I have had this sensor for well over a month but only recently started paying attention to the humidity readings. They seemed extremely low so I decided I would compare it to several of my highly accurate (Caliber IV) gauges. I placed the sensor along with 2 other gauges inside a ziplock bag noted the differences. In just over 1 hour, there was a difference of 12 % (low) between the Multi-sensor and my other gauges. I will keep the bag sealed for another 24 hours to ensure all gauges are “climatized” to this environment but I am very doubtful I will be happy with the results.
Has anyone tested other humidity sensors and found one or more with greater accuracy???
BTW: The (5) gauges used in this test are calibrated each year at 32%, 43% and 75%. Each is accurate with +/- 1%
Mine are all reading about par with my netatmo which is the most accurate sensor I have in my house. They took a while to start reading correctly. If anything mine are reading a bit high.
I’ve heard really good things about the Caliber IV line, I have a friend who uses one for his cigars.
That said, that’s a hygrometer, intended for continuous monitoring and accurate to within +/- 1%.
The Aeotec is a multisensor intended for variable sampling, accurate to within +/- 5% and only reporting every 4 minutes. In addition many sensors of this type only report if there’s been a change that exceeds a predetermined threshold, although I’m not sure if that’s true of this one. But in any case, it’s an accuracy within 10%, not 2%.
So I’d expect it to frequently be off compared to the Caliber IV.
If you want to match the Caliber IV accuracy, search for a high accuracy hygrometer and check the published specs. They exist, but will probably cost considerably more.
Yes I use 5 Caliber IV hygrometer for my guitars which are best maintained at a RH of 40-50%. The more stable the RH level the better for the guitar 
The “test environment” I created to check the Aeon Sensor is a sealed zippo bag with the sensor, 2 Caliber IV hygrometer and a cup of Potassium carbonate which maintains the RH at 43%. After several hours so far, the 2 Caliber iV read 43 %. The Aeon Sensor is reading 29%.
I have modified the sensor device type to allow adding a calibration number to be added/subtracted from the reading but 14% offset seems a bit too extreme. I’ll replace the Potassium carbonate with Sodium Chloride tomorrow (creates a 75% RH level) and if the Sensor is still off by 14 % then I wont really care. I’ll just add/sub that amount to the currentValue amount 
That definitely sounds off, it may be a bad unit. It shouldn’t be lower than 38%.
I found mine to be 10% under what an industrial calibration unit read. It seems to be very repeatable though, so I’d really love an offset option.
I have added an offset to this device type but I am currently testing the unit within a 75% RH environment. If it is still off but the same (or similar) amount then applying the offset value within preferences would work fine. Until then, this is what I have added to the default device type for this unit.
preferences {
input(name: “RHOffsetStr”, type: “enum”, title: “Humidity Offset “, options: [”-10”,“-8”,“-6”,“-4”,“-2”,“0”,“2”,“4”,“6”,“8”,“10”])
}
Followed by
def RHOffset=RHOffsetStr as Integer
def RHAdjusted = cmd.scaledSensorValue.toInteger() + RHOffset
map.value = RHAdjusted.toString()
Would you mind posting the entire device type please?
No problem. I don’t recall where the original came from but I believe its primary purpose of the revisions was to provide a better time interval for reporting data. I modified the function Configure() to suit my preferred time intervals.
=====================================================
EDIT:
Ok I cant figure this out. I am trying to paste the code and it is all screwed up. Part of it is in block quotes some is not. Several section are repeated. In short, pasted code is a mess. What am I doing wrong??
I created a github account like the other members have done. Then you can just paste a link to your code and the community site does this interesting sample representation thing.
Final results after 75.5% RH environment test:
2 Caliber IV - 74%/75%
Aeon Sensor - 58%
Oh well… Next please 
Bad device. How long have you had it?
I think its been about 4-5 weeks.
I’d return it as defective, it’s definitely not within published specs.
I’ll say… 20-22% off from known/true RH values. Surprisingly though the % amount off is consistent thoughout the 32-75% range.