RH and temp

[Séamas]

I bought the cheapest digital hygo at walmart, just to check it out. I did a salt test, with the temp around 65F (according to the hygro readout). The RH rose from 45 to to 62 after four hours... 6 hours later it was still at 62%. I though it was going to be junk. But, I left it and went to bed.

When I woke up, 13 hours after beginning the test, lo and behold, it was 75% on the dot, at 64F.

Turned on the heater, warmed the house up to 70, and it dropped down to 64%.

Wtf?

Doesn't humidity rise with temp (as it seems to be now)? I also thought the damp salt would maintain 75% more or less regardless of temp?

Few hours later, brought it into my bedroom, where the temp is 75F, and as I look now it is at 68%

Huh? Now it's rising with the temp?

It is possible that temp fluctuations are just throwing the reading out of wack, and it will stabilize back to 75% if I leave it at a constant temp?

Or that the hyrgo is junk and doesn't know what it's supposed to be doing? I was pretty impressed with that 75% reading, but now I wonder.

All this brings me to another question:

Do the heartfelt beads, and boveda humidity packs, require a certain temp to maintain their set humidity?

Thanks.

 

[Donk]

You know I have the same problem. I have three digital hydro. I've tested them all and all are accurate. But none of them will ever read the same humidity in my humi. on is high, one is low and one seems to be in the middle. Weird huh. So I use the better quality one. It is a Oregon Scientific it's from Target, if you have one by you. It is wireless and read temp and Humidity. I like it, and It seems to be the most responsive while mantaining it's accuracy. They are about $40 ish for the wireless unit and receiver. try one you'll probably like it. Well I do.

 

[Donk]

Also, from what I've learned Humidity Should remain constant, even with temp increases and decreases. the two actually are independent of each other.

 

[Jwrussell]

Yes, it will stabilize given time. Humidity actually will increase with LOWER temps and decrease with higher temp in the situation you are describing. Here's the deal. At 65 degrees where you had the hygro to start, it was settled at 75% RH. When you took it to 70 degrees you created an environment that needed more moisture to hold at 75%. Colder air holds less moisture than warm air. So when you increased the temp, the salt solution had to work to release moisture into the air so that the RH would settle at 75%.

So yes, it makes sense that the RH took a dive when you brought it into a higher temp. And it also makes sense that the RH started to rise later as the salt solution began to keep up.

Donk, I think you are mixing up things just a tad. Humidity and Temp are definately inter-related, but by no means independent of each other. With any good humidifying media you needn't worry about what the ambient temp is so long as it is within a reasonable range (say 55-80* or so), and so long as it is stable, as the media will work to keep a stable RH. However, temperature fluctuations will affect the RH reading until the media catches up.

Hope that clears things up some...

*Obviously I don't recommend temps higher than 70 degrees due to beetles, but that's a different thread.

 

[Séamas]

Yes, clears things up fine. Thanks, bro. (And it is gradually stabalizing again)

What doesn't make sense is that a $6 hygro from Wally World was dead on accurate!

I probably got lucky, but I might go buy a couple more and see.

 

[Donk]

Sorry, about the mis info guys, may bad. Thanks for the clear up

 

[DocLogic77]

JW I could be wrong but I don't think that is correct. It depends on if you are talking about relative humidity. In regards to humidity warmer temps allow the air to hold more water. I have that walmart hygrometer and it is junk. I have 4 hygrometers and that's the worst of the bunch. I don't trust it.

 

[Jwrussell]

Shawn...that's what I said bro. Absolute humidity (moisture) decreases with cold temps and increases with warm temps. Cold air holds less moisture and vice versa. Hence the RH reading going down initially when Seamas moved the setup to warmer temps. The RH had settled at a colder temp where it didn't take as much moisture to hold 75%. At the higher temp, it needed more moisture to read at 75% RH so the RH reading dropped until the salt solution could catch up releasing moisture.

As to the hygro? When you are talking cheap ones it's hit or miss.

 

[DocLogic77]

My bad humidity talk makes my head hurt anyways. But, I can say that you can't trust that Walmart hygrometer.

 

[Jwrussell]

LOL. Yeah, it took me a while to finally get the whole concept straight in my head as well. lol.

 

[Séamas]

Donk: Don't worry about it, no one is perfect. The more important thing is that you tried to help, and I appreciate it.

My bad humidity talk makes my head hurt anyways. But, I can say that you can't trust that Walmart hygrometer.

I wouldn't doubt for a second that that is usually true. But mine salt tests at 75% every time. It is, however, very slowwww to stabalize. Like 12 hours. I still don't entirely trust it, but it's just a temporary solution until I can afford something better. I ordered a little havana for my tupperdor, but needed something for my little desktop.

Humidity talk confuses me, too, but for some reason it clicked when JW explained it. Or maybe that was a brain cell popping. :dunno: