anyone know how hygrometers work???

[Grant vg]

like, how they actually measure humidity??? lol
The science behind it????

gvg

[Edwin]

I am just guessing, but for analog hygrometers, there is a piece of metal (or something) that contracts and expands depending on the amount of humidity it is exposed to. The contractions and expansions move the pointer on the hygrometer.

[Grant vg]

interesting, thanks for the info edwin! :)

[Lisa]

I'm told digital ones work by measuring the conductivity of air.

[nouserpif]

I believe the "acoustic" ones are basically what Ed Said... A small piece of material (probably metal) that is coild around, and as it is subjected to more humidity, the coil expands, and pushing the needle or whatever further into the "wet" zone on the hydrogometer... something like that. I spent an hour trying to figure it out a few days ago... Neat idea, them theres are.
Dan Conner

[Bryce Masuk]

Grant I talked to a fried of mine about hygrometers he said the only ones that are acurate for about +/- 1 to .5 % are about $100 are made by some german company if i knew it i would list it. H0e also told me the ones you buy in the store are really inacurate and mostly for show and are often +/- 10% but this is just what he told me but he is pretty smart so i think its true or close to

[Edwin]

Your friend is absolutely right, Bryan. Analog hygrometers do not have good accuracy, I guess +/- 10 to 20% would be common, and its accuracy deteriorates at extreme ranges. For digital hygrometers, they often list an accuracy range. For example, the one I purchased from Radioshack has:

+/- 5% RH below 40% to 80%
+/- 7% RH below 40% and above 80%

In my opinion, herpers in general do not really need to spend on a highly accurate hygrometer, as the gains from measuring 40% humidity to 41.1% humidity would be trivial. In selecting a hygrometer, I would look for durability (to withstand the tough love from herps), ease of cleaning, in addition to fairly accurate readings.

Just my 2 cents (Canadian). Hope this helps.