ASTM D 4935-10 Standard Test Method for Measuring the Electromagnetic Shielding Effectiveness of Planar Materials
ASTM D-4935 shielding effectiveness testing focuses on planar materials. As a leader in shielding effectiveness, Keystone Compliance works with manufacturers to the shielding properties of their materials on a daily basis. Our lab feature seven test chambers and multiple work stations.
Our team provides constant communication from the creation of the test plan to the issuance of the ASTM D-4935-10 test report. The customer experience we provide is unmatched. From a capability standpoint, we can test samples of any size and have a wide spectrum of frequency range.
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The remainder of this page provides an overview of ASTM D-4935 electromagnetic shielding effectiveness of planar materials.
The ASTM D 4935-10 test method provides a procedure for measuring the electromagnetic shielding effectiveness of a planar material for a plane, far-field electromagnetic wave. From the measured data. near-field shielding effectiveness values may be calculated for magnetic sources for electrically thin specimens. Electric field shielding effectiveness values may also be calculated from this same far-field data. However, their validity and applicability have not been established.
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. This displacement current results from two things. First, there is a decreased capacitive coupling at lower frequencies. Second, overmoding (excitation of modes other than the transverse electromagnetic mode at higher frequencies for the size of the 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-field 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.
This test method is not applicable to cables or connectors. Also, 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.
To gain an understanding of ASTM-D4935, it is important be familiar with some of the technical terms. The dynamic range is the difference between the maximum and minimum signals measurable by the system. The term electrically thin means the thickness of the specimen is much smaller than the electrical wavelength within the specimen.
A far field is the region where vectors arc orthogonal to each other and both arc normal to the direction of propagation of energy. The near field is the region where vectors are not related by simple rules.
Lastly, shielding effectiveness is the ratio of power received with and without a material present for the same incident power.
ASTM D4935-10 EMC testing applies to the measurement of shielding effectiveness of planar materials under normal incidence, far-field, plane-wave conditions. The uncertainty of the measured shielding effectiveness values is a function of material, mismatches throughout the transmission line path, dynamic range of the measurement system, and the accuracy of the ancillary equipment.
An uncertainty analysis is provided in the ASTM D 4935-10 test standard to illustrate the uncertainty that may be achieved by an experienced operator using good equipment. Deviations from the procedure in this test method will increase this uncertainty.
This test method measures the net shielding effectiveness caused by reflection and absorption. Separate measurement of reflected and absorbed power may be accomplished by the addition of a calibrated bidirectional coupler to the input of the holder.
The final test report includes test specimen identification and measured values of shielding effectiveness at each frequency of measurement. Values of shielding effectiveness based on measured values from 8.7 that were within 10 dB of the smallest detectable signal of the measurement system should be noted as exceeding the DR of the measurement system.
As an ISO-17025-accredited test lab, our shielding effectiveness test reports are recognized and accepted around the globe. We offer short lead times on scheduling and work expeditiously to deliver test reports within one week of the completion of the test program.
In addition to shielding effectiveness testing, we also provide traditional EMC testing, ESD testing, indirect lightning testing and many other forms of product certification testing. We also have a full mechanical testing and package testing lab.