ASTM C657-93(2003)
(Test Method)Standard Test Method for D-C Volume Resistively of Glass
Standard Test Method for D-C Volume Resistively of Glass
SIGNIFICANCE AND USE
This experimental procedure yields meaningful data for the dc volume resistivity of glass. It is designed to minimize space charge, buildup polarization effects, and surface conductances. The temperature range is limited to room temperature to the annealing point of the specimen glass.
SCOPE
1.1 This test method covers the determination of the dc volume resistively of a smooth, preferably polished, glass by measuring the resistance to passage of a small amount of direct current through the glass at a voltage high enough to assure adequate sensitivity. This current must be measured under steady-state conditions that is neither a charging current nor a space-charge, buildup polarization current.
1.2 This test method is intended for the determination of sensitivities less than 1016 Ω ·cm in the temperature range from 25°C to the annealing point of the glass.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 5.
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Designation:C657–93 (Reapproved 2003)
Standard Test Method for
D-C Volume Resistivity of Glass
This standard is issued under the fixed designation C 657; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Significance and Use
1.1 This test method covers the determination of the dc 4.1 This experimental procedure yields meaningful data for
volume resistivity of a smooth, preferably polished, glass by the dc volume resistivity of glass. It is designed to minimize
measuring the resistance to passage of a small amount of direct space charge, buildup polarization effects, and surface conduc-
current through the glass at a voltage high enough to assure tances. The temperature range is limited to room temperature
adequate sensitivity. This current must be measured under to the annealing point of the specimen glass.
steady-state conditions that is neither a charging current nor a
5. Cautions
space-charge, buildup polarization current.
5.1 Thermal emfs should be avoided. Connections involv-
1.2 This test method is intended for the determination of
resistivities less than 10 V·cm in the temperature range from ing dissimilar metals can cause measurement difficulties. Even
copper-copper oxide junctions can produce high thermal emfs.
25°C to the annealing point of the glass.
1.3 This standard does not purport to address all of the Clean, similar metals should be used for electrical junctions.
Platinum is recommended. Welded or crimped connections
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- rather than soldered joints avoid difficulties. Specimen elec-
trodes shall have sufficient cross section for adequate electrical
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For specific hazard conductance.
statements, see Section 5.
6. Apparatus
2. Referenced Documents
6.1 Resistance-Measuring Devices, and the possible prob-
lems associated with them are discussed thoroughly in Section
2.1 ASTM Standards:
D 257 Test Methods for DC Resistance or Conductance of 9 and Appendixes A1 and A3 of Test Methods D 257. Further
Insulating Materials discussion of electrometer circuitry is covered in Annex A1 to
this test method.
D 374 Test Methods for Thickness of Solid Electrical Insu-
lation 6.2 Heating Chamber (Fig. 1)—For heating the specimen, a
suitable electric furnace shall be used. The construction of the
D 1711 Terminology Relating to Electrical Insulation
D 1829 Test Method for Electrical Resistance of Ceramic furnace shall be such that the specimen is subjected to a
uniform heat application with a minimum of temperature
Materials at Elevated Temperatures
fluctuation. An adequate muffle should be provided to shield
3. Summary of Test Method
the specimen from direct radiation by the heating elements.
3.1 The dc volume resistance is measured in accordance This may be made of a ceramic such as aluminum oxide or
with Test Methods D 257, with the specimen located in a equivalent. A grounded metallic shield shall also be provided
heating chamber with adequate temperature control, electrical within the furnace, preferably of silver, stainless steel, or
shielding and insulation of the sample leads as described in equivalent, to isolate electrically the specimen test circuit from
Test Method D 1829. the heating element. Furnaces for more than one specimen can
be constructed. The control thermocouple may be located in
the heating chamber outside the metallic shield, as shown in
This test method is under the jurisdiction of ASTM Committee C14 on Glass
Fig. 1, or inside the metallic shield.
and Glass Products and is the direct responsibility of Subcommittee C14.04 on
6.3 Two Flat Contacting Electrodes, smaller in diameter
Physical and Mechanical Properties.
Current edition approved May 15, 1993. Published July 1993. Originally
than the specimen electrodes (see 7.6), shall be used to
approved in 1970. Last previous edition approved in 1988 as C 657 – 88.
sandwich the specimen. Sufficient thickness should be used to
Annual Book of ASTM Standards, Vol 10.01.
Annual Book of ASTM Standards, Vol 15.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C657–93 (2003)
NOTE 1—Heating elements attached to fused alumina core—covered with baked-on refractory cement.
FIG. 1 Heating Chamber
maintain an adequate pressure and to provide heat equalization specimen may have any practical form that allows the use of a
between the specimen and the contacting electrodes. third electrode, when necessary, to guard against error from
6.3.1 Fig. 2 shows the specimen setup in the heating surface effects.” For practical reasons, a flat disk or square that
chamber. The bottom electrode shall be placed at the end of a is easy to set up in a furnace box is recommended. Other
metal rod and shall support the specimen in the center of the configurations are possible. The descriptions will apply to flat
furnace. The unguarded specimen electrode, No. 3 of Fig. 3, samples but can be modified for other configurations. Recom-
shall be placed in contact with this bottom contacting elec- mended limitations in the diameter of a disk are 40 to 130 mm.
trode. The top contacting electrode shall be placed on the This is not a critical dimension as the effective area of
guarded, specimen electrode, No. 1 of Fig. 3. This top measurements is defined by the area of the applied electrodes,
contacting electrode has leads connected to an off-center metal as stated in 7.7.
rod. The specimen guard electrode, No. 2 of Fig. 3, shall be 7.2 Astheelectricalpropertiesofglassaredependentonthe
connected to the second off-center metal rod with platinum thermal condition of the specimen, this condition should be
wire or strap. One end shall be connected to the specimen known and reported.
guard electrode; the other end shall be connected to the metal
NOTE 1—The glass could be annealed or have had a special heat
rod.
treatment which should be clearly defined.
6.3.2 All rods should be supported by insulation outside the
7.3 Polished surfaces are preferable as they permit easier
furnace in a cool zone to minimize electrical leakage at
cleaning and application of metallic electrodes.
elevated temperatures.
7.4 Thickness of the specimen should be determined with
6.3.3 Fig. 4 shows a top view of the specimen setup in the
micrometer calipers, calibrated to 0.01 mm, averaging several
heating chamber.
measurements on the specimen, as described in Test Methods
6.4 A Temperature-Control System should be provided so
D 374. Recommended limitations on thickness are from 1.0 to
that temperature-time fluctuations within the heating chamber
4.0 mm with a maximum variation of 60.1 mm.
are less than 0.01 T (where T is the temperature in degrees
7.5 There are two main reasons for cleaning a specimen: (1)
Celsius), during the time interval when resistance measure-
to assure better contact between an applied electrode and the
ments are made. Two thermocouples should be used for
surface of the specimen and (2) to remove contaminants that
accurate temperature readings, one in the heating chamber,
may lower the surface resistivity, thereby introducing an error
supplying the emf to the temperature controller and the other
in the measurements. If the glass is chemically durable, a
on the guard ring of the specimen. The latter should be used to
recommended cleaning procedure is: (1) trichloroethylene, (2)
measure the specimen temperature as instructed in the Appa-
detergent-water solution, (3) distilled water rinse, and (4)
ratus section (Temperature-Control Device) of Test Method
alcohol rinse, air dry. Special surface treatments, poor durabil-
D 1829.
ity, or the desire to include the effect of surface treatment
7. Test Specimen
require modification or elimination of the cleaning procedure.
7.1 The Test Specimens section (Volume Resistance or 7.6 Specimen Electrodes, preferably of gold (vacuum-
Conductance Determination) of Test Methods D 257 describes evaporated), should be applied to clean surfaces in a three-
in detail the specimen requirements.To quote in part, “The test
...
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