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

[Tom Wiltshire]

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