BobaMosfet
- Joined Jul 1, 2009
- 2,110
You're going to see digital noise on the ground. Ground is never perfectly 0V in a digital environment. Digital circuitry pulls current in fits and starts. Bypass caps help with this, but it's there, and you may also be coupling your incumbent supply frequency (In the US, it's 60Hz AC). It can take some clever effort to minimize it, if it's a pain. You can also use isolation techniques for portions of your circuit that are impacted.Thanks for the reply.
The noise is pretty much everywhere, and it behaves a lot like the sort of thing you see with a ground loop (although I haven't been able to identify such a loop so far). On my 'scope's 20mv range, I can see the noise wherever I probe, and can tune it a little by adding or moving ground conductors. It's like ground bounce, but it happens regardless of how I load the supplies.