This is a fantastic unit. The bad reviews are not based on any genuine or accurate technical testing. However my review is based on fairly good technical testing as well as experience.I had been searching for an accurate, affordable and reliable hygrometer for use with my vintage and collectible guitars. Because of the value of my collection, I wanted a Hygrometer that was consistently accurate. I also needs an easy way to calibrate the Hygrometer to my Reference Standard.After going through many, many, many Hygrometers, I found this one to be the best. This company also makes a round version of this that is the equal to this in accuracy and features. This review is for both models since I own both.All of these inexpensive meters are off out of the box from the factory ... some more than others. The Quality Importer Hygroset Meters reviewed here were always the closest ... within 2% of my reference and sometimes less.Once out of the box, I calibrate all Hygrometers with my NIST Calibrated Laboratory Reference Room Humidity Meter capable of +/ 2% maximum accuracy. Calibrations is very easy to do with the knob on the Hygroset Meters. One click is about 2% which works out well.Once calibrated, I compare the inexpensive Hygrometers several times daily to the Calibrated Reference Reference Room Humidity Meter. I do this for at least Ten (10) days.To calibrate the inexpensive meters, I keep adjusting thm until they are stable and match my Calibrated Laboratory Reference Room Humidity Meter for at least Seven (7) Days in a row without adjustment. Once they do, I consider them calibrated.I then do a quick spot check mostly to make sue they are still holding the calibration. I am going on 9 months now with any need to recalibrate. All of my Hygrosets maintain the exact same reading as my Calibrated Laboratory Reference Room Humidity Meter.I also get my Calibrated Laboratory Reference Room Humidity Meter re-calibrated to NIST Standards annually.These Hygrosets are superb a...
