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Siglent SDG1032X sine distortion at 1 kHz ?
rf-loop:
--- Quote from: electr_peter on December 28, 2022, 09:36:12 am ---Does 20MHz limit has an effect on this noise?
--- End quote ---
Yes, naturally. Not directly just only reduced by BW ratio, there is so many different noise sources and noise is not pure straight white noise coming to then BW filtering.
Example just I measured (very roughly and same 100mV/div and all just as in previous image) full BW 600uVacrms (stdev) and 20MHz BW 450uVacrms for example. Also we know this noise is not flat white noise.
Here nice info: Intersil (Renesas)/ "Understanding Noise in the Signal Chain"
https://www.renesas.com/us/en/document/ppt/understanding-noise-signal-chain
electr_peter:
Alternative title for this topic and related comparison-between-siglent-sdg1000x-and-2000x:
"Siglent SDG*000X low noise output highlights limitations of Siglent SDS2000X HD scope". Oh, the irony :-DD
2N3055:
--- Quote from: electr_peter on December 28, 2022, 04:05:59 pm ---Alternative title for this topic and related comparison-between-siglent-sdg1000x-and-2000x:
"Siglent SDG*000X low noise output highlights limitations of Siglent SDS2000X HD scope". Oh, the irony :-DD
--- End quote ---
You are so funny... You make no sense, but funny....
So it's a limitation that oscilloscope has spurs 20 db below it's native dynamic range... Who knew it works that way...
electr_peter:
--- Quote from: 2N3055 on December 28, 2022, 04:30:44 pm ---
--- Quote from: electr_peter on December 28, 2022, 04:05:59 pm ---Alternative title for this topic and related comparison-between-siglent-sdg1000x-and-2000x:
"Siglent SDG*000X low noise output highlights limitations of Siglent SDS2000X HD scope". Oh, the irony :-DD
--- End quote ---
You are so funny... You make no sense, but funny....
So it's a limitation that oscilloscope has spurs 20 db below it's native dynamic range... Who knew it works that way...
--- End quote ---
Humor is different for everyone.
To be serious, it is clear from specs and experiments that SDG has very low noise and SDS HD is great 12-bit low noise scope. FFT stuff is just a reminder to be careful with readings near noise floor. Just the fact that this nuance gets attention signifies bright future for scopes with 10-12 bit ADCs and low noise AFEs.
electr_peter:
Simulations showed that ADC dither is not an issue (noise is high enough to hide quantization effect), but small non-linearities in AFE could cause FFT to show "comb". Assuming non-linear behavior is stable over time, it can be estimated by downloading raw time domain samples and comparing with "ideal" input signal. Not sure if at such low distortion level it is possible to do a digital non-linear correction after the fact or whether it is worth the effort, this requires more modeling. Of course, correction would be scope and input setting specific and would require very pure input signal.
FFT view at different input levels and SDS HD scope settings could get small insight at which AFE part causes distortion, maybe there is a sweet spot somewhere.
FFT shows something non-linear from AFE because noise is so low. IMO that's better than to drown (hide) distortion in high noise floor.
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