《过程控制技术》课件-检测仪表的性能指标

Performanceindicatorsofdetectioninstruments检测仪表的性能指标落版在此检测仪表的性能指标Performanceindicatorsofdetectioninstruments谢聪XieCong主讲教师Teacher生产的方向Productiondirection精准的数据Accuratedata检测仪表的性能指标Performanceindicatorsofdetectioninstruments检测仪表就是获得参数量化数据并进行显示、标准化转换和远距离传输的工具。Detectioninstrumentisatooltoobtainquantifiedparameterdataanddisplay,standardizeconversionandlong-distancetransmission.检测仪表Detectioninstruments实现这些精准数据获取的关键：Thekeytoachievingtheseaccuratedataacquisition：检测仪表的性能指标Performanceindicatorsofdetectioninstruments测量指示仪表Measurementindicatinginstruments测量变送器MeasurementtransmitterCaseimport案例导入在某化工企业的生产车间，原本用于监测反应釜温度的检测仪表频频出现偏差。起初只是小小的数值波动，没引起足够重视，可后来偏差越来越大，导致反应温度失控，最终引发了一场生产事故。Intheproductionworkshopofachemicalcompany,thedetectioninstrumentoriginallyusedtomonitorthetemperatureofthereactorfrequentlydeviated,atfirstitwasjustasmallnumericalfluctuation,sufficientattentionwasnotpaid.Butthenthedeviationbecamebiggerandbigger,causingthereactiontemperaturetogetoutofcontrol,eventuallytriggeredaproductionaccident.Caseimport案例导入Caseimport案例导入检测仪表的性能指标PerformanceindicatorsofdetectioninstrumentsPerformanceindicatorsofdetectioninstruments检测仪表的性能指标Performanceindicatorsofdetectioninstruments检测仪表的性能指标检测仪表的指示值X与被测量真值Xz之间的差值：Δ=X−Xz

ThedifferenceΔ=X−XzbetweentheindicatedvalueXofthedetectioninstrumentandthemeasuredtruevalueXz.绝对误差Absoluteerror由于真值无法获取，实际计算时用精确度高的标准表测得的标准值

X₀代替真值

Xz，此时绝对误差Δ=X−X₀.Sincethetruevaluecannotbeobtained,useastandardinstrumentwithhighaccuracyinactualcalculationthemeasuredstandardvalueX₀

replacesthetruevalueXz,atthistime,theabsoluteerrorΔ=X−X₀.仪表在其标尺范围内各点读数的绝对误差中绝对值最大的绝对误差称为最大绝对误差Δmax。TheabsoluteerrorwiththelargestabsolutevalueamongtheabsoluteerrorsofeachpointreadingoftheinstrumentwithinitsscalerangeiscalledthemaximumabsoluteerrorΔmax.

Performanceindicatorsofdetectioninstruments检测仪表的性能指标基本误差又称引用误差或相对百分误差，是一种简化的相对误差。Basicerror,alsoknownascitationerrororrelativepercentageerror,isasimplifiedrelativeerror.基本误差Basicerror基本误差表示仪表在规定工作条件下测量时，允许出现的最大误差限。Thebasicerrorrepresentsthemaximumerrorlimitallowedbytheinstrumentwhenmeasuringunderspecifiedoperatingconditions.若仪表使用条件超出规定范围，如温湿度超限或电源质量不满足要求等引起的额外误差则称为附加误差。Iftheinstrumentoperatingconditionsexceedthespecifiedrange,suchasadditionalerrorscausedbytemperatureandhumidityexceedingthelimitorpowerqualitynotmeetingtherequirements,itiscalledadditionalerrors.Basicerror𝜷Performanceindicatorsofdetectioninstruments检测仪表的性能指标模拟仪表的精确度用基本误差来表示。仪表工业规定将基本误差去掉“±”号及“%”号后称为仪表精度，它体现了在规定工作条件下测量结果与实际值的接近程度。Theaccuracyofanaloginstrumentsisexpressedbybasicerror.Theinstrumentindustrystipulatesthatthebasicerroriscalledinstrumentaccuracyafterremovingthe"±"and"%"signs,whichreflectstheproximitybetweenthemeasurementresultsandtheactualvaluesunderspecifiedworkingconditions.精度Accuracy国家规定了仪表的精确度（精度）级系列，如0.05、0.1、0.2

等，精度等级数值越小，仪表精确度越高。ItstipulatestheaccuracylevelseriesofinstrumentsinChina,suchas0.05,0.1,0.2,thesmallertheaccuracylevelvalue,thehighertheaccuracyoftheinstrument.符号标注在仪表面板SymbolsaremarkedoninstrumentpanelPerformanceindicatorsofdetectioninstruments检测仪表的性能指标【例1】已知该测温仪表测温范围为-100~500℃，全量程内最大绝对误差为+7.8℃，请试着确定该仪表的精度等级。[Example1]Itisknownthatthetemperaturemeasuringrangeofthetemperaturemeasuringinstrumentis-100-500℃,themaximumabsoluteerrorinthefullrangeis+7.8°C,pleasetrytodeterminetheaccuracyleveloftheinstrument.解：首先计算基本误差：Solution:First,thebasicerroriscalculated:1.3仪表精度等级中没有1.3级，且该仪表误差超过1.0级仪表允许的最大绝对误差，所以确定这台测温仪表精度等级为1.5级。Thereisnolevel1.3accuracylevelfortheinstrumentsandtheinstrumenterrorexceedsthemaximumabsoluteerrorallowedbylevel1.0instrument,therefore,itisdeterminedthattheaccuracylevelofthistemperaturemeasuringinstrumentis1.5.Performanceindicatorsofdetectioninstruments检测仪表的性能指标【例2】已知测压仪表测压范围为0~12MPa，工艺要求测压示值误差不超过±0.055MPa，应如何选择仪表精度等级才能满足以上要求？[Example2]Itisknownthatthepressuremeasuringrangeofthepressuremeasuringinstrumentis0~12MPa,theprocessrequiresthattheerrorofpressuremeasurementindicationvalueshouldnotexceed±0.055MPa.Howshouldtheinstrumentaccuracylevelbeselectedtomeettheaboverequirements?解：根据公式计算出仪表的允许基本误差：Solution:accordingtotheformula,theallowablebasicerroroftheinstrumentiscalculated:0.458由于选择0.5级仪表时，允许的最大绝对误差±0.06MPa超过工艺允许数值，所以应选择精度等级为0.4级的仪表。Becausewhenselecting0.5levelinstrument,themaximumallowableabsoluteerror±0.06MPaexceedstheallowablevalueoftheprocess,aninstrumentwithanaccuracylevelof0.4shouldbeselected.Performanceindicatorsofdetectioninstruments检测仪表的性能指标灵敏度S表示仪表对被测参数变化的敏感程度，用仪表在x处输出变化Δy与输入激励变化量Δx的比值表示，它是仪表输入/输出特性曲线在该检测点的斜率。SensitivitySrepresentsthesensitivityoftheinstrumenttochangesinmeasuredparameters,whichisexpressedastheratiooftheoutputchangeΔyoftheinstrumentatxtotheinputexcitationchangeΔx,itistheslopeofthemeterinput/outputcharacteristiccurveatthisdetectionpoint.灵敏度与灵敏限Sensitivityandsensitivitylimit当特性曲线为线性时，灵敏度为常数；当仪表不完全线性时，k表示平均灵敏度。Whenthecharacteristiccurveislinear,thesensitivityisconstant;Whentheinstrumentisnotperfectlylinear,krepresentstheaveragesensitivity.Performanceindicatorsofdetectioninstruments检测仪表的性能指标灵敏限指指针式仪表在量程起点处，能引起指针动作的最小被测参数值，小于此值指针不动作，也叫仪表死区。Theminimummeasuredparametervaluethatcancausethepointertomoveatthestartingpointofthemeasuringrangeof

thesensitivepointer-limitinginstrumentislessthanthisvalue,andthepointerdoesnotmove,whichisalsocalledtheinstrumentdeadzone.灵敏度与灵敏限Sensitivityandsensitivitylimit×10℃

0

100

Performanceindicatorsofdetectioninstruments检测仪表的性能指标对于数字显示仪表，常用分辨率和分辨力表示灵敏度和灵敏限。Fordigitaldisplayinstruments,commonlyusedresolutionandresolutionpowerrepresentsensitivityandsensitivitylimit.灵敏度与灵敏限Sensitivityandsensitivitylimit分辨率体现数字仪表显示值的精细程度，仪表显示位数越多，分辨率越高，例如四位显示仪表分辨率为千分之一。Theresolutionreflectsthefinenessofthedigitalinstrumentdisplayvalue,themoredigitstheinstrumentdisplays,thehighertheresolution,suchasonethousandthofafour-digitdisplayinstrumentresolution.Performanceindicatorsofdetectioninstruments检测仪表的性能指标灵敏度与灵敏限Sensitivityandsensitivitylimit对于数字显示仪表，常用分辨率和分辨力表示灵敏度和灵敏限。Fordigitaldisplayinstruments,commonlyusedresolutionandresolutionpowerrepresentsensitivityandsensitivitylimit.分辨力指数显仪表能够显示的最小被测值，比如温度指示仪最末一位数字表示的温度值为0.1℃，则该表分辨力为0.1℃；某数字电压表量程0~1.99999V，五位半显示，最末一位数字表示电压值为10μV，其分辨力即为10μV。Resolutionpoweristheminimummeasuredvaluethattheindexdisplayinstrumentcandisplay,forexample,thetemperaturevalueindicatedbythelastdigitofthetemperatureindicatoris0.1°C,thentheresolutionpoweroftheinstrumentis0.1℃;Adigitalvoltmeterhasarangeof0~1.99999V,fiveandahalfdigitsdisplay,thelastdigitindicatesthatthevoltagevalueis10μV,itsresolutionpoweris10μV.Performanceindicatorsofdetectioninstruments检测仪表的性能指标变差是指在外界条件不变时，用同一仪表对被测量进行往返测量（正行程和反行程），产生的最大差值与测量范围的比值（用百分比表示）。Variationreferstotheratio(expressedasapercentage)ofthemaximumdifferencetothemeasurementrangegeneratedbytheround-strokemeasurement(forwardstrokeandreversestroke)ofthemeasuredobjectwiththesameinstrumentwhentheexternalconditionsremainunchanged.变差VariationPerformanceindicatorsofdetectioninstruments检测仪表的性能指标变差Variation造成变差的原因：

Reasonsforvariation:传动机构的间隙

Transmissionclearance运动部件的摩擦

Frictionofmovingparts弹性元件的弹性滞后影响

Elastichysteresiseffectofelasticelements仪表机械传动部件越少，变差越小。Thefewermechanicaltransmissioncomponentsoftheinstrument,

thesmallerthevariation.变差是指在外界条件不变时，用同一仪表对被测量进行往返测量（正行程和反行程），产生的最大差值与测量范围的比值（用百分比表示）。Variationreferstotheratio(expressedasapercentage)ofthemaximumdifferencetothemeasurementrangegeneratedbytheround-strokemeasurement(forwardstrokeandreversestroke)ofthemeasuredobjectwiththesameinstrumentwhentheexternalconditionsremainunchanged.Performanceindicatorsofdetectioninstruments检测仪表的性能指标响应时间是指用仪表检测被测量时，被测量突然变化后，仪表值经过一段时间才能准确显示被测量，这段时间即为响应时间。Responsetimemeansthatwhenthemeasurandisdetectedbyaninstrument,afterthemeasurandsuddenlychanges,ittakesaperiodoftimefortheinstrumentvaluetoaccuratelydisplaythemeasurand.Thisperiodoftimeistheresponsetime.响应时间Responsetime0

0

它是从被测量阶跃变化到检测仪表指示值稳定在新稳态值95%范围内所用的时间。若参数变化频繁而仪表响应时间较长，测量结果会失真。Itisthetimetakenfromthemeasuredstepchangetothetimewhentheindicatedvalueofthedetectioninstrumentstabilizeswithin95%ofthenewsteady-statevalue.Iftheparameterschangefrequentlyandtheinstrumentresponsetimeislong,measurementswillbedistorted.检测仪表的性能指标Performanceindicatorsofdetectioninstruments准确度高，那就要求其精度等级要满足要求，不能误差过大。Iftheaccuracyishigh,thenitsaccuracylevelisrequiredtomeettherequirements.Itserrorcannotbetoolarge.稳定性好，数值不会轻易波动，就要求仪表变差要小。Withgoodstability,

thevaluewillnotfluctuateeasily;Itisrequiredthattheinstrumentshouldbesmallinvariation.响应速度快，能及时反馈温度变化，就要求其灵敏度要满足要求。fastinresponsespeed,andcanfeedbacktemperaturechangesintime,itssensitivityisrequiredtomeettherequirements.ResearchQuestions问题研究在食品加工行业的杀菌环节，温度的精准控制直接关系到食品安全和产品品质。Inthesterilizationprocessofthefoodprocessingindustry,precisetemperaturecontrolisdirectlyrelatedto