测控技术与仪器专业英语课后阅读翻译

第五章课后Arandomerrorisduetoacontrolled，largenumberofindependentsmalleffectsthatcannotheidentifiedoritisastatisticalquantity.Assuch，iteachreplicationoftheobservations.Ifalargenumberofreadingsiswillvaryforthesamequantity.thescatterofthedataaboutameanvaluecanbeevaluated.Thescattergenerallyfollowsaguassiandistributionaboutameanvalue.whichisassumedtobethetruevalue.Accuracyisthedeviationoftheoutputfromthecalibrationinputorthetruevalue.Iftheaccuracyofavoltmeteris2%fullscaleasdescribedintheprecedingsection·themaximumdeviationi、士2unitsforallreadings.一个随机误差是由于控制,大量的独立影响小,不能他发现或这是一个统计量。因此,它每个复制的观察。如果大量的读数是同样数量的不同而不同。散射的数据值可以评估。散高斯分布通常遵循关于意味着value.which被认为是真正的价值。准确性是偏差的输出的输入或真正的校准价值。如果把电压表的准确性2%全面描述在前面的部分·最大偏差我,士2units所有阅读资料。第五章.NoncontactTemperatureMeasurementAnyobjectatanytemperatureaboveabsolutezeroradiatesenergy.Thisradiationvariesbothinintensityandinspectraldistributionwithtemperature.Hence.temperaturemaybededucedbymeasuringeithertheintensityorthespectrumoftheradiation.Thetotalenergydensityradiatingfromanideal‘blackbody’(moreonthatlater)isgivenbytheStefan-boltzmannlaw·E=6T'·whereEisenergydensityinW/cmz.6IstheStefan-boltzmannconstant(5.6697X10'zW/cmzK’)andTistheabsolutetemperature(K).Inotherwords·thetotalradiatedenergyisproportionaltothefourthpoweroftheabsolutetemperature.A11objects.particularlyidealblackbodyobjects.alsoabsorbincidentradiation.(Uiventimetoequilibrate.andpresumingtheyareinsulatedfromtheheatingorcoolingeffectsofsurroundingairorothermaterials.theywilleventuallyreachapointwheretheyabsorbandradiateenergyatequalrates.()neconsequenceofthisisthatifanobject(atemperaturesensor.forexample)isanidealblackbody.isperfectlyinsulated.andisfloodedonitsentiresurfacewithradiationfromaradiatingsource.itwilleventuallyreachanequilibriumsourcesandblackbodycalibrationsourcesareavailable).thetemperatureofthesensorisameasureofthetemperatureoftheradiatingobject.任何物体在任何温度高于绝对零度的辐射能量。这种辐射无论是在不同强度和在光谱分布和温度。因此。通过测量温度可以推导出要么强度或频谱的辐射。总能量密度辐射从理想'blackbody”(稍后详细介绍)鉴于法律的Stefan-boltzmann·E=6T'·E在是能量密度在W/cmz。6Stefan-boltzmann的常数(5。6697X10'zW/cmzK”)和T是绝对的温度(K)。换句话说·总辐射能量是成正比的第四绝对温度的力量。A11对象。特别是理想黑体对象。也会吸收入射辐射。(Uiven时间一致。和他们隔绝放肆的加热或冷却周围空气的影响或其他材料。他们最终会达到一个临界点他们吸收和辐射能量在相同的利率。()东北的后果是,如果一个对象(一个温度传感器。例如)是一种理想的黑体。是完全绝缘。和是在整个表面淹没与辐射发射源。它最终将达到平衡来源和黑体校正源可用),温度传感器是一个测量辐射的温度对象。AninfraredradiationthermometermaybecreatedinamannersimilartothatinFigure1theradiatedenergyfromthehot(orcold)objectisfocusedonatemperaturesensor.whosetemperaturethenisindicativeoftheintensityoftheradiationfallinguponit.Thesensorshouldbesmallandlowmassforreasonableresponsetime.Thermistorsofferhighsensitivityforlowtemperaturemeasurementswhilethermocouplesprovidetheoperatingrangenecessaryforhighlevelsofradiatedenergy.Insomedesigns.thesensorisinsulatedfromambientconditionsbyplacingitinavacuum.Thesensor'soutputisamplified.linearized.andfedtoanoutputindicatororrecorder.Theopticsareapttobeabitdifferentthanshownindiagram.Inmostapplications.particularlyatlowertemperatures.muchoftheradiationwillbefarinfrared.whichisnotpassedwellbymostglasses.Itmaybepreferabletouseareflectiveconcavemirrortofocustheincomingenergy.ratherthanalens.Theremayalsobearedorinfraredfilterovertheinlettokeepdowninterferenceduetostrayambientlight.Forhighertemperatureuseitmaybenecessarytoreducethetotalincomingenergyusingagrayfilter.shutter.orotherobstruction.TheStefan-boltzmannlaw.andtheproperoperationofthesethermometers.presumesthattheradiationiscomingfromaperfectblackbody'radiator.tooversimplify(anditisnotourintentionheretowhichdoesnotreflectanyradiationwhichmayfalluponit.Allincidentenergyisabsorbed.Anon-blackbodyobjectwhichreflectsexternalradiationwillalsoreflectinternallygeneratedradiation.loweringtheamountofenergyradiatedatanygiventemperature.红外辐射温度计可以创建的方式类似,在图1的辐射能量从热(或冷)对象都聚焦在一个温度传感器。其温度然后表明辐射强度落它。应该是小的传感器和低质量为合理的响应时间。热敏电阻提供高灵敏度低温度的测量而热电偶提供必要的工作范围为高水平的辐射能量。在一些designs.the传感器是隔绝外界条件下通过将它放置在真空中。传感器的amplified.linearized输出。和美联储到输出指标或录音机。光学往往稍有不同,图中所示。在大多数应用程序。特别是在较低的温度下。大部分的辐射将远红外线。这不是大多数眼镜了。这可能比使用凹面镜反射来聚焦入射能量。而不是一个镜头。也许也是一个红色或红外过滤器在进口为了压制干扰由于流浪环境光。温度较高的使用可能需要减少总传入的能源使用灰色filter.shutter。或其他阻塞Stefan-boltzmann的法律。和适当的操作这些温度计。是假定辐射是来自一个完美的黑体的散热器。粗略的(和它不是我们的这里的意愿,没有反映出任何辐射可能落在它。所有入射能量被吸收。一个non-blackbody对象反映外部辐射也将反映出内部产生的辐射。降低辐射的能量在任何给定的温度。Anysurfacehasareflectivityandanemissivity.Reflectivity，r，issimplytheratioofreflectedenergytoincidentenergy:aperfectreflectorhasareflectivityofone;ablackbody，zero.Emissivity，。，turnsouttobsimply。=1一re,fZecl:二:Cyreflectivity.Aperfectblackbodyhasemittedbyanobjectatagiventemperatureisproportionaltoitsemissivity:areflectivityobjecthasemissivity(weexpectmoreheatfromarough，blackradiatorthanfromasmooth，polishedone).Allthishasaseriousimpactonradiationthermometry.Aninfraredradiationthermometercalibratedagainstablackbodyradiatorwillreadseriouslylowwhenaimedatareflectiveobject.Mostcommercialradiationthermometersincludeacontrolallowingtheusertodialintheemissivityoftheobjectbeingmeasured，plusatableoftypicalemissivityvalues.Mistorganicandnonmetallicmaterialshaveemissivityvalues.Mostorganicandnonmetallic