SENSORSIGNALCONDITIONINGUSINGFIELDPROGRAMMABLEANALOGUEARRAYS(FPAA)傳感器信號(hào)調(diào)理應(yīng)用現(xiàn)場(chǎng)可編程模擬陣列(FPAA)ABSTRACTFieldProgrammableAnalogueArray(FPAA)isanewanaloguedesignsystem.ThispaperintroducestheapplicationofFPAAinthesignalconditioningofthetemperaturesensors.Themajorsignalconditioningtasksundertakenarelinearization,amplificationandoffsetremoval.Signalconditioningisveryimportantfordevelopingasensorwithgoodperformance.Althoughtherearemanytechniquesforthesignalconditioning,usingFPAAhassomesignificantadvantagescomparedwiththetraditionalmethods.Inthispaper,thedesign,simulationandmeasurementresultsofsensorconditioningcircuitusingthesecond-generationFPAAwillbepresented.TheresultsobtainedshowthatFPAAcanprovideaneasy,convenientandreliablewayforthesignalconditioningoftemperaturesensor.1INTRODUCTIONSensorsarewidelyusedinprocesscontrol,automation,dataacquisition,testequipment,instrumentationandcommunicationsystems.Allthesensorspropertiesareinfluencedbytemperature,dirtandotherenvironmentalparameters.Thereforesomedataprocessingcircuitsareusuallyintegratedwiththesensorunitsdependingontherequirements.Sensorsignalconditioningcanbedefinedasthemanipulationoftheoutputsignalofasensor,probeortransducerincludingsignalconversion,attenuating,amplifying,filteringandlinearising.linearising。Signalconditioningofanyanaloguesignalisrequiredwhentheoutputsignalisnotuptothelevelorforminwhichitisrequiredbythesystem.Previoustechniquesofsensorsignalconditioningusingdiscretecircuitshavemajordisadvantagessuchaslackofprecisionduetocomponenttolerancesandmismatches;techniquesdevelopeddidnotsupportcomplexfunctionsandsignalconditionerdevelopedwasconfinedtothespecificsensorandcannotbeusedformultiplesensors.Themainchallengeforthesensorsignalconditioningistodevelopasystemthatcaneasilymodifythesensoroutputasrequiredwithgoodaccuracyandlinearity.UsingFPAAcanachievethispurpose.FPAAintroducesaradicalsoftware-centricapproachtoanaloguecircuitdesignwhereeasy-of-useisamajorfeature.Thetechnologyhastheeconfigurationflexibility,allowingcompleteanaloguesignalconditioning/processingsystemstobeintegratedusingaGraphicalUserInterface(GUI).BecauseFPAAisprogrammableandreconfigurable,justonedevicecanprovidemultiplesensorconditioningcircuitsunderthereal-timecontrolofadigitalmicroprocessor.Sensorsignallinearisation,offsetcompensation,calibration,andsignalmodulationcircuitscannowbeimplementedinminutesonadrift-freeintegratedsiliconplatform.2SYSTEMDESIGNThesystemdesignchallengesincludesourcingstablereferencesandstimulus;multiplesensorswithdifferingsignalconditioningneeds,methodsofcalibrationandmaintenanceandmanufacturingconsiderations.FPAAcanprovidethesensorsignalconditioningwithanalternativesolution.FPAA，DesignofthesystemusingFPAAinvolves:(1)Amplification,offsetremovalandlinearizationofthesignalsfromsensors;(2)SimulationusingFPAAsoftwarebeforeusingthecircuitsforrealtimesystem;(3)InterfacingtheSensorsystemwiththeFPAA;(4)CarryingouttestinordertoconditionthesignalobtainedfromdifferentSensors.TheFPAAwastheheartofthewholesystemwhichtakestheinputsignalthatwasinitiallyconvertedfromthephysicalsignalbythesensors.Thebasicpurposeofthesystemwastomanipulatethesensorsignalintoasignalthatwasappropriateforanycontrolsystem.TheFPAAsthatareusedisAnadigm'sAN220E04whichisalsocalledas“DynamicallyReconfigurableFPAA”.AsthesignalpassesthroughtheFPAA,theoffsetisfirstlyremoved,andthenthesignalisamplifiedandfiltered.ThusbyusingtheFPAAsignalconditioningthesensorsignalwithhigherprecisioncanbeachieved.Figure1SystemblockdiagramofFPAAsensorsignalconditioningFigure1showsasystemblockdiagramofFPAAsensorsignalconditioning.Themainfeaturesofthesystemare:(1)Performance:ThesystemshouldacceptthevoltagesignalfromthetemperaturesensorinterfacedtotheFPAAandprocessitaccordinglydependingonthespecificfeatureselectedamongthedifferentsignalconditioningtasks.Thesystemshouldconvertthesensoroutputsignalintoagoodqualitysignalthathasbeenamplified,linearisedandcanbedirectlyfedtoacontrolsystem.TheFPAAshouldalsoprovideapredictableandastablestimulationtothesensorsinterfacedtoit.。(2)Powersupply:+5volts.(3)Sensors:Thesensorsusedforsignalconditioningaretwodifferenttypesoftemperaturesensors,specificallythermistorbasedandthermocouplebasedtemperaturesensors.(4)Input:TheinputtotheFPAAsystemisthesignalsobtainedfromthetemperaturesensors.Thesignalsfromthetwodifferentsensorsareasfollows:(a)Signalfromthermocouple:TheoutputsignalfromthethermocoupleisavoltagesignalthatinturncorrespondedtothechangeintemperatureandisdirectlyfedtotheFPAAinadditionwithacoupleofresistorstoprovideacommonmodebiassignal.(b)Signalfromthermistor:Theresistanceobtainedfromthethermistorterminalscorrespondstothechangeintemperature.InordertoconverttheresistanceobtainedintoavoltagesignalawheatstonebridgeisconstructedsothatthesignalcanbefedtotheFPAAandserveastheinputsignaltotheFPAA.(5)Process:Theprocessbasicallyinvolvedtheconversionofthesensorsignaltoalevelthatcouldbedirectlyconnectedtoacontrolsystem.Thewholeprocessofsignalconditioninginvolvesoffsetremoval,amplification,filteringandlinearization.Thedesignprocedureforthesystemisasfollows:(1)DesignthecircuitswithrequiredfunctionsinFPAAusingFPAAsoftwareandvariousConfigurableAnalogueModules(CAMs);(2)SimulatethedesignedcircuitsusingFPAAsoftwaretoviewtheperformanceofsystem;(3)DownloadthedesignedcircuitstotheFPAAdevelopmentboard,interfacethesensorsignalandtesttherealsystem.3SYSTEMIMPLEMENTATIONTheimplementationofsysteminvolvestheselectionofthesensorsandthedesignofthecircuitsinFPAA(AN220E04).3.1SelectionofthesensorsThefirsttaskinvolvedintheimplementationofthedesignistofindthesuitablesensorsthatexhibitthecharacteristicsrequiredforinterfacingittotheFPAAandeasilyallowthesuccessfulsignalconditioningusingtheFPAA.Thesensorparameterthatisparticularlyselectedforsignalconditioningistemperature.Thenextstepforselectingthesensorsistoselectthemfromthedifferentavailablecategories.Thermocoupleandthermistorsareselectedastheoutputsignalsfromthemneedamplificationandlinearised.Ascanbeseen,thepurposeofthedesigncanbeeasilydefinedandprovedbyusingthesetwosensors.(1)SelectionofthermocoupleThermocouplesprovideaneconomicmeansofmeasuringtemperaturewithmanypracticaladvantages,theyareextremelyrobust,capableofmeasuringoveraverywidetemperaturerangesandveryeasytoinstall.Forconveniencetwothermocouplesareselected:BayonetTypeJ(RS219-4747)andTypeK(RS290-5042).Themainfeaturesandspecificationsofthesetwothermocouplescanbefoundintheirdatasheets.(2)SelectionofthermistorAthermistorisanelectroniccomponentthatexhibitsalargechangeinresistancewithachangeinitsbodytemperature.ThethermistorthatwasselectedisthePT100type(RS376-1477).ThesensorcontainsaPositiveTemperatureCoefficient(PTC)andisplatinumtemperaturesensor.Theresistanceofthesensorcanbetakendirectlytoacontroller.Inordertomeasuretheresistanceorspecificallythechangeintemperaturetwoterminalsaregivenwhichcanbeconnectedtoadevicemeasuringresistanceortoawheatstonebridgetoconverttheresistancetoavoltagesignal.3.2DesignofthecircuitsusingFPAAsoftwareThissectiondescribesthestepsfordesigningsensorsignalconditioningcircuitsbyusingFPAAsoftware:AnadigmDesigner2?.Thedesignisdividedintotwosteps:(1)Gainrequirements;(2)Linearization.(1)Designofthesignalconditioningcircuitsforthermocouple(a)GainrequirementforthermocoupleThegainrequiredforathermocoupleisdefinedbythetemperaturerangerequiredandthesensitivityofthethermocouple.Toachieveperfectresults,thethermocouplevoltagesrequirestobeamplifiedbeforeanyfurthersignalconditioningisdone.InordertopreventtheamplifiertogointosaturationduetooffsetvoltagesaChopperamplifierisusedastheinputcell.Thistechniquecanachievegainsupto128withverylittleoffsetattheoutputsignal.Thechopperclockfrequencyissetto125kHzandtheclockfrequenciesforallotherCAMsaresetto250kHz.TheChopperoutputisfilteredbyusingtheFilterBiquadCAM,andthenconnectedtoaGainHoldCAMwhichcanprovideahighqualityoutputsignalswithautomaticoffsetcompensation.Fig.2(a)showsthegainrequirementcircuitforthethermocouple.Itisnecessarytosetthegainforthechopperamplifierto64orlessthanthatforoptimalperformanceofthecircuit.(a)(b)Figure2Signalconditioningcircuitsforthermocouple(b)ThermocouplelinearisationAtypicalthermocoupleresponsefortemperatureversusvoltagerelationshipisnonlinear,whichmeansthattheoutputvoltageisnotideallyproportionaltotheinputtemperature.InordertocalculatethetemperaturethethermocouplevoltagerequiresaLook-UpTable,oranaloguelinearizationtechnique.FPAAsoftwareprovidesabuiltinLook-UpTablewith256values.TheTransferFunctionCAMinFPAAchiphasa256valueLook-UpTable,thereforeitistheimportantblockinbuildingthelinearisationcircuitforthethermocouple.TheTransferFunctionCAMisusedtogenerateananaloguevoltageinaccordancewiththechangeintemperaturebeingsensed.TheCAMusesaninternalADCtodigitisetheinputsignal,whichusesthe8-bitdigitalwordastheaddressforaLook-UpTable.The8-bitdatawordfromtheLook-UpTableisconvertedbacktoananalogueoutputvoltagesignal.ThecontentoftheLook-UpTableisuserdefined.TheTransferFunctionCAMcanbeusedtotakeaninputvalueandreturnbackalinearisedoutputvalue.InordertoachievethelinearisationtechniqueitisnecessarytouseaSumDiffCAMwiththeTransferFunctionCAM.A“straightline”transferfunctionisprovidedbythelowerinputoftheSumDiffCAM,andtheTransferFunctionCAMprovidestherequiredperturbationsfromthe“straightline”.ThegaincircuitdesignedinthepreviousstageisincludedinthelinearisationcircuitwithsomeaddedCAMswithprogrammableDCshift.InthiscaseavoltageCAMisaddedtogenerate+3VconstantvoltageandisscaledusingthelowerinputoftheSumDiffCAMaddedtothefilteredcoppersignal.Acompletethermocouplelinearisationcircuit,showninFig.2(b),isrealisedbyabovedesignedCAMssuchasTransferFunctionandgainaswellasthecircuittomaximisethedynamicrange.(2)DesignofthesignalconditioningcircuitsforthermistorThedesignprocedureofthesignalconditioningcircuitsforathermistorissimilartothatforthethermocouplediscussedin3.2.1.TherealisedcircuitsareshowninFig.3,where(a)isthegainrequirementcircuit,and(b)thelinearisationcircuit.(a)(b)Figure3Signalconditioningcircuitsforthermistor4.SIMULATIONANDMEASUREMENTRESULTSThecircuitsshowninFig.2and3canbesimulatedbyusingFPAAsoftware,anddownloadedtotheFPAAdevelopmentboardforpracticalmeasurement.ThesimulationandpracticalmeasurementhavebeencarriedoutforthelinearisationcircuitsforthetypeJandKthermocouplesbecausethelinearisationcircuitprovidesthegainrequirementresult.ThesimulationandpracticalmeasurementresultsforthetypeJthermocoupleareshowninFig.4,(a)showsthesimulationresult,and(b)themeasurementresult.Inbothoftheresults,theupperlineindicatesthecircuitoutputvoltage,andthelowerlineindicatesthethermocoupleoutputvoltage.(a)(b)Figure4ThesimulationandmeasurementresultsforthetypeJthermocouple5CONCLUSIONSUsingtheFPAAsoftwaretodesignthecircuitsfordifferentapplicationsofthesensorscanprovideasimpleimplementationofcomplexfunctionsandhelpinrapidprototypingandtesting.Thesignalconditioningofthesensorisundertherealtimecontrolandwithhighprecision.Clearly,usingtheFPAAcanobtainaneasyandconvenientwayforsignalconditioningofthetemperaturesensors.ThecircuitsdevelopedinAN220E04providehighgain,highlinearityandhighaccuracyfortemperatureSensors.

附錄B外文翻譯－譯文部分傳感器信號(hào)調(diào)理應(yīng)用現(xiàn)場(chǎng)可編程模擬陣列(FPAA)摘要現(xiàn)場(chǎng)可編程模擬陣列（FPAA）是一種新的模擬設(shè)計(jì)系統(tǒng)。本文介紹了FPAA的應(yīng)用中溫度傳感器的信號(hào)調(diào)節(jié)。主要信號(hào)調(diào)理任務(wù)是進(jìn)行線性化，擴(kuò)增和抵消清除。信號(hào)調(diào)理對(duì)發(fā)展具有良好的性能的傳感器是非常重要的。雖然有許多方式的信號(hào)調(diào)理，與傳統(tǒng)的方法比較使用FPAA有一些重要的優(yōu)勢(shì)。在本文件中，使用第二代FPAA設(shè)計(jì)，模擬和測(cè)量結(jié)果的傳感器調(diào)理電路將實(shí)現(xiàn)。結(jié)果表明，F(xiàn)PAA可以對(duì)溫度傳感器的信號(hào)調(diào)理提供一種簡(jiǎn)單，方便，可靠的方式。1導(dǎo)言傳感器被廣泛應(yīng)用于過(guò)程控制，自動(dòng)化，數(shù)據(jù)采集，測(cè)試設(shè)備，儀器和通訊系統(tǒng)。所有的傳感器性能都會(huì)受到溫度、灰塵和其他環(huán)境參數(shù)的影響。因此，有些數(shù)據(jù)處理電路通常是根據(jù)規(guī)定的要求結(jié)合傳感器單位。傳感器信號(hào)調(diào)理可以被界定為操縱的輸出信號(hào)的傳感器，探測(cè)器或傳感器包括信號(hào)轉(zhuǎn)換，衰減，放大，濾波和整形。信號(hào)調(diào)理任何模擬信號(hào)時(shí)，需要的輸出信號(hào)是沒(méi)有達(dá)到的水平或形式，它是所要求的系統(tǒng)。前技術(shù)的傳感器信號(hào)調(diào)理電路采用分立的主要缺點(diǎn)，如缺乏準(zhǔn)確性由于部分公差和錯(cuò)位；技術(shù)開發(fā)不支持復(fù)雜的功能和信號(hào)調(diào)節(jié)良好性能只限于特定的感應(yīng)器，并不能用于多個(gè)傳感器。傳感器的信號(hào)調(diào)理面臨的主要挑戰(zhàn)是建立一個(gè)系統(tǒng)，可以很容易地修改傳感器的輸出，要求具有良好的精度和線性度，使用FPAA可達(dá)到這個(gè)目的。FPAA介紹了一種先進(jìn)的軟件為中心的方法來(lái)模擬電路的設(shè)計(jì)，易于使用的是一個(gè)主要特點(diǎn)。這項(xiàng)技術(shù)的重新配置的靈活性，允許完成模擬信號(hào)空調(diào)/處理系統(tǒng)，以綜合使用的圖形用戶界面(GUI)。因?yàn)镕PAA可編程和重構(gòu)，只需一臺(tái)設(shè)備可以提供多個(gè)傳感器調(diào)節(jié)電路的實(shí)時(shí)控制的數(shù)字微處理器。傳感器信號(hào)線性，抵消補(bǔ)償，校準(zhǔn)和信號(hào)調(diào)制電路，現(xiàn)在可以實(shí)施分鐘漂免費(fèi)集成芯片平臺(tái)。2系統(tǒng)設(shè)計(jì)傳感器信號(hào)調(diào)理系統(tǒng)的設(shè)計(jì)挑戰(zhàn)包括采購(gòu)穩(wěn)定參考信號(hào)和響應(yīng)；，多個(gè)傳感器信號(hào)調(diào)理的需求不同方法的校準(zhǔn)和維修制造的考慮。FPAA能提供傳感器信號(hào)調(diào)節(jié)的替代解決方案。系統(tǒng)設(shè)計(jì)使用FPAA包括：(1)傳感器信號(hào)的放大，抵消漂移和線性；(2)使用FPAA仿真軟件，才能使用的電路實(shí)時(shí)系統(tǒng)；(3)傳感器系統(tǒng)與FPAA的接口；(4)進(jìn)行測(cè)試，以條件的信號(hào)不同的傳感器。該FPAA的核心是整個(gè)系統(tǒng)考慮傳感器的輸入信號(hào)從最初的物理信號(hào)的轉(zhuǎn)換。其基本目的是為了操縱系統(tǒng)的傳感器信號(hào)轉(zhuǎn)換成一個(gè)信號(hào)，也是適當(dāng)?shù)娜魏慰刂葡到y(tǒng)。該FPAAs所使用的是Anadigm的AN220E04，這也是被稱為“動(dòng)態(tài)重構(gòu)FPAA”。當(dāng)信號(hào)經(jīng)過(guò)FPAA時(shí)，首先刪除漂移，然后篩選和放大信號(hào)。因此使用信號(hào)具有較高精度的FPAA信號(hào)調(diào)理傳感器是可以實(shí)現(xiàn)的。圖1FPAA傳感器信號(hào)調(diào)理系統(tǒng)方框圖圖1顯示FPAA傳感器信號(hào)調(diào)理系統(tǒng)方框圖。系統(tǒng)的主要特點(diǎn)包括：(1)性能：該系統(tǒng)應(yīng)接受電壓信號(hào)的溫度傳感器連接到FPAA和進(jìn)程取決于相應(yīng)的具體特點(diǎn)選擇不同的信號(hào)調(diào)理任務(wù)。該系統(tǒng)應(yīng)轉(zhuǎn)換傳感器輸出信號(hào)轉(zhuǎn)換成高質(zhì)量的信號(hào)，表明已放大，線性化，可以直接連接到控制系統(tǒng)。該FPAA還應(yīng)提供一個(gè)可預(yù)見的和穩(wěn)定的信號(hào)傳感器連接到它。(2)電源：5伏特。(3)傳感器：傳感器用于兩種不同類型的溫度傳感器的信號(hào)調(diào)節(jié)。特別是熱敏電阻和熱電偶的溫度傳感器的基礎(chǔ)。(4)輸入：輸入的FPAA系統(tǒng)是溫度傳感器的信號(hào)。信號(hào)從兩個(gè)不同的傳感器如下：(a)信號(hào)熱電偶：從熱電偶的輸出信號(hào)是一個(gè)電壓信號(hào)，從而符合溫度的變化，并直接向FPAA與一對(duì)電阻器來(lái)提供了一個(gè)共模偏差信號(hào)。(b)信號(hào)熱敏電阻：電阻從熱敏終端對(duì)應(yīng)溫度的變化。為了轉(zhuǎn)換成一個(gè)阻力獲得電壓信號(hào)惠斯登電橋的建造，使信號(hào)可以連接到FPAA提供服務(wù)，并作為輸入信號(hào)FPAA。(5)過(guò)程：這個(gè)過(guò)程基本上涉及轉(zhuǎn)換的傳感器信號(hào)的水平，可直接連接到一個(gè)控制系統(tǒng)。全過(guò)程的信號(hào)調(diào)理涉及抵消刪除，放大，濾波和線性。設(shè)計(jì)程序的制度如下：(1)設(shè)計(jì)的電路功能的FPAA需要使用的軟件和各種FPAA配置模擬模塊（分子）；(2)模擬電路設(shè)計(jì)使用的軟件，以查看FPAA的性能系統(tǒng)；(3)下載設(shè)計(jì)FPAA的電路擴(kuò)展卡，傳感器信號(hào)界面和真正的測(cè)試系統(tǒng)。3系統(tǒng)實(shí)現(xiàn)實(shí)施系統(tǒng)涉及到的傳感器選擇和電路FPAA(AN220E04)的設(shè)計(jì)。3.1傳感器的選擇參與執(zhí)行的設(shè)計(jì)第一項(xiàng)任務(wù)是要找到合適的傳感器，擴(kuò)展需要的特性的接口給FPAA，輕松地讓FPAA的信號(hào)調(diào)理成功使用FPAA。傳感器的參數(shù)，特別是選擇信號(hào)調(diào)理的溫度。下一步選擇從不同的可用類別選擇傳感器。選定熱電偶，熱敏電阻的輸出信號(hào)，它們需要擴(kuò)增和線性。可以看出，其設(shè)計(jì)的目的可以很容易地定義，并通過(guò)使用這兩種傳感器證明。(1)選擇熱電偶熱電偶提供經(jīng)濟(jì)手段測(cè)溫與許多實(shí)際的優(yōu)勢(shì)，