shè)備用來(lái)調(diào)制較大的信號(hào)而且不直接連接在小的信號(hào)傳感器上。盡管單端設(shè)備有較低的共模抑制比和較大的直流抵消，它們更便宜。對(duì)長(zhǎng)距離傳感器設(shè)備而言，同軸電纜足夠用于信號(hào)傳導(dǎo)和共地。Finally,apseudo-differentialinputtopologyisahybridofthetwo.ItsDCoffsetperformanceapproachesthatofadifferentialdevice,butitsCMRRisclosertoaSEdevice.Thistypeofdeviceisusedincost-sensitivedesignswithDCsensorswherehighfrequencyvariationsfromnoisecanberemovedattheendofthesignalchainorthroughdigitalprocessing.句中DC是directcurrent的縮寫(xiě)，意為“直流電”。譯為：最終，一個(gè)擬微分輸入拓?fù)涫莾煞N的混合，它的直流抵消能力接近與差分裝置，但它的共模抑制比更接近單端設(shè)備。這種類型的裝置用于有直流傳感器的代價(jià)敏感的設(shè)計(jì)中，這種裝置能在信號(hào)鏈的終端或通過(guò)數(shù)字信號(hào)處理去除噪聲的高頻變化。Amplification

Forcircuitswithsmallvoltageoutputs,aprecisionamplifiergainstageisneeded.Assensoroutputsaretypicallyprocessedbyanalog-to-digitalconverters,thesensoroutputneedstobeamplifiedsothatitcantakeadvantageofthefull-scaleinputrangeofthedesiredADC(analog-to-digitalconverters).

譯為：對(duì)小電壓輸出的電路，一個(gè)準(zhǔn)確的放大增益級(jí)是需要的。因?yàn)閭鞲衅鞯妮敵霰荒?數(shù)轉(zhuǎn)換裝置按特定方式處理，傳感器輸出需要被放大以此使它能夠利用要求的模數(shù)轉(zhuǎn)換器的寬頻輸入的優(yōu)勢(shì)。Forverylow-levelinputsignals,multiplelevelsofamplificationandhighgainsaresometimesrequired.Becauseoftheoperationalamplifier’s（運(yùn)算放大器）architecture,inputoffsetvoltageandinputbias（偏差，偏移，偏置）currentcanadderrortotheamplifier’sinput.

譯為：對(duì)于低電平輸入信號(hào)，有時(shí)需要多級(jí)放大和高增益。因?yàn)檫\(yùn)算放大器的結(jié)構(gòu)，輸入電壓偏移和輸入電流偏移會(huì)增加放大器的輸入的誤差。TheeffectsofinputoffsetvoltagesandinputbiascurrentsareshowninFigure6.1.Aspreviouslystated,highgainsalsoamplifyinputoffsetvoltages,potentiallyaddinglargeamountsoferrortotheamplifiedsensorsignal.

譯為：輸入電壓偏移和輸入電流偏移的作用如圖6.1.正如之前說(shuō)過(guò)的，高增益也會(huì)放大輸入電壓偏移，可能給放大的信號(hào)增加大量誤差。Figure6.1VoltageoutputsensingNon-idealfeaturesofoperationalamplifiers：運(yùn)算放大器的非理想特性：

VoltageOffset(電壓偏移):Inputoffsetvoltageresultsprimarilyfromtheinherentmismatchofanoperationalamplifier’sinputtransistors.

譯為：電壓偏移：輸入電壓偏移主要由運(yùn)算放大器的輸入晶體管固有的不匹配產(chǎn)生。InputBiasCurrent(輸入偏移電流):Whileanidealoperationalamplifierhaszerocurrentflowingintotheinputtransistors,asmallamountofcurrentdoesflowintooroutoftheinputtransistors.譯為：

輸入偏移電流：當(dāng)一個(gè)理想運(yùn)算放大器沒(méi)有電流流入輸入晶體管，一小部分電流流入或流出輸入晶體管。CommonModeRejection(共模抑制):Inasingle-endedinputoperationalamplifier,noiseontheinputsignalsisamplifiedwiththegainofacircuit.Inadifferentialinputstage,noisecommontobothinputsisrejected,passingonlythesignalofinterest.譯為：共模抑制：在一個(gè)單端輸入運(yùn)算放大器中，輸入信號(hào)中的噪聲在增益的回路中放大。在差分輸入級(jí)，兩個(gè)輸入端共同的噪聲被抑制，僅允許需要的信號(hào)通過(guò)。Toavoidlargeoffsetvoltageswithverylow-levelvoltageoutputs,aninstrumentationamplifiershouldbeused.Instrumentationamplifiersaredesignedusingthreediscreteoperationalamplifiers,withnon-invertingoperationalamplifiersusedasinputbufferstoeachdifferentialinput.譯為：為避免低電平輸出中的大的電壓偏移，需要使用儀器放大器。儀器放大器由3個(gè)分離的運(yùn)算放大器設(shè)計(jì)而成，其中，非反相運(yùn)算放大器用于每個(gè)不同輸入信號(hào)的輸入緩沖。Thisconfigurationistypicallyintegratedintoasingledevice.Manysensors(withdifferentialoutput)connectdirectlytotheinstrumentationamplifier.Inmanycases,theinstrumentationamplifiergainissetrelativelylowandthenfollowedupbyahighgainoperationalamplifier.Instrumentationamplifiers,showntotherightinFigure6.2,haveverylowinputoffsetvoltages,lowinputbiascurrentsandhighcommonmoderejection,reducingerrorintheinitialgainstage.

譯為：這種結(jié)構(gòu)合成為一個(gè)單獨(dú)的裝置。許多傳感器（與差分輸出）直接與儀器放大器相連。在許多情況中，儀器放大器的增益設(shè)置的相對(duì)低并且后面跟隨一個(gè)高增益的運(yùn)算放大器。儀器放大器，顯示在圖6.2的右側(cè)，有很低的輸入電壓偏移和輸入電流偏移，以及高共模抑制比，降低起始增益環(huán)節(jié)的誤差。Followingtheinitialgainstage,aprogrammablegainamplifiercanbeusedtofurtheramplifythesignalasneeded.Aprogrammablegainamplifiercanbedigitallyprogrammedtoensurethatthefullscalesensoroutputmatchestheinputvoltagerangeoftheanalog-to-digitalconverter.譯為：在起始增益環(huán)節(jié)之后的是一個(gè)可編程增益放大器，它可以用來(lái)根據(jù)需要進(jìn)一步放大信號(hào)。一個(gè)可編程起始增益放大器可以進(jìn)行數(shù)字化編程以確保傳感器輸出的滿量程與模數(shù)變換器的電壓輸入范圍相匹配。Figure6.2InstrumentationamplifieroffsetvoltagesNoise

Sensorsignalsrunninglongdistancesoverwireandcableessentiallybecomeantennas,pickingupelectricalandmagneticinterferencefrommanyRFsources.Groundloops（地回路，接地環(huán)路）onsingle-endedsignalscanalsosignificantlyraise/lowerthenoisepotentialofasensorsignalwithrespecttothesignalconditioningcircuits.

譯為：傳感器信號(hào)經(jīng)長(zhǎng)距離傳輸，必然變得像天線一樣，容易受到許多射頻源的電磁干擾。單端信號(hào)的接地回路也能夠顯著的提高/降低傳感器信號(hào)關(guān)于信號(hào)調(diào)制回路產(chǎn)生的噪聲勢(shì)。Usingbalanced(differential)signals,sensiblegroundingstrategies,twistedpairwiresandappropriatefilteringattheamplifierstagecansignificantlyimprovenoiseimmunity(抗噪聲度).

譯為：使用平衡（差分）信號(hào)，合理的接地策略，雙絞線和放大級(jí)中適當(dāng)?shù)倪^(guò)濾可以顯著提高抗噪聲度。IsolationSomesensorenvironmentsandconditioningcircuitshavesignificantlydifferentpotentialsandcanbesubjecttoveryhigh-voltagetransientsonthesensorsignalpath.Thesesituationscanpotentiallydamagelow-voltagedataconversionandprocessingcircuits,creatingtheneedforanisolationcircuittoprotectthecircuitry.Thesensorhalfofthesystemissaidtobeisolatedfromtherestofthesystem.句中high-voltagetransient意為“瞬時(shí)高壓”。譯為：有些傳感器環(huán)境和信號(hào)處理電路有明顯不同的電位，在傳感器信號(hào)傳輸路徑中，容易受到瞬時(shí)高壓的影響。這些情況可能破壞低電平數(shù)據(jù)轉(zhuǎn)換和運(yùn)算電路，由此需要一個(gè)隔離電路來(lái)保護(hù)電路。系統(tǒng)內(nèi)一半的傳感器因此需從系統(tǒng)其余部分隔離出來(lái)。Isolationcircuitsarecreatedbytakingadvantageofelectricandmagneticfieldpropertiesinstructuressuchastransformers,capacitors,photoelectricdevicesandRFsignalpropagationtotransmitdataacrossaninterfacewithoutaphysicalconnection.Isolationamplifiershavetheisolationbarriernecessarytoprotectdownstreamcircuitsintegrateddirectlyintothedevice.Transformer,capacitor,opticalandRFisolationamplifiersallhavedifferingaccuracy,linearityandbandwidths（帶寬）.譯為：隔離電路利用電磁原理的構(gòu)件制成。如變壓器、電容器、光電元件和RF信號(hào)發(fā)射元件，通過(guò)沒(méi)有物理連接的界面來(lái)傳送數(shù)據(jù)。隔離放大器有隔離柵的需要以保護(hù)下游直接與設(shè)備集成的電路。變壓器，電容器，光學(xué)和射頻隔離放大器都有不同的準(zhǔn)確率，線性度和帶寬。FilteringAtsomepointinthesignalchain,generallyjustbeforedigitization,thesignalisfilteredtoattenuateunwantedcross-talk（聲道串?dāng)_，串音）componentssuchas60Hzhum（交流聲；干擾；發(fā)嗡嗡聲）,switchingtransients（開(kāi)關(guān)瞬態(tài)；操作瞬變現(xiàn)象）,RFinterferenceaswellasaliasingartifacts（混疊偽像）suchaswidebandnoise.Analogsignalfilteringcanbebrokenintotwobasictypes:passiveandactive.譯為：在信號(hào)鏈的某些點(diǎn)，通常是在數(shù)字化之前，信號(hào)被過(guò)濾以減弱不需要的串音成分如60hz的交流聲，開(kāi)關(guān)瞬態(tài)，射頻干涉混疊偽像例如寬頻噪聲。模擬信號(hào)的過(guò)濾可以分為兩種基本類型：被動(dòng)型和主動(dòng)型。Passiveanalogfiltersusediscretecomponentssuchascapacitors,inductorsandresistors.Activeanalogfiltersusediscretecomponentsinconjunctionwithoperationalamplifiersforamoreprecisefilterdesign.句中Passiveanalogfilters指“被動(dòng)模擬濾波器”，也稱無(wú)源濾波器。Activeanalogfilters指“主動(dòng)模擬濾波器”，也稱有源濾波器。譯為：被動(dòng)模擬濾波器由電容、電感和電阻這樣的獨(dú)立元件構(gòu)成。主動(dòng)模擬濾波器將這些獨(dú)立元件連接在運(yùn)算放大器上，得到更高的設(shè)計(jì)精度。Filters,whetheractiveorpassive,canbebrokendownintothreebasicfunctionalareas:low-passfilters,high-passfiltersandbandpassfilters.Low-passfilters(LPFs)（低通濾波器）onlyallowelectricalsignalsunderadeterminedfrequencytopassthrough,oftencalledthecut-offfrequency.High-passfilters(HPFs)（高通濾波器）allowelectricalsignalstopassthoughthatisabovethecut-offfrequency.

譯為：濾波器，不論主動(dòng)式或被動(dòng)式，可以分成三種基本功能類型：低通濾波器，高通濾波器和帶通濾波器。低通濾波器僅允許低于一定頻率，通常成為截?cái)囝l率的電信號(hào)通過(guò)。高通濾波器允許頻率高于階段頻率的電信號(hào)通過(guò)。Bandpassfilters（帶通濾波器）areacombinationofanLPFandanHPF.Theyallowelectricalsignalstopassthroughthatareabovealowercut-offfrequencyandbelowahighercut-offfrequency.Designershavetotakecarewhenchoosingtheappropriatetypeandfunctionalareatoachieveoptimalcircuitperformance.譯為：帶通濾波器是低通濾波器和高通濾波器的混合。他們?cè)试S高于一個(gè)較低截?cái)囝l率且低于一個(gè)較高截?cái)囝l率的電信號(hào)通過(guò)。設(shè)計(jì)人員應(yīng)注意選擇合適類型和功能的濾波器以達(dá)到理想的電路性能。Analog-to-analogconversion

Someprimaryelementsconvertchangesinthemeasuredvariableintosmallchangesinresistance.Straingages（應(yīng)變儀）andresistancetemperaturedetectors(RTDs)aretwoexamples.Abridgecircuitisoftenusedtoconvertthechangeinresistanceintoasmallchangeinvoltage.Thissmallvoltageisthenamplifiedandconvertedtoanelectriccurrentsignalsuitableforusebythecontroller。注意句中changes強(qiáng)調(diào)轉(zhuǎn)換的不是被測(cè)量本身，而是被測(cè)量的“變化量”。譯為：一些基本元件將被測(cè)量的變化量轉(zhuǎn)換成電阻的很小的變化量。應(yīng)變儀和電阻溫度檢查器是兩個(gè)例子。一個(gè)橋路常被用來(lái)將電阻的變化轉(zhuǎn)換為電壓的微小變化。這個(gè)小的電壓隨后本放大并轉(zhuǎn)化為一個(gè)適合被控制器使用的電流信號(hào)。Offsetvoltagecorrection

Sometimes,theoutputofeitherasensororanampl