ASTM D374-99
(Test Method)Standard Test Methods for Thickness of Solid Electrical Insulation
Standard Test Methods for Thickness of Solid Electrical Insulation
SCOPE
1.1 These test methods cover the determination of the thickness of several types of solid electrical insulating materials employing recommended techniques. Use these methods except as otherwise required by a material specification.
1.2 The values stated in inch-pound units are the standard.
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.
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An American National Standard
Designation: D 374 – 99
Standard Test Methods for
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Thickness of Solid Electrical Insulation
This standard is issued under the fixed designation D 374; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope H) employ different micrometers that exert various pressures
for varying times upon specimens of different geometries.
1.1 These test methods cover the determination of the
Table 1 and Table 2 display basic differences of each test
thickness of several types of solid electrical insulating materi-
method and identify methods applicable for use on various
als employing recommended techniques. Use these methods
categories of materials.
except as otherwise required by a material specification.
1.2 The values stated in inch-pound units are the standard.
5. Significance and Use
1.3 This standard does not purport to address all of the
5.1 Some electrical properties, such as dielectric strength,
safety concerns, if any, associated with its use. It is the
vary with the thickness of the material. Determination of
responsibility of the user of this standard to establish appro-
certain properties, such as relative permittivity (dielectric
priate safety and health practices and determine the applica-
constant) and volume resistivity, usually require a knowledge
bility of regulatory limitations prior to use.
of the thickness. Design and construction of electrical machin-
2. Referenced Documents ery require that the thickness of insulation be known.
2.1 ASTM Standards:
6. Apparatus
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D 1711 Terminology Relating to Electrical Insulation
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6.1 Apparatus A— Machinist’s Micrometer Caliper with
D 6054 Practice for Conditioning Electrical Insulating Ma-
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Calibrated Ratchet or Friction Thimble:
terials for Testing
6.1.1 ApparatusAis a micrometer caliper without a locking
E 252 Test Method for Thickness of Thin Foil and Film by
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device but is equipped with either a calibrated ratchet or a
Weighing
friction thimble. By use of a proper manipulative procedure
3. Terminology and a calibrated spring (seeAnnexA1), the pressure exerted on
the specimen is controllable.
3.1 Refer toTerminology D 1711 for definitions pertinent to
6.1.2 Use an instrument constructed with a vernier capable
this standard.
of measurement to the nearest 0.1 mil.
3.2 Definitions of Terms Specific to This Standard:
6.1.3 Use an instrument with the diameter of the anvil and
3.2.1 1 mil, n—a dimension equivalent to 0.0010 in.
spindle surfaces (which contact the specimen) of 250 6 1 mil.
3.2.2 absolute uncertainty (of a measurement), n—the
6.1.4 Use an instrument conforming to the requirements of
smallest division that may be read directly on the instrument
7.1, 7.2, 7.5, 7.6.1, and 7.6.2.
used for measurement.
6.1.5 Periodically, test the micrometer for conformance to
3.2.3 micrometer, n—an instrument for measuring any di-
the requirements of 6.1.4.
mension with absolute uncertainty of 1 mil or smaller.
6.2 Apparatus B—Machinist’s Micrometer Without a
4. Summary of Test Methods
Ratchet:
6.2.1 Apparatus B is a micrometer caliper without a locking
4.1 This standard provides eight different test methods for
device.
the measurement of thickness of solid electrical insulation
6.2.2 Use an instrument constructed with a vernier capable
materials. The test methods (identified as Methods A through
of measurement to the nearest 0.1 mil.
6.2.3 Use an instrument with the diameter of the anvil and
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spindle surfaces (which contact the specimen) 250 6 1 mil.
These test methods are under the jurisdiction of ASTM Committee D-9 on
Electrical and Electronic Insulating Materials and are the direct responsibility of 6.2.4 Use an instrument conforming to the requirements of
Subcommittee D09.12 on Electrical Tests.
7.1, 7.2, 7.5.1, 7.5.2, 7.5.3, 7.6.1, and 7.6.3.
Current edition approved March 10, 1999. Published June 1999. Originally
published as D 374 – 33T. Last previous edition D 374 – 94.
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Annual Book of ASTM Standards, Vol 10.01
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Annual Book of ASTM Standards, Vol 10.02.
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Annual Book of ASTM Standards, Vol 02.02. Hereinafter referred to as a machinist’s micrometer.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D374–99
TABLE 1 Methods Suitable for Specific Materials
6.3.2 The preferred design and construction of manually
Material Method operated dead-weight dial-type micrometers calls for a limit on
the force applied to the press
...
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