I am trying to power my Arduino Mega 2560 from a benchtop power supply. I plan to essentially feed in a 9V supply directly on the Vin pin and connect the GND pin to the floating ground pin on the power supply. I noticed on the schematic that the UGND is connected to GND through this jumper. On the Arduino that I have these two pins are tied together. Does this mean that even with the external power supply the Arduino will be connected to the UGND, and in effect the protective earth?
What is the best way to float the Arduino? Would it be ok to remove the jumper connection between UGND and GND? Or should I try something like a linear USB isolator like this?