毕业设计文献翻译热电偶温度传感器

《毕业设计文献翻译热电偶温度传感器》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、ThermocoupleTemperatursensorIntroductiontoThermocouplesThethermocoupleisoneofthesimplestofallsensors.Itconsistsoftwowiresofdissimilarmetalsjoinednearthemeasurementpoint.Theoutputisasmallvoltagemeasuredbetweenthetwowires.Whileappealinglysimpleinconcept,thetheorybehindthethermocoupleissubtl

2、e,thebasicsofwhichneedtobeunderstoodforthemosteffectiveuseofthesensor.ThermocoupletheoryAthermocouplecircuithasatleasttwojunctions:themeasurementjunctionandareferencejunction.Typically,thereferencejunctioniscreatedwherethetwowiresconnecttothemeasuringdevice.Thissecondjunctionitisreallytwo

3、junctions:oneforeachofthetwowires,butbecausetheyareassumedtobeatthesametemperature(isothermal)theyareconsideredasone(thermal)junction.Itisthepointwherethemetalschange-fromthethermocouplemetalstowhatevermetalsareusedinthemeasuringdevice-typicallycopper.Theoutputvoltageisrelatedtothetempera

4、turedifferencebetweenthemeasurementandthereferencejunctions.ThisisphenomenaisknownastheSeebeckeffect.(SeetheThermocoupleCalculatortogetafeelforthemagnitudeoftheSeebeckvoltage).TheSeebeckeffectgeneratesasmallvoltagealongthelengthofawire,andisgreatestwherethetemperaturegradientisgreatest.If

5、thecircuitisofwireofidenticalmaterial,thentheywillgenerateidenticalbutoppositeSeebeckvoltageswhichwillcancel.However,ifthewiremetalsaredifferenttheSeebeckvoltageswillbedifferentandwillnotcancel.InpracticetheSeebeckvoltageismadeupoftwocomponents:thePeltiervoltagegeneratedatthejunctions,plu

6、stheThomsonvoltagegeneratedinthewiresbythetemperaturegradient.ThePeltiervoltageisproportionaltothetemperatureofeachjunctionwhiletheThomsonvoltageisproportionaltothesquareofthetemperaturedifferencebetweenthetwojunctions.ItistheThomsonvoltagethataccountsformostoftheobservedvoltageandnon-lin

7、earityinthermocoupleresponse.EachthermocoupletypehasitscharacteristicSeebeckvoltagecurve.Thecurveisdependentonthemetals,theirpurity,theirhomogeneityandtheircrystalstructure.Inthecaseofalloys,theratioofconstituentsandtheirdistributioninthewireisalsoimportant.Thesepot