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| How much noise floor and other things matter in oscilloscope usability |
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| Fungus:
--- Quote from: 2N3055 on December 29, 2021, 10:22:45 am ---I 'm reading some of these posts and :-// It is obvious MSO5000 has much more noise, and that it is a problem, unless you only look at digital signals and just want to look at general shape and some timing information. --- End quote --- Fiorenzo originally said his main work was digital. --- Quote from: 2N3055 on December 29, 2021, 10:22:45 am ---Scope with low noise is always going to be better instrument than the one with high noise. Why is that even a discussion? --- End quote --- Because: "Price" (ie. This isn't a 100% technical discussion, if it was we'd all be driving 10-bit R&S 'scopes) --- Quote from: 2N3055 on December 29, 2021, 10:22:45 am ---On this test I would call MSO5000 from Rigol useless for this measurement. --- End quote --- The Rigol displayed "14.003mV" on screen and the Siglent displayed "14.0482mV" That's 0.3% difference between them. --- Quote from: 2N3055 on December 29, 2021, 10:22:45 am ---Little Micsig STO1104C/E, or Siglent SDS1104X-E could do equally good job here. --- End quote --- Yep. My original recommendation was to save 1000 Euros and get the SDS1104X-E. |
| Fungus:
--- Quote from: Fiorenzo on December 29, 2021, 12:18:04 pm ---No. Actually i did many experiment about It. If you set the Rigol so it has a lower sampling speed the noise doesn't become lower. --- End quote --- That's because it won't actually change the ADC clock speed, it just discards samples. What's being discussed is the sample rate to bandwidth ratio. When it approaches a ratio of 2 you'll start to see artifacts in the display. The Siglent has 350Mhz bandwidth and can drop to 1Ghz sample rate if you enable all channels. This can produce visibly different results at maximum zoom. You'll see it most on digital signals. The Rigol doesn't drop below 2GHz sample rate so it should never have a problem. |
| nctnico:
--- Quote from: Fungus on December 29, 2021, 12:25:42 pm --- --- Quote from: Fiorenzo on December 29, 2021, 12:18:04 pm ---No. Actually i did many experiment about It. If you set the Rigol so it has a lower sampling speed the noise doesn't become lower. --- End quote --- That's because it won't actually change the ADC clock speed, it just discards samples. What's being discussed is the sample rate to bandwidth ratio. When it approaches a ratio of 2 you'll start to see artifacts in the display. The Siglent has 350Mhz bandwidth and can drop to 1Ghz sample rate if you enable all channels. This can produce visibly different results at maximum zoom. You'll see it most on digital signals. The Rigol doesn't drop below 2GHz sample rate so it should never have a problem. --- End quote --- In the end neither is suitable for looking at 350MHz signals using 4 channels. The Siglent SDS2k due to low samplerate, the Rigol MSO5000 due to excessive noise. Also note what David Hess wrote: Rigol typically performs math on decimated data which can give the wrong results when doing measurements on noise. All in all, if you venture into the HF arena, you'll need to look at more expensive scopes. For a general purpose daily driver scope, low noise is king all day long. |
| 2N3055:
--- Quote from: nctnico on December 29, 2021, 12:35:40 pm --- --- Quote from: Fungus on December 29, 2021, 12:25:42 pm --- --- Quote from: Fiorenzo on December 29, 2021, 12:18:04 pm ---No. Actually i did many experiment about It. If you set the Rigol so it has a lower sampling speed the noise doesn't become lower. --- End quote --- That's because it won't actually change the ADC clock speed, it just discards samples. What's being discussed is the sample rate to bandwidth ratio. When it approaches a ratio of 2 you'll start to see artifacts in the display. The Siglent has 350Mhz bandwidth and can drop to 1Ghz sample rate if you enable all channels. This can produce visibly different results at maximum zoom. You'll see it most on digital signals. The Rigol doesn't drop below 2GHz sample rate so it should never have a problem. --- End quote --- In the end neither is suitable for looking at 350MHz signals using 4 channels. The Siglent SDS2k due to low samplerate, the Rigol MSO5000 due to excessive noise. Also note what David Hess wrote: Rigol typically performs math on decimated data which can give the wrong results when doing measurements on noise. All in all, if you venture into the HF arena, you'll need to look at more expensive scopes. For a general purpose daily driver scope, low noise is king all day long. --- End quote --- MSO5000 actually can use all data.it has propper implementation of math but it is let down by noise.. Shame. |
| Fiorenzo:
Yes fungus I think so. In regard of your suggestion to buy a cheaper scope my thinking was in line with you but i needed some function that are only in the Siglent sds2000. About this topic my need was to understand how more important is sample rate against front end noise. Because of my bad english maybe i could not explain well my doubts. In the end if you or other have suggestions i can do some other test with the limited equipment i have until I have both the scopes at home..... because i am going to send back the Rigol as soon as possible. |
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