温度传感器中英文对照外文翻译文献.docx

温度传感器中英文对照外文翻译文献.docx

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温度传感器中英文对照外文翻译文献

中英文资料外文翻译文献

原文：

TemperatureSensorICsSimplifyDesigns

Whenyousetouttoselectatemperaturesensor,youarenolongerlimitedtoeitherananalogoutputoradigitaloutputdevice.Thereisnowabroadselectionofsensortypes,oneofwhichshouldmatchyoursystem'sneeds.

Untilrecently,allthetemperaturesensorsonthemarketprovidedanalogoutputs.Thermistors,RTDs,andthermocoupleswerefollowedbyanotheranalog-outputdevice,thesilicontemperaturesensor.Inmostapplications,unfortunately,theseanalog-outputdevicesrequireacomparator,anADC,oranamplifierattheiroutputtomakethemuseful.

Thus,whenhigherlevelsofintegrationbecamefeasible,temperaturesensorswithdigitalinterfacesbecameavailable.TheseICsaresoldinavarietyofforms,fromsimpledevicesthatsignalwhenaspecifictemperaturehasbeenexceededtothosethatreportbothremoteandlocaltemperatureswhileprovidingwarningsatprogrammedtemperaturesettings.Thechoicenowisn'tsimplybetweenanalog-outputanddigital-outputsensors;thereisabroadrangeofsensortypesfromwhichtochoose.

ClassesofTemperatureSensors

Fourtemperature-sensortypesareillustratedinFigure1.Anidealanalogsensorprovidesanoutputvoltagethatisaperfectlylinearfunctionoftemperature（A）.InthedigitalI/Oclassofsensor（B）,temperaturedataintheformofmultiple1sand0sarepassedtothemicrocontroller,oftenviaaserialbus.Alongthesamebus,dataaresenttothetemperaturesensorfromthemicrocontroller,usuallytosetthetemperaturelimitatwhichthealertpin'sdigitaloutputwilltrip.Alertinterruptsthemicrocontrollerwhenthetemperaturelimithasbeenexceeded.Thistypeofdevicecanalsoprovidefancontrol.

Figure1.SensorandICmanufacturerscurrentlyofferfourclassesoftemperaturesensors.

"Analog-plus"sensors（C）areavailablewithvarioustypesofdigitaloutputs.TheVOUTversustemperaturecurveisforanICwhosedigitaloutputswitcheswhenaspecifictemperaturehasbeenexceeded.Inthiscase,the"plus"addedtotheanalogtemperaturesensorisnothingmorethanacomparatorandavoltagereference.Othertypesof"plus"partsshiptemperaturedataintheformofthedelaytimeaftertheparthasbeenstrobed,orintheformofthefrequencyortheperiodofasquarewave,whichwillbediscussedlater.

Thesystemmonitor（D）isthemostcomplexICofthefour.InadditiontothefunctionsprovidedbythedigitalI/Otype,thistypeofdevicecommonlymonitorsthesystemsupplyvoltages,providinganalarmwhenvoltagesriseaboveorsinkbelowlimitssetviatheI/Obus.Fanmonitoringand/orcontrolissometimesincludedinthistypeofIC.Insomecases,thisclassofdeviceisusedtodeterminewhetherornotafanisworking.Morecomplexversionscontrolthefanasafunctionofoneormoremeasuredtemperatures.Thesystemmonitorsensorisnotdiscussedherebutisbrieflymentionedtogiveacompletepictureofthetypesoftemperaturesensorsavailable.

Analog-OutputTemperatureSensors

Thermistorsandsilicontemperaturesensorsarewidelyusedformsofanalog-outputtemperaturesensors.Figure2clearlyshowsthatwhenalinearrelationshipbetweenvoltageandtemperatureisneeded,asilicontemperaturesensorisafarbetterchoicethanathermistor.Overanarrowtemperaturerange,however,thermistorscanprovidereasonablelinearityandgoodsensitivity.Manycircuitsoriginallyconstructedwiththermistorshaveovertimebeenupdatedusingsilicontemperaturesensors.

Figure2.Thelinearityofthermistorsandsilicontemperaturesensors,twopopularanalog-outputtemperaturedetectors,iscontrastedsharply.

Silicontemperaturesensorscomewithdifferentoutputscalesandoffsets.Some,forexample,areavailablewithoutputtransferfunctionsthatareproportionaltoK,othersto°Cor°F.Someofthe°Cpartsprovideanoffsetsothatnegativetemperaturescanbemonitoredusingasingle-endedsupply.

Inmostapplications,theoutputofthesedevicesisfedintoacomparatororanA/Dconvertertoconvertthetemperaturedataintoadigitalformat.Despitetheneedfortheseadditionaldevices,thermistorsandsilicontemperaturesensorscontinuetoenjoypopularityduetolowcostandconvenienceofuseinmanysituations.

DigitalI/OTemperatureSensors

Aboutfiveyearsago,anewtypeoftemperaturesensorwasintroduced.Thesedevicesincludeadigitalinterfacethatpermitscommunicationwithamicrocontroller.TheinterfaceisusuallyanI²CorSMBusserialbus,butotherserialinterfacessuchasSPIarecommon.Inadditiontoreportingtemperaturereadingstothemicrocontroller,theinterfacealsoreceivesinstructionsfromthemicrocontroller.Thoseinstructionsareoftentemperaturelimits,which,ifexceeded,activateadigitalsignalonthetemperaturesensorICthatinterruptsthemicrocontroller.Themicrocontrolleristhenabletoadjustfanspeedorbackoffthespeedofamicroprocessor,forexample,tokeeptemperatureundercontrol.

Thistypeofdeviceisavailablewithawidevarietyoffeatures,amongthem,remotetemperaturesensing.Toenableremotesensing,mosthigh-performanceCPUsincludeanon-chiptransistorthatprovidesavoltageanalogofthetemperature.（Onlyoneofthetransistor'stwop-njunctionsisused.）Figure3showsaremoteCPUbeingmonitoredusingthistechnique.Otherapplicationsutilizeadiscretetransistortoperformthesamefunction.

Figure3.Auser-programmabletemperaturesensormonitorsthetemperatureofaremoteCPU'son-chipp-njunction.

Anotherimportantfeaturefoundonsomeofthesetypesofsensors（includingthesensorshowninFigure3）istheabilitytointerruptamicrocontrollerwhenthemeasuredtemperaturefallsoutsidearangeboundedbyhighandlowlimits.Onothersensors,aninterruptisgeneratedwhenthemeasuredtemperatureexceedseitherahighoralowtemperaturethreshold（i.e.,notboth）.ForthesensorinFigure3,thoselimitsaretransmittedtothetemperaturesensorviatheSMBusinterface.Ifthetemperaturemovesaboveorbelowthecircumscribedrange,thealertsignalinterruptstheprocessor.

PicturedinFigure4isasimilardevice.Insteadofmonitoringonep-njunction,however,itmonitorsfourjunctionsanditsowninternaltemperature.BecauseMaxim'sMAX1668consumesasmallamountofpower,itsinternaltemperatureisclosetotheambienttemperature.Measuringtheambienttemperaturegivesanindicationastowhetherornotthesystemfanisoperatingproperly.

Figure4.Auser-programmabletemperaturesensormonitorsitsownlocaltemperatureandthetemperaturesoffourremotep-njunctions.

ControllingafanwhilemonitoringremotetemperatureisthechieffunctionoftheICshowninFigure5.Usersofthispartcanchoosebetweentwodifferentmodesoffancontrol.InthePWMmode,themicrocontrollercontrolsthefanspeedasafunctionofthemeasuredtemperaturebychangingthedutycycleofthesignalsenttothefan.Thispermitsthepowerconsumptiontobefarlessthanthatofthelinearmodeofcontrolthatthispartalsoprovides.BecausesomefansemitanaudiblesoundatthefrequencyofthePWMsignalcontrollingit,thelinearmodecanbeadvantageous,butatthepriceofhigherpowerconsumptionandadditionalcircuitry.Theaddedpowerconsumptionisasmallfractionofthepowerconsumedbytheentiresystem,though.

Figure5.Afancontroller/temperaturesensorICuseseitheraPWM-orlinear-modecontrolscheme.

ThisICprovidesthealertsignalthatinterruptsthemicrocontrollerwhenthetemperatureviolatesspecifiedlimits.Asafetyfeatureintheformofthesignalcalled"overt"（anabbreviatedversionof"overtemperature"）isalsoprovided.Ifthemicrocontrollerorthesoftwareweretolockupwhiletemperatureisrisingtoadangerouslevel,thealertsignalwouldnolongerbeuseful.However,overt,whichgoesactiveoncethetemperaturerisesabovealevelsetviatheSMBus,istypicallyusedtocontrolcircuitrywithouttheaidofthemicrocontroller.Thus,inthishigh-temperaturescenariowiththemicrocontrollernotfunctioning,overtcouldbeusedtoshutdownthesystempowersuppliesdirectly,withoutthemicrocontroller,andpreventapotentiallycatastrophicfailure.

ThisdigitalI/Oclassofdevicesfindswidespreaduseinservers,batterypacks,andhard-diskdrives.Temperatureismonitoredinnumerouslocationstoincreaseaserver'sreliability:

atthemotherboard（whichisessentiallytheambienttemperatureinsidethechassis）,insidetheCPUdie,andatotherheat-generatingcomponentssuchasgraphicsacceleratorsandhard-diskdrives.Batterypacksincorporatetemperaturesensorsforsafetyreasonsandtooptimizechargingprofiles,whichmaximizesbatterylife.

Therearetwogoodreasonsformonitoringthetemperatureofahard-diskdrive,whichdependsprimarilyonthespeedofthespindlemotorandtheambienttemperature:

Thereaderrorsinadriveincreaseattemperatureextremes,andaharddisk'sMTBFisimprovedsignificantlythroughtemperaturecontrol.Bymeasuringthetemperaturewithinthesystem,youcancontrolmotorspeedtooptimizereliabilityandperformance.Thedrivecanalsobeshutdown.Inhigh-endsystems,alertscanbegeneratedforthesystemadministratortoindicatetemperatureextremesorsituationswheredatalossispossible.

Analog-PlusTemperatureSensors

"Analog-plus"sensorsaregenerallysuitedtosimplermeasurementapplications.TheseICsgeneratealogicoutputderivedfromthemeasuredtemperatureandaredistinguishedfromdigitalI/Osensorsprimarilybecausetheyoutputdataonasingleline,asopposedtoaserialbus.