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Rigol DHO800 memory depth / bandwidth upgrades and noise level!
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ebastler:

--- Quote from: iMo on November 07, 2023, 08:28:07 am ---The standard deviation of 2.44uV is the STD for the set of measurements (the 51 measurements of that 80uVrms), not to mix it with the "rms".

--- End quote ---

It does get a bit confusing though, since the measured property is not called "rms" here, but also "StdDev". So there is a measured StdDev, and it is measured with a certain StdDev. All correct, and the table layout does make it clear what's what; but it does invite mis-reading it at a quick glance.
iMo:
Yep, there is AC.rms, AV+DC.rms, Vpp (or Vpk-pk), and STD.
Btw., the noise levels of that Siglent and Rigol as depicted above are "almost the same" (20% diff in the noise is negligible). Thus the question is how the 8bit vs 12bit comparison would apply here..
2N3055:

--- Quote from: iMo on November 07, 2023, 08:46:32 am ---Yep, there is AC.rms, AV+DC.rms, Vpp (or Vpk-pk), and STD.
Btw., the noise levels of that Siglent and Rigol as depicted above are "almost the same" (20% diff in the noise is negligible). Thus the question is how the 8bit vs 12bit comparison would apply here..

--- End quote ---

It depends. Since SDS1104X-E has 500µV/div real range, for small signal it would be pretty much the same.
SDS2000X+ shown above has much less noise than DHO800, despite being 8 bit. At 50Ω it would be even better (but so would DHO800 with external terminator).

So like I said many times before, it is not that simple.

All in all, Rigol finally made an inexpensive scope with quite competitive noise levels. It is not as good as good 12 bit scopes, and not even as good as best 8bit ones, but good nevertheless. Noise is no longer a problem. Especially for the price bracket.

It would be interesting to see how well DHO4000 fares.
Serg65536:

--- Quote from: Fungus on November 06, 2023, 09:56:17 pm ---Oh, yeah, I haven't done self-cal for a while. I have no idea what the bandwidth configuration was last time I did it.  :-DD

--- End quote ---

Please, share your experience:

1) What is the DC accuracy of your DHO804 scope with DHO924 firmware?
     The good way to measure it is to test some precisely known voltage around 8V on 100mV/div range with offset.

2) You use vendor.bin upgrade or whole 924 firmware image?

My 804 has worst accuracy of 1.6% with 924 firmware image, when zero offset is calibrated.
ebastler:

--- Quote from: iMo on November 07, 2023, 08:46:32 am ---Btw., the noise levels of that Siglent and Rigol as depicted above are "almost the same" (20% diff in the noise is negligible). Thus the question is how the 8bit vs 12bit comparison would apply here..

--- End quote ---

I would expect that at the very low end of the range (high amplification), noise levels are dominated by the analog front end. ADC resolution comes into play when you look at the dynamic range. So an 8-bit scope with a carefully designed front end can fare pretty well in this test.

The Siglent SDS2000X plus in 10-bit mode has the lowest RMS noise in the measurements above. That makes sense to me, since the oversampling & averaging it performs in that mode should also help to reduce the (digitized) front-end noise.
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