The contour creation for force calculation

["matthewc_98" <matthewc_98@xxxxxxxxx>]

Hi All,

I use FEMM to simulate the solenoid and so far, it works pretty well. 
But there is a question I cannot understand and hope you can help me 
to explain it. The question is as following:

Currently, when I would like to calculate the pull force of the 
solenoid, I always creat the contour path as close as possible to the 
surface of core steel bar (the contour is away from the steel bar 
which means the path is within air). But while I read the User's 
Manual, I found that Dave suggested user to creat the contour at 
least two elements from any interfaces and boundaries. 
Could you tell me that what the definition of the element (distance ?
inch ???)? 

So far, I used the force data of FEMM to campare force data that from 
our force tester in the lab, and found that the error is within 15%. 
(Assume the force data of force tester is ideally correct). 
Is there any way to narrow the error of force simulation of FEMM?

Anyway, I really appreciate and satisfy FEMM. 
Thank you so much, Dave.

Best Regards,

Matthew