Now that I’m acquiring some wooden flutes and whistles, I’d like to get a hygrometer. I’ve read through several topics on the forum, but I haven’t been able to find a gauge/meter/sensor that has been recommended. It’s possible I just missed it.
I also went to the Martin Guitar Forum, as one forum member suggested, but there was almost too much information.
Any advice/help would be appreciated. Thanks.
If you are going to buy it from a shop, look at as many as you can in the shop, and particularly the expensive ones. Then buy one that reads about the same as the average expensive one.
Logic behind this is that it doesn’t cost much to make a hygrometer, but it costs a lot to calibrate one, as that requires human intervention. So, even though the cheap ones are often calibratable, they aren’t calibrated!
Terry
What kind of a shop has hygrometers?
Cigar shops…
…and hardware stores.
I use this one and have been happy with it.
Pat
Radio Shack also carries one or two hygrometer/thermometer models. Mine seems to register accurately.
… and music stores, and guitar shops / violin shops (luthiers). Science/learning stores like The Nature Store or Nature et Découvertes. Even Wal-Mart sells hygrometers and home weather stations.
As Terry said, the problem is accuracy and reliability. And for that, you can’t beat a wet/dry bulb hygrometer or a sling psychrometer. The first is fixed (wall mounted) and not too expensive. The second is more pricey and … awkward. Not that I’ve always thought swinging one around at a session wouldn’t be totally cool.
To me, the ideal is a small, portable hygrometer that can be calibrated at will against a wet/dry bulb. Unfortunately, user adjustability seems to be rare (however ridiculous that seems in a measuring instrument). My Planet Waves (D’Addario) unit from Guitar Center is no different, and I don’t really trust the numbers. Then again, at my location humidity usually varies between very very dry and insanely dry. 
Thanks
I have one small enough for instrument cases, even some flute cases.
Made by “Oasis”. 30 x 10 x 8 mm. Purchased from Elderly Instruments in Michigan.
They recommeded it because they said it agrees very well, out of the box, with their rather expensive ones used in rooms storing vingage guitars, etc.
They implied that many makes didn’t…
For whatever that’s worth.
There is a fun article on Wikipedia discussing hygrometers. Clearly a hygrometer using a strand of hair under tension may easily need calibration! Surprisingly I found the sling bulb hygrometers are not the most accurate. . .the were found to read high by 2 to 5 degrees R.H.
Chilled mirror dewpoint hygrometers are now considered the most accurate but are probably not very portable! They give a good rundown on both resistive and capacitive hygrometers. . .both need calibration. I don’t think I’ve ever seen a listing for which type was on any of the very many hygrometers I have employed over the years (mushroom cultivation) they just said “electronic”.. Thermal conductivity hygroometers provide absolute humidity (not much use to musicians) and are pricey. I’ve never used one. Relative humidity is more meaningful for most of us. After spending a sizeable sum of money over a period years on hygrometers, I found the appearance of the mushrooms in my growing room were a better and more immediate measure of the R.H. Again, not much use to a musician. . .!
Bob
And they can cost as much or more than your flute, up to thousands of dollars. Whereas you can get a dry/wet bulb for around $40.
I guess by degrees you mean percentage points of relative humidity (RH). Actually, if you’re reading within 2% or so, that’s about the accuracy limit of any consumer grade hygrometer anyway, and more than good enough for checking instrument humidification.
By contrast … Happily, there are a number of home weather stations in my neighborhood live on the internet and checkable online (e.g. via Weather Underground). So it’s easy to get an average outdoor RH for my area. And the last time I deliberately left my electronic hygrometer outside in an appropriate location on a fairly humid day, the reading was off by 30% RH or more, IIRC. Which hardly inspires confidence.
It’s also hard to figure out the thing’s response time. If I test it by breathing warm, moist breath into the sensor, it may take minutes to register the higher humidity, and then hours to settle back down to some ambient value. Which is fine for a once-a-day room check. But if you want a hygrometer to keep with your case, that you can check for humidity issues when you first walk into a new venue without waiting for hours, sluggish response is essentially useless.
Unfortunately, Terry’s good buying advice above may be hard to implement in practice. If you buy a single hygrometer online, there’s nothing to compare. A store may carry only one kind or brand or all cheapies, and they may all be wrong (so the average may be wrong). At least with a wet/dry bulb on hand you can, in theory, calibrate the thermometers, then have a reliable at-home reference to check portable devices against.
But I do like the idea of the shrooms. Maybe a miniature mushroom garden in your case. When you open it up, everyone will shout: “Oh, look, fungi!” And you can reply: “Why yes … yes I am!”
My neighbour has a bunch of seaweed hanging in the porch next to the barometer. I know he calibrates the barometer against the local met station. Not sure about the seaweed.
Unfortunately an acquaintance in the shiitake biz, who used to own “Fun Guy Farm” strayed from the straight and narrow and is now a long term guest of the Canadian Government. . . 
Bob
How to Calibrate a Hygrometer - http://exoticpets.about.com/od/herpresources/ss/hygrometer.htm
may be of use to someone
The best bet is to get a small, portable hygrometer. I have the “Little Havannah” which is about the size and shape of a small cigar and fit’s nicely next to my flute parts in the tupperware box i have them stored in with a damp sponge in a cup. I keep the humidity somewhere between 50-60 percent.
I really like the above suggestion of a dry/wet bulb hygrometer to check the accuracy a few times/year and calibrate if possible/necessary.
A small, portable hygrometer is not super accurate because it does not need to be and unless you have a flute shop or are a museum curator you shouldn’t need that much accruacy either. The goal is to keep the flute(s) from cracking and to protect the wood from extreme changes and not just humidify. My own headjoint cracked not because it got too dry but because it got too dry too fast. I check my hygrometer every day but favor stability over a number value.
Yes, that’s good. Here’s a more detailed table (PDF) for different salts, and correlated with temperature:
http://www.omega.com/temperature/z/pdf/z103.pdf
In theory, the salt should be pure (e.g. not iodized) and the water distilled. And ideally, you’d also want to check the calibration at a lower RH (e.g. Potassium Carbonate), since hygrometer response may be non-linear.
Oops, didn’t read all the way through that salty article before responding (typical, impatient me). The salt in a bag thing does seem like the way to go for periodic calibration.
Question: if it is recommended to keep the flute around 60% humidity and protect it from extreme changes in humidity and if you live in a place where summer air reaches up to 80% would it be a good idea to store the flute in winter at a higher average humidity (say 70%) in anticipation of the summer weather?
No, if you try to reach that level of humidity, you will grow mold, best to keep it 50 to 60, when the humidity reaches 80% naturally, the flute will be on Holiday! 
Thanks Jon C!