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Hacking the Siglent SDM3055 Bench DMM

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tv84:

--- Quote from: alexvg on August 16, 2019, 11:23:49 pm ---I've successfully running the remote debug using Texas Instrument Code Composer Studio...

--- End quote ---

Must study that.   :clap:

alexvg:
I've done a very long measurement to check the quantification level.
All measured values are using 22.5bits (slow mode or 4.7SPS). There's no loss during calculation.
22.5 bits corresponding to 6.77 digits. A full 24bits ADC (as seen in the SDM3065X) could provide 7.2 digits.
A long integration time with a sinc filter could provide more bits.

alexvg:
I need your help, and I've added 2 questions on the first post :
https://eevblog.com/forum/testgear/hacking-the-siglent-sdm3055/msg2605347/#msg2605347


I've done multiple meaures with an AD584 at 2.5V with 7.5 digits.
- Statistic averaging of 500 samples give 2.496551V
- Averaging of 23 values in 5 seconds give 2.49655078V
- Sinc filter of these 23 values give 2.4955098V

measurements of a 10K 0.1% 30ppm resistor with 7.5 digits
- Statistic averaging of 500 samples give 10.005007k
- Averaging of 23 values in 5 secondes give 10.0050084k
- Sinc filter of these 23 values give 10.0050086k
- Statistic averaging of 4k samples give 10.005006k


The noise level during A/D conversion is very low in Resistance mode (much more lower than DCV).

maginnovision:
Are you comparing what you get to something that is actually more accurate, or are you just assuming this is giving you relevant data(not noise)?

alexvg:

--- Quote from: maginnovision on August 19, 2019, 08:09:23 pm ---Are you comparing what you get to something that is actually more accurate, or are you just assuming this is giving you relevant data(not noise)?

--- End quote ---
Actually I trying to identify all most important noise sources (ADC, Voltage ref, op-amp, relay...).
I measure the distribution of data to see if internal processing maintain all available bits (from ADC).

The SDM3055 PCB analog-part is the base of the 4.5 and 6.5 digits DMM and I think it could be go to 7.5 digits (but with another ADC and some addtitionnal important modifications).
I don't know if 7.5 digits could be really possible with less minor modification, but I'm currently working on these little hardware modifications to check that (with software modifications and/or new software).

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