Cable Shielding Effectiveness Measurement

When a cable specification calls for 90 db of rf shielding the 100 db dynamic range allows a 10 db margin in the measurement range.

Cable shielding effectiveness measurement.

For example housings connectors or cables all use shields and each application requires a unique test fixture to ensure accurate and repeatable se measurements. An efficient and repeatable measurement method for determining shielding effectiveness of cable feedthroughs based on the use of nested reverberation chambers is presented. This is a typical margin recommended by various industry specifications. A plot of the chamber s dynamic range is shown in figure 2.

Ventilation is another example and one that is usually problematic with regards to shielding effectiveness. Measurement method for determining shielding effectiveness of cable feedthroughs. For these products we primarily use two techniques the triaxial fixture method and the mode stirred method. There could also be changes in compliance standards.

The method is offered as a standard technique for measuring the shielding effectiveness of shielded cables. The test method permits measurement of long specimens using high currents with a uniform current distribution along the cable shield. Measurements were made in the frequency range 0 5 to 100 mhz. 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. To verify the periodic calibration two gold standards are employed. A shielding unit is inserted through the box s opening. Our most common request is to measure se for connectors and cables.

Making accurate measurements is a challenge because shields have many different shapes and purposes.