Noise level of Power Supply

[schmitt trigger]

Chinese price means Chinese customer service.

Don’t get me wrong. Most times Chinese products will deliver an excellent performance commensurate with the price. But if something goes wrong, you are usually on your own.

[radiolistener]

I understand I can keep looking for the source of issue or I can add some capacitors to fix it. My point is why Korad cannot produce the same result as Instek. Because it is cheap or because it is bad or defective?

it is unclear what is the source. Most of all the source is your measurement wires which receive RFI noise from environment. Because your setup looks very weak for noise RFI. For example, ground clip of oscilloscope probe is a good antenna for such noise. Also received noise depends on PSU output impedance and many other things that needs to be taken into account.

Try to not connect probe to PSU output but place it's ground clip shortened on probe pin at the same position near PSU, does it receive noise? Then try to touch PSU ground with ground clip shortened on probe pin. Does noise appears?

[David Hess]

As a sanity check, to rule out weird ground loops via EMI caps between line voltage and chassis, connect both the probe tip and ground clip to the power supply's negative output:

^^^ This ^^^

Or use a differential probe but do this test first.

[Doctorandus_P]

Additionally, I'm quite certain you see a lot less noise if you buy a EUR1500 power supply and view it's output with an EUR80 oscilloscope 

[pdenisowski]

Personally, I think outside of a lab environment it's very difficult to measure PARD on a PSU.

For testing the supply noise one should use a more passive load, like a resistor, not an RF or µC project that causes switching artifacts.

Yes and yes.  I'm actually working on a presentation on this very topic right now and could not agree with both of you more.

[pdenisowski]

Additionally, I'm quite certain you see a lot less noise if you buy a EUR1500 power supply and view it's output with an EUR80 oscilloscope 

  

[PinheadBE]

Still on topic, but with a different supply.

I have a (switching) PS from Meanwell laying around that I would like to put to good use.   It's a RS-150-5 capable of delivering 26 A under 5 V.
Of course, I will rarely use it at full power; more likely in the range 1 - 3 A.   But since I have it and do not use it for anything else....

https://www.meanwell.com/productPdf.aspx?i=419#1

The specs states 80 mV p-p (max) Ripple and noise.

Is there a way I could filtering a significant part of that, to be under the 10 mV p-p or even less ?

I know I could add a big fat cap on the output, but:
- what about the peak current when turning on ? 
- What about the cap discharge when powering off ?  In this case, adding a diode will add a voltage drop that could not be compensated by 0.5 V overhead the PSU can supply (the ouptut is adjustable from 4.5 to 5.5 V)

Any suggestions ?

[Electro Fan]

might be something useful in here…

probe connections - both tip and ground clip - definitely can impact the results

https://www.eevblog.com/forum/testgear/korad-kd3005d-bench-supply-power-on-spike/msg3509594/#msg3509594

https://www.eevblog.com/forum/testgear/rigol-scope-probe-to-bnc-adapter/msg672014/#msg672014

https://youtu.be/zodpCuxwn_o?si=WB1it9-i5zzl0BCV