I have a couple of grounding questions that I am hoping can be answered.

Can the common ground between each RS-485 node be the same conductor as the shield of the twisted pair? I would expect that this may not work if each node was also individully grounded to earth as ground loop currents may result.

Also, if the transmitter is galvanically and optically isolated, is a common ground for communication no longer required? If not, and if the device is battery powered and has no external metal parts, can individual nodes totally float without any grounding?

George Younkin