Bests & Worsts Reviews from Amazon

There are many digital hygrometer options out there. People often get fooled into buying one upon which a cigar company stamps approval; or, they assume that all are created about equal. Caveat Emptor! Digital hygrometers are just as inaccurate as analog hygrometers, they're just faster to adjust to the Rh. Almost all digital hygrometer are only reliable to +/- 3% Rh. And quite a few are only as good as +/- 5%. Ensure you understand the accuracy range before you buy ANY model. The Calibre IV is accurate to +/- 1.5% Rh. That is damned accurate for such an inexpensive hygrometer. Laboratory hygrometers calibrated for +/- 1% Rh accuracy run into the thousands of dollars. I've had three C-IV models for 18 months now. Every time I've calibrated them with Boveda 75% calibration kits. On calibration, the C-IVs all matched exactly. Further, regardless of into which humidity I placed them, they stayed matched. I experimented with five C-IV models, two units as controls (75% and 84% in a fixed 0.25 liter volume of air at 65 and 75 degrees respectively,) and three test units. Each test unit was calibrated to the control before starting a test cycle. The test units consistently reported accuracy readings within 1% of each other at each test. The tests were three containers of 0.25 liters. Starting with testing at 65 degrees, I varied the humidity in the containers by using one Boveda pack in each container. 65, 69 and 72%. All containers were at the same temperature and I took readings at 12, 24, 36, and 48 hours. The hygrometers changed containers twice and I repeated the 48 hour observation. Then I repeated the entire test at 75 degrees. Now, keep in mind that the units didn't read 65, 69 and 72 because the regular Boveda paks are only +/- 3% Rh. The consistency was impressive. Again, all devices reported within 1% at each level of humidity and at each time reading. Buy these. If you have one that has any problems, Amazon is good for it. Don't buy from another seller just to save a buck or two. (The Boveda One-Step Calibration kits are accurate to +/- 0.3% according to Boveda, but I seriously doubt they have a scientific hygrometer that accurate. And I don't believe the manufacturing quality control to be that accurate either. Most likely this 0.3% is a theoretical 'best case' based upon design and materials. But I did find them definitely within 1%)