4-pack Mini Hygrometer Thermometer Fahrenheit or Celsius Meter Digital LCD Monitor Indoor Room Round Humidity Temperature Gauge for Humidors Home Humidifiers Car Greenhouse Babyroom

I bought several 10 packs of other brands that mostly looked identical but those were all off more than 20% humidity and way off temp too (yes 20%... room is 30% and others showed 50%!). If the screen has a green hue and the circuit board looks brown... better test them to see if they are accurate. The ones I tested with the green hue screen and brown or tanish boards were terrible.This brand is SPOT ON accurate and consistent. Screen has a gray hue. Usually +/- 1% humidity and +/- .2 degrees temp.. in short... ACCURATE! They also COME WITH EXTRA BATTERIES! OTHERS DO NOT!

I don’t know how accurate these are but they do work. Humidity was reading at 40% when I installed these in my machine. After adding desiccant, it dropped to 10% so they do work in helping me to monitor when I need to change the desiccant.

As you can see the temperatures are off within about 1° but there's an outlier on the one with the humidity. They're cheap what can you expect? Thankfully I only need three.

I am a professional musician in a house full of musical instruments. This 4 pack was perfect for monitoring the humidity in all the rooms where violins/violas/cellos live. You can even put one in the case. They seem accurate enough for every day use and were inexpensive.

Works well

The units themselves are a great design to fit into things, and for the design I'd get these again. Great for 3D printing. But for some reason, these do not come with battery tabs, so when you get them they've been on and running since manufactured. So I had 2 dead ones out the gate, and I'd be surprised if the other two last for over a month.I'm regards to sensors, they're reading within 2% of two other styles of temperature/humidity sensors so I'd say they're accurate enough for most things.Should the units fail significantly, I'll update my post. In the meantime, I'm off to hunt cheap batteries for these.

I bought these to put in my thermo holder for traveling with insulin to ensure it is being kept at the appropriate temperature. It works perfectly for that task.

All seem to show the correct temp, but one of the 4 shows a very different humidity, off by about 30% from the rest. I tossed that one. There is no calibration that I can see. Of course there are no instructions...