Cable Shielding Effectiveness Measurement

There could also be changes in compliance standards.

Cable shielding effectiveness measurement.

It involves the use of a sealed box with an opening. A shielding unit is inserted through the box s opening. 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.

For these products we primarily use two techniques the triaxial fixture method and the mode stirred method. Measurement method for determining shielding effectiveness of cable feedthroughs. Cable interconnects which allow cables inside the cage to connect to cables outside may undergo modification for additional connectors that damage the shielding integrity. 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.

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

An efficient and repeatable measurement method for determining shielding effectiveness of cable feedthroughs based on the use of nested reverberation chambers is presented. This method is effective for frequencies less than 500 megahertz. The shielding effectiveness is measured by comparing the reading of reference and the load devices. Measurements were made in the frequency range 0 5 to 100 mhz.

For example housings connectors or cables all use shields and each application requires a unique test fixture to ensure accurate and repeatable se measurements.