Cable Shielding Effectiveness Measurement

To verify the periodic calibration two gold standards are employed.

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. It involves the use of a sealed box with an opening. The method is offered as a standard technique for measuring the shielding effectiveness of shielded cables. For example housings connectors or cables all use shields and each application requires a unique test fixture to ensure accurate and repeatable se measurements.

A shielding unit is inserted through the box s opening. Measurement method for determining shielding effectiveness of cable feedthroughs. This method is effective for frequencies less than 500 megahertz. An efficient and repeatable measurement method for determining shielding effectiveness of cable feedthroughs based on the use of nested reverberation chambers is presented.

Our most common request is to measure se for connectors and cables. This is a typical margin recommended by various industry specifications. For these products we primarily use two techniques the triaxial fixture method and the mode stirred method. 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. A plot of the chamber s dynamic range is shown in figure 2. 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.

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