Calibrating and adjusting hygrometers - steps and questions

I am currently testing my hygrometers in a Tupperware bowl with the salt slurry. I understand how to calibrate my Bluetooth and wifi units, but my question is: Do the cheap ones that come in the 12 packs have any adjustment if you crack open the case? Or once they have settled out, can I just use a bit of math to make the mental adjustment accurately? Like, say they read 68% instead of 75% can I assume that it is always about 9% low?



For those wanting to test accuracy of their hygrometers, here are the steps.

1. Fill a bottle cap or milk cap with plain table salt. Add enough water that it becomes a slurry. You don't want standing water on top of the salt.

2. Place cap with contents into a ziploc bag or sealable container (I use a Gladware bowl with lid) add your hygrometer(s) and seal it up for 12 hours or so. You want the atmosphere to get even and steadied out. Same with meters.

3. Check meters after 12ish hours. They should read 75%

I just mark them with plus or minus %.. 68 would be +7, 80 would be -5..

HydoDan said:

I just mark them with plus or minus %.. 68 would be +7, 80 would be -5..

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This was my plan. So I'm guessing that they are off by a percentage that stays similar throughout the range.

TCH said:

This was my plan. So I'm guessing that they are off by a percentage that stays similar throughout the range.

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Yes, I only checked em one time about a month after they were marked and they were the same.. I should check again before I harvest my outdoor crop..

Look into the Govee Bluetooth device, I use them in my tents and you can buy an extra one or two to use as hygrometers in jars. Last I saw they were like $20 apiece but worth it, VERY accurate, moreso than those cheapie little guys you have

PopAndSonGrows said:

Look into the Govee Bluetooth device, I use them in my tents and you can buy an extra one or two to use as hygrometers in jars. Last I saw they were like $20 apiece but worth it, VERY accurate, moreso than those cheapie little guys you have

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I have several of the govee units. I love them. Ultimately, I will end up with a whole bunch of them. I currently.use them in the Koolatron because I like that they constantly update. Not every 5 or 10 minutes.

After 24 hours in the bowl with the slurry, the cheapies were lower by about 8.7% so I put a piece of tape on them with "x1.087" on them so I can quickly figure out where the rh is actually at. The govee was off just a couple points so I opened the app, made the adjustment, and we are good to go.

Im using the exact same ones and they all differ by a percent or two... not sure if its that big of a deal for anyone.
In case they are off by alot considering the true value... yeah mark them as people mentioned.

Maybe if you're really that meticulous I would suggest you shouldn't buy the cheapest stuff, no offense...

TCH said:

After 24 hours in the bowl with the slurry, the cheapies were lower by about 8.7% so I put a piece of tape on them with "x1.087" on them so I can quickly figure out where the rh is actually at. The govee was off just a couple points so I opened the app, made the adjustment, and we are good to go.

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Best advert for govee I've seen! LOL thanks TCH. Of course I need more of them.

sh0wtime said:

Im using the exact same ones and they all differ by a percent or two... not sure if its that big of a deal for anyone.
In case they are off by alot considering the true value... yeah mark them as people mentioned.

Maybe if you're really that meticulous I would suggest you shouldn't buy the cheapest stuff, no offense...

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If I'm storing 10 jars or bags, I'm not going to drop a $20 govee unit into each one to monitor. I'll use the cheapies. This is a great way to know if you are in the ballpark. $1-2 each and a little variation is far better than $15-20 each.

curious2garden said:

Best advert for govee I've seen! LOL thanks TCH. Of course I need more of them.

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I really love them. Their graphs and the fact they are basically a constant update make them the best for me. I do love the inkbird stuff as well but you can't set them to update constantly. They are great in a tent or room where there arent big swings, but makes for real wonky readings and graphs in the Koolatron when it is constantly going up and down.

TCH said:

If I'm storing 10 jars or bags, I'm not going to drop a $20 govee unit into each one to monitor. I'll use the cheapies. This is a great way to know if you are in the ballpark. $1-2 each and a little variation is far better than $15-20 each.

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Oh for the jars, they are good enough 4 sure. But again... a percent or two won't kill your bud in there I'd say...

sh0wtime said:

Oh for the jars, they are good enough 4 sure. But again... a percent or two won't kill your bud in there I'd say...

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Correct. But 6 points (8.7%) off can be flirting with danger. My reason for checking them all out was so I can actually get my Koolatron dialed in and actually know where that is rh wise before I toss the bud in jars or bags.

Fresh batteries all around so I decided to go ahead and toss them into a bowl for some testing/calibration this morning.



I want to test/calibrate my inkbird humidity controllers as well, but I need to figure out a system to do it with the wired lead in a container but still have it air tight. Gonna have to get creative with a couple containers maybe. At least try to make it closer to air tight. Lol

TCH said:

Fresh batteries all around so I decided to go ahead and toss them into a bowl for some testing/calibration this morning.

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I want to test/calibrate my inkbird humidity controllers as well, but I need to figure out a system to do it with the wired lead in a container but still have it air tight. Gonna have to get creative with a couple containers maybe. At least try to make it closer to air tight. Lol

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Just do 'em the same way in a 1 or 2 gallon ziploc bag and use a bit of tape to seal off the bit right by the sensor cables.

LeastExpectedGrower said:

Just do 'em the same way in a 1 or 2 gallon ziploc bag and use a bit of tape to seal off the bit right by the sensor cables.

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That is pretty much what I was thinking about doing.

TCH said:

If I'm storing 10 jars or bags, I'm not going to drop a $20 govee unit into each one to monitor. I'll use the cheapies. This is a great way to know if you are in the ballpark. $1-2 each and a little variation is far better than $15-20 each.

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I took a different approach this time. Since the AC Infinity temp/humidity probe is the most accurate I have, I inserted it through a hole drilled in a masson jar lid and moved it from jar to jar. After final checks, it all went into Grove bags.

Fwiw, I've had much better results with 62% Bovida packs. I cut the bag of a Bovida pack open, slip in a second pack, slip the probe between the packs and seal with painters tape. Readings stabilize in minutes rather than hours and theres no chance of contaminating a sensor with salt.