CE Noise Immunity and testing

[w3amd]

Hi all,

During testing we found we have an issue in: Conducted RF Immunity (EN 61000-4-6)

Noise near 30 Mhz can somehow jump onto the instrumentation measuring circuits and seems to push the signal to one rail or another on the instrumentation op-amps from what I can determine. It also takes a very long time between starting the RF @ 2W on the cables and the final bad result (takes about 30 seconds or so).

Is there a way with the Rigol DS815-TG to set up for a test to see how the chassis behaves at let's say 30 Mhz. I'm thinking we don't have a low enough impedance path on the shields from the wires through the chassis to PE. We've determined that by looping the cables (which happens to be 1/4 wavelength of 30 Mhz) between it's normal physical connector on the chassis and placing the shield to another area of the cabinet this causes the same problem.

Can the Rigol TG be dead shorted? I'm assuming our cabinet does not have 0 ohms impedance at 30 Mhz but if it does will I break it?

I think I should be measuring between the shield to chassis ground on the suspect connector and the actual star ground point back to the mains and seeing how much impedance this is near 30 Mhz? Am I on the right track? And how to go about doing this test?

TIA,
John