The IEC 62153-4-6 standard published by the International Electrotechnical Commission (IEC) defines a test method for determining the shielding effectiveness of a shielded metallic communication cable by applying a well-defined current and voltage to the cable shield and measuring the induced voltage to determine the surface transfer impedance. Measurements in the frequency range from a few kHz to 1 GHz are made using normal high frequency instrumentation.
-yuzey-transfer-empedansi-hat-enjeksiyon-yontemi.jpg "IEC 62153-4-6 Test Methods for Metallic Cables and Other Passive Components - Part 4-6: Electromagnetic Compatibility (EMC) - Surface Transfer Impedance - Line Injection Method")
The magnitude of the noise induced in the communication cable from electromagnetic influences is reduced by the shielding properties of the metallic shield. One of these properties is surface transfer impedance. Surface transfer impedance relates the current induced on one side of a shield to the longitudinal voltage appearing on the other side due to this current. At low frequencies, the surface transfer impedance for impermeable materials is equal to the direct current resistance of the screen. It decreases rapidly at higher frequencies. The frequency at which the decrease begins is a function of the metal's thickness and conductivity. For cylindrical shields with longitudinal seams, the transfer impedance increases at slightly higher frequencies. The size of the stitch opening indicates the frequency at which the increase starts. It is not easy to control the size of the seam opening, but the experimental results are relatively good with theoretical calculations.
Briefly, if a current is caused to flow from the outside of a cable shield, an induced longitudinal voltage is created on the inside of that shield. The ratio of this induced voltage to the driving current represents an impedance or surface transfer impedance.
Protecting signal cables against external interference is critical to ensuring the reliability of transmitted signals and data. This test is the most common method of evaluating whether a cable's shielding can protect the circuits it contains from electromagnetic interference. But materials and construction play an important role in shielding effectiveness. Surface transfer impedance testing is a reliable way to evaluate shield performance at any frequency.
Our organization, among the numerous tests, measurements, analyses, and evaluations it provides for businesses in various sectors, also offers electromagnetic compatibility (EMC), surface transfer impedance, and line injection method testing services within the scope of the IEC 62153-4-6 standard, using a trained and expert staff and advanced technological equipment, for metallic cables and other passive components.
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