HOW TO: Salt Test (hygrometer calibration)

[mmpjim]

that'll fix it

[sboyajian]

beware the cheap digital ones at Walmart are either extremely accurate or even more extremely off..

mine took almost a week in the salt test and still hadn't passed 70.

IIRC they are about $7.. spend the extra and get the adjustable ones from CI (or CBid.. if you dare).

[wisdomwalker]

I just got back from Wally world! I set out to purchase the $6.95 Hygrometer. As my luck would have it they were sold out. They Did however have an Acu-rite for about $8.00. This unit was small in size, but seemed a little thick to fit on the lid of my humi. So I went with a larger one. Acu-Rite Model 00891 Digital thermometer price was $12.95 not including the AAA battery.

When I got home I couldn't wait to salt test the unit. So I grabbed a Zip-Lock bag. Placed the unit inside along with a bottle cap filled half way with table salt. I put a few drops of tap water on the salt and sealed the bag. I put a puff of air inside to make a pillow.

With in a minute the Humidity jumped from 50% to 76%. This seemed really fast. Concidering that most of what I read about the salt test stated to let it sit for about 12-24 hours. Seems odd that it would be this fast.

Since I started typing this post it now sits at 65%. I guess I will let it sit for a day and let it stabilize.

Just a quick side note. I also found that they have 1 gallon jugs of Distilled water for .87 cents. I couldn't pass that up. Especialy since I was making my own prior to the Wally World trip.

Happy 4th

[wisdomwalker]

well, now I'm stumped, it's been 32 hours since the salt test started. The Humidity reading sits at a solid 66% I guess it could be off that much.

However I decided to retest. This time with a larger container to hold the salt mixture. My thinking is that maybe more surface area is needed. So I'm using a lid from my girlfriends makeup. It's about 2 inches in diameter. Also I measured the salt at 1TBS and water at 1TSP. (this is per another thread on this forum)
It's only been an hour since the test started and Humidity reading is at 75% I'm going to let it sit over night and check it in the morning.

[Egis]

I did my salt test twice both times for 24 hours, and kept it in dark. First time was 69/70, second time 70/70. So I'm happy the way it is!!!!

[wisdomwalker]

Here are the results so far.
24 HR first try
RH= 66%

Second try started at 7:00PM on July 5
1hr in RH=75%
3hr in RH=73%
10hr RH=72%

[golfermd]

I ran mine on Saturday. Nailed at 75% after 12 hours.

[wisdomwalker]

Originally Posted by wisdomwalker

Here are the results so far.
24 HR first try
RH= 66%

Second try started at 7:00PM on July 5
1hr in RH=75%
3hr in RH=73%
10hr RH=72%

23hr RH=72%

I think it's safe to say that 72% is the magic number for me. So I just add 3% to the reading. much better than the 66 from the first try. I'm happy with that. If you think there is an error with my test. PLEASE let me know!
Thank you everyone for all the information that you provided in these forums.

[madurolover]

Scott, let it go for another 10 - 12 hours. It may not move any but it also may move a few points in either direction.

[wisdomwalker]

OK, So I contacted Chaney Instruments. (The manufacture of the ACU-RITE Brand)
Here is what I wrote...
I recently purchased the ACU-RITE 00891 Digital Thermometer.
My goal was to use this instrument to measure the temperature and
Humidity inside of a cigar Humidor. optimal RH is 65%-68% for keeping
cigars. Many cigar smokers use instruments such as this one for this
purpose. I'm told that the Hygrometer in instruments such as this one
can be off by as much as 10% in either direction. So most Cigar smokers
use a salt based test to calibrate the hygrometer. I'm told that using
1Tbs of salt and 1Tsp of water inside an air tight container over a
period of 24-48 hours will create a RH of 75%. Thus allowing one to
determine how far off the Hygrometer is. I preformed this test on the
ACU-RITE model that I purchased and found that the RH inside the
container was 65% I am now retesting the instrument. to verify my
findings. Is there a +or- veritable that is except
able for your hygrometers. Is this test an accurate
way of testing the accuracy of a hygrometer? What
steps does your company use to test and calibrate your
hygrometers? How accurate are they known to
be? I understand that this is not ment to be a scientific grade
instrument, but +or- 10% seems like a lot. I would surely appreciate any
information you can give me on this subject and hopefully answer all of
my questions. Thank you for your
time. Scott

Here is the Responce...
The Industrial Standard is that it should be within +/- 5%. So if the
actually humidity was 60%, the unit could read anywhere between 55% and
65%. Our units are usually within about +/- 3% from my personal
experience of working here for a year.

Please let us know should you have any further questions or concerns.

Thank You,
Chaney Technical Support


Interesting that they feel that +/- 5% is acceptable.

[RJT]

If you bought these from Wally World just keep your receipt and return it if it is not accurate. I went through about 5 of these one time until I got one that was accurate. If you got the time and patience it is ok. I found it was easier to just buy three at a time and take back the ones that didn’t work.

However you can spend a little more and get one that is adjustable from a dedicated cigar accessory dealer.

[Plop007]

A quick question regarding the hygrometer calibration.

I start calibrating my hygrometer yesterday at 3:48pm

Now its 11:58AM. Should I keep calibrating it or can I take it out now?

Also I had the degrees in celsius but it was at 25 I looked on online and someone did the math and it said 25 celsius is 77 F So I think Im doing good.

[madurolover]

Originally Posted by Plop007

A quick question regarding the hygrometer calibration.

I start calibrating my hygrometer yesterday at 3:48pm

Now its 11:58AM. Should I keep calibrating it or can I take it out now?

Also I had the degrees in celsius but it was at 25 I looked on online and someone did the math and it said 25 celsius is 77 F So I think Im doing good.

Let it go for at least 24 hours. 36 is even better.

[Plop007]

Alright Ill keep it going.

[pontiacbird]

Another way to judge consistency of the readings and your calibration is to have two of the same model.

After calibration, both should read the same RH when placed in the same quarters, and if it is off by more than a few %, it may warrant re-calibration.

I do this from time to time, and mine are usually spot on or +/- 1%.

It would be difficult to tell which one is acting up if you did have an issue, but it would tell you that you need to re-calibrate.