I've had two Fieldstar systems...my first and last. My experience has been is that it is accurate when you get it set for a crop in a field, buy if you change hybreds, moisture levels, etc. you can be way off. Ours always asks for zero point calibrations. You can run a zero point and it may go all day without asking for another or it may want one in 5 minutes. Having come from an agleader and having friends with AFS I have found that the Fieldstar is pretty poor. I hear they've made some improvements, but the only way I'd get another is if it comes with a money back guarantee.