Oasis Digital/Analog Look Hygrometer and Humidity Sensor - High Precision Temperature and Humidity Monitor with Reliable Accuracy, Ideal for Care and Maintenance of Various Storage Environments

READ THIS FOR CALIBRATION: My unit did not need calibration! I followed the majority of the instructions that I found for performing the salt test. They were a bit wrong in that they instructed me to let sit for anywhere from 6-12 hours. This hygrometer took longer.CORRECT METHOD: Add salt (1 tsp) to a small, shallow container (e.g. bottled water lid). Add several drops of distilled water to the salt so that a paste or very thick slurry is formed. There shouldn't be standing water above the salt, but as long as the salt is not dissolving, it should be alright.Seal salt solution in a zip-lock bag (I doubled up) with the hygrometer.LEAVE ALONE FOR 24 HOURS. If greater or less than 75%, adjust without opening bag and leave alone for another 6 hours, at least.I originally performed this for 12 hours and I thought I had a little too much water in my salt due to it being more of a slurry than a paste, though I now realize that did not matter. I saw the hygrometer was reading 4% under. So adjusted it by +4% at which point it began jumping around because, I presume, I was stirring the air in the bag around by moving it. After another hour, it was reading 76%.I reset the hygrometer to +/- 0%, took the salt solution out, made a new one, replaced it, sealed the bag again, and placed the sandwich sized bag inside of a double lock freezer bag sealing them both. 24 hours later, checked the hygrometer to find it reading exactly 75%.When I placed it in my humidor, which is currently seasoning, it matched the built-in analog hygrometer at 85% within 20-30 minutes.Now on to the review: This is a great looking classy yet modern hygrometer which, thus far, seems dead-on accurate and sensitive. From what I understand, that is very rare for non-laboratory hygrometers. Now, I have a glass-top humidor so if I had to lift the lid to verify the humidity I may not appreciate the sensitivity of this hygrometer as it will drop within a short time upon opening the lid. Also, you do have to look at this hygrometer from straight on in order to read it, but the color-coded humidity range and gold-colored trim are appreciated touches of convenience and class.Temperature reading is nice as well, though that's rather expected from the current digitals.Wouldn't purchase a different hygrometer if I had to do it over again.

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%)

The out of box accuracy was off by about 2%, but the calibration procedure is easy and effective. I used three different Boveda humidity packs to set and calibrate it, 49%, 62% and 69%. After sitting in a small, sealed container with the 62% pack for about 12 hours I was confident that the reading was stable and gave it a +2 adjustment, and then let it set for another 12 hours and verified it was reading 62%. I then swapped out the humidity pack for a 69% and resealed the container. After another 12 hours or so it was accurately reading 69%, so a successful 2-point verification. However, my only gripe about this unit is the lack of resolution below 60%. In the "sweet spot" it has 1% resolution, but outside 60-75% RH it drops to 5% resolution...so there really isn't any way to accurately measure below 60% or above 75%. So for example if you are trying to measure the RH inside a safe, as opposed to a humidor, it will only give you a rough idea of the actual humidity. I would say if this is important to you, go with the Caliber 4, not the 4R, since it displays the digital value directly.Pro's:Looks nice and feels well built. Appears to have a glass bezel and metal ring. Feels substantial, not like a cheap plastic toy.Easy and effective RH calibration procedure with Boveda packsCon's:Poor resolution outside humidor rangeCan be difficult to read the display unless you are looking at just the right angleThe temperature reading on mine is about 1.5° high and no way to adjustIt would be nice if there were a way to alternate the digital display to show either temperature or humidity, instead of being temperature only. This would alleviate the issue with low resolution of the analog display at low RH values.