6-Pack Mini Hygrometer Indoor Humidity Meter, Mini Digital Thermometer Humidity Gauge Meter, Indoor Thermometer Hygrometer Monitor Fahrenheit (℉) for Reptile Thermostat, Jars Reptile, Fridge

Cheap, effective. Not a precision instrument, but will get you close.
I’ll jump in with the pros and the cons. There will be some overlap.Pros:- A cost effective solution for knowing the temperature and humidity level. Considering you get six of these guys, it’s an amazing buy.- Small and compact measuring approximately 1.875 by 1.25 inches. Numbers are easy to read with the humidity number being displayed most prominently.- Fairly accurate. Measuring them against each other on my desktop, all read between 68.7 and 69.4 degrees F with humidity registering 36-38 percent with one showing 36, three displaying 37 and two showing 38. I’d note I do have a small heater running at one end of my desk, so this to me falls into the fairly accurate for the price category.Cons:- No way to calibrate.- These were designed to clip into something, though I don’t know what. There are clips on the sides of the units.- While they are free standing, there is no way to set them at an angle.- They do feel pretty cheap, so durability and battery life are questions I can’t currently address.Recommendation? Yes, I think I would recommend them for simple, basic information. I intend to put a few of them into my seed starter trays to keep an eye on humidity and temperature when I start my plants, so who knows how they’ll do in that warm, humid environment. But I’d order them again given my overall first impressions.

Very inexpensive and pretty accurate
Got these just to have, but wound up using them in the plastic bags I store filament for my 3D printer in (along with desiccant packs). It’s important to keep this stuff dry.The humidity reading is always within a point or two of what my dehumidifier says, which is impressive.They’re powered by 2 standard LR44 coin cells which are easily replaceable. They’ve been going for months and I haven’t needed to change batteries yet.

I can’t test calibration, but 18 units side by side were reading together. HIGHLY consistent
Fast changing, extremely sensitive, and in tight sync on humidity. I bought 18, and placed then in a row across my work bench. After they settled in, they were within 1% of each other in a very interesting way… You could see waves of change, if one went up by 1%, usually it’s neighbor would, and that would ripple across the line. Or there might be several waves sweaping from an end and the middle… It was interesting to see that they were all responding to the environment in sequence with the neighbor. This tells me they are quick responding and fairly sensitive.I am in an extremely dry environment, with humidity artificially increased by a swamp cooler, so I am testing the low end of the range, 20% to 30%. If your humidity dwells higher, you may get different results. These type of i9nstruments are more accurate at 75-85% than they are down where I use them, so accuracy is not pertinent in my use case, Instead I will be using these as a quality of storage indicator and alarm, so when I pull a roll of 3 year old nylon down, I can tell if it needs a 2 hour dry cycle or if it needs days more. A “freshness” indicator that I can read without opening the package.Humidity was within 1% of the units neighbor. However temperature was closer together, but the fractional degrees were all over the place… Most of the temperature sensors are closer than the humidity, but because the temperature scale is hundreds of points in either direction, the temperature looks like they are a little father apart, but really they are as close or closer than the RH%.The quality of the sensors are very high to all be in agreement, but these are too cheap to be calibrated, if that is important to yo, do some testing with a calibrated meter. I have a wet bulb and a calibrated meter in the shop, but like I said mine are not being used in a way for best accuracy, but these seem surprisingly high quality so I suspect accuracy is either very good, or at least very repeatable and consistent. These are the best I have tested so far.I will package these with sealed and dry filament, and the levels read will be wrong… Th