粒度分析仪的准确度和精密度英文

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1、AccuracyandPrecisionofMicrotracParticleSizeAnalyzersPhilipE.Plantz,PhDApplicationNoteSL-AN-06RevAProvidedBy:Microtrac,Inc.ParticleSizeMeasuringInstrumentationIntroductionAccuracyandprecisionhavedistinctmeanings.Generally,accuracyreferstotheabilityofananalyticaldevicet

2、oprovideameasurementthatiswithinadefinederrorfromanestablished,true,andverifiablevalue.Precisionisameasureoftherecurrenceofavaluewhetheritisaccurateornot.Twotypesofprecisioncanbedescribed:repeatabilityandreproducibility.Intermsofparticlesizemeasurement,repeatabilityre

3、ferstotheabilityofaninstrumenttorepeatitsownmeasurementwhilethesamesampleresidesinthecirculatingsystem.Reproducibility,ontheotherhand,isrelatedtothecomparisonoftwoormoreinstrumentsinwhichrepresentative(repeatablesamplingassumed)samplesareintroducedtoeachoftheinstrumen

4、ts.Repeatabilityisstatisticallymorevariation-freethanreproducibilitybecauseasingleinstrumentmeasuresthesamerecirculatingsamplewhenfluidsuspendedparticlesaremeasured.AccuracyAccuracyisaconceptthatisdifficulttodefineforparticlesizemeasurementofirregularlyshapedparticles

5、.Forasphere,onecaneasilydefineitssurfaceanddiameterusingtheradiusoftheparticleandthebasicsofgeometry.If100%oftheparticlesaresphericalandarethesamesize,aninstrumentcanbedesignedtomeasurethatsize.Sinceprobably99%oftheindustrialparticlesmeasuredarenotspherical(theyareusu

6、allyveryirregularlyshaped),onecannotusesimplegeometrytodefinethesizesincemanydimensionswillexistforeachparticle.Thissituationismademorecomplexsincewhilemostpowderprocessesproducereproducibleparticlesizedistributions,theyusuallydonotproduceparticlesofexactlythesameshap

7、eandsize.Sincetherearebillionsuponbillionsofparticlesbeingproducedinaprocess,itisverydifficult,ifnotimpossible,toaccuratelydeterminethesizeofeachacicularparticleinadistributionwith100%accuracy.Theirregularparticleshapesandthefactthatshapehasadifferenteffectoneachmeasu

8、rementmethodalsocontributeMoreAccurateMoreAccurateMorePreciseLessPreciseLessAccurateLessAccurateMorePreciseLessPreciseThesep