Inkbird ITH-10 Digital Thermometer and Hygrometer Temperature Humidity Monitor Humidor Guitar Ukulele Mason Jar.

Works fine. I can check the humidity in the guitar case to make sure it's where I want it to be. Or in a room. These small instruments are not calibrated, so you have to check their accuracy. One way I know of is to use another hygrometer you trust and compare the results.Since your guitar case may not be humidified enough, the hygrometer lets you check the environment of the case before you put in your guitar and humidity device. No use putting the instrument in a dry case and try to keep it at 40% humidity. The water in the humidity pack will simply equilibrate with the dry environment of the case and you will dry out your humidity pack while not getting moisture in the air around the guitar. So first, use the hygrometer to check the case's moisture, then humidify your case if you need to.Unfortunately, small measurement devices are prone to being uncalibrated. So you have to calibrate it to see how far off it is. You can do with with the salt test and then make a note on your reading versus reality: this little unit is not able to be adjusted.A salt test is an easy test that basically puts your hygrometer into an isolated 75% RH (relative humidity) environment, in which you can then determine how inaccurate the reading is and adjust accordingly.How to do the salt test:You will need:Sandwich sized ziploc bagBottle cap from 2 liter soda bottleTable salt (do not use fancy grey salt: plain white salt)Your hygrometerSTEP 1:Fill cap 3/4 of the way up with table saltSTEP 2:Add filtered or distilled water (not tap) to the bottle cap and saturate the salt. Make a slurry (slushy mix) No water should be floating on top of the salt slurry.STEP 3:Place the hygrometer and cap with salt/water mixture inside of the ziploc bag.STEP 4:Let cap and hygrometer sit in closed bag for 6 hours. It should read 75% after this time.If your hygrometer reads 80%, subtract five points from any reading. If it reads 70%, add five points.If you want to be fancy, you can buy a test kit: Boveda One-Step Hygrometer Calibration Kit - 75% RH - Standard Small The advantage of this is you can do a 32% test, because the inaccuracy of the hygrometer may not be linear and if you are reading for near 40%, it may be better to test at the lower portion of the scale.I keep the hygrometer, which is no bigger than several sticks of gum, in the small compartment in the case--under the neck. It's there to make sure the case is always at the right level of humidification.

I put these two in a zip lock bag overnight with a 69% Boveda. One is -1° off. The other is right on. I'd say that's pretty good.

IT'S A GREAT HYGROMETER BUT THE NUMBERS ARE VERY SMALL WHICH MAKES IT HARD TO READ SOMETIME. BUT THE READING IS SPOT ON ACCURATE WHEN COMPARED TO MORE EXPENSIVE HYGROMETER.

Mine was very accurate! I ordered this because the Caliber IV does not seem to be available from Amazon now. I was worried because this one is not adjustable like the Caliber IV is, but I did an overnight salt test and it is spot on. About 12 hours into it, it read 74%. Next day it read 76%, but when I pressed the plastic ziplock a bit it settled right at 75%. If it stays 74-76% it's ranging from -1.4% to +1.3%, and for the price that's good enough for me! I would definitely test one if you buy it, because it is not adjustable, just in case. But I got lucky. Could not be happier.

Tried a higher end brand (very similar looking except name) and it would never read above 58% even with a calibration kit.Out of the box this one was spot on with a Boveda calibration kit and was accurate with 3 other hydrometers / thermometers.So far call me impressed for the cost. We will see how it does over the next few weeks in the humidor.

I have to first say that I, like others here, have read some of the bad reviews that the Inkbird has received from some purchasers. I did something that I almost never do and that was to purchase this without first doing a lot of research and really scouring other's reviews of this product. After I received it, I read the instructions, put the battery in and then placed it inside of a Boveda One-Step Calibration Kit (75% RH) bag for, per instructions, 24 hours at room temperature. This was about a week ago. It calibrated fine (74% when I removed it, of course, well within the margin of error) and I then placed it in a glass jar/container that held 22 cigars. Checking the readings daily, they have held steady so far, between 73% (I took the reading in the photo on 8/7 at approx. 4:19 PM) and 74% (the actual reading before I opened the jar to place 5 more cigars into it). The temperature reading is high (79.8⁰ F) because it was a bit warm where I had the jar stored at that time but it was also accurate. I realize that a lot of folks aren't happy with this hygrometer and I'm sure that there are some duds out there but, thankfully (so far), I have not had any issues with mine.

nice and small, convienient. calibration is not adjustable, most of mine were about +5%RH off, so not very accurate...