ASTM_D_374_-_D_374M_-_16.pdf

Designation:D374/D374M16An American National StandardStandard Test Methods forThickness of Solid Electrical Insulation1This standard is issued under the fixed designation D374/D374M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 These test methods cover the determination of thethickness of several types of solid electrical insulating materi-als employing recommended techniques.Use these test meth-ods except as otherwise required by a material specification.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D1711 Terminology Relating to Electrical InsulationD6054 Practice for Conditioning Electrical Insulating Mate-rials for Testing(Withdrawn 2012)3E252 Test Method for Thickness of Foil,Thin Sheet,andFilm by Mass Measurement3.Terminology3.1 Refer to Terminology D1711 for definitions pertinent tothis standard.3.2 Definitions of Terms Specific to This Standard:3.2.1 1 micron,m,na dimension equivalent to0.03937 mils.3.2.2 1 mil,na dimension equivalent to 0.0010 in.3.2.3 absolute uncertainty(of a measurement),nthesmallest division able to be read directly on the instrument usedfor measurement.3.2.4 micrometer,nan instrument for measuring any di-mension with absolute uncertainty of 1 mil 25 m or smaller.4.Summary of Test Methods4.1 This standard provides eight different test methods forthe measurement of thickness of solid electrical insulationmaterials.The test methods(identified as Test Methods Athrough H)employ different micrometers that exert variouspressures for varying times upon specimens of different geom-etries.Tables 1 and 2 display basic differences of each testmethod and identify test methods applicable for use on variouscategories of materials.5.Significance and Use5.1 Some electrical properties,such as dielectric strength,vary with the thickness of the material.Determination ofcertain properties,such as relative permittivity(dielectricconstant)and volume resistivity,usually require a knowledgeof the thickness.Design and construction of electrical machin-ery require that the thickness of insulation be known.6.Apparatus6.1 Apparatus AMachinists Micrometer Caliper4withCalibrated Ratchet or Friction Thimble:6.1.1 Apparatus A is a micrometer caliper without a lockingdevice but is equipped with either a calibrated ratchet or afriction thimble.By use of a proper manipulative procedureand a calibrated spring(see AnnexA1),the pressure exerted onthe specimen is controllable.6.1.2 Use an instrument constructed with a vernier capableof measurement to the nearest 0.1 mil 2 m.6.1.3 Use an instrument with the diameter of the anvil andspindle surfaces(which contact the specimen)of 250 6 1 mil6.35 6 0.05 mm.1These test methods are under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and are the direct responsibility ofSubcommittee D09.12 on Electrical Tests.Current edition approved June 1,2016.Published August 2016.Originallyapproved in 1933.Last previous edition approved in 2004 as D374 99(2004)which was withdrawn January 2013 and reinstated in June 2016.DOI:10.1520/D0374_D0374M-16.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Hereinafter referred to as a machinists micrometer.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.1.4 Use an instrument conforming to the requirements of7.1,7.2,7.5,7.6.1,and 7.6.2.6.1.5 Periodically,test the micrometer for conformance tothe requirements of 6.1.4.6.2 Apparatus BMachinists Micrometer Without aRatchet:6.2.1 Apparatus B is a micrometer caliper without a lockingdevice.6.2.2 Use an instrument constructed with a vernier capableof measurement to the nearest 0.1 mil 2 m.6.2.3 Use an instrument with the diameter of the anvil andspindle surfaces(which contact the specimen)250 6 1 mil6.35 6 0.05 mm.6.2.4 Use