文献翻译——湿度传感器

第1页外文文献资料Soilhumiditysensor1.Sensorintroduction1.1.HumiditysensorbackgroundInmanyindustries,suchaspowergeneration,textile,food,medicine,storage,agricultureandsoon,areverystricttotherequirementoftemperatureandhumidityparameter.Atpresent,undertheconditionoflowtemperature(usuallyreferstounder100oc),humiditymeasurementhasbeenrelativelymature,therearecommercialproducts,andiswidelyusedinvariousindustries.Manyindustryneedsundertheenvironmentofhightemperaturehumiditymeasurement,suchasaerospace,ships,locomotivepowersubstation,metallurgy,mining,measurementofscientificresearch,powerplants,ceramics,industrialpiping,fermentationenvironmentexperimentbox,hightemperatureexperimentbox,blastfurnace,etc.Atthistime,thehumiditymeasurementsareoftennotidealmeasurementresultsaslowtemperatureenvironment.Inaddition,workinharshconditions,suchasairvelocity,temperature,humiditychangesharplyormeasuringpollutedindustrialgases,willmaketheprecisionisgreatlyreduced.Degreeofdrywetairhumidity,commonlyusedabsolutehumidityandrelativehumidity,comparativehumidity,mixingratio,poorsaturatedanddewpointtorepresentthephysicalquantities.Usually,thehigherthetemperatureoftheair,thegreaterthemaximumhumidity.Relativehumidityistheratioofabsolutehumidityandhighhumidity,watervaporsaturation.Theairrelativehumidityis100%iswatervapoursaturatedair.Relativehumidityisalsolinkedwiththetemperature.Throughtherelativehumidityandtemperaturecanalsorepresenttemperatureconversionofotherparameters.Relativehumiditycalculationisasfollows:Typeofabsolutehumidity,theunitg/m3;Max-highhumidity,theunit第2页g/m3;E-saturatedvaporpressureofunitPa;S-humidityratio,unitg/kg;S-thehighesthumidityratio,unitofg/kg.Thesamegoesfortheother.Earlyhumiditymeasurementusuallyusepsychrometerandhairhygrometer.Theformerwaterevaporationistheprincipletoheatandcooling,andspeedofevaporation(cooling)andthentherelativehumidityoftheair,soimmersedintwothermometerinthewetbulbisexpressedwiththemoisturerelatedtothetemperaturedifference.Thelatterprincipleisskimhairscalechangewithrelativehumidityvalue,connectedtothehairofpointercanindicateonthedialairrelativehumidityvalue.Absolutehumidityisacertainvolumeofwatervaporintheair,thequalityoftheunitisg/m3,itisthelimitsofthesaturatedstateofhighhumidity.Absolutehumidityisonlymeaningfulwithtemperature,becauseofthechangeswiththetemperatureandhumidityintheair.FormulaforcalculatingabsolutehumidityTypeofe-vaporpressure,theunitPa;-watergasconstantis461.52J/(kgK);T-temperature,theunitK;M-thequalityoftheairdissolvedinwater,unitg;V-volumeofair,theunitm3.1.2.thedevelopmentofthehumiditysensorEarlyhumiditymeasurementusuallyusepsychrometerandhairhygrometer.Withtheprogressofscienceandtechnology,withpsychrometerorhairmoisturemetertomeasurethehumiditymethod,alreadycouldnotsatisfytheneedsofthedevelopmentofmodernscienceandtechnology.Thisisbecausethemeasurementofhumidityaremuchmorecomplexthanthemeasuredtemperature,thetemperatureisaindependentismeasured,andthehumidityisaffectedbyotherfactors(atmosphericpressure,temperature).Inaddition,thestandardofhumidityisalsoaproblem.Foreignproductionofhumiditycalibrationequipmentisveryexpensive.Inrecentyears,bothathomeandabroadhasmadegreatprogressinthefieldofresearchanddevelopmentofhumiditysensor.Moisturesensorisfromsimplemoisturesensortointegration,intelligent,thedirectionoftherapiddevelopmentofmulti-parameterdetection,forthedevelopmentofanewgenerationofhumidity/temperaturemeasurementandcontrolsystemhascreated第3页favorableconditions,andtoincreasethehumiditymeasurementtechnologytoanewlevel.1.3.ThetypesofhumiditysensorMoisturesensoristhemostsimplehumiditysensor,moisturesensormainlyhastwotypes:resistiveandcapacitive.Thecharacteristicsofthehumiditysensitiveresistorisinthesubstrateiscoveredalayerofmembranemadewithasenseofwetmaterials.Whentheadsorptionofwatervapourintheairinthesenseofwetfilm,resistivityandresistanceofcomponentsarechanging.Usethisfeaturetomeasurehumidity.Manydifferentkindsofhumiditysensitiveresistor,suchasmetaloxidehumiditysensitiveresistor,siliconhumiditysensitiveresistor,ceramichumidity-sensitiveresistance,etc.,humiditysensitiveresistoristheadvantageofhighsensitivity,maindrawbackisthatlinearityandpoorcompatibilityoftheproduct.Humidity-sensitivecapacitanceiscommonlymadeofpolymerfilmcapacitance,thecommonlyusedpolymermaterialssuchaspolystyrene,polyimide,butyricacid,aceticacidfiber.Whentheenvironmenthumiditychange,humidity-sensitivecapacitanceofthedielectricconstantchange,makeitscapacitancealsoproduceschange,thecapacitancevariationisproportionaltotherelativehumidity.Mainadvantageofhumidity-sensitivecapacitanceishighsensitivity,goodproductcompatibility,fastresponsespeed,smallamountofhumidityhysteresis,easytomanufacture,easytorealizeminiaturizationandintegration,itsprecisionloweraveragespecifichumiditysensitiveresistor.2.thesoilhumidityconceptisintroducedandtestingmethodSoilmoistureaccordingtocertaindepthsoilofwetsoil,degreeofphysicalquantities.Alsoknownasthesoilwatercontent.Soilmoistureoftherestrictionofthefarmlandwaterbalanceeachcomponent.Soilmoistureonagrometeorologicaloftenadoptthefollowingmethodswiththeunitsaid:第4页1)weightpercent.Theweightofthesoilwaterpercentage(%)ofdrysoilweight.Thismethodappliedwidely,butwithdifferentsoiltype,soilmoistureofthesamesoilmoistureeffectivenessisdifferent,isnotconvenienttocomparebetweendifferentsoil.(2)Thepercentageoffieldcapacity.Thesoilmoistureofthesoilfieldcapacitypercentage(%).Forcomparisonsindifferentsoils,theconceptofwaterbutnotspecific.(3)Soilwaterstoragecapacity.Referstoacertaindepthofsoillayerintheabsolutenumberofwater,ofteninmillimeters,facilitatecomparedwithprecipitationandevaporation.SoilmoisturestoragecapacityW(mm)calculationformulais:W=0.1,h.d.W.Htypeisthesoillayerthickness,dforthesoilbulkdensity(g/cm3),0.1isunitconversionfactor,wforsoilmoisture(weightpercentage).Soilwaterpotentialandwaterpotentialisexpressedintheenergyofsoilwatercontent.Theunitforatmosphericpressureorfocalpergram.Forconvenientuse,desirablevalueofcommonlogarithm,abbreviatedsymbolforpF,knownasthepFvalueofthesoilwater.Methodofmeasurement(1)Theweightmethod.Tubesampledrying,weighingdrysoilweightandwetweightcalculation.(2)Theresistancemethod.Usingresistancetypesoilmoisturemeter.Accordingtotheconductivityofsoilsolutionandthedeterminationoftherelationshipbetweensoilmoisturecontentsoilmoisture.(3)Negativepressuremetermethod.Usingnegativepressuremeter.Whenthenegativeinunsaturatedsoilsuctionforceandpressurebalance,pressuregaugeasshowninthenegativepressureisthesoilsuctionforce,thenaccordingtoinordertocalculatesoilwatercontent.(4)Neutronmethod.Usingtheneutrondetectorsaredetermined.3.ResistancetypesoilmoisturesystemimplementationandrelatedtechnologyAstheglobalwatershortage,especiallytheshortageoffreshwater第5页resourcesinourcountry,alongwithourcountrysagriculturalpower,inveryhightotherequirementoftherain,nowmanyscientistsdevotedtohumiditysensorinordertoachievetheeffectofagriculturalwatersaving.3.1.TherealizationofthesystemSystemismainlycomposedofsinglechipmicrocomputermodule,humiditydetectionmodule,displaymodule,A/Dconversionmoduleandpowermodule.Insingle-chipmicrocomputermeasurementandcontrolsystemcomposedofthemeasurementandcontrolparameterissometimessomecontinuousvariationofnon-electricityanalogsignal,suchastemperature,humidity,pressure,etc.Thesesignalsmustbeconvertedintoelectricalsignalsthroughthesensor,thenconvertedintodigitalsignalbyA/Dconverterintosinglechipmicrocomputerforprocessing,finallycompletehumidityvaluethroughtheLCDdisplay.4.YL-69LM393insoilhumiditysensorisintroduced4.1.TheLM393isdualvoltagecomparatorintegratedcircuit.Thecharacteristicsofthecircuitisasfollows:Workwiderangeofsupplyvoltage,andsinglepowersupply,powersupplycanwork,singlepowersupply:236v,dualpowersupply:+1+18v.Currentconsumptionissmall,theIcc=0.8mA.Inputoffsetvoltageissmall,theVIO=+2mv;Common-modeinputvoltagerangewide,Vic=0Vcc-1.5V.OutputandTTL,DTL,MOSandCMOScompatible;Withopencollectoroutputcanbeconnectedordoor;Usingdualin8pinplasticpackage(DIP8)andmicroshapeofdoublerow8feetplasticpackage(SOP8)newartgallery第6页Figure4-1LM393internalstructure第7页Application:LM393ishighgain,wideband,likemostofthecomparator,iftheoutputtotheinputparasiticcapacitancecoupling,itseasytogenerateoscillation.Thiskindofphenomenontoappearonlywhenthecomparatorchangestate,theclearancebetweentheoutputvoltagetransition.Thepowerandthebypassfilterdoesnotsolvethisproblem,astandardPCboarddesigntoreducetheinput-outputparasiticcapacitancecouplingishelpful.Reducetheinputresistancetolessthan10kwillreducethefeedbacksignal,andincreaseevenasmallamountofpositivefeedback(1.010mvhysteresis)canleadtorapidtransformation,whichiscausedbytheparasiticcapacitanceoscillationmaybeproduced.Unlessusinglag,ordirectlyinsertICandapinwithresistancewillcausetheinput-outputinashortperiodoscillationoftheconversion,iftheinputsignalisthepulsewaveform,andtherisingandfallingtimefairlyquickly,thehysteresiswillnotneed.Thecomparatoralluselesspinsmustbegrounded.LM393offsetnetworkestablisheditsstaticcurrenthasnothingtodowiththepowersupplyvoltagerangefrom30vto2.0v.Usuallypowerdoesnotneedtoaddthebypasscapacitor.DifferentialinputvoltagecanbegreaterthantheVccdoesnotdamagethedevice.Protectpartmustbeabletopreventtheinputvoltagetothenegativesidemorethan0.3v.LM393,theoutputofthepartisopencollectoremitterNPNtransistoroutputofground,canprovideorfunctionswithmultiplecollectoroutput.Theoutputloadresistorcanjoininallowinganysupplyvoltage,supplyvoltagerangeisnotlimitedbyvoltageoftheVccvalue.TheoutputcanbeusedasasimpleofSPSopencircuit(whennoloadresistanceisnotused),thesinkcurrentoutputsarelikelytogetthedriveandthedeviceislimitedbybeta.Whenthelimitingcurrent16(ma),theoutputtransistorwillexitandtheoutputvoltagewillrisesoon.Outputsaturationvoltageisoutputtransistorisabout60ohmgammaSATlimit.Whenloadcurrentisverysmall,lowoffsetvoltageoftheoutputtransistor(about1.0mV)allowstheoutputclamptozerolevel.第8页中文翻译稿湿度传感器1.传感器的介绍1.1.湿度传感器的背景很多行业中，如发电、纺织、食品、医药、仓储、农业等，对温度、湿度参量的要求都非常严格。目前，在低温条件下(通常指100oC以下)，湿度的测量已经相对成熟，有商品化产品，并广泛应用于各种行业。另有许多行业需要在高温环境下测量湿度，如航空航天、机车舰船、发电变电、冶金矿山、计量科研、电厂、陶瓷、工业管道、发酵环境实验箱、高温实验箱、高炉等场合。这时，湿度测量结果往往不如低温环境下的测量结果理想。另外，在恶劣条件下工作，例如气流速度、温度、湿度变化非常剧烈或测量污染严重的工业气体时，将使精度大大降低。空气的干湿程度叫做湿度，常用绝对湿度、相对湿度、比较湿度、混合比、饱和差以及露点等物理量来表示。通常空气的温度越高，最大湿度就越大。相对湿度是绝对湿度与最高湿度的比值，表示水蒸气的饱和度。相对湿度为100的空气就是水蒸气饱和的空气。相对湿度同样也与温度联系起来才有意义。通过相对湿度和温度也可以换算出表示温度的其他参数。相对湿度计算如下：%10e%10maxwSsE，式中-绝对湿度，单位g/m3；，max-最高湿度，单位g/m3；E-饱和蒸汽压，单RR位Pa；s-比湿，单位g/kg；S-最高比湿，单位g/kg。其他同上。早期的湿度测量通常用干湿球湿度计和毛发湿度计。前者原理是水蒸发要吸热降温，而蒸发的快慢(即降温的多少)和当时空气的相对湿度有关，这样浸在于湿球内的两支温度计就表示出与湿度相关的温度差。后者原理是脱脂毛发的伸缩随相对湿度值变化，与毛发相连的指针便可在刻度盘上指示空气相对湿度值。绝对湿度是一定体积的空气中含有的水蒸气的质量，单位是g/m3，它的极限是饱和状态下的最高湿度。绝对湿度只有与温度联系起来才有意义，因为空气中湿度随温度而变化。计算绝对湿度的公式为第9页VmTRe式中e-蒸汽压，单位Pa；-水的气体常数为46152J/(kgK)；T-温度，单位RK；m-空气中溶解的水的质量，单位g；V-空气的体积，单位m3。1.2.湿度传感器的发展早期的湿度测量通常用干湿球湿度计和毛发湿度计。随着科技的进步，用干湿球湿度计或毛发湿度计来测量湿度的方法，早已无法满足现代科技发展的需要。这是因为测量湿度要比测量温度复杂的多，温度是个独立的被测量，而湿度却受其他因素(大气压强、温度)的影响。此外，湿度的标准也是一个难题。国外生产的湿度标定设备价格十分昂贵。近年来，国内外在湿度传感器研发领域取得了长足进步。湿敏传感器正从简单的湿敏元件向集成化、智能化、多参数检测的方向迅速发展，为开发新一代湿度/温度测控系统创造了有利条件，也将湿度测量技术提高到新的水平。1.3.湿度传感器的种类湿敏元件是最简单的湿度传感器，湿敏元件主要有电阻式和电容式两大类。湿敏电阻的特点是在基片上覆盖一层用感湿材料制成的膜。当空气中的水蒸气吸附在感湿膜上时，元件的电阻率和电阻值都发生变化。利用这一特性即可测量湿度。湿敏电阻的种类很多，例如金属氧化物湿敏电阻、硅湿敏电阻、陶瓷湿敏电阻等，湿敏电阻的优点是灵敏度高，主要缺点是线性度和产品的互换性差。湿敏电容一般是用高分子薄膜电容制成的，常用的高分子材料有聚苯乙烯、聚酰亚胺、酪酸醋酸纤维等。当环境湿度发生改变时，湿敏电容的介电常数发生变化，使其电容量也发生变化，其电容变化量与相对湿度成正比。湿敏电容的主要优点是灵敏度高、产品互换性好、响应速度快、湿度的滞后量小、便于制造、容易实现小型化和集成化，其精度一般比湿敏电阻要低一些。2.土壤湿度概念介绍和测试方法土壤湿度表示一定深度土层的土壤干湿程度的物理量。又称土壤水分含量。土壤湿度的高低受农田水分平衡各个分量的制约。农业气象上土壤湿度常采用下列方法与单位表示：重量百分数。即土壤水的重量占其干土重的百分数(%)。此法应用普遍，但土壤类型不同，相同的土壤湿度其土壤水分的有效性不同，不便于在不同土壤间进行比较。第10页田间持水量百分数。即土壤湿度占该类土壤田间持水量的百分数(%)。利于在不同土壤间进行比较，但不能给出具体水量的概念。土壤水分贮存量。指一定深度的土层中含水的绝对数量，通常以毫米为单位，便于与降水量、蒸发量比较。土壤水分贮存量W（毫米）的计算公式为:W=0.1hdw。式中h是土层厚度，d为土壤容重（克/厘米3）,0.1是单位换算系数，w为土壤湿度（重量百分数）。土壤水势或水分势是用能量表示的土壤水分含量。其单位为大气压或焦/克。为了方便使用，可取数值的普通对数，缩写符号为pF，称为土壤水的pF值。测量方法重量法。取土样烘干，称量其干土重和含水重加以计算。电阻法。使用电阻式土壤湿度测定仪测定。根据土壤溶液的电导性与土壤水分