檢測(cè)技術(shù)與過控fundamentals of sensors and detection膨脹式溫度計(jì)

傳感器與檢測(cè)基礎(chǔ)FundamentalsofSensorsandDetection信息與控制工程學(xué)院Temperature

Measurement溫度測(cè)量Slide206信息與控制工程學(xué)院Slide3信息與控制工程學(xué)院TemperatureMeasurementExpansionthermometer（膨脹式溫度計(jì)）

1.1Liquid-in-GlassThermometerSlide4信息與控制工程學(xué)院TemperatureMeasurement1.1Liquid-in-GlassThermometerTheliquid-in-glassthermometerisawell-knowntemperature-measuringinstrumentusedinawiderangeofapplications.Thefluidusedisnormallyeithermercuryorcoloredalcohol,whichiscontainedwithinabulbandcapillarytube.Asthetemperaturerises,thefluidexpandsalongthecapillarytubeandthemeniscuslevelisreadagainstacalibratedscaleetchedonthetube.Expansionthermometer（膨脹式溫度計(jì)）

Slide5信息與控制工程學(xué)院TemperatureMeasurement1.1Liquid-in-GlassThermometer（玻璃管液體溫度計(jì)）Linearexpansionofamaterialisthechangeinlineardimensionduetotemperaturechanges.VolumeexpansioninamaterialduetochangesintemperatureisgivenbyV2=V1[1+b(T2?T1)]whereV2=finalvolumeV1=initialvolumeb=coefficientofvolumetricthermalexpansionT2=finaltemperatureT1=initialtemperatureExpansionthermometer（膨脹式溫度計(jì)）

Slide6信息與控制工程學(xué)院TemperatureMeasurement1.1Liquid-in-GlassThermometerusedinawiderangeofapplications.Thefluidusedisnormallyeithermercuryorcoloredalcohol,whichiscontainedwithinabulbandcapillarytube.Asthetemperaturerises,thefluidexpandsalongthecapillarytubeandthemeniscuslevelisreadagainstacalibratedscaleetchedonthetube.Commonlyscanfrom-200to600°CIndustrialversionsoftheliquid-in-glassthermometerarenormallyusedtomeasuretemperatureintherangebetween-200and1000°CExpansionthermometer（膨脹式溫度計(jì)）

Slide7信息與控制工程學(xué)院TemperatureMeasurement1.1Liquid-in-GlassThermometerMeasurementinaccuracyistypically1%offull-scalereading,althoughaninaccuracyofonly0.15%canbeachievedinthebestindustrialinstruments.Themajorsourceofmeasurementerrorarisesfromthedifficultyofcorrectlyestimatingthepositionofthecurvedmeniscusofthefluidagainstthescale.Expansionthermometer（膨脹式溫度計(jì)）

優(yōu)點(diǎn)：簡(jiǎn)單，精度高，便宜

缺點(diǎn)：讀數(shù)不便；玻璃易碎；不能遠(yuǎn)傳，常用于實(shí)驗(yàn)室

Slide8信息與控制工程學(xué)院TemperatureMeasurement1.2Pressurethermometer（壓力式溫度計(jì)）Expansionthermometer（膨脹式溫度計(jì)）

Slide9信息與控制工程學(xué)院TemperatureMeasurementusedwhereremoteindicationisrequiredThepressure-springdevicehasametalbulbmadewithalowcoefficientofexpansionmaterialwithalongmetaltube,bothcontainmaterialwithahighcoefficientofexpansion;thebulbisatthemonitoringpoint.ThemetaltubeisterminatedwithaspiralBourdontubepressuregage(scaleindegrees)Expansionthermometer（膨脹式溫度計(jì)）

1.2Pressurethermometer（壓力式溫度計(jì)）溫包bulb毛細(xì)管capillary彈簧管bourdonspring封閉系統(tǒng)Slide10信息與控制工程學(xué)院TemperatureMeasurementAsthetemperatureinthebulbincreases,thepressureinthesystemrises,thepressurerisebeingproportionaltothetemperaturechange.ThechangeinpressureissensedbytheBourdontubeandconvertedtoatemperaturescale.canbeaccurateto0.5percentandusedforremoteindicationupto100mbutmustbecalibrated,asthestemandBourdontubearetemperaturesensitive.Expansionthermometer（膨脹式溫度計(jì)）

1.2Pressurethermometer（壓力式溫度計(jì)）Slide11信息與控制工程學(xué)院TemperatureMeasurementthreetypesorclassesofpressure-springdevicesClass1:LiquidfilledClass2:VaporpressureClass3:GasfilledLiquidfilledthermometerworksonthesameprincipleastheliquidinglassthermometer,butisusedtodriveaBourdontube.Thedevicehasgoodlinearityandaccuracyandcanbeusedupto550°C.（體積膨脹）Expansionthermometer（膨脹式溫度計(jì)）

1.2Pressurethermometer（壓力式溫度計(jì)）感溫介質(zhì)：液體（水銀或有機(jī)液體）氣體（氮?dú)?、氫氣）蒸汽（低沸點(diǎn)丙酮、乙醚）Slide12信息與控制工程學(xué)院TemperatureMeasurementVapor-pressurethermometersystemispartiallyfilledwithliquidandvaporsuchasmethylchloride,ethylalcohol,ether,toluene,andsoon.InthissystemthelowestoperatingtemperaturemustbeabovetheboilingpointoftheliquidGasthermometergivesalinearrelationshipbetweenabsolutetemperatureandpressureExpansionthermometer（膨脹式溫度計(jì)）

1.2Pressurethermometer（壓力式溫度計(jì)）PV/T=C特點(diǎn)：有限遠(yuǎn)傳指示，精度低，受環(huán)境溫度影響大Slide13信息與控制工程學(xué)院TemperatureMeasurement1.3Bimetallicthermometer（雙金屬溫度計(jì)）Expansionthermometer（膨脹式溫度計(jì)）

Slide14信息與控制工程學(xué)院TemperatureMeasurementcommonlyusedinthermostatsasaswitch(ON/OFF)incontrolapplicationsoperateontheprinciplethatmetalsarepliableanddifferentmetalshavedifferentcoefficients

ofexpansion.（膨脹系數(shù)）Iftwostripsofdissimilarmetalssuchasbrassandinvar(copper-nickelalloy)arejoinedtogetheralongtheirlength,theywillflextoformanarcasthetemperaturechangesExpansionthermometer（膨脹式溫度計(jì)）

1.3Bimetallicthermometer（雙金屬溫度計(jì)）

由兩種膨脹系數(shù)不同的金屬片疊焊在一起，一端固定，另一端自由。溫度t↑膨脹系數(shù)大的伸長多向膨系小的彎曲

彎曲程度與溫度成比例x—雙金屬片自由端的位移；l—雙金屬片的長度；d—雙金屬片的厚度；Δt—雙金屬片的溫度變化量；G—彎曲率Slide15信息與控制工程學(xué)院TemperatureMeasurementinaccurate,slowtorespond,notnormallyusedinanalogapplicationstogiveremoteindication,andhashystersis.Theiroperatingrangeisfrom?180to430°Candcanbeusedinapplicationsfromoventhermometerstohomeandindustrialcontrolthermostats.Expansionthermometer（膨脹式溫度計(jì)）

1.3Bimetallicthermometer（雙金屬溫度計(jì)）特點(diǎn)：就地指示，精度低，應(yīng)用廣泛Slide16信息與控制工程學(xué)院TemperatureMeasurementExpansionthe