How reliable are hygrometers?

Mivo

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I've had a digital hygrometer for a year or so. A few days ago I picked up a few extra ones from a different maker. Smaller ones to go into uke cases. As an experiment, I placed them all in the same spot of the room where my larger hygrometer sits at.

Watching them for a few days, they don't agree on the humidity level. The difference is up to 6%. Not necessarily a huge discrepancy (though 45% makes me feel a lot better than 39%), but now I wonder how reliable these devices really are.

Are mechanical hygrometers more accurate than digital ones?
 
Mine are like that as well. I put them all together and watched them over several days. The differences were consistent so I just made a little sticker for the ones that were different to remind me what the actual reading is. Ex. "+4-5 degrees = actual".
 
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I have read that they are not terribly accurate, but mine seems to stay between around 55% to 65%. I figure it can be out by 10% and I'm still fine, so I stopped worrying about it.
 
Not only are they not terribly accurate they may not respond to changes. I'd suggest putting them in a humid environment like a bathroom after taking a shower to compare them at that point as well (should be 90-100%).

As others have suggested, they may still be accurate enough.
 
Well I only have one digital but a few ways to check that it's accurate. You can try the salt test but use the salt that calibrates for 43% RH, which is Potassium carbonate. Sometimes it's available on ebay. I also have a sling psychrometer. The first two digital hygrometers I purchased were way off, one as much as 10%. I finally found one that was within 3%. That was 12 years ago and quite surprisingly it's still within 3%. That's more than adequate for our purposes.
I also have one of these that I made for the workshop. It tracks the digital. it works on a similar principle to the bi metallic strip but relies on how two different woods react to changes in humidity rather than temperature. Given that we are wanting to know how our instruments react to changes in humisity it's not all that surprising that it works, our instruments are made of wood too. I wouldn't use it as my only source but I read this much more often than my digital.
If you want an accurate digital look up David Burgess violins on google. He's done some testing of digital hygrometers and knows the accurate ones.

 
I have two and they differ a lot more than 6%. So I did a salt test, where I filled a water bottle cap with regular salt, add just enough water to make it sort of a slurry and then put it in a ziplock bag with both hygrometers and let it sit overnight. This salt solution result in a relative humidity of about 75%. This helped me get a relative difference between the two hygrometers and a rough estimate of readings vs. an absolute measurement. It doesn't need to be all that accurate.
 
That tells you the accuracy at 75% though. That's not much good. We need to know the accuracy in the 35% to 50% range.
Let us assume that the instrument was built at 45% RH (very common). We aren't really concerned if the humidity climbs to 75%. That won't do the damage. It's low humidity that does. Going from 45% RH to under 30% RH for any length of time and there's a danger something unfortunate is going to happen. It may not but the danger is present. You can use the Hygrometer as a traffic light signal - 40% RH is amber (probably best to do something about it) 35% RH is red (you are starting to push your luck).
 
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The caliber IV hygrometer is the most accurate consumer level digital hygrometer available today based on plenty of tests and data that are currently out. I have 4 myself and all are within +-1% of a calibrated reference. My reference came from a violin luthier in Wisconsin who sells calibrated calibers using a variation of the salt test and told me most calibers he gets require zero offset.
 
It's my understanding from the hygrometers I have and have researched (not scientific grade instruments) that they are generally rated to +/- 5% accuracy over a wide range, often from 10-90%. Since I don't have another easy way to gauge the absolute accuracy, I used the salt test to get an idea.

But I'll see if I can locate some potassium carbonate salt and repeat it with that.
 
Michael,

Just read your post and the luthier in question in my post is David burgess.


+1 to Recstar24, since by his recommendation to me a while back, I bought one of the calibrated Caliber IV hygrometers from David Burgess. It was only a few dollars more than a generic Caliber IV from Amazon +$6 shipping. I have used it ever since (a few yrs now) on the original battery even and been happy with it.

If you do order one from him, be advised that he does not ship it with a tracking number. 2 days after the order I called him to inquire about one since nothing came via email except the original PayPal confirmation, and he was rather annoyed that I bothered him on the phone, and told me 'No I dont mess with any of that stuff, I sent it yesterday and if you dont get it in a week's time let me know and I will send another'. I simply thanked him and he then hung up. I guess he was very busy.

Prior to purchasing from him, I read literally every page on his web site, and he seemed to be an authority on humidification of wooden instruments, and if I played a violin, I'd want one from him...

Any way, Kudos to Recstar24 and thank you for pointing me in the right direction. :)
 
I have two and they differ a lot more than 6%. So I did a salt test, where I filled a water bottle cap with regular salt, add just enough water to make it sort of a slurry and then put it in a ziplock bag with both hygrometers and let it sit overnight. This salt solution result in a relative humidity of about 75%. This helped me get a relative difference between the two hygrometers and a rough estimate of readings vs. an absolute measurement. It doesn't need to be all that accurate.

Get the caliber IV and don't bother with testing. At worse it's 2% offset.
 
I have a digital and an analog hygrometer. I check both of them as different as they are and keep the humidity between 45-55 average between the two.
 
+1 to Recstar24, since by his recommendation to me a while back, I bought one of the calibrated Caliber IV hygrometers from David Burgess. It was only a few dollars more than a generic Caliber IV from Amazon +$6 shipping. I have used it ever since (a few yrs now) on the original battery even and been happy with it.

If you do order one from him, be advised that he does not ship it with a tracking number. 2 days after the order I called him to inquire about one since nothing came via email except the original PayPal confirmation, and he was rather annoyed that I bothered him on the phone, and told me 'No I dont mess with any of that stuff, I sent it yesterday and if you dont get it in a week's time let me know and I will send another'. I simply thanked him and he then hung up. I guess he was very busy.

Prior to purchasing from him, I read literally every page on his web site, and he seemed to be an authority on humidification of wooden instruments, and if I played a violin, I'd want one from him...

Any way, Kudos to Recstar24 and thank you for pointing me in the right direction. :)


I think you would have to pay a very substantial amount for your Burgess violin. It would be much cheaper not to play violin at all.
 
I have a cheap hygrometer that I bought at the hardware store. There is also one connected with my thermostat because I have a humidifier attached to my furnace. They are pretty consistent with each other. I don't know if they are particularly accurate or not. But seriously, my ukulele doesn't know what the numbers are when it comes to humidity, the numbers are for us, and then they are just a bench mark. I do know that the joints in my wood floors will open up if the air gets too dry. I also know that my nose drys up, it is hard to sleep, and a lot of static electricity builds up when my hygrometer reads below 35%. At 45% life is good for me, my nose, my floor, my wife's lime tree, and I'm assuming then that it is good for my uke. So regardless of how accurate my it is, 45-50% on my hygrometer is where I keep the house. I might add, that in the winter, especially when it is really cold and the furnace runs a lot, regardless of what the hygrometer says, I throw the Oasis in with my uke
 
I've had good luck with the $5 analog dial cigar hygrometers (brass & glass with a needle dial , no batteries required). The one in my office at work seems to be fairly reliable to the general relative humidity. My work office varies from about 15% to about 85% relative humidity. It correlates pretty well to how I feel it .
 
I've had good luck with the $5 analog dial cigar hygrometers (brass & glass with a needle dial , no batteries required). The one in my office at work seems to be fairly reliable to the general relative humidity. My work office varies from about 15% to about 85% relative humidity. It correlates pretty well to how I feel it .
I've got a couple of those too. They are generally within 5% of the reading on the HVAC system. Not bad for a few $.
 
I ordered one yesterday and also ordered some sodium carbonate to check calibration at 43%.

That's how David burgess calibrated them as well. I've ordered two of them from him, and he supplies the offset he used if any. My first one only had a 1% offset, my 2nd one required no offset. Now I just buy them from amazon and get those to match.
 
Slightly off-topic, but to add more humidity than the current cool-mist ultrasonic room humidifier that I'm currently running as per my post above, I was thinking of taking an small 8 watt aquarium air pump (for a fish tank air stone) and running a sizable (3" diameter) stone in a 5 gallon bucket full of water as a cheap room humidifier, but I am unsure about the output rate.

I use to have a couple of larger (55 gallon) fish-tanks, and other than water changes to keep the water clean, as I recall you could lose about 5-10 gallons per week just due to evaporation and the water being agitated by the air stones...(but no fish-tanks now for a few years in my house)

Anybody here ever try something like this?

Crazy idea? or is it better to just get another similar room humidifier, or better to add a warm-mist humidifier?

The air pump + stone ($10 maybe) in a bucket full of water is much cheaper than a new 3-gal-per-day room humidifier (~$40+), but if the bucket system puts out too little moisture, then it seems it would be a waste of time and electricity...
 
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