I have never had any trouble with mine at my courthouse or at the airport. However, I did a "bling bing-bing" at the bigger courthouse in the next county. No questions were asked there either, though I caught signals being flashed between the officers manning the equipment.
I think most systems show them a magnetic picture. I do one thing most guys do not do often though. The last, meaning top, item I place in the pocket-trash bowl is a spare ring sealed in a sterilization pouch that is clearly labeled "Spare Ring." Now I have enough metal BTB that all I am doing is carrying spare parts just in case i lose a segment or ball, and letting them know what those circles down there are. Besides, I'm sure there are some guys new to the screening job who would like to see a PA. Be nice and show it to them! Those stories you hear of removal being required are from the early days before the screeners got very well trained in their jobs.
a.k.a. Mitch E. "Sticky" Gander