[sdiy] How to measure 1-bit DAC performance?

[Roman Sowa]

Measure DC and AC specs like with any other DACs.
For example write a little program in the PIC that outputs every code in 
the range, or limit that to reasonable number of levels like 1024 and 
measure actual voltage with multimeter. Good if your multimeter can log 
data.
When you export multimeter data to spreadsheet, you can do all 
calculations and what's more fun - graphs, to see DAC performance 
clearly, especially INL.

For AC specs, make your PIC generate a sine and record the output with 
your computer running ARTA software or anything similar. A very slow 
wave could also help determining noise at various DC levels, because as 
PWM, it may whistle.

 From that you will get Effective Number of Bits which is what you're 
after I think.

Roman

W dniu 2017-04-25 o 15:09, Tom Wiltshire pisze:
> Hi All,
>
> I've been using the PWM output module on the PIC chips as a cheap DAC for years. It does this job reasonably well, all things considered. Whilst the quality and 10-bit resolution aren't great, it's cheap and convenient, and those are big pluses.
>
> However, I've been looking at using the NCO peripheral as a Pulse Density Modulated output instead. This would in theory produce a higher frequency output and allow a greater resolution.
>
> In order to determine if the results I can get out of it are genuinely an improvement, I need to be able to accurately measure the performance of both styles of "DAC".
>
> How would I do this?
>
> My current method is to send an incrementing count to the DAC and then have a look at the post-reconstruction filter output on a 'scope. How wiggly the line is is my measure of quality! Not very exact!
>
> I've got a digital oscilloscope, a multimeter, and a laptop. No other test equipment is available, unless I make it.
>
> Thanks,
> Tom
>
>
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