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Measuring power supply ripple with Siglent 1202X-E

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BillyO:

--- Quote from: nctnico on September 02, 2023, 06:12:09 pm ---What you can try is reverse +/- and see which part of the noise flips up-side-down and what remains the same.

--- End quote ---
Well, grounding one side makes things significantly worse (800mVp-p).  I guess since the PS is already grounded that just created a big loop antenna.

If I reverse things the ripple may indeed reverse, but the spikes are quite random and roughly symmetrical.  They'll look the same anyway.


--- Quote from: nctnico on September 02, 2023, 06:12:09 pm ---It is quite possible the PSU is pushing HF current through the ground connection of the probe
--- End quote ---

BTW, the PSU is being supplied with a ground.  The only way to deal with this properly would be a differential set-up.  Would two probes and the math "-" function work?

dophuc:
You can use an isolation transformer to power the PSU, which ensures the PSU is not grounded. And that's how I do it when testing PSU ripple/noise

tautech:

--- Quote from: dophuc on September 02, 2023, 06:56:32 pm ---You can use an isolation transformer to power the PSU, which ensures the PSU is not grounded. And that's how I do it when testing PSU ripple/noise

--- End quote ---
Any decent PSU output should be isolated from mains Gnd.

BillyO:

--- Quote from: BillyO on September 02, 2023, 06:22:56 pm ---Would two probes and the math "-" function work?

--- End quote ---

Nope!

nctnico:

--- Quote from: tautech on September 02, 2023, 07:04:36 pm ---
--- Quote from: dophuc on September 02, 2023, 06:56:32 pm ---You can use an isolation transformer to power the PSU, which ensures the PSU is not grounded. And that's how I do it when testing PSU ripple/noise

--- End quote ---
Any decent PSU output should be isolated from mains Gnd.

--- End quote ---
Define isolated... You'll still have capacitance towards ground and neutral has a reference to ground as well. Together with the X and Y caps, you have all kinds of ground paths together with capacitive coupling to the surroundings.

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