What are the values of the sacling coefficients returned from the 6008, and what terminal configuration (RSE, Differential) are you using? I'm trying to track down a 6008 to compare. Also, what are the binary values returned at those voltages? We seem to be close, but just off somewhere...
You may want to check how you (or possibly my code) are doing calculations. When I do it by hand:
+1.62 V = 0x9200 = 10010010:00000000 = 37376 decimal.
37376 *0.0003180253475693 + -10.2685031890869 = 1.62
I did note that with such large numbers, the number of significant digits really matter - cutting the calc off at .000318 yields significant error.
Did you use my direct code for the calcuations or do something different?