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Which one is lying?

welshweed

welshweed

New member
Compare the humidity reading on my dehumidifier with that on my hygrometer.
One of them must be wrong - or maybe both!
Any opinions?
 

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Hygrometers (humidity measuring devices, including the one installed in your dehumidifier) are notoriously inaccurate. I see about 46% on your standalone hygrometer and 39% on your dehumidifier, that’s honestly not too bad of a difference. If you want to measure with better accuracy than that, I recommend something like a Sensor Push, or similar device, and even then you’ll want to calibrate both the temperature and the humidity readings. You can buy 75.5% calibration packs from Boveda and put the sensor push in a sealed container with the pack and watch where the readings settle, then program in a calibration offset compared to 75.5%. That’s how you know whether or not your measurement is accurate.
 
I bought some 62% packs, could those work or are there special calibration packs? I bought 2 sensors and the only way to calibrate them are by changing the info myself and Im not comfortable with that. If there are special packs, do I need to get multiple like I would for pH packets or would 1 work for a long time?
 
welshweed Google how do I calibrate my hygrometer with salt and water. It will tell you a way of figuring out how far your hygrometer is off. Basically salt in a plastic soda bottle lid and get it wet but not runny and place it in a sandwich bag with your hygrometer and zip it up. If you wait at least 8 hours 24 hours is better the humidity in the sandwich bag should be 75%. If your hygrometer is off from that then you know how far and which direction. Good luck and happy growing
 
panalilies I’m not sure if there is a decent scientific rationale behind using 75.5% as the standard calibration ideal or not. I probably wouldn’t want to calibrate with a value that’s too different than that, but 62% might give you a decent calibration. That said, these things are pretty cheap so my recommendation would be to just use the advised 75.5%. Like all humidification packs, they will eventually dry out and crystallize, so they don’t last forever. I would just buy one 75.5% pack and calibrate both of your hygrometers at the same time by sealing them both up together with the humidipack.
 
Boveda for Cigars | One-Step Calibration Kit | Preloaded with 75% RH 2-Way Humidity Control | Precise Salt Test for Digital and Analog Hygrometers and Humidity Sensors | 1-Count https://www.amazon.com/dp/B000A3UBLA/ref=cm_sw_r_cp_api_glt_fabc_RYA2YCHK7XH9CH18HAP6

It’s advertised as “75%” but you’ll find in the fine print that it’s actually 75.5%. But at half a percentage point now we’re starting to split hairs. FYI my hygrometer took a very long time to reach the final stable value, I’m talking weeks. Here’s a snapshot of the last time I calibrated it.
 

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Blimey! You learn something new every day on this forum.:)
Thanks, Larry for that home-made DIY calibration trick, and to Rik for introducing me to the world of Boveda, which I'd never heard of.

BTW how do you guys copy and paste the avatar and @link of somebody into the body of the text?
 
It’s obvious the analog is off by approx 25% the digital approx 15%. The actual obvious humidity is approximately 50%.


I say anything when I’m stoned
 
As Rik said Hygrometers are for the most part very inaccurate. Humidity standard way of measurement is by wet and dry bulb calibrated thermometers. Electronic Hygrometers typically have a specification of 10%. Average out the reading from a few and you will be in the ballpark.
 
My hygrometer fell into a water basin today. Pulled the battery and put everything into a bag of rice. I just rec'd my bozos order today, gonna have to use some jar hygrometers for the weekend or longer. Wish I knew a reliable mid-priced one, and I know mid-price is a relative term.
 
The one I dropped was $25-30. I'll see what happens with it first. The little jar ones are OK for right now. I almost just want a simple analog if it works OK. I'm close to the room, no need for another phone app. Thnx!
 
Reporting back having conducted the Larry1 DIY calibration test:

Seems my cheapo £3.50 hyg is pretty reliable. - it's been showing dead on 75% for the past 12 hours or so.
 
welshweed👍. That's good news. I bought a 10 pack of those cheapos for I think 20-25 bucks. Every single one of them is off anywhere between two and five points. Glad it worked out for you. Happy growing
 
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