View Full Version : Electronic Hygrometers

Feb-21-2004, 5:50pm
I recently purchased an electronic hygrometer for my case. It is distributed through Martin guitars. If I compare it to other hygrometers it is usually about 12 points off. It is either off or my conditions are very dry. Is anyone else out there using an electronic hygrometer and if so, is it accurate? Help, I need something that is accurate and don't know what to make of these readings.

John Flynn
Feb-21-2004, 6:09pm
"Inexpensive" electronic hygrometers (less than hundreds of dollars) are notoriously innaccurrate, so much so that they routinely need to be calibrated. I have several and they are as much as 20 points off. People in the cigar world know a lot more about this than those of us in the music world, IMHO, so the links below are from that realm.

There is the wet-towel calibration method:
http://cigars.about.com/c....769.htm (http://cigars.about.com/c/ht/00/07/How_Calibrate_Hygrometer0962934769.htm)

And the salt method:

I would try both and average them. If you can adjust the device internally, do so and then re-check. There will still be some variance. I use a label maker to display variances on all my hygrometers, like "Plus 2%" or "Minus 3%." I re-check every year, before the dry season. I know there is still some error, but if I can get within a few points accuaracy, it is good enough to keep my instruments in the Martin Guitars recommendation of 45% to 55%.

Bob DeVellis
Feb-21-2004, 10:18pm
Gee, I have two hygrometers, one that came with an Ameritage case and another that's part of an indoor/outdoor electronic temp/humidity/brametric pressure sensor. The two, in the same room, are never more than 1 or 2 percentage points away from each other. The indoor/outdoor also gives outdoor readings that very closely track the local weather broadcasts' humidity reports.

John Flynn
Feb-21-2004, 10:57pm

Consider yourself fortunate, sometimes that happens. I have five hygrometers. Two are pretty accurate, two are so-so and one is not even in the ballpark. I also bought a Planet Waves hygrometer once that was made for musical instrument cases. I returned it because it was neither accepatably accurate or even consistent in how far off it was. Also, I have noticed that even ones that start out on the mark can change over time.

Feb-21-2004, 11:23pm
I've never had a cheap hygrometer that was accurate. I have a good (expensive) electronic one that doesn't do me any good because I got tired of feeding it batteries.
I think the best ones are mechanical and expensive.

It wont go in your case, but I've always wanted to make a "moisture widget" as described by Hoadly in Understanding Wood. Not only is it accurate and cheap, but it drives home the point of what wood does in responce to humidity changes.