《傳感器技術(shù)與應(yīng)用》課件第六章熱電式傳感器

《傳感器技術(shù)與應(yīng)用》課件第六章熱電式傳感器熱電式傳感器是一種常用的溫度傳感器，利用兩個不同金屬的熱電勢差隨溫度的變化而變化。本章將介紹熱電式傳感器的原理、類型、優(yōu)缺點(diǎn)和應(yīng)用，以及相關(guān)測量技術(shù)、誤差和校準(zhǔn)方法。ThermoelectricPrinciple1SeebeckEffectWhentwodifferentmetalsarejoinedtogether,atemperaturedifferencebetweenthetwojunctionscreatesanelectromotiveforce(EMF)inthecircuit.2PeltierEffectWhenacurrentflowsthroughajunctionoftwodifferentconductors,heatisabsorbedorreleaseddependingonthedirectionofthecurrent.3ThomsonEffectWhenatemperaturegradientexistsalongaconductor,acurrentisgeneratedinthedirectionperpendiculartoboththetemperaturegradientandthedirectionofcurrentflow.TypesofThermocouplesNobleMetalThermocouplesArethemostaccurateandstable,andareusedinhigh-temperatureapplicationssuchasfurnaces,ovens,andkilns.BaseMetalThermocouplesArecheaperandhaveawidertemperaturerange,butarelessstableandaccurate.Theyareusedinprocesscontrol,HVAC,andotherindustrialapplications.SinteredMetalThermocouplesAremadebycompressingmetalpowdersintoaspecificshape.Theyhavefastresponsetimesandareusedinhigh-temperatureandhigh-pressureenvironments.DesignandConstructionofRTDsMaterialPlatinumisthemostcommonmaterialusedinRTDsduetoitsstabilityandrepeatability.ConstructionRTDsconsistofalong,thinwirewoundaroundaceramiccore.Thewire'sresistancechangeswithtemperature.ApplicationsRTDsareusedinprecisetemperaturemeasurementapplicationssuchaslabequipment,medicaldevices,andaerospacetechnology.TypesofThermistors1NegativeTemperatureCoefficient(NTC)Theresistancedecreasesasthetemperatureincreases.Theyareusedinautomotive,homeappliance,andHVACapplications.2PositiveTemperatureCoefficient(PTC)Theresistanceincreasesasthetemperatureincreases.Theyareusedintemperaturesensors,heatingelements,andmotoroverheatprotection.InfraredTemperatureSensorsThermopileSensorsArecomprisedofmultiplethermocoupleswhichdetecttheinfraredradiationemittedbyanobjectandconvertitintoatemperaturereading.PYROMETERSUseasinglethermocoupletomeasurethetemperatureofanobjectbycomparingthetemperaturesattwodifferentwavelengths.TypesofPyrometersOpticalPyrometerMeasuresthetemperatureofveryhotobjectsthroughitscolor,orspectralradiationintensity.InfraredPyrometerMeasuresthetemperatureofhotobjectsbydetectingtheinfraredradiationtheyemit.Thermo-LuminescentRadiationPyrometerMeasuresthetemperatureofobjectsbydetectingthelighttheyemitwhenheated.ApplicationsofThermocouples1IndustrialSettingsUsedinindustrialprocessessuchaschemicalprocessing,oilandgasrefining,andpowergenerationfortemperaturemonitoringandcontrol.2FoodIndustryUsedfortemperaturemonitori