Products > Test Equipment
Rigol DHO800 memory depth / bandwidth upgrades and noise level!
Martin72:
At the moment I am working on the ENOB measurement from the linked page as a kind of side project.
I have already finished the 10Mhz oscillator and successfully put it into operation, I have summarized the filters used for it and designed 2 circuit boards for it, I will soon know if this works.
And open a new thread for it, the test object will of course be my HD from siglent - but I also have the DHO804.
The website operator is a user from here, he has measured a DHO4000 there and an MX04.
At first I was amazed that he came up with such "high" results, over 10 bits after all.
Rigol had simply stated "over 8bit" in the data sheet, siglent is a bit more precise and declares values between 8.4 and 8.7.
When I later looked into the ENOB thing, it was clear why.
And therefore it is also clear why this thread comes to just under 11bit, because the frequency is left out or is much lower(10Mhz) than used by the manufacturers.
Very professional, by the way:
Rigol simply states "over 8 bit" and conceals the measuring circumstances.
Siglent also states the underlying frequency (50 or 100Mhz) in addition to the more precise values.
It was clear to me that ENOB depends on the frequency, among other things.
More on this soon, probably towards the end of the year when I don't have to work. ;)
gf:
--- Quote from: Martin72 on November 12, 2023, 09:34:36 pm ---Determining the ENOBs ( at 10Mhz) of a DHO4000 and R&SMX04:
https://electronicprojectsforfun.wordpress.com/to-enob-or-not-to-enob/
--- End quote ---
Let me supplement this with a fairly comprehensive application note from LeCroy:
https://cdn.teledynelecroy.com/files/appnotes/computation_of_effective_no_bits.pdf
gf:
--- Quote from: Martin72 on November 13, 2023, 10:55:59 pm ---https://electronicprojectsforfun.wordpress.com/to-enob-or-not-to-enob/
--- End quote ---
If the aim is to measure only at a single frequency, then I wonder, why not use a high-Q bandpass filter?
Google found for me e.g. these crystal filters:
https://www.amazon.de/Kristallfilter-Schmalbandfilter-Langlebig-spezielle-Instrumente/dp/B09MJP1Y14
They seems to be available from various sellers, and also for a couple of different frequencies, e.g. here
https://de.aliexpress.com/item/1005003627277580.html
They promise > 80dB stopband attenuation, and if they deliver what they promise, this should be more than enough for measuring a 12-bit ADC (-74dBFS quantization noise), in conjunction with an AWG like SDG2000X which achieves already -65dB harmonic distortion up to 10MHz and -70dB non-harmonic spurs out of the box (according to the datasheet).
Martin72:
Interesting comments, but I would like to take them up in a separate thread.
That would go beyond the scope of this article.
JDW:
--- Quote from: Fungus on November 12, 2023, 09:21:29 pm ---
--- End quote ---
When I try to repeat the same test using the same settings, even when testing only a single channel (leaving the probe disconnected as Fungus apparently did), I get 60Hz noise that makes it impossible to detect the true noise floor. Noise remained unchanged with or without the ground cable attached to wall socket Earth Ground.
Note that my Probe switch was set to 10x, and the "Probe" setting (in CH1) was also set to 10x.
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