ASTM C657-1993(2003) Standard Test Method for D-C Volume Resistively of Glass《玻璃的直流体电阻系数的标准试验方法》.pdf
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1、Designation: C 657 93 (Reapproved 2003)Standard Test Method forD-C Volume Resistivity of Glass1This standard is issued under the fixed designation C 657; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the dcvolume resistivity of a smooth, preferably polished, glass bymeasuring the resistan
3、ce to passage of a small amount of directcurrent through the glass at a voltage high enough to assureadequate sensitivity. This current must be measured understeady-state conditions that is neither a charging current nor aspace-charge, buildup polarization current.1.2 This test method is intended fo
4、r the determination ofresistivities less than 1016Vcm in the temperature range from25C to the annealing point of the glass.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
5、-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see Section 5.2. Referenced Documents2.1 ASTM Standards:D 257 Test Methods for DC Resistance or Conductance ofInsulating Materials2D 374 Test Methods for Thickn
6、ess of Solid Electrical Insu-lation2D 1711 Terminology Relating to Electrical Insulation2D 1829 Test Method for Electrical Resistance of CeramicMaterials at Elevated Temperatures33. Summary of Test Method3.1 The dc volume resistance is measured in accordancewith Test Methods D 257, with the specimen
7、 located in aheating chamber with adequate temperature control, electricalshielding and insulation of the sample leads as described inTest Method D 1829.4. Significance and Use4.1 This experimental procedure yields meaningful data forthe dc volume resistivity of glass. It is designed to minimizespac
8、e charge, buildup polarization effects, and surface conduc-tances. The temperature range is limited to room temperatureto the annealing point of the specimen glass.5. Cautions5.1 Thermal emfs should be avoided. Connections involv-ing dissimilar metals can cause measurement difficulties. Evencopper-c
9、opper oxide junctions can produce high thermal emfs.Clean, similar metals should be used for electrical junctions.Platinum is recommended. Welded or crimped connectionsrather than soldered joints avoid difficulties. Specimen elec-trodes shall have sufficient cross section for adequate electricalcond
10、uctance.6. Apparatus6.1 Resistance-Measuring Devices, and the possible prob-lems associated with them are discussed thoroughly in Section9 and Appendixes A1 and A3 of Test Methods D 257. Furtherdiscussion of electrometer circuitry is covered in Annex A1 tothis test method.6.2 Heating Chamber (Fig. 1
11、)For heating the specimen, asuitable electric furnace shall be used. The construction of thefurnace shall be such that the specimen is subjected to auniform heat application with a minimum of temperaturefluctuation. An adequate muffle should be provided to shieldthe specimen from direct radiation by
12、 the heating elements.This may be made of a ceramic such as aluminum oxide orequivalent. A grounded metallic shield shall also be providedwithin the furnace, preferably of silver, stainless steel, orequivalent, to isolate electrically the specimen test circuit fromthe heating element. Furnaces for m
13、ore than one specimen canbe constructed. The control thermocouple may be located inthe heating chamber outside the metallic shield, as shown inFig. 1, or inside the metallic shield.6.3 Two Flat Contacting Electrodes, smaller in diameterthan the specimen electrodes (see 7.6), shall be used tosandwich
14、 the specimen. Sufficient thickness should be used to1This test method is under the jurisdiction of ASTM Committee C14 on Glassand Glass Products and is the direct responsibility of Subcommittee C14.04 onPhysical and Mechanical Properties.Current edition approved May 15, 1993. Published July 1993. O
15、riginallyapproved in 1970. Last previous edition approved in 1988 as C 657 88.2Annual Book of ASTM Standards, Vol 10.01.3Annual Book of ASTM Standards, Vol 15.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.maintain an adequate pr
16、essure and to provide heat equalizationbetween the specimen and the contacting electrodes.6.3.1 Fig. 2 shows the specimen setup in the heatingchamber. The bottom electrode shall be placed at the end of ametal rod and shall support the specimen in the center of thefurnace. The unguarded specimen elec
17、trode, No. 3 of Fig. 3,shall be placed in contact with this bottom contacting elec-trode. The top contacting electrode shall be placed on theguarded, specimen electrode, No. 1 of Fig. 3. This topcontacting electrode has leads connected to an off-center metalrod. The specimen guard electrode, No. 2 o
18、f Fig. 3, shall beconnected to the second off-center metal rod with platinumwire or strap. One end shall be connected to the specimenguard electrode; the other end shall be connected to the metalrod.6.3.2 All rods should be supported by insulation outside thefurnace in a cool zone to minimize electr
19、ical leakage atelevated temperatures.6.3.3 Fig. 4 shows a top view of the specimen setup in theheating chamber.6.4 A Temperature-Control System should be provided sothat temperature-time fluctuations within the heating chamberare less than 0.01 T (where T is the temperature in degreesCelsius), durin
20、g the time interval when resistance measure-ments are made. Two thermocouples should be used foraccurate temperature readings, one in the heating chamber,supplying the emf to the temperature controller and the otheron the guard ring of the specimen. The latter should be used tomeasure the specimen t
21、emperature as instructed in the Appa-ratus section (Temperature-Control Device) of Test MethodD 1829.7. Test Specimen7.1 The Test Specimens section (Volume Resistance orConductance Determination) of Test Methods D 257 describesin detail the specimen requirements. To quote in part, “The testspecimen
22、may have any practical form that allows the use of athird electrode, when necessary, to guard against error fromsurface effects.” For practical reasons, a flat disk or square thatis easy to set up in a furnace box is recommended. Otherconfigurations are possible. The descriptions will apply to flats
23、amples but can be modified for other configurations. Recom-mended limitations in the diameter of a disk are 40 to 130 mm.This is not a critical dimension as the effective area ofmeasurements is defined by the area of the applied electrodes,as stated in 7.7.7.2 As the electrical properties of glass a
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