Calibration of a Hygrometer...would this work

[equetefue]

In the middle of calibrating all my hygrometers using the salt test.

After 48 hrs they are all (5 of them) reading dead on 73% which is 2% lower than they should. The kicker is that the are all reading the dead same % since I calibrated them last week to a 75% calibration kit, meaning that the calibration kit is 2% over.

From now on salt test for me.