Cable Shielding Effectiveness Measurement

An efficient and repeatable measurement method for determining shielding effectiveness of cable feedthroughs based on the use of nested reverberation chambers is presented.

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. Measurement method for determining shielding effectiveness of cable feedthroughs. There could also be changes in compliance standards. The test method permits measurement of long specimens using high currents with a uniform current distribution along the cable shield.

Making accurate measurements is a challenge because shields have many different shapes and purposes. 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. Ventilation is another example and one that is usually problematic with regards to shielding effectiveness. 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. The shielding effectiveness is measured by comparing the reading of reference and the load devices. To verify the periodic calibration two gold standards are employed. Our most common request is to measure se for connectors and cables.

A shielding unit is inserted through the box s opening. The method is offered as a standard technique for measuring the shielding effectiveness of shielded cables. A plot of the chamber s dynamic range is shown in figure 2. This is a typical margin recommended by various industry specifications.

This method is effective for frequencies less than 500 megahertz.