I have the following problem: I am currently debugging an electronic sensor board which is connected to the USB port of a laptop. The USB port is used both for communication via UART and to supply power to the sensor. The sensor shows some erratic behaviour and I want to check whether that is caused by an insufficient power supply of the USB port.
Therefore I want to connect the sensor board to an external lab supply like this:
Since the laptop is not gonnected to mains ground (MGND) I would be connecting the floating laptop ground (LGND) directly to the mains ground (MGND). My question is whether that is okay or do I need to ground the laptop to be sure?