RS485 bus: common ground wire needed or not?

Diver300 said:

If the there is common power supply, there is no need for a separate earth, as Nigel says.

Click to expand...

Diver300 said:

That transducer will work with several volts ground difference between transmitter and receiver.

Click to expand...

earckens said:

Does a RS485 bus preferably have a common ground between connected devices?

Since a RS485 bus uses differential signals between two bus wires I would think not, but reading online comments on chip failures I now think otherwise. Correct?

EDIT: this is with a common power supply for all communicating devices.

Click to expand...