Transcription of Temperature Sensor Interface Module for …
1 400 300 200 100 01002003004005006007008009001000 Error (SC) Temperature (SC) C002 Measure ADC Error in SC Target specification for -200SC to +850SC TI DesignsTemperatureSensorInterfaceModulef or ProgrammableLogicControllers(PLC)SPACERT I DesignsTI Designsprovidethe foundationthat you needDesignFeaturesincludingmethodology,t estingand designfiles to Two DifferentSensorInputChannels:quicklyeval uateand customizethe Designs K-TypeThermocoupleInputwith CJChelpyouaccelerateyourtime to market. Compatibleto 2-, 3-, or 4-WireRTDP robesDesignResources RatiometricMeasurementfor RTD MeasurementAccuracyfor Thermocouple 1 CToolFolderContainingDesignFilesTIDA-000 18 ADS1220 ProductFolder MeasurementAccuracyfor RTD CLM5017 ProductFolder SensorOpenCircuit/SignalOut-of-RangeDete ctionLM5069 ProductFolder DigitalIsolationfor I/O ControllerInterfaceISO7141 CCProductFolder 24 V 20%InputPowerSupplyOperationISO1540 ProductFolder IEC-61000-4-4:EFT Up to 1 KV at 5 KHz onTPS71533 ProductFolderSignalPortsTPS7A4901 ProductFolderTCA6408 AProductFolder IEC-61000-4-2.
2 ESDUp to 4-KVContactand 8-KVLM94022 ProductFolderAir DischargeLMP275 ProductFolder IEC-61000-4-5:SurgeUp to 1-KVLine-EarthTS5A23159 ProductFolder(CM)on SignalPortsSPACERF eaturedApplications ProgrammableLogicControllers FactoryAutomationand ProcessControlASKOur AnalogExperts PortableInstrumentationWebBench CalculatorTools DataAcquisitionSystems IndustrialRoboticsMeasuredErrorof RTDI nputacrossTemperatureRangeof -200 C to 850 CAll trademarksare the propertyof May 2014 TemperatureSensorInterfaceModulefor ProgrammableLogicControllers(PLC)SubmitD ocumentationFeedbackCopyright 2014,TexasInstrumentsIncorporatedDesignS pecificationsand IMPORTANTNOTICEat the end of this TI referencedesignaddressesauthorizeduse, intellectualpropertymattersand otherimportantdisclaimersand FeaturesTable1 showsthe designspecificationsof theTemperatureSensorInterfaceModulefor ProgrammableLogicControllers(PLC) FEATURESI nputsTwo channelsK-Typesthermocouple2-, 3-, and 4-wirePT100 RTDprobesSensorTypes(HardwaresupportsRTD swith resistanceup to 2 k , whereasexistingTIVAMCU softwareisimplementedfor PT100 RTDonly)For thermocouplechannel: C.
3 Overthe entireTC temperatureRange: 200 C toOverallMeasurementAccuracy1372 C(excludingsensorerrors)For RTDchannel: C; Overthe entireRTDtemperatureRange: 200 C to 850 CFor CResolutionFor CColdJunctionCompensationOn-boardlocalte mperaturesensorIC(CJC)TypeColdJunctionCo mpensation0 C to 60 CTemperatureRangeMeasurementTypeRatiomet ricfor RTDPT100 RTD( 200 C to 850 C) and Thermocouple( 200 C to 1372 C) lookuptablesSensorLinearInterpolationimp lementedin TIVA MCUsoftwareModuleCalibrationADC s offsetand gain calibrationPowerSupplyRange18 V to 32-VDCI solation250-VDC (Continuous),Basicisolation1500-VAC for one minuteESDI mmunityIEC 61000-4-2:4 kV contactdischarges,8 kV air dischargesEFT ImmunityIEC 61000-4-4: 1 kV at 5 kHz on signalportsSurgeTransientImmunityIEC 61000-4-5.
4 1 kV line-earth(CM)on signalportsOperatingTemperatureRange0 C to 60 CStorageTemperature 40 C to 85 CTemperature,SurroundingAir60 C50-pinconnectorpluggabletoPLCI/O ModuleFront-EndControllerUsinga Tiva C SeriesARM Cortex -M4 MCU(TIDU191)Connector(s)4-pinscrewtermin alblockfor 2-, 3-, and 4-wireRTDprobes2-pindedicatedK-typetherm ocoupleconnectorFormFactor(L x W) x (Smallindustrialformfactor)2 TemperatureSensorInterfaceModulefor ProgrammableLogicControllersTIDU271 May 2014(PLC)SubmitDocumentationFeedbackCopy right 2014, sole objectiveof this referencedesignis to focuson the completecircuitdesignguidelinesthat helpengineersand systemarchitectsto develophigh precisiontemperaturemeasurementsolutions using24-bit delta-sigmaADCand mostwidelyusedtemperaturesensorslike thermocouplesand ResistanceTemperatureDetectors(RTDs).
5 This referencedesignaddressessensorsignalcond itioning,thermocouplecold junctioncompensation,ratiometricmeasurem enttechniquefor RTDs,recommendedsoftwareflow,sensorlinea rization,sensordiagnostics,transientprot ection,PCBlayout,and otherpracticaldesignconsiderationsfor achievinghigh-precisionrobustdesignfor TemperatureSensorInterfaceModuleis a fully isolateddesignwhichis essentialfor signalchainand powerline galvanicisolationbarrierbetweenthe host controllerside and the measurementside havebeenachievedusingdigitalisolatorsand a flybacktransformer, heartof this referencedesignis the ADS1220device,a 24-bitdelta-sigmaADC,whichprovidesa high resolution,high integration,low noise,and low cost completesensoranalogfront-endforDC designis also suitableto interfacewith differenttypesof boardspace,reducesdesignefforts,reducest ime to market,and demonstratesotherTI products,suchas hot swapand in-rushcurrentlimitcontroller,isolatedFl y-Buck controller,low noiseLDO,digitalisolators,localtemperatu resensors,analogswitchand I2C to GPIO expanderthat can be usedin the ,externalprotectioncircuitryis circuitryhas beensuccessfullytestedand verifiedfor compliancewith regulatoryIEC61000-4standards.
6 EFT,ESD,and standardIEC61000-4is necessaryto ensurethat the designnot only survivesbutalso performsas intendedin harshor the relevantdesignfiles like Schematics,BOM,LayerPlots,AltiumFiles,Ge rber,and TIVA C-SeriesMCUsoftwareare executablewith an easy-to-useGraphicalUserInterface(GUI).U sersmay downloadthe files at BlockDiagramof TemperatureSensorInterfaceModulefor PLC3 TIDU271 May 2014 TemperatureSensorInterfaceModulefor ProgrammableLogicControllers(PLC)SubmitD ocumentationFeedbackCopyright 2014, TemperatureSensorInterfaceModuleprovides two differentialinputchannelsto take measurementsfromtwo channelsupports2-, 3-, and designusesa singleADS122024-bitdelta-sigmaADCwithan externalTS5A23159dual channel2 x 1 multiplexerswitchesthe twodifferentialanaloginputsto sharethe host controllercommunicateswith TCA6408A- I2 Cto the GPIO expanderoveran I2C bus, crossingthe isolationbarriervia the routeone of the two inputsto the inputchannelselectionis donein signalcomingin or goingout of the moduleis protectedagainsthigh voltagefast transientevents.
7 Whichare oftenexpectedin protectioncircuitrymakesuse of TVSand temperaturesensors(especiallythermocoupl es)produceoutputin the millivoltrange,whichmakessensorsproneto RC low-passdifferentialand commonmodefiltersare usedon eachanaloginputbeforeit reachesthe filterseffectivelyeliminatesany high frequencynoisepickupwhichmay be designprovidestwo localtemperaturesensorICs to sensethe cold junction(or referencejunction) a multi-gainanalogoutputtype temperaturesensorfed to ADS1220afterpassingthrougha low passfilter and one additionalTS5A23159dual channel2 x 1 is the TMP275,whichis a two-wiredigitaloutputtemperaturesensordi rectlyinterfacedto the I2C datareadysignal(DRDY)fromADS1220reportst he conversionstatus,whichconnectsto the GPIOpin of TCA6408A,configuredas convertedsensordata,the host controllerpollsfor the datareadystatuslatchedinsidethe inputport registerof TCA6408 Aoverthe I2C ProgrammableLogicControllersTIDU271 May 2014(PLC)
8 SubmitDocumentationFeedbackCopyright 2014, Operation5 Theoryof OperationTemperatureis one of the the mostessentialfactorthatneedscontinuousme asurement,monitoring,and controlin variousprocessesin ,industrydemandsaccurate,repeatable,and reliablemeasurementof Temperature ,becausetemperaturecan havesignificantimpacton productcost,quality,efficiencyand temperaturesensorsmeasuretemperatureby sensingsomechangein materialphysicalcharacteristicsas a functionof availablein a widevarietysuchas: Thermocouple ResistanceTemperatureDetector(RTD) Thermistor SemiconductorTemperatureSensorICTable2. Comparisonof DifferentTemperatureSensorsRESISTANCESEM ICONDUCTORTHERMOCOUPLETEMPERATURETHERMIS TORTEMPERATUREDETECTOR(RTD)SENSORICR ange 270 C to 2000 C 200 C to 850 C 50 C to 300 C 55 C to 200 CChangingPhysicalVoltageResistanceResist anceVoltageor currentCharacteristicExcitationSelf-powe redCurrentexcitationCurrentexcitationPow erSupply( A)CostLowHighLow to moderateLowResponseMediumto fastMediumMediumto fastMediumto fastAccuracyLessBestGoodBetterRepeatabil ityReasonableExcellentFair to GoodGoodto excellentVeryhigh (CanwithstandRuggednessLessHighMediumhig h shockand vibration)
9 Amplification,Filtering,ColdLeadCompensa tion,Powersupply,Self-SpecialRequirement sjunctioncompensation,LinearizationFilte ringcontainedLinearizationLow (40 V per C for K-Sensitivityat 20 CMediumVeryhighHigh(Typically10 mV/ C)Type)Self-HeatingNoVerylow to lowHighVerylow to lowLeadWireResistanceNot a problemProblematicNot a problemNot a problemInterchangeabilityGoodExcellentPo orto fairBetterStableoverlong period; CPoorGoodper yearNoiseSusceptibilityHighMediumLowMedi umLinearityFairGoodPoor(Logarithmic)Good Smallto mediumbut limitedSizeSmallto largeMediumto smallSmallto mediumpackagechoicesAmongdifferenttypeso f temperaturesensors,the mostfrequentlyusedonesin industrialapplicationsarethermocouplesan d resistancetemperaturedetectors(RTDs).
10 5 TIDU271 May 2014 TemperatureSensorInterfaceModulefor ProgrammableLogicControllers(PLC)SubmitD ocumentationFeedbackCopyright 2014,TexasInstrumentsIncorporated5 V5 2F5 2 FCDIFCCM2 CCM1RF1RF2RB1RB2 Low Drift OscillatorReference MuxPrecision Temp SensorAIN0 AIN1 AIN2 AIN3 SCLKCSAVDDAVSSDOUT/DRDYDIND eviceDRDYDGNDREFP0 REFN0 Internal ReferenceCLK10 A mAMuxDVDDPGA24-bit ADCD igital Filter and SPI InterfaceTheoryof ThermocoupleMeasurementCircuitUsingADS12 206 TemperatureSensorInterfaceModulefor ProgrammableLogicControllersTIDU271 May 2014(PLC)SubmitDocumentationFeedbackCopy right 2014,TexasInstrumentsIncorporated()HOTCO LDVSTTD = Backto Basics NOTE:Any conductorsubjectedto thermalgradientwill generatea voltagebetweenits simplemetalbar producesa voltagewhenthereis a temperaturedifferencebetweenthe two the hot end are morethermallyagitatedthanthe electronsat the morethermallyagitatedelectronson the hot end beginto diffusetowardsthe redistributionofelectronscreatesa negativechargeat the coolerend and an equalpositivechargeat the electrostaticvoltagebetweenthe two opencircuitvoltageproducedin thisway is knownas SeebeckVoltage.