How to tell what the humidity is

A man with one watch knows what time it is. A man with two watches is never sure.

I just bought two more hygrometers, so now I have three hygrometers of different kinds and manufacturers and they have all been laying next to each other on a shelf all night.

Stand-up unit from the local hardware store . . . 75.9 F, 65%
Little round analog unit from China... 70 F, 55%
Flat unit from Amazon 76.2, 59%
House thermostat on the wall 77 F, 60%

Any comments? Should I buy a thermometer and learn how to wet it swing it around?

I would ignore the China unit (seems to be quite far off). I know Hygrometers sometimes need calibrating? Someone with more knowledge may be able to help.

You could also put them in a case - more of a controlled environment, and see what the readings are then?

Here's the famous picture along with instructions on how to spend a chunk of time calibrating etc: http://www.burgessviolins.com/humidity.html

I had one, the little Stretto from Shar but I couldn't find a battery locally so hasn't been used in a few years. it's mostly humid year round where I live so I just need to put damp sponges in the mandolin, violin and cello cases when it gets cold outside: https://www.sharmusic.com/shop.axd/S...rds=hygrometer

On the other hand if you live in the upper Midwest, New England, Canada, etc, old threads advise to look at room humidifiers for multiple instruments. Use the Search box.

Well, excluding the Chinese cheapo, you have a variance of 1.1º F, or 1.5%, in temperature, and 6%, or 10%, in relative humidity readings. While the variance in humidity seems relatively large, for the purposes you're using the hygrometers -- maintaining acceptable environment for stringed instruments -- it's within usable parameters, IMHO. The difference between 65% and 59% humidity is unlikely to be the threshold for instrument damage. You need to worry when the humidity gets well below 45-50% for an extended period of time. Even then, damage to your mandolin(s) is far from certain; it's more precautionary than an emergency.

It would be nice to have a really reliable hygrometer, but if you have one (or more) that's generally accurate -- and you inspect your instruments regularly for signs of dryness, like lowered action, fret ends protruding, etc. -- even a "ballpark" humidity gauge can be helpful, mainly at showing changes in the environment, and warnings of possible extreme conditions.

Just my 2¢...

Any cigar smoker worth his salt (hint hint) knows how to calibrate a hygrometer using plain old NaCl. Hopefully at least one of your four allows for adjustment afterwards to dial in the accuracy, or at least you'll know how off they all are.

This should get you started: https://www.google.com/search?q=Salt...ion+hygrometer

C.

Maybe you should invest in a German weather house: https://en.wikipedia.org/wiki/Weather_house

86 the Chinese stuff. The rest are close enough. You're not running a laboratory.

Most likely all four were made in china... Do salt test and I would go for MgCl (magnesium chloride) for testing at 33%RH which is more important for instruments than the higher levels around 75% that you test with NaCl.

Look here :- https://www.neptunecigar.com/tips/ho...our-hygrometer There are also several YouTube vids.describing how to calibrate a hygrometer as well,
Ivan

I'll add one more hygrometer to the list. I've used the Caliper IV, a cigar humidor hygrometer that has proven to be very accurate and very reliable for me. It's a small unit that will fit easily into a mandolin case, and claims to be within 1% accuracy straight out of the box. I check it's accuracy with a Boveda One-Step Calibration Kit that is supposed to be more accurate than the salt test. The Caliper IV can be calibrated, so if it varies from the test kit it's easy to get it spot on. Both the Caliper and the Boveda are available on Amazon and eBay. The Caliper goes for about $24, and the calibration kit for about $8.

I don't think 1% accuracy is necessary. If my hygrometer reads 50% and it actually 48%...well, I'm certainly good with that.

I have several Digital Hygrometers. None overly expensive ($8-$40) and they are all off by a few percent. Even with hundreds of instruments, I consider this close enough. It is nearly impossible to maintain humidity without some fluctuation. As soon as a heater or AC kicks on, your relative humidity changes, so a small percentage isn't enough to matter.

Keep it close, keep it stable (within reason), past that don't stress too much. :)

The commonly performed "salt check" is a single point cal check. A real calibration sets the instrument zero, span, linearity (if applicable) and confirms tolerance throughout the indicating range using 5 cardinal points. This provides confidence that the instrument is providing accurate readings throughout its range. Calibration needs to be repeated at some frequency since all measuring instruments drift over time. Calibration returns the instrument to standard performance and accuracy by actually adjusting the response from sensing element to output indication/control function.

All a single point cal check tells you is how accurate the instrument reading is at one point (75% RH for the standard salt test). There is no reason to expect the same accuracy throughout the instrument's range. There is no way in most consumer electronics to adjust the instrument output if the reading differs from the standard. If you keep your relative humidity around 75% then this cal check may be helpful. If you prefer an RH of 40 - 50% you still don't know how accurate your hygrometer is in that range. It would be incorrect to assume that if your hygrometer read 78% in the salt check you should then subtract 3% from all readings throughout its range - you don't know enough about the instrument's circuitry, designed response, linearity, quality of your salt solution, etc. to make that assumption.

Here is a simpler way to do a single point cal check - I recently checked my Extech hygrometer by putting it outside. Per my phone local weather app and weather underground the RH was 64%. The Extech read 62%. Being as reported weather data usually comes from a local airport which is ~4 miles from me and reported no more frequently than hourly, I consider this reasonably accurate. This can be repeated over a range of actual outdoor RH values to get a better idea of how your hygrometer performs.

I think that the 'salt check;' is purely a starting point,so that you know that the hygrometer is 'correct' at that single point,& not wildly off. Other than that,we need to trust the manufacturer to have produced a 'stable' item,one which will measure the humidity as correctly as that in the 'salt check' starting point. Maybe the manufacturers should produce & include a set of readings taken at various humidity levels as measured with their specific product, to demonstrate their accuracy over several humidity levels,
Ivan;)

Yesterday, due to an unusual weather system that stretched from New England to North Carolina, both the dew point and the relative humidity dropped precariously throughout the day. In the morning my hygrometer read a comfortable 51%. By 11:00PM, the dew point was at 17 degrees and the hygrometer was reading 31%. I agree that we don't need to be accurate to 1 or 2%, but if we can, why not take advantage of it? Having confidence in my Caliper IV, I filled and put case humidifiers into my cases. I wasn't so much worried about damage to my mandolins overnight, but I'm playing in a jam this morning and I want my instrument to sound as good as it can. With a humidifier in my Flatiron case, RH is reading 47% this morning. I have NFI in this post and was simply passing on what I thought might be of interest to somebody, so no harm, no foul.

Quote:

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Originally Posted by Mike Arakelian

I agree that we don't need to be accurate to 1 or 2%, but if we can, why not take advantage of it?

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I would certainly take advantage of it.....if it mattered. Over the course of a year, I manage to keep the humidity between about 40% to 65% but it usually hovers somewhere between 45% & 55%. I happy with that.