I use cheap non-digital hygrometers that are adjustable. Funny thing is I've seldom if ever had to adjust them. I really have no use for expensive digital hygrometers. Can digital hygrometers be adjusted?

If you use beads then you'll notice your hygrometers rarely move anyway so being accurate to the exact degree isn't necessary.

When the hygrometer reading starts to fall, all you have to do is add a very small amount of water to the beads and you're right back at the perfect RH level.