Calibrating a Digital Hygrometer

This video is going to demonstrate how to properly calibrate a brand new digital hygrometer using the salt test.
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[@eri-dug8143]

For those that asked why this works, and how to get more accuracy: In pure water the molecules, energized by their temperature, jump into the air until the rate at which they jump into the air (fighting against their Van der Waals attraction to the other water molecules in the liquid phase) and fall back into the liquid are equal, which depends on the density of water molecules in the air. (The more water molecules in the air the more likely they will hit the water and stick. That rate has to equal the rate of leaping off.) That fixes the relative humidity, for pure water that is 100% RH. The water molecules in the salt paste are bound by much stronger Van der Waals forces to the salt molecules. It is harder for them to leap into the air. Lower density of water molecules in the liquid phase balances the rate at which they leap into the air (due to thermal energy fluctuations). if there is a higher density of water molecules in the air then they will land more than they leap until the two rates are equal, and similarly if there is less than the equilibrium value. If you wait long enough, and it may take a while since the surface area of the paste is very small compared to the size of the container, the RH will reach the equilibrium value determined by the degree of binding of the water molecules to that particular salt at that temperature (and perhaps pressure.) For each type of salt the molecular binding / Van der Walls force is different and that causes a different relative humidity (at the same temperature). There may be other forces involved than Van der Waals. Some water molecules are probably bound by strong dative / covalent bonds to some salts (even some dry salts have water molecules in their crystals), but in a paste others may be glued by Van der Waals. My guess would be only the weaker bound water molecules contribute to the RH. For example MgCl salt gives about 33.3% RH and Na,2Cr20 gives about 55% RH at room temperature. NaCl is just over 75.5%. (pure water = 100% RH, desiccators could give 0% RH). It would make sense if you can only calibrate one value to pick one near the desired RH. nvlpubs.nist.gov/nistpubs/jres/53/jresv53n1p19_a1b.pdf What I do is use several references and put marks on less expensive analog meters to show the correct values. For digital meters that don't calibrate, or if you want accurate values over a larger range, you can make a table of the true readings vs. the nominal readings. If you want high accuracy, the reading can change quickly when you open the bag. For analog meters you can remember where to put the mark. For digital meters you can hit the buttons through a flexible bag. I have read in some places that you should not calibrate some digital meters. However I don't think digital meters with calibration work differently than ones that don't have built in calibration, and I can't imagine how it could harm a digital meter to stick it in a bag with known RH.

[@bastienroy9220]

will it work with salt water instead of table salt

[@eri-dug8143]

No. For the NaCl or other salt to work the water has to be tightly bound to the salt. That means there can be no clear liquid floating on top. You want a wet white paste, wet salt, not salt water. Also for the most accuracy you want pure NaCl (or whatever salt you are using). This means not sea salt, and better without Iodine added (although I don't know if that will make a serious difference). Distilled water in theory is better; I don't know how much difference hard water will make, probably not much. A plastic baggy and some pure table salt are so cheap this is essentially a free way to do the calibration.

[@eri-dug8143]

No. You don't even want liquid water floating above the wet salt. You want a white salt paste, damp salt rather than liquid water. This is because the water molecules have to be tightly bound to the salt.

[@MagPencho]

A very good explanation but you are missing a point: Temperature and pressure matter a great deal when you are calibrating. Air retains different amount of water vapour at different temps and pressures. The best temperature to calibrate a hygrometer using the saturated salt solution method is around **25°C (77°F)**. This temperature is often recommended because it is a standard reference point for many hygrometers, and the expected relative humidity for a saturated sodium chloride solution at this temperature is well-documented and relatively stable. You cant control pressure but you can control temperature. Anyway if you want to be super accurate you should monitor daily pressure and calibrate your hygrometer when it is 1013.25hpa outside and you can get the temp to 25C. That would be ideal, but who has time for that 😅

[@juankam075]

I realized I had misread the instructions, and saw that it was to remove and replace the battery before the recal, and not to leave the battery out. Thanks for the reply!

[@worcesterexchange554]

What sort of accuracy for humidity is required for cigars?

[@PipingHammer]

i did all this and my hydrometer, before hitting the calibrate button, it read 64%, is that OK?

[@T1k3mys0n]

1:37 so salt in the container will make the humidity in it exactly 75%, and we compare it with the actual reading on the hygrometer, and since it shows 71%, does that mean we have to offset it with +4% ?

[@theultimatetime8029]

But humidity is also affected by temps so how can be this create a good logic

[@1v4n27]

@@theultimatetime8029 Temp. 19-21°C

[@abudankmeme1477]

same i cant adjust

[@zaca911]

@@theultimatetime8029 while different temps hold a different volume of water. It doesn't matter at which temp you calibrate at as when you're calibrating it does so while the temp is static. by your logic a calibrated humidity meter would have to be set at the current temp to read properly. That would suck lol

[@wayneclark6624]

Is this traceable to NIST???

[@worcesterexchange554]

For information the salt solution should have some liquid solution on top of the salt. This will be a saturated salt solution and will adsorb moisture if the atmospheric relative humidity is above 75%.

[@marineman2298]

Which goes against every other instruction I have ever read or seen on how to do this. Not saying you are incorrect. Only that you are the Lone Ranger on this.

[@mtkkuluckaTuncay]

Merhaba Mükemmel Uygulama Aynı Formülü Kullanmaktayım..

[@henley777]

how much space can one bottle cap with salt "cover"? What should be the volume of the zip bag or container?

[@JustinS06]

For those that see this in the future, it doesn't matter. The amount of salt doesn't need to be accurate nor does the size of the container. Just do something similar to whats shown in the video, no need for precise measurements as it should always result in 75%

[@IvanRossS]

Surprisingly nobody talking about temperature it's super important to have a temperature... make sure when you do humidity test your environment supposed to be 70%

[@mettlemane]

I have two xikar non adjustable hygrometers. I did a standard salt test on them,and they were off. I called xikar,and they said the standard standard salt test was wrong.

[@matyoka]

metalshaper Salt test is necessary at least once a year for the Digital... Xikar employs idiots or you didn't call them. This calibration method is straight from Xikar... xikar.com/files/salt_test_instructions.pdf

[@user-lc7qs7gy5d]

do not fall , it will kill the LCD and Zebra connector

[@liudmilaantropova3773]

I don’t understand why mine isn’t working. The humidity keeps dropping every time I put it in the ziplock bag. Like wtf? I take it out and it says 65… I put it in the bag with the salt and it drops to 54…

[@tilberry19]

can i use this test with analog hygro???

[@SilencedByYoutube]

Yes

[@tucosalamanca7037]

This works with pretzel salt

[@Scarface7629]

If I have a Hygrometer that has 3 buttons 1) C/F (Celsius &Fahrenheit) 2) Min/Max 3) Reset what would I press after 24 hours in the container with the salt paste?

[@Christian.B.Martin]

Is there one that says retard ?

[@spikesecho724]

@@Christian.B.Martin You're a douchbag

[@XoxJasonReynoldsxoX]

@@Christian.B.Martin Come back when you are grown up speed racer; or should I say Burnie Rubber? Don't you have a piece of toast in the shape of Dale Earnhardt's face to be praying to?

[@juankam075]

My xikar hygrometer states to remove the battery when calibrating using the salt calibration system, would leaving the battery in be okay?

[@XoxJasonReynoldsxoX]

Not sure how it's supposed to function in any way, shape, or form without power.......

[@sutil5078]

legend has it that Juan Carlos is doing the experment for 10 years to calibrate humidity reading.. .. 10 years comment. The chinese product has an average life of 2 months. A friend told me that Juan got his degree in meteorology and work in weather station.

[@juankam075]

@@sutil5078 ok, so I’m not the only one that thinks it’s funny I got a reply to a question I asked ten years ago. Good to know, thanks! LOL

[@Dr._Spamy]

middle button, 75%, doesn't seem to do anything... Are there really Digital Hygrometer that ment to be callibratet at all !?

[@AKbarEltoago]

there is no button to calibrate in my digital hygrometer.. Iam also have do the "salt test" before , and the results was 99% RH... so what can i do man?

[@bastienroy9220]

will it work with sea salt?

[@SilencedByYoutube]

Yes

[@Nostromo_1]

Use distilled water

[@kerry_yeieh16]

don't the digital hygrometers come calibrated already

[@XoxJasonReynoldsxoX]

Are you new? Have you ever owned a Chinese product before? Half the time they can't even sell a functioning product brand new out of the box.

[@Walking_on_Chips]

Here are my finding on the subject of humidity. Humidity is directly affected by temperature. Ever notice when its cold out you have a higher humidity reading versus when its warm/hot the humidity is lower? When it is hot there is less moisture in the air. When its cold more moisture. I have played the game of chasing dialing in hygrometers. IMHO its a waste of time. Buy Boveda packs with the humidity % you want, and call it done. Even Boveda states on the back of their 10 pack of 60g, 65% packs the range is 60-69%.

[@13panda13]

So why would I waste money on bodeva then, if they are also inaccurate.

[@populousmass]

Hi-grom-iter :)

[@tabbithasmith3716]

yuurr-knot-speshall

[@13panda13]

​@@tabbithasmith3716KZbin-support-sux- balls

[@DeepSouthernTX]

Why can't you have free standing water on top? I believe as long as there's undissolved salt at the bottom humidity equilibrium will be reached

[@marineman2298]

Because it says so on the internet and the internet is never wrong. For pete's sake man, don't you know anything?

[@rogermorse_]

I'm ignorant. Why does this method give exactly 75% of humidity, not less, not more ?

[@rogermorse_]

this doesn't answer my question....i asked *why* it gives 75%. Also how influent is the quantity of salt (or of water) so let's say salt/water ratio how much does it influence the actual humidity value?

[@eri-dug8143]

The water binds to the salt electrostatically more than to other water molecules, so it sticks more to the paste then to pure water, which means less water leaps into the air to humidify it then if the cap had pure water (100% RH). I wrote a more detailed explanation in a comment above "For those that asked why this works"

[@richardcabello5028]

Lol, other videos say 8-12 hours!

[@AKbarEltoago]

okay , thanks anyway missle :)

[@missle25]

send it back! if you we're talking about maybe a 3%-4% difference then I wouldnt care, but that much difference? Somethings bad with your Hygro! Happens every day!

[@PlanktoniusRex]

Hi Grow Meter....LMAO

[@MagPencho]

Here you are wrong… Calibrating a hygrometer with salt, specifically using a saturated salt solution, is a common method, but it has its limitations. Here are some reasons why it might not be accurate: 1. **Environmental Variations**: Temperature and air pressure can influence the humidity level, which can affect the calibration process. 2. Volume of container matters, the smaller the better as there might not be enough time to saturate the air inside if volume of it is too big. In order for this to work somewhat accurate you need to have the temperature at around 25 Celsius. There is a reason why airports give humidity readings with temperature/dew point not relative humidity. The reason is because as air gets hotter it can contain more water vapour before it becomes saturated (100%). If it is colder the air gets denser and cannot hold as much vapour as there is no room for water molecules. So in order for you to have an accurate reading you need your temp to be 76F or 25C. You cant control pressure but using only temp will get you close enough. Watch a video on relative humidity vs dew point and you will get the picture.

[@jpnoll1781]

my instruction manual tells me to take my brain out before calibration :O

[@marineman2298]

Well, that will obviously be impossible for you.

[@wadepatton2433]

HY GROM EAT ERR

[@kchiem]

po-tay-to, po-tah-to. Look it up.

[@mushmush161]

>digital

[@eduyncastro6165]

Good Fellas Cigars, you didn't pronounce the word "hygrometer" correctly. You also forgot to press the "Calibrate" button on your hygrometer. It read 71%! Pronounce it like this: "hy-groh-meter". Not like this: "hy-gro-mee-ter"! :)

[@dontgettoknowm9864]

You obviously have horrible need to be right. Both pronunciations are correct. Have you ever talked to an English person? They say things differently. English is very flexible. Don’t be a jerk.

[@ricklaf2000]

It's pronounced hy-GR(AH)-m(uh)ter, not hy-gro-ME-ter. Look it up.

[@micheloliveira6718]

Learn to spell your own language, mr. cigar man

[@philwilliams8328]

It's not pronounced hyDROmeter! *hy GRO meter*