1、Designation:D1425/D1425M14Standard Test Method forEvenness of Textile Strands Using Capacitance TestingEquipment1This standard is issued under the fixed designation D1425/D1425M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the yea
2、r of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the indirect measurement ofevenness(mass variation)of non-conductive textile strands,including
3、 top,comber lap,sliver,roving,and yarn producedfrom staple fibers and continuous filament yarns,by means ofcapacitance testing equipment.1.2 Strands made from fiber blends can be tested using thistest method only if the different fibers are uniformly distributedthroughout the strand.1.3 The test met
4、hod provides numeric values for the mea-surement and evaluation of short-,mid-,and long-term massvariations of the tested strand in terms of frequently occurringfaults classified as thin places,thick places,and neps andgraphical representations of evenness values in the form ofdiagram charts,spectro
5、grams,length variation curves,andhistograms.1.4 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 sy
6、stems may result in non-conformancewith the 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 and health practices and determine the applica-bility of r
7、egulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD1776 Practice for Conditioning and Testing TextilesD2258 Practice for Sampling Yarn for TestingD4849 Terminology Related to Yarns and FibersE177 Practice for Use of the Terms Precision
8、and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions:3.1.1 The following terms are relevant to this standard:electric constant;evenness;imperfections;length between,Lb;length capacitance zone,Lc;mass
9、variation;mean deviation ofevenness,U%;sample length Ls;strand;strand irregularity;and total imperfections.3.1.2 For definitions of other textile terms used in this testmethod,refer to Terminology D123 and Terminology D4849.4.Basic Principles of Test Method4.1 Properties of strand irregularity measu
10、red along itslength are measured in terms of mass variation.4.2 The direct method of evenness testing utilizes thetechnique of cutting and weighing strand segments of length Lband is the reference method of determining evenness(massvariation).Utilization of the capacitance measurement tech-nique is
11、an indirect testing method.The accuracy of an indirectmethod of testing can be judged by a comparison of evennessvalues between it and the direct method(cutting and weigh-ing).4.3 In capacitance testing,a high frequency electric field isgenerated in the space between a pair of capacitor plates(measu
12、ring slots).If the mass of a strand moving between theplates changes,the electrical field between the plates changesaccordingly,and results in electrical signal output variationproportional to the mass variation of the strand.4.4 Evenness is always expressed as variation betweensuccessive lengths L
13、and over a total length Ls.When the Lcevenness is measured,it corresponds to the length capacitancezone width,i.e.,8 mm 0.3 in.for yarns,12 mm 0.5 in.forrovings and fine slivers,and 20 mm 0.8 in.for slivers that arereferred to as short-term evenness.Longer-term evenness mayalso be evaluated by elect
14、ronically increasing the Lc.1This test method is under the jurisdiction ofASTM Committee D13 on Textilesand is the direct responsibility of Subcommittee D13.58 on Yarns and Fibers.Current edition approved July 1,2014.Published August 2014.Originallyapproved in 1956.Last previous edition approved in
15、2009 as D1425/D1425M-091.DOI:10.1520/D1425_D1425M-14.2For 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 AST
16、M International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.Summary of Test Method5.1 A textile strand is passed through a length capacitancezone of an evenness tester at a constant speed.The massvariation of successive Lcinterval lengths is measured andfrom which other values of evenness are derived:coefficient ofvariation,short-,mid-and long-term variations,and imperfec-tions.6.Significance and Use6.1 This test method for the determination of evenness oft
