"I have a collection of hygrometers and I know a good one when I see it. I also know that it is hard to make an accurate, stable hygrometer. I fully expected the OpticsPlanet "Control Company Jumbo Temperature/Humidity Meter 4184 Vwr THERMO-HUMIDITY Meter" to be just adequate at best. I bought it because it was SIMPLE and had LARGE numerals that I could read without finding a pair of glasses. Also, it wasn't cluttered up with options I didn't want. What I found was that it was well designed, of solid construction, and ACCURATE. I couldn't believe it. I do my own calibrations nowadays so I ran the tests on the 4184 twice, using three set points (33, 75, 100%) each time. It was within 1% on the 33 and 75 set points, and 2% on the 100% point. If you know about hygrometers you know you can ignore the 2% "error" on the 100% point because it is notoriously hard to achieve and being off by only 2% doesn't mean anything at all. So, I admit it, I'm impressed. The 4184 i
s a little bit too expensive but then take my word for it, if you buy a cheap hygrometer you will get junk. I would recommend this product to anyone."