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| How much noise floor and other things matter in oscilloscope usability |
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| Kleinstein:
--- Quote from: Fungus on December 25, 2021, 08:42:21 pm --- --- Quote from: Kleinstein on December 25, 2021, 08:34:41 pm ---Averaging only works well if one has a good signal to trigger from - so if there is only a small / noisy signal this will not help. --- End quote --- If the ripple is too small to trigger from then the power supply is probably OK and there's nothing to worry about. --- End quote --- It is not just triggering, just a stable triggger to see fast parts too. Often there is a stable trigger available, but one may have to find it. An extra trigger and than looking at the ripply would even separate contricbutions to the ripple if there are multiple asyncronous parts (e.g. mains and a SMPS). It really depends on how much ripple you still care. Sometime 0.1 mV could be too much. |
| oz2cpu:
1mV div, here is where you really see the internal noise :-) |
| G0HZU:
--- Quote ---The picture show 10 Ms/s. So there is anditional BW limit (~ 5 MHz) there. To do a fair comparison one would have the switch the faster scope also a slower hirizontal rate to get the lower sampling rate. --- End quote --- I'm not sure there will be a 5MHz bandwidth limit. With the 30MHz limiter enabled I think the bandwidth limit for signals is still 30MHz on this scope even at low sample rates. One would have to be wary of aliasing but the signal being viewed here is noise. |
| Fungus:
--- Quote from: Kleinstein on December 25, 2021, 08:54:19 pm ---It is not just triggering, just a stable triggger to see fast parts too. Often there is a stable trigger available, but one may have to find it. --- End quote --- Yep. No arguments there. That's why I was wondering if OP can actually do it in practice. He already posted a screenshot of his ripple here so let's see what the 'scope is capable of. It looks like a triggerable signal to me but I don't have an MSO5000 to play with.. |
| nctnico:
--- Quote from: Fungus on December 25, 2021, 07:51:23 pm --- --- Quote from: G0HZU on December 25, 2021, 07:30:59 pm ---If it helps, I can switch the scope to 1Meg input and attach a 50R load and it looks pretty much the same. There might be a tiny bit more noise but any change is barely perceptible. --- End quote --- There's no point. Everybody here knows (and freely admits) that lower noise oscilloscopes exist. They make for pretty screenshots and youtube videos. The questions is: How much advantage does it give you in real life? For digital signals? None at all. For that you need bandwidth and high sample rates which is where the MSO5000 shines. For periodic signals in the mV range? --- End quote --- :palm: You keep taking the wrong turn when only focussing on small signals. Your screenshot clearly shows a wide band of noise where any detail on any signal level is lost. The noise is easely 40% of a division. With 8 divisions and 8 bits you have 32 LSB per division but with 40% noise you might as well have a 5 bit ADC and still get the same result. Needing to use averaging or high-res mode is just a crutch when the noise comes from the DSO itself. There are so many lower noise alternatives out there from GW Instek, MicSig and (if you have the budget) R&S as well that it makes no sense to buy a noisy Rigol at all. |
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