Designation: D4935 - 10
Standard Test Method for
Measuring the Electromagnetic Shielding Effectiveness of
Planar Materials
1
This standard is issued under the ?xed designation D4935; the number immediately following the designation indicates the year of
original adoption or, in the caseof revision, the year of last revision. A number in parenthesesindicates the year of last reapproval. A
superscript epsilon (′) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method provides a procedure for measuring the
electromagnetic (EM) shielding effectiveness (SE) of a planar
material for a plane, far-?eld EM wave. From the measured
data, near-?eld SE values may be calculated for magnetic (H)
sources for electrically thin specimens.
2,3
Electric (E) ?eld SE
values may also be calculated from this same far-?eld data, but
their validity and applicability have not been established.
1.2 The measurement method is valid over a frequency
range of 30 MHz to 1.5 GHz. These limits are not exact, but are
based on decreasing displacement current as a result of
decreased capacitive coupling at lower frequencies and on
overmoding (excitation of modes other than the transverse
electromagnetic mode (TEM)) at higher frequencies for the
size of specimen holder described in this test method. Any
number of discrete frequencies may be selected within this
range. For electrically thin, isotropic materials with frequency
independent electrical properties of conductivity, permittivity,
and permeability, measurements may be needed at only a few
frequencies as the far-?eld SE values will be independent of
frequency. If the material is not electrically thin or if any of the
parameters vary with frequency, measurements should be made
at many frequencies within the band of interest.
1.3 This test method is not applicable to cables or connec-
tors.
1.4 Units —The values stated in SI units are to be regarded
as standard. No other units of measurement are included in this
standard.
1.5 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 appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
4
D1711 Terminology Relating to Electrical Insulation
3. Terminology
3.1 De?nitions —For de?nitions of terms used in this test
method, refer to Terminology D1711.
3.2 De?nitions of Terms Speci?c to This Standard:
3.2.1 dynamic range (DR), n—difference between the maxi-
mum and minimum signals measurable by the system.
3.2.1.1 Discussion —Measurement of materials with good
SE require extra care to avoid contamination of extremely low
power or voltage values by unwanted signals from leakage
paths.
3.2.2 electrically thin, adj —thickness of the specimen is
much smaller (<
1
?
100
) than the electrical wavelength within the
specimen.
3.2.3 far ?eld, n—that region where vectors E and H are
orthogonal to each other and both arenormal to the direction of
propagation of energy.
3.2.4 near ?eld, n—that region where E and H are not
related by simple rules.
3.2.4.1 Discussion —The transition region between near
?eld and far ?eld is not abrupt but is located at the distance
close to λ/2πfrom a dipole source, where λis the free-space
wave length of the frequency of the source. This concept of
regions is further blurred by reradiating as a result of scattering
by re?ecting materials or objects that may be distant from the
source. The interior of metallic structures often contains a
mixture of near-?eld regions.
3.2.5 shielding effectiveness (SE), n—ratio of power re-
ceived with and without a material present for the same
incident power.
1
This test method is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of
Subcommittee D09.12 on Electrical Tests.
Current edition approved May 1, 2010. Published June 2010. Originally
approved in 1989. Last previous edition approved in 1999 as D 4935–99.DOI:
10.1520/D4935 –10.
2
Wilson, P. F., and Ma, M. T., “ＡStudy of Techniques for Measuring the
Electromagnetic Shielding Effectiveness of Materials, ”NBS Technical Note 1095,
May 1986.
3
Adams, J. W., and Vanzura, E. J., “ShieldingEffectiveness Measurements of
Plastics, ”NBSIR 85-3035, January 1986.
4
For referencedASTM standards, visit the ASTM website, www.astm.org, or
contactASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standardsvolume information, refer to the standard ’ｓDocument Summary pageon
the ASTM website.
Copyright ? ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
Copyright ASTM International
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