I lost the thread now, but some time ago someone enquired about a 16 or 24 bit serial bit AD. I had a suggestion, but couldn't find the info I was thinking of at that time (about a month ago). Anyway I came across the data   sheet now - coincidently. 

The LTC2400 from Linear technology looks good to me (haven't tried it). This is a high accuracy device; NOT a fast one (15 Hz). 1000 pieces costs $ 6.95 ea. SO 8 package.

So - whoever out there that asked for a high res serial AD - check out:

www.linear-tech.com/go/LTC24001/edes


Sven in Sweden