Harvest & Curing Hygrometer calibration

[Surfer Joe]

I bought 4 hygrometers for curing- two are the caliber IV type and two are a bit larger black and white temp humidity readers that you see in many forum pics.
I put them all into an airtight container with some boveda 62 packs for a day and the two caliber meters read 62 while the other two read 64 and 65.
I marked their differences from the expected result so that I can adjust their readings when I use them in drying and curing.

The weird thing is that when I put them on the same shelf, next to each other in the room that I am going to use for drying, they no longer read with the same differences.
The calibers read about 1 to 2 points different and the other two can be 4 to 5 points different.
Why would hygrometers that read the same in a sealed container then start to vary when placed in the same room environment right next to each other?
There was no fan going in the room at the time and no open windows.

 

[Soylent Green]

Because this are consumer goods that have no high standards in calibration and slope and bias!
@ work we have professional hygrometers that get a 2 point calibration but cost for one of those is a few hundred dollars!

 

[Happy Horticulturist]

They also change their readings at various speeds. Say the humidity in your room is 62% so one reads 62% and the other reads 64% and then the humidity in your room drops by 10% for whatever reason. One of the hygrometers is going to start adjusting it's reading faster or slower than the other one so this is going to make the difference more different. If you put them back into a seal container again you'll see the difference won't be as much again anymore. Temperature and humidity are very fine precise things. You can have a room with a closed door and windows and the relative humidity will still raise and fall by however much. Very few homes (well no homes) are 100% airtight and insulated. There's always going to be some drift in temperature, air pressure and humidity.

All you can do is calibrate your hygrometers and then you've got a fairly close measure of the humidity in the room. Baring in mind that even calibrated hygrometers that you buy for $20-$30 bucks aren't perfect. IF you want perfect hygrometer like Soylent Green says, be prepared to fork out the big bucks. But for that money you're better with the hygrometers you have and spend the rest on something more important.

 

[komach]

I posted a manual a while ago Click Me + , maybe will be useful

 

[ripster]

I'd say your seals on the lids are worn out. Replace the lids...

 

[ripster]

Try these

https://www.autoflower.org/f23/hygrolid-curing-27358.html

 

[Surfer Joe]

They also change their readings at various speeds. Say the humidity in your room is 62% so one reads 62% and the other reads 64% and then the humidity in your room drops by 10% for whatever reason. One of the hygrometers is going to start adjusting it's reading faster or slower than the other one so this is going to make the difference more different. If you put them back into a seal container again you'll see the difference won't be as much again anymore. Temperature and humidity are very fine precise things. You can have a room with a closed door and windows and the relative humidity will still raise and fall by however much. Very few homes (well no homes) are 100% airtight and insulated. There's always going to be some drift in temperature, air pressure and humidity.
All you can do is calibrate your hygrometers and then you've got a fairly close measure of the humidity in the room. Baring in mind that even calibrated hygrometers that you buy for $20-$30 bucks aren't perfect. IF you want perfect hygrometer like Soylent Green says, be prepared to fork out the big bucks. But for that money you're better with the hygrometers you have and spend the rest on something more important.

Thanks. After a few further tests, I got a sense of how the hygrometers vary and at least they are consistent in their variations under sealed conditions.
I also used a data logger during the tests to see how the drying room humidity varies between day/night, etc. and am able to put things like the oil radiator and the dehumidifier on timer switches to go on when needed.
So far, the drying area has a humidity of 53-58% and the temps stay between 16-19C day or night. It is kept totally dark too and has a little air movement from the small open window and from the dehumidifier moving air through itself.
Should I aim for a higher room humidity? Should I include a fan to move the air around more?

 

[Happy Horticulturist]

For drying I would say that environment is perfectly fine. Follow the guide on here in the stickies that tell you in exact detail how to dry and cure your buds and they'll come out fine. Get yourself some Boveda packs to put in your curing jars as explained in the document as well.