How to Download ASTM D4935 99 PDF for Free: A Complete Guide
If you are looking for a standard test method for measuring the electromagnetic shielding effectiveness of planar materials, you might be interested in ASTM D4935 99. This test method provides a procedure for measuring the electromagnetic (EM) shielding effectiveness (SE) of a planar material due to a plane-wave, far-field EM wave. From the measured data, near-field SE values may be calculated for magnetic (H) sources for electrically thin specimens. Electric (E) field SE values may also be calculated from this same far-field data, but their validity and applicability have not been established.
astm d4935 99 pdf free
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ASTM D4935 99 is a useful test method for evaluating the shielding performance of materials such as fabrics, films, foams, laminates, coatings, and composites. It can also be used to compare different materials or to optimize the design of shielding structures. However, this test method is not applicable to cables or connectors.
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 due to 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-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.
So, how can you download ASTM D4935 99 PDF for free? Here are some steps you can follow:
Step 1: Visit the ASTM International website
ASTM International is an organization that develops and publishes voluntary consensus standards for various materials, products, systems, and services. It has over 12,000 standards in its online collection, covering topics such as metals, plastics, textiles, petroleum, construction, energy, environment, consumer products, medical services, and more.
To access ASTM D4935 99 PDF for free, you need to visit the ASTM International website at https://www.astm.org/. This is the official source of ASTM standards and other technical information.
Step 2: Search for ASTM D4935 99
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This will take you to a page with a list of search results related to your query. You should see a result with the title \"ASTM D4935-99 - Standard Test Method for Measuring the Electromagnetic Shielding Effectiveness of Planar Materials (Withdrawn 2005)\". This is the test method you are looking for.
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to pass through. The SE of a material depends on various factors, such as the frequency of the EM wave, the thickness and shape of the material, the electrical properties of the material, and the angle of incidence of the EM wave.
The ASTM D4935 99 test method measures the SE of a material in terms of its transfer impedance (Zt), which is defined as the ratio of the voltage across the material to the current through it. The transfer impedance is related to the SE by the following equation:
SE = 20 log10(Z0/Zt)
where Z0 is the characteristic impedance of free space (377 Ω) and Zt is the transfer impedance of the material.
The transfer impedance of a material can be calculated from the measured transmitted and reflected power by using the following equations:
Zt = Z0(1 + Γ)/(1 - Γ)
Γ = (Pr/Pi)e
where Γ is the complex reflection coefficient, Pr is the reflected power, Pi is the incident power, and φ is the phase difference between the incident and reflected waves.
Step 5: Prepare your test setup and specimen
To perform the ASTM D4935 99 test method, you need to prepare your test setup and specimen according to the specifications given in the standard. The test setup consists of a signal generator, a receiver, a flanged coaxial transmission line with two conical sections, and a specimen holder. The signal generator and receiver should be capable of generating and measuring EM waves over a frequency range of 30 MHz to 1.5 GHz with sufficient accuracy and resolution. The flanged coaxial transmission line should have an inner diameter of 50 mm and an outer diameter of 100 mm. The conical sections should have an angle of 30 and a length of 200 mm. The specimen holder should be made of non-conductive material and have a circular opening with a diameter of 50 mm.
The specimen should be a planar material with uniform thickness and electrical properties. The specimen should have a circular shape with a diameter of 50 mm and fit snugly into the specimen holder. The specimen should not have any holes, cracks, or defects that could affect the measurement results. The specimen should also be clean and dry before testing.
Step 6: Perform the measurement procedure
To perform the measurement procedure, you need to follow these steps:
Connect the signal generator to one end of the flanged coaxial transmission line and connect the receiver to the other end.
Insert an empty specimen holder into the transmission line between the two conical sections.
Set the signal generator to produce a plane-wave, far-field EM wave at a desired frequency within the range of 30 MHz to 1.5 GHz.
Measure and record the transmitted and reflected power at this frequency using the receiver.
Repeat steps 3 and 4 for any other frequencies you want to test.
Remove the empty specimen holder from the transmission line and insert your specimen into it.
Repeat steps 3 to 5 for each frequency with your specimen in place.
Calculate the SE of your specimen at each frequency using the equations given in step 4.
Analyze and report your results according to your objectives and requirements.
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