hi hubitat friends,
I have a couple of aeotec multisensor 6 for heating control , and an aerq air quality sensor (+ a ton of garbage grade chinese zigbee sensors) . My painpoint is humidity in my apartment and of course as many sensor chips, showing different humidity readings. The ones I want to calibrate / trust are the aeotec ones as I'm running them from 5v adapters so getting measurements every few minutes.
question: how can I make sure that humidity readings are accurate ? (within the documented +/- 3% range)
1, I was thinking about getting a reference hygrometer which is as I saw super expensive
2, or, doing some sort of calibration (with special salt, microclimate, etc..) but I'm not sure its a good idea putting the whole sensor with housing, etc to a salty microclimate.
problems: humidity even after calibration will probably not be accurate within the whole 20%-99% range but I only care about the 45-75%range really
in winter months aeotec sensors are measuring scary 65-70% humidity in our place and that's way above the healthy/recommended. - even with heating, taking care for air ventillation, etc. so we did what we could but this is another story.
I nearly drove myself insane over this. At one point I had five different temp and humidity sensors sitting next to each other and they all showed different readings. Temp was very close on all of them, but humidity was different on all of them.
Somewhere here I saw a recommendation for an Oasis Digital Hygrometer that was recommended as a reference. It was only about $30 so I bought it. The one I have isn't available on Amazon anymore but there is a similar one here:
My use case is to turn on the exhaust fans in our bathrooms when humidity gets high. I'm using a combination of Sonoff SNZB-02, SNZB-02D and Zooz ZSE44 sensors. The Zooz is the reference in the main part of the house, and the others are in the bathrooms.
I gave up trying to calibrate them so they all reported the same value when they were in the same room. Not sure it really makes any difference and it may not be reasonable to expect a cheap device to report humidity with single-digit precision. It all ended up working well enough that it doesn't seem to matter. The fans go on/off when they should so I stopped stressing about it.
You can create a test environment by putting your sensors in a container that has a saturated sodium chloride (aka table salt) and water solution. The "air" space humidity will be almost exactly 75% when the solution in near room temps. Google this for a better description and explanation. There are other salts that will provide other % humidity but most are inconvenient to procure.
I put all my sensors in my setup and read them at the same time. Noted the offset for each. Now this is a one point calibration but it's the best I've found.
