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| How much noise floor and other things matter in oscilloscope usability |
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| Fungus:
--- Quote from: Fiorenzo on December 28, 2021, 10:08:00 pm ---Ripple same settings on both oscilloscope AC, normal mode, 1x probe --- End quote --- I disagree that there's a huge difference in useful information. Sure, the Siglent line is thinner but The Rigol is showing the ripple just fine. You should also be able to change the displayed part of the signal (the red bit) by twisting the selection knob on the Rigol (ie. intensity setting). And again: What does averaging mode do if you turn it on in this situation? Why is this being avoided? |
| Fungus:
--- Quote from: nctnico on December 28, 2021, 10:19:06 pm ---This is even worse than I expected ( :wtf: ). I don't care about the open / shorted inputs at the most sensitive V/div (Rigol does digital zoom there so it is not an apples for apples comparison) but I do care about the display of an actual signal. On the Siglent you can clearly see spikes on the signal which are completely obscured on the Rigol. --- End quote --- I dunno what those "spikes" are but they're not ripple. To me it seems liek the Rigol is perfectly capable of showing the ripple from that power supply. Is there anybody here who can't see the ripple in this image or thinks that the 14.003mV displayed value is somehow massively different than the 14.048mV displayed by the Siglent? (and this is without averaging, apparently, averaging can only improve this) Is the Siglent display or the number displayed by the Siglent worth 400 Euros more? I dunno. It's all relative, but I could buy all sorts of useful stuff for 400 Euros. :-// However you look at it: You'll have a hard time convincing me that the Rigol is a disaster. Sure the Siglent's line is thinner but the Rigol is perfectly capable of showing the ripple on screen and measuring it. That's what really counts, and is the subject of this thread. |
| nctnico:
Just stop trying to make right what is clearly wrong. The small spikes that the trace shows on the Siglent (or any other modern DSO other than Rigol mentioned in this thread) can point to other problems. An FFT will tell more but again, on the Rigol the HF component riding on the lower frequency ripple likely gets drowned in the noise. The Rigol MSO5000 is outright horrible. Claiming anything else is delusional. Edit: pay close attention to the excellent example G0HZU posted below. It may save your bacon one day trying to find an illusive problem in a circuit. At some point cheap doesn't make up for poor performance. In the end you'll need to buy an extra instrument to make the measurement cheaper gear can't do. Been there, done that and wasted enough money on cheap gear which in the end didn't deliver. |
| G0HZU:
--- Quote ---And again: What does averaging mode do if you turn it on in this situation? Why is this being avoided? --- End quote --- OK I'll bite...If you want to see the effects of averaging then see the example below. I've just set up a couple of function generators and summed the waveforms into my old HP Infinium scope. I've set the scope to 50R input and done everything in x1. The scope is set to 1mV/div and I've turned on the 30MHz bandwidth limit. Waveform 1 is a triangle wave at about 500Hz and it is about 5mV pkpk. Waveform 2 is a series of narrow positive pulses each of amplitude 1mV and they occur every 768us. The plots below show the low noise performance of this old scope and also show how averaging can cause information to be lost. See below for a single shot capture and see also for what happens with averaging. The information about the pulses is totally lost in the averaged screenshot because the period of the triangle wave and the pulses is different. I hope this helps? |
| bdunham7:
--- Quote from: Fungus on December 28, 2021, 11:32:30 pm ---However you look at it: You'll have a hard time convincing me that the Rigol is a disaster. Sure the Siglent's line is thinner but the Rigol is perfectly capable of showing the ripple on screen and measuring it. That's what really counts, and is the subject of this thread. --- End quote --- What are you going to do when the ripple is even smaller? For example, here is a ~150uVrms 10MHz signal being clearly triggered and displayed. This signal was displayable--triggerable and above the noise threshold on a Tek 2465B (shown), a Tek 2221A (digital and analog) and the Siglent 1104X-E (although just barely and not as reliably). I was able to do the same thing with a 1MHz and 100Hz signal of approximately the same amplitude. What would it look like on the Rigol? You can't average your way out of this when you are looking for noise--possibly non-periodic--in the first place. On the Tek 2221A and the Sig 1104X-E, averaging made the signal look nicer but I'm not convinced that means better. |
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