Look into doing a salt test on the hygrometer to test it's accuracy. Analog hygros can be more accurate and reliable especially if they have an adjustment screw to adjust calibration. All hygros lose accuracy with time a salt test can tell you by how much.
Also most of them are not accurate at the extremes, so it could be your device is fine, if it is one of the cheap ones you might consider getting a 2nd and do a salt test on both of them and adjust or make a mental note of how much they are off.
Edit: here is how to do a salt test: http://www.cigarsinternational.com/c...e/29/salt-test
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