Am 14.07.19 um 09:48 schrieb 'Paul D. DeRocco' pderocco@...
[chromapolaris]:

> You should always have a connection between the scope ground and a
> circuit ground near where you're trying to look.

Just another pitfall: I once mis-seated a connector, so there was no
ground connection between a troublesome pcb and the supplies. But due to
the circuits circumstances the pcb itself had created a virtual ground,
which made me measure "reasonable" values on the pcb itself. My lesson
from that is, that I now measure the ground lines first.

Florian