If you read my last log, you know that I am satisfied with this revision. The upgrade to STM32F373 was totally worth it - all the extra analogue features enabled me to reach accuracy of ±0,1 % plus minus a few least significant digits. And I believe that with a more careful calibration, you could do even better. For a price of around 15 dollars and all the functions it has, I think it is pretty amazing. Here's for example accuracy on the 6 V range: 

The yellow lines represent ±0,1 % FS ±5 LSD. 

Here's again a short video demonstrating it during use:

What now?

The project is finished. I am making more than a couple of these for my lab and I intend to use them as a daily multimeter for electronics development. There are still things in software which need to be done and things which could be done - I'll work on these and release a new SW revision soon.

So far the multimeters work reliably, the only thing I don't like much are the buttons (which are much harder to press and clickier then I would like). Also, what I found out as a limiting factor during developent was the display (which also looks ugly, IMHO) - the DMM could measure more information, actually, but there is just nowhere to display it. So what I have in mind as a future project (which I do not know if I'll ever find time for) is a similar device, but with a 2,8" touchscreen, closer to a benchtop DMM. This would allow you to log your measurements, display more values at once & with bigger font, setup warnings, show histograms, more modes of operation would be possible & switching between them would be faster...

Well, time will show if I ever start that project. For now, all the files for this one are open source on GitHub or on my blog.