I am in the middle of a calibration. The hygro was holding steady for a few days at 75, but now it reads 77. What do you think the actual calibration is?
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I would go with the reading that I got at about the 48 hour mark. How long were you planning on testing it for? :-)
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Not sure why it would go up after a few days, but go with the 48 hour mark. That's the reading that is guaranteed. Looks like your hydro is only .5 low - congrats!
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the sticky said a week... it went up after about 3 days. ill go with the 75% then.
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I do 24 - 48 hrs. You are not actually waiting for the hygro to respond but for the conditions in the container to level off. I dont use a zip lock for this reason. I use a an air tight tuperware and I place the container into a closet out of the sun and make sure my air conditioner is on. Spikes in temperature can raise RH by releasing more humidity from the medium.
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I was going to say what Bigloo said. Keep an eye on what the temp is when you look at what the RH is. The temp will change the RH reading.

For me I would rather get one of those calibration kits that Boveda sells.
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