Yep, that is interesting. You are right and that us exactly the way we built and tested the cages. I remember when we wired the various factories for ESD static control, there was some question as to the best grounds to use. I ended up running wiring up into the ceiling and tapping into structural steel. Even though there were still differentials, they were pretty minimal at the building's framework.aj81spider wrote:Hi Pete,
You're right. In that situation the chassis is effectively the shield and needs to be at the same potential and continuous. You'll find that inside the box there should be (if designed right) single path grounds from all the boards to the power supply.
The analogy to the car situation would be if you had several boxes all shielded you would want to connect each to a common ground point with a single wire and you wouldn't want to have shields between the boxes connected at both ends or you might get current flow between the boxes on the shield wires.
Pete