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PostPosted: Mon Feb 16, 2009 9:46 pm 
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Proud Rooster
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Location: Mackay, QLD
G'day All,

I promised this some time back, but am often working away.

Basically, a simple test for your hygrometer that is supposed to be very accurate.

In a small tupperware container, say 10cm x 10cm x 5cm (or thereabouts), place something like an egg cup full of table salt (actually in an egg cup or small dish, not just loose in the tupperware container).

Add drops of water to the salt until it is moistened and translucent, but not runny.

Put your hygrometer in the container near the dish/cup.

Seal the lid and leave it over night.

In the morning, open the container and immediately read your hygrometer.

IT SHOULD READ EXACTLY 75%.

You will be amazed at how crap some of those cheap dial type hyrometers are. I have tested heaps of them, and they are way out as often as they aren't.

Denis, would you mind attaching that link you sent me when we talked about this? I don't know how to.

Cheers.

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PostPosted: Mon Feb 16, 2009 11:00 pm 
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Golden Swan
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Wow! I will try it with mine (just because I like doing 'experiments" :lol: and not that I think it is way out)

NellyG

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PostPosted: Tue Feb 17, 2009 1:23 am 
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Superior Bird
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Here's some links, can't locate the other one.

Quote:
Simplified scientific explanation:
A saturated solution at a stable temperature and pressure has a fixed composition and a fixed vapor pressure. Thus, at constant temperature, no matter how much salt and how much water are present, the (RH) relative humidity that is produced is fixed, just as long as both the water and the solid phase are present. So, unless the water dries up, or the salt is made so wet that it liquefies, a predetermined humidity can be produced.
this is from here: http://ezinearticles.com/?Prevent-Mold!-Hygrometer-Calibration--Tips-from-a-Bellingham-WA-Home-Inspector&id=602308

http://www.stogieguys.com/2006/07/stogi ... -test.html
http://www.natmus.dk/cons/tp/satslt/satsalt.htm
http://exoticpets.about.com/od/herpreso ... ometer.htm
http://www.shroomery.org/38/Calibrate-Your-Hygrometer


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PostPosted: Tue Feb 17, 2009 1:36 am 
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Superior Bird
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Nick;
I think some hygrometers only work at all if there is some air movement, is this correct?

One of mine actually corresponds pretty well with the one at the Bendigo Airport, http://www.eldersweather.com.au, but it reads 50% under said test. Is it worth rigging up a tiny fan in the tupperware container?


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PostPosted: Tue Feb 17, 2009 10:39 am 
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Assist Admin
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Thanks - that is what I've been waiting for :)


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PostPosted: Tue Feb 17, 2009 4:09 pm 
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Golden Swan
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Well I tried mine last night and this morning it read 75% spot on! Amazing (that the test works and that my hygrometer is accurate!).

NellyG :biggrin:

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PostPosted: Tue Feb 17, 2009 9:46 pm 
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Proud Rooster
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Joined: Sun Oct 26, 2008 12:14 pm
Posts: 256
Location: Mackay, QLD
[code][/code]Denis,

I don't know, actually.

I just discovered that link some time ago and tried it (without a fan).

Only one of my five hygrometers read close 76%, and was closest to the factory setting on my RCOM.

Obviously, this is something that could do with some experimentation. eg, You could try the fan you mentioned, with the same hygrometer and see how you go.

I'm in a mines camp at the moment, on a laptop, so I won't get to it for some time.

Cheers

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