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:
simulate this circuit – Schematic created using CircuitLab
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?
Best Answer
It is typically safe to connect the laptop chassis to mains earth. If it isn't already in the power brick.
Any peripheral might also ground chassis to mains earth, or create leakage current.
Just be aware of ground loops.
To prevent all of these power and noise problems I have a collection of USB isolators, and an isolated USB HUB*
*this one is mains earth referenced though (bb-elec UHR204)