Can anyone tell me how a hygrometer works? I bought a humidor on sale and discovered the hygrometer does not seem to be working. I took it apart and it only has a coiled spring inside. How does moisture affect a coil of metal?

Too scientific ... do a 'Google' sarch, and you will get lots of technical data ...

... just buy another. They are not worth trying to fix, if they are broken.

Also, it may not be broken at all. It just may need to be calibrated.

Dampen a towel (not dripping wet, but good and damp), then wrap the hygrometer in the towel for 30 to 45 minutes. Then unwrap it and read the humidity (quickly). If your hygrometer is perfectly calibrated (few are) it will be reading exactly 100% humidity. Most likely, it will be reading somewhere between 80 and 90%. That's ok - if it's reading 90%, then you know that when it's in your humidor and reading 65, your humidor is really at 75%. From now on you can just make this simple adjustment and you won't have to mess with the calibration screw. Feel free to send us a email if you have any questions.

Want to get a little more technical? No problem.


Luckily, as nature would have it, when salt and water, are in a saturated solution at equilibrium, the resultant humidity is 75%. This gives a fantastic reference point to calibrate our hygrometers.

Here's the procedure you should use:

Get a bottle cap of some sort, fill it with regular table salt. Then drop a few drops of water on the salt. DO NOT put to much water on the salt. The salt should only be damp, and not a liquid solution. It should be like moist sand, not like soft mud.

Then put the bottle cap of salt and your hygrometer in a see-through, sealable container. I like to use a large freezer bag. Seal the freezer bag or other container. Wait several hours (about six). The humidity inside the bag will be 75%. Compare it to your hygrometer. You will then know exactly how far off your hygrometer is, just like with the damp towel test, above.

dingasm

everything slim said is perfect.

the reason the coil o wire is able to measure moisture and show it on a guage is because the wire is sensitive to moisture and contracts and expands.

sort of like the adjustment you make on your water heater. it has a dodad that is sensitive to heat and it also contracts and expands and when it does it turns the flame on or off to get to the setting you wanted.

i don't know much about what is under the hood of a car, but there used to be an automatic choke that would make the mixture of gas and air richer until the desired temperature of the engine was reached and then the choke would shut off and the mixture would be the proper amount for driving.

and if anyone wants to discuss the manual spark arrestor on my modal a, please let me know.

dodad so thats what it is called lol

Dingasm,

Old hygrometers worked by using human hair. When the hair would absorb water is would expand, and would shrink when it dried.. this was a fairly linear method.. Attach a hair to an arm, and you have a hygrometer... Then we started using alloys with different porosities.. I believe aluminum is one of the metals in the alloys..

Now we are using semiconductors.. The Current semiconductors use a porous metal layer with a thermoset, and a non porous layer of the same material.. For example.. look up the honeywell HIH-3605 sensor. It uses a platinum layer with a thermoset, then a porous platinum layer to create a shear differential on the thermoset. Imagine an Oreo Cookie with the top being porous, and the bottom magically not being porous, and the middle being the thermoset. as the humidity changes, the the top will expand more than the bottom, because it is more porous and can absorb more. This in turn causes the middle of the cookie to stretch. When this material stretches, it changes the conductivity (resistance) of the thermoset. This gives you a way to measure to Relative Humidity (RH)

Analog Vs. Digital.. If you get a good Digital, then there is no comparison. Analog's have hi Hysteresis.. this is bad, they are sensitive to heat flux, and they just simply arnt accurate over a large motion.. Buy a $25 Digital sensor.. and make sure you (test)calibrate it with the methods mentioned by slim..

Ezell

Let me make one adjustments to my statement.. the thermoset changes in capacitance, not resistance.. sorry for the error..

buffallo

too late. we have all learned it wrong.

Have had the same problem. Too bad. I find the analog hygrometer is much more appealing to the eye in a humidor, or any other setting for that matter, but is terribly inaccurate. The digital models are MUCH more accurate, but in comparison look like crap in, through, or outside of a humidor. I have one humidor that has the analog outside for looks, but when I want to REALLY check the humidity, I check the digital one inside (where you can't see it). Stupid?.......Yes, but then so is having so many cigars that you can't smoke them all in five years!!!!!!!!!