Below is the question asked during the live event, along with its respective answer.
Q: Steve, can you address the differences between performing the CS114 test with two signal cable bundles of x lines, each bundle in a shield, both enclosed by the probe vs the same number of cable lines, 2x, enclosed in one shield, enclosed by the probe?
A: Good question! The two cables will react differently because the impedance of the shield and shield proximity to the wires will have different parasitic effects. The dielectric between the cables (assuming the shield is insulated is another coupling mechanism so resonant points will vary between the two shields cable and the single shield cable. The shield to wire coupling varies based on proximity to the shield carrying the interference. The analysis is fairly complex but there will be differences. The real question – how is it installed? The test should try to mimic the real installation where possible. If two shielded cables are used and they are routed together, then test together. If they are routed separately then test individually. If installed in a single cable, then configure to test a single cable.