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Measuring power supply ripple with Siglent 1202X-E
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BillyO:

--- Quote from: u666sa on September 02, 2023, 11:58:51 am ---.
.
E) You gotta use 20 Mhz bandwidth limit
F) You gotta use 1x probe
.
.

--- End quote ---
If you want to match the fairy tale the manufacturer is telling, that's the way to do it.  If you want to see what is really going on use a 10X low capacitance probe and as much BW as you have available.

I also really hate that they all require additional filtering to be added for the noise/ripple tests.  The noise/ripple figures they provide should be as the power supply is.  If they require that filtering, then they should include it in the power supply.

Seems like it's all a smoke and mirrors fairytale throughout the PS industry.  Why can't they just be honest?
MarioBros69:

--- Quote from: BillyO on September 02, 2023, 02:21:46 pm ---
--- Quote from: u666sa on September 02, 2023, 11:58:51 am ---.
.
E) You gotta use 20 Mhz bandwidth limit
F) You gotta use 1x probe
.
.

--- End quote ---
If you want to match the fairy tale the manufacturer is telling, that's the way to do it.  If you want to see what is really going on use a 10X low capacitance probe and as much BW as you have available.

I also really hate that they all require additional filtering to be added for the noise/ripple tests.  The noise/ripple figures they provide should be as the power supply is.  If they require that filtering, then they should include it in the power supply.

Seems like it's all a smoke and mirrors fairytale throughout the PS industry.  Why can't they just be honest?

--- End quote ---

My English is not too good..., but I understand that you advise me to use the probe at x10 and not activate 20Mhz?
BillyO:

--- Quote from: MarioBros69 on September 02, 2023, 03:19:06 pm ---My English is not too good..., but I understand that you advise me to use the probe at x10 and not activate 20Mhz?

--- End quote ---
It is certainly up to you, but you need to decide what it is your after.

If you want to match the manufacturers specifications you will need to use a 1x probe and use the 20MHz BW limit.  Those along with other precautions like finding the and eliminating the source of ambient noise you are experiencing.  Most PS manufacturers also apply additional filter capacitors too, like both a 10uF electrolytic and a .47uF ceramic across the output then attach the probe directly (no ground wire) as close as possible to the output.

However, if you want to see the real noise and ripple you PS is generating use a 10X probe, full BW and do not put on the additional filter capacitors.  You will still need to eliminate any ambient noise and attach the probe directly to the output.
BillyO:
For this test I'm using a small 5V 3A Mornsun SMPS.

In both cases the supply was loaded to 2.5A

The first two pictures (next post) show the added capacitors and the 1X probe attached within 1cm of the PS terminals

The green traces are with: Added 10uF and 1uF capacitors, 20MHz BW limit, and 1X probe.  The first of these traces shows the ambient noise with this setup.


The blue traces are with: No added capacitors, full 600MHz BW, and a Tek 10X P6205 750MHz 1.5pF probe.  Again, the first of these traces shows the ambient.

Note also the time base and vertical changes between the green traces and the blue traces.

You can see that using all that filtering you really don't see the actual noise being produced by your PS.  The ripple is essentially the same but there is a significant amount of HF noise that you would not otherwise see.  You are figuratively sweeping the dirt under the carpet when using the ancient "industry standard" method.

BillyO:
Other pictures...
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