want high-accuracy measurement of force between 2 magnets

["mikeshonle" <mike@xxxxxxxxxxxxx>]

Hi, I'm trying to measure the force vs. distance between two magnets 
over the range of 3 to 3.5 inches. I have a script running, etc., 
but the final result is not monotonic and varies considerably and is 
sometimes even negative.
What all can I do to increase the accuracy? Is a finer mesh more 
important than the solver accuracy? What is a good minimum mesh 
spacing and accuracy limit? What is the practical limit of accuracy?
Thanks,
-Mike