I second this. I had trouble getting a salt test to work properly. Bite the bullet and spend $8 on Amazon for the Boveda Calibration Kit
You can get a boveda calibration kit to see how accurate the one you have is. https://www.amazon.com/Boveda-One-Step-Hygrometer-Calibration-Kit/dp/B000A3UBLA I have a few tupperdors so I bought a 12 pack of those cheap hygrometers for $30 and a then tested them. If they were off, I marked on them what the difference was. Most were accurate and some were off by 1 or 2%.
You have entered a minefield here I have been through this many times and was pulling out my hair using just three monitors to check calibration, you think you have it then the other one goes out,I have lots of hygrometers from Mi, Switchbot, Thermopro, Govee etc all attached to ha using the HACS Passive Ble integration and the easiest way to answer your question is to calibrate your monitors using a Boveda calibration kit…
https://www.amazon.co.uk/dp/B000A3UBLA?ref_=cm_sw_r_cp_ud_dp_Q71FQVWFB6W0B73TF56C
And for the temps probably advisable to calibrate this first and you can use the melting point of ice calibration if needed it is better than not calibrating.
Your best bet is to buy a humidity calibration kit like this one to calibrate your Acurite. Then use the reading from the Acurite to calibrate your ecobee humidity sensor. My ecobee was off by 9%.
No problem you can also order calibration kits on Amazon or from Boveda. It’s the same as the “salt method”, but you don’t have to do anything but stick the unit in the bag. https://www.amazon.com/Boveda-One-Step-Hygrometer-Calibration-Kit/dp/B000A3UBLA
Above 72 is not recommended as it could lead to beetles. Before moving to a fridge, a closet or basement might be a better option. Typically these areas are cooler.
Hygrometers should be calibrated every 6 months or so to make sure they are accurate. Google how to do a Salt Test or you can order a Calibration Kit from Amazon.
Edit: Changed the beetle temp from 70 to 72.
The salt test can be weird at times. Not enough water or to much water. I have tried it numerous times and it works for me about 60% of the time. So with that being said I bit $8 the bullet with my lastest hygrometer purchase and bought one of the Boveda Calibration Kits
It worked like a charm. If you have more than one humidor or a couple of tupperdors or whatever the case maybe it says it will last 3 months.
On another note. The glass top humidor may be leaking around the glass. Buy some sealant and put it around the glass on the inside and see if that helps. I know a lot of people have trouble with leaks in glass tops and use a sealant to hold rH
I used Boveda Calibration Kit
I used one of these bovida calibration kits.
https://www.amazon.com/dp/B000A3UBLA/ref=cm_sw_r_cp_api_i_FyMtFb30WMHKT
generally always available on amazon
https://www.amazon.com/gp/product/B000A3UBLA/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
I second the Boveda packs in a bag. Or if you want to you can buy their <strong>Calibration Kit</strong>
Oh by the way...if the hygrometer is an analog one, and not digital, it likely needs to be calibrated. Otherwise It'll always be showing the wrong humidity. I use these to calibrate my hygrometers:
http://www.amazon.com/Boveda-One-Step-Hygrometer-Calibration-Kit/dp/B000A3UBLA
Easy instructions and works flawlessly. I've even used this to calibrate some digital hygrometers as well because even those can be off by 1-3% Hope this helps!
I would check out Famous Smoke since they have it for $4.99. might not be free shipping though.
Get a hygrometer:
http://www.amazon.com/b?node=13825071
and calibrate it:
And see what the humidity is in the room before you hang it. You may find you don't need a humidifier. I have a hygrometer hanging on the wall next to my ukulele, guitar, banjo and wife's violin. It's usually 60-65% which is fine for the instruments.
To be honest, I would dish out the $8 and get the Boveda Calibration Kit. I have too many sticks to be risking it with a salt test.
Get this and adjust them as needed.