6 Pack Mini Hygrometer Indoor Humidity Meter, Small Digital Thermometer Humidity Gauge Meter, Indoor Thermometer Hygrometer Monitor Fahrenheit (℉) for Humidor, Thermostat Reptile Tank, Mason Jars

I got these because PETG printing was becoming problematic as we transitioned into hot, humid weather. When I actually heard tiny “pops” from exploding water inside the filament as the filament moved through the hot end, I knew I had to do something.When I dropped one of these sensors into the zip bag holding the PETG reel, I quickly learned that the air in the bag had a humidity level much higher than the workspace. I also learned that my zip bag collection of used desiccant packets was over 40%. So I put the PETG into the filament dryer at 165 for 2 hours, and the spread-out desiccant packs into the microwave for 10” on a defrost cycle. Now I know that my PETG filament has less than 20% humidity and the desiccant supply is a bit over 10%.How did I get by without these for all these years?

Given the cheap price tag, these things are amazingly good. It's a shame that they ship them with the batteries installed. All the time since the day of manufacture until Amazon tosses them at your front door, the batteries have been running down. Be sure to order a bucket of new batteries because the ones that ship in the devices will be half-dead when you get them.

Some people complain these are not accurate because the readings don't match. I put all six together and gave them time to reach equilibrium, and they all matched within 5% for humidity and 2 degrees F. That's pretty good. Yes, the display precision (1% & 0.1 F) exceeds the accuracy of the measurement, but so what? If you need that much accuracy, you're working in a lab and and your humidity meter costs hundreds of dollars.BTW, they're made with a front bezel so they can snap into a rectangular hole in a thin-walled enclosure. That's a neat feature!

Work as backup to verify humidity.

I got the six pack of these hydrometers and five registered virtually the same results side-by-side with only one significantly different! In my mind, that is pretty awesome! I put two of these in each of my guitar cases so if they both say about the same thing, I’m happy!!

Good for the price but not completely accurate. I tested by sitting a few side to side and the humidity runs with in a 10% difference. But for the price I’ll buy more.

Great price for six! They are smaller than I expected. The sides have those little clips like automotive gauges, so I’m going to cut a hole and add one to my van. We are also using them in a humidor and greenhouse.

The really work it might a little off but it is only by one so I recommend get this on so you have more to get the exact info you need