ASTM_D_374M_-_13.pdf

Designation:D374M13Standard Test Methods forThickness of Solid Electrical Insulation(Metric)1This standard is issued under the fixed designation D374M;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 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 SI units are 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Relating to Electrical InsulationD6054 Practice for Conditioning Electrical Insulating Mate-rials for Testing(Withdrawn 2012)3E252 Test Method for Thickness of Foil,Thin Sheet,andFilm by Mass Measurement3.Terminology3.1 Refer to Terminology D1711 for definitions pertinent tothis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 absolute uncertainty(of a measurement),nthesmallest division that may be read directly on the instrumentused for measurement.3.2.2 micrometer,nan instrument for measuring any di-mension with absolute uncertainty of 25 m or smaller.3.2.3 1 micron,m,na dimension equivalent to 0.0000010m.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 Methods A throughH)employ different micrometers that exert various pressuresfor varying times upon specimens of different geometries.Table 1 and Table 2 display basic differences of each testmethod and identify 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 A Machinists 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 2 m.6.1.3 Use an instrument with the diameter of the anvil andspindle surfaces(which contact the specimen)of 6.25 6 0.05mm.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 2 m.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 Nov.1,2013.Published November 2013.Originallyapproved in 1968.Last previous edition approved in 2005 as D374M 99(2005).DOI:10.1520/D0374M-13.2For 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.2.3 Use an instrument with the diameter of the anvil andspindle surfaces(which contact the specimen)of 6.25 6 0.05mm.6.2.4 Use an instrument conforming to the requirements of7.1,7.2,7.5.1,7.5.2,7.5.3,7.6.1,and 7.6.3.6.2.5 Periodically,examine and test the micrometer forconformance to the requirements of 6.2.4.6.3 Apparatus C Manually-Operated,Dead-Weight,Dial-Type Thickness Gage:56.3.1 Use a dead-weight dial-type gage in accordance withthe requirements of 7.1,7.3,7.4,7.6.1,7.6.4,that has:6.3.1.1 Apresser foot that moves in an axis perpendicular tothe anvil face,6.3.1.2 The surfaces of the