Designation:D257−14(Reapproved2021)´1StandardTestMethodsforDCResistanceorConductanceofInsulatingMaterials1ThisstandardisissuedunderthefixeddesignationD257;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.ε1NOTE—Editorialchangesweremadeto4.1(grammarcorrection)andTable1(“p”changedto“ρ”)inMarch2021.1.Scope1.1Thesetestmethodscoverdirect-currentproceduresforthemeasurementofdcinsulationresistance,volumeresistance,andsurfaceresistance.Fromsuchmeasurementsandthegeometricdimensionsofspecimenandelectrodes,bothvol-umeandsurfaceresistivityofelectricalinsulatingmaterialscanbecalculated,aswellasthecorrespondingconductancesandconductivities.1.2Thesetestmethodsarenotsuitableforuseinmeasuringtheelectricalresistance/conductanceofmoderatelyconductivematerials.UseTestMethodD4496toevaluatesuchmaterials.1.3Thesetestmethodsdescribeseveralgeneralalternativemethodologiesformeasuringresistance(orconductance).SpecificmaterialscanbetestedmostappropriatelybyusingstandardASTMtestmethodsapplicabletothespecificmaterialthatdefinebothvoltagestresslimitsandfiniteelectrificationtimesaswellasspecimenconfigurationandelectrodegeom-etry.Theseindividualspecifictestmethodologieswouldbebetterabletodefinetheprecisionandbiasforthedetermina-tion.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplicabilityofregulatorylimitationspriortouse.1.5Thisinternationalstandardwasdevelopedinaccor-dancewithinternationallyrecognizedprinciplesonstandard-izationestablishedintheDecisiononPrinciplesfortheDevelopmentofInternationalStandards,GuidesandRecom-mendationsissuedbytheWorldTr...
