New springfield hygrometer? accurate?

[Bec]

I have one and it reads 11% below

 

[Penturner]

Quote:
Electronics can only do so much. If you want a truly accurate Hygrometer they have to be made with a hair as the mechanical part (the part that reacts to humidity) even then they have to be calibrated but those usually have an adjustment so you can do that. They also are very delicate and expensive. the type of hygrometer in the spring filed thermometer is two pieces of metal with a thin sheet of plastic sandwiched between them. the reading you see if a result of the resistance between those two metal plates. it gives you a general idea of the Humidity but will never be accurate. It will not even remain consistent in how much it is off and it is recommended you calibrate it before every hatch.

 

[A.T. Hagan]

Here is the most detailed article on calibrating hygrometers that I've yet found: http://ezinearticles.com/?Prevent-Mold!-Hygrometer-Calibration&id=602308

I've only used table salt (sodium chloride) to calibrate mine. I stuck the solution jar and the hygrometer inside of two Ziploc freezer bags. Did the test twice. The first time I could not get a consistent result. The second time I triple checked the seal of both bags and would occasionally puff the sides of the bags in and out (without opening them) to be sure the water vapor (humidity) inside was evenly distributed. Took about ten hours at a room temp in the low seventies before I was convinced that it wasn't going to change any more. I am now convinced the unit that came with my incubator consistently reads 4 points low.

.....Alan.

 

[dak]

WOW great article! .... however, I have one final question...Will altitude affect the test? I'm doing a poor job of remembering thing like partial pressures and such from physics class. I'm at about a mile high. (Yes, I know I'm probably overthinking this). Clare

 

[A.T. Hagan]

As I understand the way it works, no, altitude would not affect the test. The air pressure is lower and thus the total amount of water vapor, but it would still be 75% humidity relative to what the air is capable of holding.

.....Alan.