Getting the "feel" for a mic is a matter of time and experiece. Best thing to do is take a "known" length, and get used to the fell of the mic when checking it. Also, I have found it best when checking a journal to check it in a couple places, mostly just a check up on me!! A light hand on a mic is essential to an accurate measurement. I'm sure others here far more experienced than me have better answers. Just saying what works for me. PS, never have trusted platigage!!!!!!