Product review (1 stars): Way off and no way to calibrate
I bought this hygrometer and the first thing I did was test it out in comparison to my fully certified and tested Protimiter MMS2. After leaving them side-by-side for about 12 hours and checking them I found the Extech RH35 to consistently be over 15% off on the Relative humidity, and no way to calibrate it! This means it's a useless paperweight for anyone's purposes and Extech should be ashamed.