I have 4 dial hygrometers and they all read differently, so I got two digi hygrometers and they both read different!!!!!!!! I got a calibration bag and put both the digis in it. They both were reading the right temp and in the bag both came close to the 75.5 of the bag but when out of the bag and put in the same humidor one read 70% and the other 63%!!!!!!!!!!!!! I hate hygrometers. Now I'm just going with if not to dry and I fill up my humidifiers once every 3 weeks or so I should be OK.