Disturbances get into all my PSU

[uliano]

These traces come from 3 different PSU. As the disturbance seems coherent among them I'm assuming that it's coming from outside.

The grid? How can I tell and, more importantly, prevent it?

[BennoG]

looks more like something injected into the probes (telephone , some relay switching, dishwasher switching heater on / off)

[uliano]

Thank for orienting my attention elsewhere. It's always where you're not looking at!

This time it was the el chepo PSU of a ledstripe light.

[uliano]

Update:

By replacing the Chinese, Amazon sold, PSU "Nuova Germany" ("nuova" means "new" in Italian, WTF??) with a Taiwanese, Amazon sold, Meanwell I got *complete* rid of *those* disturbances. And that's good.

But then, I started falling into a huge rabbit hole... 

Under the big disturbances there are smaller ones and I'm afraid I'm sailing to a neverending quest   

While I'm still falling, and falling, and falling... I may also have stumbled on a bug of the SDS 1104X HD 

More on that in the next days and in an appropriate topic.

[tszaboo]

Two things. You have to define what's acceptable levels of noise, for functional reasons and for EMI compliance. Nothing is ever noiseless. And improving the probing setup often times are important, because it very well might be that the noise is picked up by the oscilloscope probe over the air and not actually present in the circuit.

[uliano]

The crappy PSU had, superimposed on top of the 24 V, a mighty 4Vpp @ 42kHz that gave rise,  radiated by 2 meters of led stripes and picked up through the air, to the above signals. That was clearly unacceptable and I got rid of it. Now I have something else I can investigate but, luckily, whith much less amplitude. Given my surroundings I’m aware that I can never hope to be in a quiet environment, so at some point l’ll need to stop.