SENSORSIGNALCONDITIONINGUSINGFIELDPROGRAMMABLEANALOGUEARRAYS(FPAA)傳感器信號調理應用現場可編程模擬陣列(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調理應用現場可編程模擬陣列(FPAA)摘要現場可編程模擬陣列（FPAA）是一種新的模擬設計系統。本文介紹了FPAA的應用中溫度傳感器的信號調節。主要信號調理任務是進行線性化，擴增和抵消清除。信號調理對發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調理，與傳統的方法比較使用FPAA有一些重要的優勢。在本文件中，使用第二代FPAA設計，模擬和測量結果的傳感器調理電路將實現。結果表明，FPAA可以對溫度傳感器的信號調理提供一種簡單，方便，可靠的方式。1導言傳感器被廣泛應用于過程控制，自動化，數據采集，測試設備，儀器和通訊系統。所有的傳感器性能都會受到溫度、灰塵和其他環境參數的影響。因此，有些數據處理電路通常是根據規定的要求結合傳感器單位。傳感器信號調理可以被界定為操縱的輸出信號的傳感器，探測器或傳感器包括信號轉換，衰減，放大，濾波和整形。信號調理任何模擬信號時，需要的輸出信號是沒有達到的水平或形式，它是所要求的系統。前技術的傳感器信號調理電路采用分立的主要缺點，如缺乏準確性由于部分公差和錯位；技術開發不支持復雜的功能和信號調節良好性能只限于特定的感應器，并不能用于多個傳感器。傳感器的信號調理面臨的主要挑戰是建立一個系統，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可達到這個目的。FPAA介紹了一種先進的軟件為中心的方法來模擬電路的設計，易于使用的是一個主要特點。這項技術的重新配置的靈活性，允許完成模擬信號空調/處理系統，以綜合使用的圖形用戶界面(GUI)。因為FPAA可編程和重構，只需一臺設備可以提供多個傳感器調節電路的實時控制的數字微處理器。傳感器信號線性，抵消補償，校準和信號調制電路，現在可以實施分鐘漂免費集成芯片平臺。2系統設計傳感器信號調理系統的設計挑戰包括采購穩定參考信號和響應；，多個傳感器信號調理的需求不同方法的校準和維修制造的考慮。FPAA能提供傳感器信號調節的替代解決方案。系統設計使用FPAA包括：(1)傳感器信號的放大，抵消漂移和線性；(2)使用FPAA仿真軟件，才能使用的電路實時系統；(3)傳感器系統與FPAA的接口；(4)進行測試，以條件的信號不同的傳感器。該FPAA的核心是整個系統考慮傳感器的輸入信號從最初的物理信號的轉換。其基本目的是為了操縱系統的傳感器信號轉換成一個信號，也是適當的任何控制系統。該FPAAs所使用的是Anadigm的AN220E04，這也是被稱為“動態重構FPAA”。當信號經過FPAA時，首先刪除漂移，然后篩選和放大信號。因此使用信號具有較高精度的FPAA信號調理傳感器是可以實現的。圖1FPAA傳感器信號調理系統方框圖圖1顯示FPAA傳感器信號調理系統方框圖。系統的主要特點包括：(1)性能：該系統應接受電壓信號的溫度傳感器連接到FPAA和進程取決于相應的具體特點選擇不同的信號調理任務。該系統應轉換傳感器輸出信號轉換成高質量的信號，表明已放大，線性化，可以直接連接到控制系統。該FPAA還應提供一個可預見的和穩定的信號傳感器連接到它。(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調節。特別是熱敏電阻和熱電偶的溫度傳感器的基礎。(4)輸入：輸入的FPAA系統是溫度傳感器的信號。信號從兩個不同的傳感器如下：(a)信號熱電偶：從熱電偶的輸出信號是一個電壓信號，從而符合溫度的變化，并直接向FPAA與一對電阻器來提供了一個共模偏差信號。(b)信號熱敏電阻：電阻從熱敏終端對應溫度的變化。為了轉換成一個阻力獲得電壓信號惠斯登電橋的建造，使信號可以連接到FPAA提供服務，并作為輸入信號FPAA。(5)過程：這個過程基本上涉及轉換的傳感器信號的水平，可直接連接到一個控制系統。全過程的信號調理涉及抵消刪除，放大，濾波和線性。設計程序的制度如下：(1)設計的電路功能的FPAA需要使用的軟件和各種FPAA配置模擬模塊（分子）；(2)模擬電路設計使用的軟件，以查看FPAA的性能系統；(3)下載設計FPAA的電路擴展卡，傳感器信號界面和真正的測試系統。3系統實現實施系統涉及到的傳感器選擇和電路FPAA(AN220E04)的設計。3.1傳感器的選擇參與執行的設計第一項任務是要找到合適的傳感器，擴展需要的特性的接口給FPAA，輕松地讓FPAA的信號調理成功使用FPAA。傳感器的參數，特別是選擇信號調理的溫度。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，它們需要擴增和線性。可以看出，其設計的目的可以很容易地定義，并通過使用這兩種傳感器證明。(1)選擇熱電偶熱電偶提供經濟手段測溫與許多實際的優勢，