ASTM_D_374_-_99.pdf

Designation:D 374 99An American National StandardStandard Test Methods forThickness of Solid Electrical Insulation1This standard is issued under the fixed designation D 374;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(e)indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the 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 methodsexcept as otherwise required by a material specification.1.2 The values stated in inch-pound 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:D 1711 Terminology Relating to Electrical Insulation2D 6054 Practice for Conditioning Electrical Insulating Ma-terials for Testing3E 252 Test Method for Thickness of Thin Foil and Film byWeighing43.Terminology3.1 Refer to Terminology D 1711 for definitions pertinent tothis standard.3.2 Definitions of Terms Specific to This Standard:3.2.1 1 mil,na dimension equivalent to 0.0010 in.3.2.2 absolute uncertainty(of a measurement),nthesmallest division that may be read directly on the instrumentused for measurement.3.2.3 micrometer,nan instrument for measuring any di-mension with absolute uncertainty of 1 mil 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 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 Caliper5withCalibrated 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(seeAnnexA1),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.6.1.3 Use an instrument with the diameter of the anvil andspindle surfaces(which contact the specimen)of 250 6 1 mil.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.6.2.3 Use an instrument with the diameter of the anvil andspindle surfaces(which contact the specimen)250 6 1 mil.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 7.6.3.1These test methods are under the jurisdiction of ASTM Committee D-9 onElectrical and Electronic Insulating Materials and are the direct responsibility ofSubcommittee D09.12 on Electrical Tests.Current edition approved March 10,1999.Published June 1999.Originallypublished as D 374 33T.Last previous edition D 374 94.2Annual Book of ASTM Standards,Vol 10.013Annual Book of ASTM Standards,Vol 10.02.4Annual Book of ASTM Standards,Vol 02.02.5Hereinafter referred to as a machinists micrometer.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.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,DialType Thickness Gage:66.3.1 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 presser foot and the anvil(whichcontact the specimen)parallel to within 0.1 mil(see 7.3),6.3.1.3 A vertical dial spindle,6.3.1.4 A dial indicator essentially friction-free and capableof repeatable readings within 60.05 mil at zero