1、Designation: C611 98 (Reapproved 2010)1An American National StandardStandard Test Method forElectrical Resistivity of Manufactured Carbon and GraphiteArticles at Room Temperature1This standard is issued under the fixed designation C611; the number immediately following the designation indicates the
2、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.1NOTEUpdated units throughout editorially in May 2010.1. Scope1.
3、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 asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to
4、 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. Terminology2.1 Definitions:2.1.1 resistivitythe p
5、roperty of a material that determinesits resistance 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 pot
6、ential contacts, mm.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 test method may result in analteration of test method ac
7、curacy.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 for making resistance measure-ments with a limit of erro
8、r 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 of cross section, each within 0.5 %.5. Test Specimen5.1
9、 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 circular cross section, or thethickness and width of a s
10、trip 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. These faces shall be perpendicu-lar to the specimen len
11、gth to within 0.001 mm/mm. Allsurfaces shall have a surface finish visually comparable to0.8 m rms. Reasonable care should be exercised to assure thatall edges are sharp and without chips or other flaws.5.2.2 The test specimen shall show no defects observablewith normal vision and shall be free of s
12、urface 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 measured. In thedirection of the length of the specimen, the dimens
13、ion 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 jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants a
14、nd is the direct responsibility of SubcommitteeD02.F0 on Manufactured Carbon and Graphite Products.Current edition approved May 1, 2010. Published November 2010. Originallyapproved in 2005. Last previous edition approved in 2005 as C611-98(2005)1.DOI:10.1520/C0611-98R10E01.1Copyright ASTM Internatio
15、nal, 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 ofthe sample. The minimum ra
16、tio 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. Conditioning6.1 The specimen s
17、hall 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 reference standard and the te
18、st 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 andpotential contact points to
19、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-ments again. Remove the sp
20、ecimen 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 measuredresistance and use this value
21、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 that changes in resistance c
22、annot 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 heating check should be run after
23、 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 holder2Pivot block 13Pivot red3Curren
24、t 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 bracket 22Set screwNOTEContact
25、s 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 ApparatusC611 98 (2010)128. Report8.1 Report the following:8.1.1 Identification and previous history of the test speci-men,8.1.2 Sample
26、 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.9. Precision and Bias29.1 A r
27、ound-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 combination of both testerror and mat
28、erial 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 fairly small within-laboratory
29、 variability from 0.5 to 0.75 % which still includes aminor 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-lab variability estimation w
30、as made on themeasurement of the same specimen between laboratories withthe obvious exception of the results from Laboratory A. Theresults still included some material variability as the resistivityvaries to some extent along the length of the specimens.9.5 The between-lab variability is fairly smal
31、l and is prob-ably a result of a minor lack of precision in the lengthmeasurement between voltage contacts on the specimen. This2Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:C05-1012.NOTEAdjustable, regulated dc power supplyli
32、ne and load regulation to 0.1 % and ripple and noise # 0.1 %.FIG. 2 Typical Schematic for Resistivity MeasurementsC611 98 (2010)13small variability could be further reduced by the use of auniform standard specimen used to periodically check theresistivity measurement apparatus. The results were esse
33、ntiallyunchanged over the range of 17 to 41 micro-ohm metres inelectrical 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 material as intended by the standardmethod of test.NOTE 1T
34、he 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 cooled toambient temperature and rerun at a lower measu
35、ring current.NOTE 3Remove the specimen from test apparatus, turn end for end and replace the specimen in the test apparatus.FIG. 3 Electrical Resistivity WorksheetC611 98 (2010)14ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item me
36、ntionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committe
37、e 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 comments will receive careful consideration at a meeti
38、ng 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 copyrighted by ASTM International, 100 Barr Harbor Drive, PO
39、 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).C611 98 (2010)15
