Designation:E1458−12(Reapproved2016)StandardTestMethodforCalibrationVerificationofLaserDiffractionParticleSizingInstrumentsUsingPhotomaskReticles1ThisstandardisissuedunderthefixeddesignationE1458;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONThereexistsalargevarietyoftechniquesandinstrumentsforthesizingofparticlesanddropletsinfluidsuspension.Theseinstrumentsarebasedonanumberofdifferentphysicalphenomenaandinterlaboratorycomparisonsofdataon,forexample,referenceliquidsprayshaveshownsignificantvariability.Thistestmethodevolvedinconjunctionwitheffortstoexplaintheobservedvariability.Theeffectivenessofthistestmethodcanbetracedtothefactitcircumventsdifficultiesassociatedwithproducing,replicating,andmaintainingastandardsampleofliquidparticlesinaspray.Thistestmethodusesaphotomaskreticletoprovideasimulationofsomeoftheopticalpropertiesofareferencepopulationofsphericalparticles.Thistestmethodisonlyapplicabletoopticalparticlesizinginstrumentsthatarebasedonmeasurementandanalysisoflightscatteredintheforwarddirectionbyparticlesilluminatedbyalightbeam.Sincemodernopticalinstrumentsgenerallyusealasertoproducealightbeam,andsincethelightscatteredintheforwarddirectionbyparticlescanoftenbeaccuratelydescribedusingdiffractiontheoryapproximations,theclassofinstrumentsforwhichthistestmethodapplieshavebecomegenerallyknownaslaserdiffractionparticlesizinginstruments.BecauseitisspecificallyFraunhoferdiffractiontheory2,3thatisusedintheapproximation,theseinstrumentsarealsoknownasFraunhoferdiffractionparticlesizinginstruments.Thediffractionapproximationtothegeneralproblemofelectromagneticwavescatteringbyparticlesisstrictlyvalidonlyifthreeconditionsaresatisfied.Theconditionsare:particlesizesmustbesignificantlylargerthantheopticalwavelength,particlerefractiveindicesmustbesignific...
