Hi Kent, you're not doing anything wrong, per se -- other than doing the salt test incorrectly (see below). I totally agree, unlike some BOTLs, that wiping down the wood inside the humidor is unnecessary and can damage humidor.
Doing the "salt test," it's best to completely remove the hygrometer from the humidor and place it in a zip-loc bag overnight with the bottle cap of moistened salt. When you do it this way, the relative humidity in the bag, after 12-24 hours, is a definitive and correct 75% RH, thus the "end result" (what the hygrometer shows whether analog or digital) may not measure the same, but whatever the hygrometer shows for RH, we know the true RH is 75%.
So that means, say, your hygrometer measures 80% RH out of the bag after the salt test. That means your hygrometer is 5% "off" -- so if you want the humidor to be kept at, say, 65% RH, your hygrometer, for your humidor to be at 65%, will measure and show 70% when the actuall correct RH is 65%. Simply keep that in mind and all is kewl.
