Galvanic isolation is important because sooner or later someone connects a scope or something else (e.g. a non-floating power supply) that is mains earth referenced to the circuit incorrectly and promptly blows up both the board and the USB ports in their computer. This is a very common problem - just google "Arduino blown USB port".
Yeah, I understand your concern.
The project is not designed as an Scope alternative. You are only supposed to power your circuits from the board itself. Connecting the board to circuits powered from elsewhere can produce all kinds of problems and could damage the PC trough its USB port.
As the communication is serial from the main MCU and converted to USB on the STLink MCU it could be quite easy to communicate the board trough an optocoupled isolation barrier.
That would need an independent power supply and in no time the needed budget starts to ramp up.
As I commented, I think that the problem is common to most low cost USB instruments.
At a lower cost that a full isolated system, a more secure version of the shield will benefit from some protection components on the external terminals.
It also helps to somewhat protect against conducted noise getting into your circuit (PC is *horrible* for that) and any oopses if someone plays with higher voltages (12V or such) on the board and manages to short the voltage to the USB bus.
I'm quite puzzled of the low noise levels I get on the AC measurements.
On DC it is much worse but, DC measurements can easily benefit from averaging.
The Marco suggestion of adding 100k resistors in series with the opamp buffers ADC inputs can easily protect them against voltages in the order of 20V.
I think that the supply hazards are somewhat protected by the nucleo board internal circuits as I think that there is a diode in series with the power line. You can always burn the nucleo board, but it is much better than ruining a PC.
All external lines on SLab, except the supplies, connect with the main MCU and the main MCU connects with the ST-Link MCU through a serial link unrelated to the external pins. It is much easier to blow the Nucleo board or the main MCU than blowing the PC, but I understand that going so low in cost can yield some potential hazards. But they are not much different than using the nucleo board in any other project.
Otherwise it is a pretty neat project, it could be very much a poor man's Analog Discovery for learning analog electronics.
Thanks
That's the Idea. I have an Analog Discovery (Version 1) and it is a quite neat piece of equipment. Version 2 is much better.
I wish it was something like the SLab Python layer for the Analog discovery. Although the Discovery software is good, I miss some easier automation capabilities.
But close to 300$ is too much money if you want a low budget Small Lab for on-hands electronic learning.