1、Designation: C 611 98 (Reapproved 2005)e1An American National StandardStandard Test Method forElectrical Resistivity of Manufactured Carbon and GraphiteArticles at Room Temperature1This standard is issued under the fixed designation C 611; the number immediately following the designation indicates t
2、he 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.e1NOTEEditorial changes were made to Figure 3 in May 2005.1.
3、 Scope1.1 This test method covers the determination of the elec-trical resistivity of manufactured carbon and graphite articles atroom temperature.1.2 The values stated in SI units are to be regarded as thestandard.1.3 This standard does not purport to address all of thesafety concerns, if any, asso
4、ciated 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. Terminology2.1 Definition:2.1.1 resistivitythe property of a material that determinesits resistan
5、ce to the flow of an electrical current. It is defined asthe value of r, in milliohm metres, as follows:r5RA!/Lwhere:R = resistance of a specimen of the material of uniformcross section, ohms,A = uniform cross section, mm2, andL = distance between potential contacts, mm.2.1.1.1 In cases where resist
6、ivity is requested in ohm-inches, multiply r in milliohm metres by 0.03937.3. Significance and Use3.1 This test method provides a means of determining theelectrical resistivity of carbon or graphite specimens. The useof specimens that do not conform to the specimen sizelimitations described in the t
7、est method may result in analteration of test method accuracy.4. Apparatus4.1 The means for applying current and potential terminalsto the specimen is specified in 5.2.3.1. A typical specimenholder is shown in Fig. 1.4.2 Bridge, Potentiometer,orSuitable Digital Voltmeter,with necessary accessories f
8、or making resistance measure-ments with a limit of error of less than 0.5 %. Fig. 2schematically depicts two wiring diagrams that have beenfound satisfactory for this purpose.4.3 The means for measuring the dimensions of the speci-men should be adequate to determine its gage length and itsmean area
9、of cross section, each within 0.5 %.5. Test Specimen5.1 The test specimen may be in the form of a strip, rod, bar,or tube.5.2 In order to determine the resistivity, each specimen shallconform to the following:5.2.1 The cross-sectional area shall be uniform within0.75 %. In general, the diameter of c
10、ircular cross section, or thethickness and width of a strip specimen shall be determined bymicrometer measurements, and a sufficient number of mea-surements shall be made to obtain a mean cross-sectional areato within 0.5 %. The test specimen shall be machined to yieldplanar and parallel end faces.
11、These faces shall be perpendicu-lar to the specimen length to within 0.001 mm/mm. Allsurfaces shall have a surface finish visually comparable to 0.8m (32 in.) rms. Reasonable care should be exercised toassure that all edges are sharp and without chips or other flaws.5.2.2 The test specimen shall sho
12、w no defects observablewith normal vision and shall be free of surface deposits.5.2.3 The minimum ratio of specimen length to maximumcross-sectional dimension (width or diameter) shall be 6 : 1.5.2.3.1 The gage length may be measured by any scale thatwill give an accuracy of 60.5 % in the length mea
13、sured. In thedirection of the length of the specimen, the dimension of eachpotential contact shall be not more than 0.5 % of the distancebetween the potential contacts. The minimum distance betweeneach potential contact and the adjacent current contact shall be1This test method is under the jurisdic
14、tion of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.F0 on Manufactured Carbon and Graphite Products .Current edition approved May 1, 2005. Published May 2005. Originallyapproved in 1969. Last previous edition approved in 1998 as C 611 98
15、.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the maximum cross-sectional dimension (width or diameter) ofthe specimen. If knife edges are used, they shall be parallel toeach other and perpendicular to the longitudinal direction o
16、fthe sample. The minimum ratio of gage length to maximumcross-sectional dimension (width or diameter) shall be 4 : 1.5.2.4 No dimension shall be smaller than five times thelength of the largest visible particle.5.2.5 No joints or splices are permissible, unless this is thevariable under study.6. Con
17、ditioning6.1 The specimen shall be dried for a minimum of2hat110C, cooled to room temperature in a desiccator, and storedin a desiccator until tested.7. Procedure7.1 Resistance MeasurementMeasure resistance with in-struments accurate to 60.5 % or less (see Note 1). To ensure acorrect reading, the re
18、ference standard and the test specimenmust be allowed to come to the same temperature as thesurrounding medium.NOTE 1For resistance below 10 V, a Kelvin bridge method may beused, and for higher resistance, a Wheatstone bridge method may be used.7.1.1 Clean the surface of the specimen at current andp
19、otential contact points to obtain good electrical contact.Mount the sample in the test apparatus, apply current, andmeasure the voltage. Take four measurements, on each side ofa rectangular specimen, or at 90 (p/2 radians) apart on a roundspecimen. Reverse the current direction and take four measure
20、-ments again. Remove the specimen from the test apparatus,turn it end for end, replace it in the apparatus, and repeat themeasurements. The total of 16 measurements is recommendedto minimize errors due to contact potential and forward andreverse currents. Average all individual values of measuredres
21、istance and use this value to calculate the resistivity.7.2 Heating of SpecimenIn all resistance measurements,the measuring current raises the temperature of the specimenabove that of the surrounding medium. Therefore, take care tokeep the magnitude of the current low, and the time shortenough, so t
22、hat changes in resistance cannot be detected. Themeasuring current shall be so small that the resistance of aspecimen is not changed, thereby, as much as 0.1 %. Thiscondition may be determined experimentally, or calculatedfrom the power expended and the surface area of the specimen.A specimen heatin
23、g check should be run after each group ofsamples. If resistance change exceeds 0.1 %, the sample shouldbe cooled to ambient temperature and rerun at a lowermeasuring current.7.3 A sample data collection work sheet that may be usedfor the testing is shown in Fig. 3.1Base block 12Wire gauze holder2Piv
24、ot block 13Pivot red3Current block adjustable 14Screw: sockethead4Current block stationary 15Roundhead screw5Clamp block 16Roundhead screw6Clamp screw 17Roundhead screw7Brush holder 18Screw, sockethead8Contacts 19Set screw9Current block support 20Neoprene10Current block guide 21Wire gauze11Pivot bra
25、cket 22Set screwNOTEContacts for the voltage and current probes may be made through channels drilled in the brush holders (7) and the current blocks (3 and 4),respectively.FIG. 1 Typical Test ApparatusC 611 98 (2005)e128. Report8.1 Report the following:8.1.1 Identification and previous history of th
26、e test speci-men,8.1.2 Sample orientation,8.1.3 Temperature of surrounding medium,8.1.4 Dimensions of specimen used,8.1.5 Method of measuring resistance, including gagelength and probe location,8.1.6 Value of resistance or potential plus the currentreadings, and8.1.7 Calculated value of resistivity.
27、9. Precision and Bias29.1 A round-robin test series was run to determine theprecision and bias. The results of evaluating 20 test specimensof two different grades from 9 laboratories are as follows:Within-Lab variability 0.75 %Between-Lab variability 2.5 %9.2 The within-lab variability is a combinat
28、ion of both testerror and material variability since repetitious measurementswere not made on single specimens within a laboratory.Material variability was, however, minimized by normalizingthe results to values averaged from consistent results from fiveLaboratories. This yielded the estimate of a f
29、airly smallwithin-laboratory variability from 0.5 to 0.75 % which stillincludes a minor material variability.9.3 Homogeneity of variance by the sensitive Barletts testwas not indicated, most likely, because of the very smallwithin-laboratory variance and sensitivity to non-normality.9.4 The between-
30、Lab variability estimation was made onthe measurement of the same specimen between Laboratorieswith the obvious exception of the results from laboratory A.The results still included some material variability as theresistivity varies to some extent along the length of thespecimens.9.5 The between-lab
31、 variability is fairly small and is prob-ably a result of a minor lack of precision in the length2Supporting data giving complete results of the round-robin testing have beenfiled with ASTM International Headquarters.NOTEAdjustable, regulated dc power supplyline and load regulation to 0.1 % and ripp
32、le and noise # 0.1 %.FIG. 2 Typical Schematic for Resistivity MeasurementsC 611 98 (2005)e13measurement between voltage contacts on the specimen. Thissmall variability could be further reduced by the use of auniform standard specimen used to periodically check theresistivity measurement apparatus. T
33、he results were essentiallyunchanged over the range of 17 to 41 micro-ohm metres (700to 1700 micro-ohm inches) in electrical resistivity.9.6 In effect, the overall conclusion is that this test methodwill yield repeatable test results giving a good estimation of theelectrical resistivity of a materia
34、l as intended by the standardmethod of test.NOTE 1The sample history, ambient temperature, and probe position should be recorded for each sample on a separate sheet.NOTE 2A specimen heating check should be run after each group of samples. If resistance change exceeds 0.1 %, the sample should be cool
35、ed toambient temperature and rerun at a lower measuring current.NOTE 3Remove the specimen from test apparatus, turn end for end and replace the specimen in the test apparatus.FIG. 3 Electrical Resistivity WorksheetC 611 98 (2005)e14ASTM International takes no position respecting the validity of any
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37、ion at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your c
38、omments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrig
39、hted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).C 611 98 (2005)e15
