Calibrating a digital hygrometer

Q. Is there a way to calibrate a digital hydrometer to see how accurate it is?
– Forrest S.
A. I’m not aware of any digital hygrometer currently on the market that can be manually calibrated. So, to answer this question, I turned to an expert in the field, Michael Chunko, president of Csonka Products. Here’s what he had to say:

“Up until recently, digital hygrometers have never been able to be re-calibrated after manufacturing. There is one out there now that is getting mixed reviews because the technology is new, so it’s not that reliable.

Currently, the best manual way of checking hygrometer calibration is with the traditional ‘salt test.’ For post-calibration on an analog (or a digital with that capability), here’s how to do the salt test.”

Even if you can’t re-adjust your digital hygrometer, at least the salt test will tell you by how much it’s off. I have a digital hygrometer that’s off by -10% RH. So when it says 59%, I know it’s actually 69%. If you can’t remember, make a notation on small piece of masking tape and affix it to the front or back of the unit.