Wow. So, in terms of ADC gain error, I treat it's output count (or rather, the reading derived from it) as y? I couldn't get my head around it because I see the word "gain" and I think of an amplifier. It's probably just me, but in your explanation it looks like you've used the term b for both gain and gain error. However, am I correct in understanding that gain error appears as an offset, and that is why the datasheet gives it in ppm of vref? That's what I really couldn't make head or tail of.
Interesting how errors add up in the same way as noise does - I didn't know that, don't think I've seen it mentioned anywhere. I am not mathematical so I would never have worked it out either.
Good point about oversampling and noise though, I will do that. How do I work out how many samples I need to get any particular reduction? I'm guessing it's going to be another sum of roots kind of thing, but I have no idea.
It's more about being able to observe effects than absolute accuracy, though I hope it's better than your version of pi! For example, I've heard about the effect of light hitting a glass bodied diode, but I want to be able to observe it. I've heard about soldered joints acting as thermocouples, but I want to observe what they do. I don't need an accurate meter for this, but I do need one with good resolution, so beyond simply needing a better meter than my 3.5 digit Mastech, that is what this is about (although accuracy is nice). I can't afford to buy a replacement for my Mastech, but I do have most of the parts for this project. I don't have any particularly accurate equipment (actually very little equipment at all) because I can't afford it.
In your previous post you say that to strip offset and gain errors would require reducing the sampling rate 3 times. Why does reducing the sampling rate reduce these errors?
Anyway, thanks for the help