Grounding with separate enclosures?

[scottjoplin]

Good point 🙂

 

[forr]

Ok, you don't want to connect 0V to chassis because PE may be noisy, fair enough. On a side note, oscilloscope 0 volts/reference is usually connected to PE, why is that done?

Safety.
But there exist safe scopes with floating inputs which just allow to avoid the connection to earth.

EDIT
Have you noticed that scopes do not have a star ground scheme ? Why is that done ?