When testing a device with multiple signal ports during an IEC 61000-4-4 test, should noise be applied by clamping each line individually with the capacitive coupling clamp, or should multiple lines be clamped together and tested? For example, a device wi

When testing a device with multiple signal ports during an IEC 61000-4-4 test, should noise be applied by clamping each line individually with the capacitive coupling clamp, or should multiple lines be clamped together and tested? For example, a device wi

Perform the test one line at a time.
For ports with the same function, test one representative port, and treat the other ports as the same type of port; testing of the other ports is not performed.
If the functions are different (for example, different communication speeds or different communication purposes), test each one. Do not test multiple lines together, because the voltage applied to each individual line will decrease.