ASTM_D_2520_-_21.pdf

Designation:D252021Standard Test Methods forComplex Permittivity(Dielectric Constant)of Solid ElectricalInsulating Materials at Microwave Frequencies andTemperatures to 1650 C1This standard is issued under the fixed designation D2520;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.Scope1.1 These test methods cover the determination of relative(Note 1)complex permittivity(dielectric constant and dissipa-tion factor)of nonmagnetic solid dielectric materials.NOTE1The word“relative”is often omitted.1.1.1 Test Method A is for specimens precisely formed to theinside dimension of a waveguide.1.1.2 Test Method B is for specimens of specified geometrythat occupy a very small portion of the space inside a resonantcavity.1.1.3 Test Method C uses a resonant cavity with fewerrestrictions on specimen size,geometry,and placement thanTest Methods A and B.1.2 Although these test methods are used over the micro-wave frequency spectrum from around 0.5 to 50.0 GHz,eachoctave increase usually requires a different generator and asmaller test waveguide or resonant cavity.1.3 Tests at elevated temperatures are made using specialhigh-temperature waveguide and resonant cavities.1.4 The values stated in SI units are to be regarded asstandard.The values given in parentheses after SI units areinch-pound units that are provided for information only and arenot considered standard.1.5 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2A893/A893M Test Method for Complex Dielectric Constantof Nonmetallic Magnetic Materials at Microwave Fre-quenciesD150 Test Methods for AC Loss Characteristics and Permit-tivity(Dielectric Constant)of Solid Electrical InsulationD1711 Terminology Relating to Electrical Insulation3.Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method,referto Terminology D1711.3.2 Definitions of Terms Specific to This Standard:3.2.1 neper,na division of the logarithmic scale whereinthe number of nepers is equal to the natural logarithm of thescalar ratio of either two voltages or two currents.NOTE2The neper is a dimensionless unit.1 neper equals 0.8686 bel.With Ixand Iydenoting the scalar values of two currents and n being thenumber of nepers denoted by their scalar ratio,then:n 5 lnelx ly!where:lne=logarithm to base e.3.3 Definitions of Terms Specific to Test Methods B and C:3.3.1 electrical skin depth,nthe effective depth of fieldpenetration at high frequencies where electric currents areconfined to a thin layer at the surface of conductors due to basicelectromagnetic phenomena.3.3.1.1 DiscussionThe skin depth for copper and silver isapproximately 0.002 mm at 1 GHz and decreases by a factor of10 at 100 GHz.1These test methods are under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.12 on Electrical Tests.Current edition approved April 1,2021.Published June 2021.Originallyapproved in 1966.Last previous edition approved in 2013 as D2520 13.DOI:10.1520/D2520-21.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.13.3.2 high Q cavity,na rectangular cavity having a Qgreater than 2000.3.3.2.1 DiscussionQ defines the bandwidth(or sharpness)of the resonance curve of field intensity plotted againstfrequency.Q is the reciprocal of the electrical loss with a highQ indicating low electrical losses of the cavity and dielectricsand is obtained by optimum choice of cavity dimensions,useof high conductivity metals(such as silver and copper)withhighly polished surfaces(that is,surface roughness mu