Cable Shielding Effectiveness Measurement

Cable interconnects which allow cables inside the cage to connect to cables outside may undergo modification for additional connectors that damage the shielding integrity.

Cable shielding effectiveness measurement.

Measurement method for determining shielding effectiveness of cable feedthroughs. For example housings connectors or cables all use shields and each application requires a unique test fixture to ensure accurate and repeatable se measurements. Measurements were made in the frequency range 0 5 to 100 mhz. It involves the use of a sealed box with an opening.

For these products we primarily use two techniques the triaxial fixture method and the mode stirred method. The shielding effectiveness is measured by comparing the reading of reference and the load devices. Our most common request is to measure se for connectors and cables. Ventilation is another example and one that is usually problematic with regards to shielding effectiveness.

The test method permits measurement of long specimens using high currents with a uniform current distribution along the cable shield. An efficient and repeatable measurement method for determining shielding effectiveness of cable feedthroughs based on the use of nested reverberation chambers is presented. The method is offered as a standard technique for measuring the shielding effectiveness of shielded cables. A shielding unit is inserted through the box s opening.

The measurement method is validated by comparing measurements on an isolated conductor penetrating the shield with a simple theory based on basic circuit theory in combination with antenna theory. This method is effective for frequencies less than 500 megahertz. Making accurate measurements is a challenge because shields have many different shapes and purposes. This is a typical margin recommended by various industry specifications.

A plot of the chamber s dynamic range is shown in figure 2.