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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 29, 2021, 10:36:03 am ---But It has also a lot more noise.... I have an idea to show you how much the signal degrade due to this problem. --- End quote --- All 'scopes degrade the signal, none are perfect. The real problem with this Rigol vs. Siglent comparison is that you're comparing two devices side by side where one of them happens to work better at 1mV then the other one does. ie. When you turn the Siglent's vertical control to "max" then it makes the Rigol look bad at that level. If you were comparing 1V signals or 5V signals in your screenshots then you wouldn't see the same difference between them. Guess what? Electronics doesn't magically stop at the exact place where the Siglent's vertical control does. There's plenty of signals below 1mV. You'll need an amplifier to see them and the exact same same amplifier would work with a Rigol, too. Plus: You originally said you do digital stuff, so... :-// |
| tautech:
--- Quote from: Fungus on December 29, 2021, 11:11:48 am --- --- Quote from: tautech on December 29, 2021, 10:42:11 am ---Which initiates another question; what would the MSO5000 sampling drop to if one more channel was activated ? --- End quote --- It's not difficult: With two channels you get 4GHz/channel, with three or four channels you get 2GHz/channel. At no point is it less than the Siglent with just a single channel. --- End quote --- It is when you overlook the full picture of each scopes acquisition system. With channels 1 and 3 of each scope activated a very different picture may emerge at some timebase settings. |
| 2N3055:
--- Quote from: Fungus on December 29, 2021, 11:07:21 am --- I'm not trying to make anything "right", I'm just trying to see if the Rigol would prevent somebody from doing their job with this signal. Get an amplifier? :-// Does ripple/noise/electronics magically stop at 1mV? There's plenty of signals that the Siglent can't see either... --- End quote --- This not a stupid debate club where we debate whether it is more appropriate to say "apply the law" or "apply the letter of law".. This is physics and measurements and math. There is no negotiation with these guys. You are wrong and stop being a spoiled child. You. Are. Wrong. Take it as an adult. Worse is worse, and if you can chose, chose better. Why on Earth would you take worse device and then spend years "figuring out" how to deal with fundamental shortcomings (that you really can't fix because of it's nature) than simply take something that actually works much better. Nothing does anything magically. Usually more than good enough is when we know scope contributes less than few percent of the error. That also coincides with what can be easily seen with naked eye and 8 bits of a scope. When scope shows 20 mV noise on top of 65mv P-P signal that is definitely bad. Unusable for that measurement. Fact that it shows something is not that useful. It needs to show it accurate enough so person looking into scope can make something with it.. Also you keep repeating about some magical amplifiers. Amplifiers that have DC-100 Mhz bandwith and less noise as even a little Micsig or Siglent SDS1104X-E cost as much as a good scope from Keysight. There are amplifiers for audio frequency range that can be used for low noise measurements. Those are useless for measuring a things mentioned here.. So no, some mythical preamps are not a solution. |
| Fungus:
--- Quote from: tautech on December 29, 2021, 11:40:55 am ---With channels 1 and 3 of each scope activated a very different picture may emerge at some timebase settings. --- End quote --- Yes, because if you enable to adjacent channels the Siglent only has 1GS/sec to look at 350Mhz signals, ie. it's getting uncomfortably close to Nyquist. Turning a channel off can bump the sample rate to 2GS/sec and give a different picture. The Rigol MSO5000 series is one of the few oscilloscopes which can maintain a comfortable Nyquist margin with any combination of channels. |
| Fungus:
--- Quote from: 2N3055 on December 29, 2021, 11:46:37 am ---Also you keep repeating about some magical amplifiers. Amplifiers that have DC-100 Mhz bandwith and less noise as even a little Micsig or Siglent SDS1104X-E cost as much as a good scope from Keysight. --- End quote --- Yes, but amplifiers from DC to 1MHz are incredibly cheap (ie. a $2 OP-amp plus power supply) and would be perfectly adequate for audio work and looking at power supply ripple. Amplifiers from 10kHz to 2GHz are also incredibly cheap. |
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