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Hi All,

Wanted to get some ideas and opinions on what you belive is the best hygrometer out there for the money. Nothing too elaborate, but VERY ACCURATE as far as reporting relative humidity. I'll wait to hear. Thanks in advance.

Dan Brooks
B & B Resophonic Guitars

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Dan Brooks
B & B Resophonic Guitars
http://www.therarelyherd.com/documents/27_ezgedit.php?action=show

My suggestion would be to buy a wet-dry bulb thermometer and an analog hygrometer that can be calibrated to the wet-dry bulb thermometer - most analogs can. Calibrate the analog hygrometer every month or so, to stay close to the wet-dry bulb. Or, at least check it frequently. Another option is to buy two analogs and only calibrate when they start showing differences in humidity readings. I try to check my analogs with my wet-dry bulb at least once a week. It only takes a few minutes. I fill up the little reservoir and hang it in the draft of an oscillating fan that's across the room that runs all the time in my shop. After about 15 minutes it settles down to a steady reading, and I can read the humidity on the chart. I then see if my analog hygrometer is reading within a % or so of the chart reading. i might check it several times during that day. If the readings are ever far off, I'll recalibrate the analogs.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I hate to say this Dan, but there is no such thing a good cheap hygrometer. I have no confidence in any digital hygrometer. I was able to pick up an Abbeon off of eBay for about $75, although they often go for $100 or more. If you decide to go that route they can be calibrated by yourself by either using a sling psychrometer or by placing it in a controlled environment (plastic bag) containing a dish of saturated aqueous potassium carbonate. In fact any hygrometer should be checked in this manner. I can explain this more when you get there.

I should mention that if you were just looking for something to stick in a guitar case, the best you can do is to keep your guitar closed in the case when it is not being played with an Oasis Plus humidifier. Just keep the humidifier full during the heating season and don't worry about trying to read the humidity.

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Randy Muth
RS Muth Guitars Website
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The only problem I see with calibrating in a bag with wet potassium carbonate is that it calibrates the hygrometer in the 75% range, and we need it to be accurate in the 40 - 50% range. Big difference, and analogs are notorious for being accurate in small ranges and way off in wider ranges. That may not be the case, though, with an Abbeon, which I know is a precision instrument.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Best for the money is two bulb thermometers, mounted side by side, with a wick on one of them that goes into a bottle on one end and covers the bulb on the other end, called a hygrometer. It's what Waddy is describing for the one in his shop. Here's one.



But they can be made quite a bit more cheaply and simply. Compare the two temps and look them up on a chart to get your RH. The charts are all over the web. Dead simple, dead accurate, and cheap.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

Those very expensive hygrometers use human hair ,which has been found to be the most reliable for measuring humidity.

I made this a few years ago and it works very well , so well in fact , I take more notice of it than my digital one. I used three strands ( about 9 inches long)of my daughters hair.





More info on this link

http://www.anzlf.com/viewtopic.php?t=47

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CRAIG LAWRENCE of AUSTRALIA
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Pat, Are you using a vacumn to move the air over the wet bulb thermometer? The water over the wet bulb must be evaporating to get a true reading. Google sling psychrometer.

Chuck

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If you are controlling your humidity, you should have a fan running all the time anyway. Otherwise, you won't have an even environment. Any breeze will stabilize the thermometers. It does not have to be a hard one, just as long as air is moving across the wet bulb. You can use a dust collector, or a vacuum, but a fan, with enough space between the fan and the thermometers will work fine. I have double checked mine with a vacuum, and it reads the same as with the fan.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Thanks Waddy. I really like Pat"s set up. I've just always periodicaly checked my digital hygrometer with two thermometers, a saturated wick and a vacumn. I think I'll have to build a little stand so as to have a continuous check.

Thanks Chuck

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Chuck,

I use a small computer fan that hangs a couple of feet away. I've compare temps on the dry side with the fan and without; very little difference. Plenty accurate for me, I believe. I still have a Caliber III digital, but I only look at it to get F since my thermometers are in C. I keep tape over RH side of the Caliber III so I won't be tempted to pay any attention to it.

BTW, that pic is just an example. Mine is pretty primitive. Didn't mean to mislead.
Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

Waddy, potassium carbonate creates an environment at 43% RH, NOT 75%. That is why I use it. It is sodium chloride that creates a 75% RH. This is an extremely accurate and precise method for seeing whether your hygrometer is measuring correctly at 43% RH. Of course you need to make sure the hygrometer actually changes its reading with changing humidity. This is why I use an Abbeon.

Craig, I believe that they now have a polyamide that surpasses human hair in precision. Human hair is what is used in the humidistat I use to control my humidifier.

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Randy Muth
RS Muth Guitars Website
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I have the one that StewMac sales.
http://www.stewmac.com/shop/Tools/Measu ... Gauge.html

McMaster Carr sells very inexpensive Taylor hygrometers:

http://www.mcmaster.com/#hygrometers/=4js2sv ("A" at the top of the page)

I have three of them in different locations in my shop. I check them from time to time with a sling psychrometer, and recalibrate them as necessary, but I usually have to make only very small adjustments when I do this. Before I recalibrate them, I move all three to the same spot and wait a while. At that point they always read very close to each other (and, as I said, very close to what the sling psychrometer says). Considering how cheap they are, I've been very impressed with how accurate they are.

If you figure that the definition of a hygrometer is something that gives you a reasonably accurate idea of what the RH is, then all those digital things aren't hygrometers at all. They're just useless objects with numbers on them. I think the sole reason for their existence is that people buy them. I bought a few myself until I finally realized this.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

OK, I know that a lot of folks won't like a recommendation like this, but I got an inexpensive Caliber III hygrometer and it has done a good job. When I first got it, and a few times since, I checked it with a BK Percision 625 hygrometer and it was spot on. BK Percision makes a lot of test equipment and I recall seeing a recommendation from someone with NOAA saying that the BK Percision 625 was an accurate and fairly inexpensive hygrometer that could be used in the field. In any case, that what I have been using and have had no problems.

That's the StewMac hydrometer.

The Caliber III is plenty accurate for lutherie. We are talking about maintaining an approximate RH of 45%. If it is 47% or 43%, it doesn't really matter. You just want to be pretty close to 45%. For what its worth, cigar afficionados swear by this hygrometer. I buy a couple every year or so for replacement and they are ALWAYS identical. I also have a cheap radio shack hygrometer that is also in agreement.

Simon, you are confusing precision and accuracy. Two very different things. Even the best hygrometers aren't more precise than plus or minus 3% RH. That's fine and as good as you are going to get, but the question is accuracy, which is are they reading the correct RH within that degree of precision.

The Caliber may be accurate at 45% or not. I have not used this particular brand so I am not going to discredit it out of hand. However, cigar aficionados are looking at 75% RH. This is very different than 43% RH, and it is well known that hygrometers, including analog ones, are only accurate in a fairly narrow range or in the range that they are calibrated for. In fact some are manufactured to operate in targeted range. This in fact may be the case for the Caliber since it is sold for humidors.

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Randy Muth
RS Muth Guitars Website
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Todd,

I just looked at the hygrometer that you pointed out in McMasters. I would guess that the accuracy is good, but the precision is only plus or minus 6%, so if it is reading 42% it could be 36% or 48%. That's a bit wider range than I'm comfortable with. Still, its better than the digital ones. It's funny that McMaster also seems to be confused about the terms, precision and accuracy. They state accuracy where they should be stating precision.

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Randy Muth
RS Muth Guitars Website
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Hi Randy,
I can assure you that I am quite familiar with precision and accuracy. I was about to pursue a doctorate in virology before I stumbled into guitar building many years ago. My background is in biochemistry - a field that is heavy in physics and chemistry.

My point was simply this - how accurate do we really need to be. We control the humidity in a room via AC or a humidifier or dehumidifier. It is a real challenge to get the humidity to remain perfect constant. The reality is that TRUE RH of most of our controlled rooms go up and down a few points but it isn't a big deal. In other words, we are just looking for a range that stays around 45% -- give or take a few points. Lutherie requires no more than that. To pursue more rigid standards is simply unnecessary.

My understanding is that these cheap hygrometers usually are pretty accurate. I have heard glowing reviews regarding the Caliber III agreeing with measurements by highly-accurate hygrometers. Just check the net for many comparisons between expensive calibrated hygrometers and the Caliber III. The Caliber III's have all had excellent "precision" in my experience (identical readings when placed side by side). It stands to reason that they are probably fairly "accurate" as well. A hygrometer is simply a tool. I bought Starrett measuring devices when I was first acquiring tools and paid a fortune for them. In retrospect, I realize that I could get by with much cheaper instruments. My point was that the Caliber III is probably good enough and has a good enough reputation for me to feel confident in it.

And yes, I do understand the "relative accuracy" of hygrometers. But I am pretty sure I read somewhere where these devices were tested to "accurate hygrometers" at various RH's.

Please don't take this as combative. I just want the original poster to be aware of my sentiments -- and that is I believe that most of these inexpensive hygrometers do the job well enough. However, I do recommend buying several. If they are all in close range to each other, I think one can be somewhat confident that you are in the general ballpark of where you need to be.

Of course, if anyone has a high-quality hygrometer that has been calibrated in the 45% RH range -- I would be more than happy to purchase a couple Caliber III and send them to you. I need to replace mine in the near future anyway and would be interested to see how accurate they are. Email me at info@fayguitars.com if you would like to take me up on that offer.

Kind Regards,
Simon

I am very satisfied with this one:
http://www.fine-tools.com/hygrometer.html#ziel309635

Understood, Randy. My experience, though - that they always check out to be within a couple of percentage points of each other and of my sling psychrometer readings - suggests that they are actually more precise than that. Or is that faulty methodology on my part?

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

I have a cheap digital and a sling psychrometer. The digital gets checked against the psychrometer every 3 months. My digital unit is always within a few points of the psychrometer, that's good enough for me. I glue the important components within the range of 45 50%, other components within a range that is a little broader than that. After the instrument leaves my premises I haven't got a clue what environment it is kept in. I suspect that the humidity range will vary enormously.

The Caliber III is what SM sales so I would think they checked it out before selling them for lutherie needs. I really haven't read anything bad about them yet.

Regarding the OP's question - "Best hygrometer for the (limited) money?" the answer is....... drum roll please....... : NONE - There is no such thing as a best commercially available hygrometer for limited money and I am not sure that there would be one to recommend if money was not an issue.

But.... You can make a very accurate, near perfectly accurate hygrometer for about $10 by making a wet bulb or sling psychrometer as mentioned by some of the others above.

Here is a link to a thread on the ANZLF in which I recently made a wet bulb in an effort to learn to calibrate my Abbeon. Along the way I also checked the accuracy of the Caliber III's which I have had many of and have in the past recommended them... Check out this link and I think that it would be helpful to those who have some questions here. http://www.anzlf.com/viewtopic.php?t=2116

Wet bulbs can be as simple as two matched thermometers taped to a bench with air drawn over them. Just keep the actual wet side down wind/toot of the dry side. Using one of the many available charts as mentioned and Bob's your uncle.

But be prepared to learn that what you have been using AND trusting MAY be off and it may be way off too.... I found the current pair of Caliber III's in my shop to be 9-10% off - this is not acceptable when I too am looking for a 42 - 48% good-to-build range.

The Abbeon is a very nice instrument but they do need to be checked and perhaps calibrated up to 4 times a year depending on how anal you personally are. Previously I was sending my Abbeon back to Abbeon twice a year for calibration of which they offer two levels, at two prices of calibration. Now that I have a wet bulb that I can slap on the bench as needed I will be calibrating my Abbeon myself. When I checked it as in the link above it did not need to be calibrated which was nice to know even though I missed out on getting to do the actual calibration this time.

What has been said about the range that one calibrates for has been my experience too. Hygrometers may be accurate in specific ranges and way out in others.

At the end of the day checking your RH is super important if you don't want to spend more time learning to repair your guitars than building them... And although I know of no off-the-shelf solution that will provide us with accurate RH readings we can for $10 or so have RH measuring capability that is excellent AND learn too that our hygrometers just may not be telling us the truth. You can also purchase wet bulb type hygrometers ready to go if you don't want to build one.

Once you do know the rate of error for your hygrometers you can adjust, in your own mind if it can't be calibrated, and they are useful quick glance indicators of change. But I would never trust anything that has not been recently calibrated with a wet bulb or wet bulb type method (there are at least several including the sling method).

Back to the OP - if it were me and I wanted to save my chump change for zoot buy two thermometers from physics.com ($10) and then ask Craig nicely for info on making the very cool hygrometer using human hair that he has made and pictured above. Once you calibrate your shop-made hygrometer with several wet bulb tests you will have all that you need to know the RH and will have spent probably little more than the price of a couple of thermometers.

At this point all you have to do it do what ever it takes to seal off your shop so that it is a controlled humidity environment... Piece of cake.....

Good luck and welcome to the OLF!

Todd, it doesn't surprise me that they are actually more precise than claimed. Your methodology is good. They are probably being conservative in this case, since they are not certified.

Simon, I don't want to be combative either. While we're dropping qualification, you should know that I have a Ph.D. in organic chemistry.

Now here's the deal. Even a device based on human hair, one of the most sensitive and precise available can only determine RH to within plus or minus 3%. You can see that relative humidity is not easy to measure. The Caliber III on their website claims to measure RH to within plus or minus 1%. How can this be? This kind of statement does not lend credibility to the company. Most digital hygrometers only claim to measure within plus or minus 5%. Now they may be great hygrometers that are far better than all other digital hygrometers, but they can't be as accurate or precise as claimed.

I admit I do not have any personal experience with the Caliber III, but I really don't think the technology they use is that different than that used in other "quality" digital hygrometers. The fact that they are marketed for cigar humidors means that they are most concerned about being accurate and precise at an RH of 75%. I had three digital hygrometers with two of them in agreement. I erroneously assumed that those two must be correct. I then purchased an Abbeon and looked at all of them in 43.1% RH environment. The Abbeon was right on and all three digital hygrometers were off. Not only were they off, but the two that agreed were outside of the range claimed.

Again, the Caliber III's may be fine, but I would make sure to calibrate them to a known standard. Rather than sending them to me, do the following and you will be set up to test all of your hygrometers. Place the hygrometers in a chamber, a one gallon zip lock bag works fine, with a small dish of saturated potassium carbonate in it. Make sure some of the potassium carbonate is undissolved. This creates an atmosphere with an RH of 43.1% that is constant over a wide temperature range. Leave them in there overnight and see what they read. Also make sure that the reading changes with changes in humidity and you should be good as long as your shop is in that range.

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Randy Muth
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