FYI: After relying on analog hygrometers for years, I finally spent the money on a very nice digital unit for my humidor.

Guess what I found out?

The analog readout was accurate to within 1/10 of a %. Had it exactly right. All this time I've worried about whether I was in that stable 65-68% range (70% is a little wet for me), and it turns out it was dead on.

Just something to consider before you worry about it too much.