Floating power supply for Arduino - Is it still connected to the USB ground?

Question

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?

Answer 1

Does this mean that even with the external power supply the Arduino will be connected to the UGND, and in effect the protective earth?

Yes.

Would it be ok to remove the jumper connection between UGND and GND?

No. I don't know quite why they provided that jumper. I can see no scenario in the datasheet where it suggests the two can be separate.

Or should I try something like a linear USB isolator like this?

If you want it to float then you need galvanic isolation on all USB pins. The device you link to will do that for you. There are others as well.

Personally in these situations I prefer to use a wireless communication system so there is no worry about grounds and isolation - it's naturally isolated.