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Some thoughts about hygrometers

Jared Nomack

Vintage Human
Joined
Feb 12, 2021
Messages
54
Howdy All,

I've had a lifelong relationship with humidity issues, mainly due to a lifelong sickness of acquiring good acoustic musical instruments that require care. Generally, this has been much easier than the level of care apparently needed for cigars (just keep the room about 45% RH, basically), so I have had to reconsider my approach to hygrometers.

A couple of pics taken today. This first is a pair of cheap, relatively new "ThermoPro" units on a shelf. I have four of these, mostly purchased in the last two-four years. They tend to read pretty much the same. Not capable of being calibrated. They are reading 70.5 and 70.2 F, 47 and 49% RH. Next to them is a pair of older Rat Shack units, that feed a base unit. Again, they are not calibratable, read about the same unit to unit. They show 71.6 F, 51% RH. I have several more of these scattered about. This pic is in my basement mancave, humidified with a simple steam unit (Levoit).

20210222_141612 (2).jpg

Next up, a quick show inside my Audew humidor, which has four 72% 60g Boveda packs in it. There you can see two more of the ThermoPro units, reading 68.2 and 67.6 F, and 64% RH. On the bottom, two super cheap units from amazon, I think they were $12 for six of them (not a typo). I bought them mainly out of curiousity. They show 67.4 and 68 F, 69 and 67% RH. Above them is a Cigar Oasis Caliber IV, that has been calibrated (salt method), showing 67.6 F and 67% RH. Next to it, and below next to the cheapos, are two Govee units. These are the Bluetooth ones, around $14 on amazon, connect to a phone app. All the Govees here have been calibrated (salt). They are showing readings very close to the CO. More on that below. FWIW, you can also see the analog unit that came with the Audew, showing somewhere in the mid-60's. It tends to read pretty close to what the CO and Govees are showing, somewhat surprisingly.

20210222_142431 (2).jpg

Next, the inside of a Savoy desktop, which has two 69% 60g Boveda packs (in a holder attaced to the lid). There, you see three of the cheapos, showing 70.3, 69.6 and 69.6 F, and 66, 69 and 67% RH. Also in there is a Govee. The Savoy, btw, was seasoned for about three months, first with Boveda 84's and then 72's. It holds pretty consistent wherever it sets.

20210222_142514 (2).jpg

Finally, the app reading for the Govees. The Audew and Govee 3 are in the Audew, the Savoy is (you guessed it) in the Savoy. As you can see, the two in the Audew are reading 67.7 and 68.2 F, and 67.7 and 67.3% RH. So, the Govee's are very close (were calibrated separately so quite possibly my fault for any variation), and are also very close to the Cigar Oasis. FWIW, I consider these readings pretty accurate at this point.

On the Savoy, note that two of the cheapos are reading the exact same temp as the Govee, 69.6; the third cheapo is reading 70.3, pretty close. For RH, two of the cheapos show 66 and 67, probably not very accurate; the third shows 69%, pretty close to the Govee's 70.4%.

Screenshot_20210222-142500_Govee Home (2).jpg


What conclusions do I draw from this? Well, nothing earth-shattering, and probably no surprise to most of you. I have long felt that it's pretty easy to get reliable temp readings even from really cheap thermometers, but it is *much* more of a challenge to get reliable RH readings. So I'm actually pretty impressed that these various hygrometers, all of which are pretty inexpensive, come in within a few percentage points of each other. For general purposes, recognizing that there could easily be a 3-4% margin of error, even the super cheapo ones are not bad (I have several others, in acrylic canisters with what I guess people call "yard gars"). The old Rat Shack ones, I wouldn't count on for much, they adjust very slowly and seem to be capable of larger margins of error (but they are probably ten years old). The ThermoPro, pretty much the same, I think they all seem to be reading low on the RH readouts.

My best takeaway is, both the Cigar Oasis, and more especially the Govees, are remarkably accurate for relatively low cost units. The CO was the most costly of all of them, at $24. The ability to do a salt calibration is a big plus. If I were only buying one unit, I would go with the CO, because it can be read any time without a phone; otherwise, the Govees are really cool. (All this said, there are lots of others I haven't really tried (yet); so all this is FWIW, from a cigar newbie.)

jn
 

bfreebern

Yada, Yada, Yada.
Joined
Jun 22, 2004
Messages
15,341
Great info. It always amazes me, how different readings can be, in the same environment.

Even though you can't calibrate cheaper hygros, you can always write the +/- difference on the units themselves, after salt testing.
 

smellysell

Go Vols!!!
Joined
Jan 9, 2007
Messages
6,333
Great info. It always amazes me, how different readings can be, in the same environment.

Even though you can't calibrate cheaper hygros, you can always write the +/- difference on the units themselves, after salt testing.
I always wonder how effective calibrating them at 75% is for a humidity that sits at 68%?
 

CigarStone

For once, knowledge is making me poor!
Joined
Mar 7, 2007
Messages
3,960
It's not about calibrating it to a certain %, it's about calibrating the hygrometer to see how far off (75%) it is.
I think what he meant was what I was going to say. I've put five hygrometers in the same humidor and they vary by 3%. Put the same five somewhere in my house which is at 35% roughly and they vary 10%.
 

smellysell

Go Vols!!!
Joined
Jan 9, 2007
Messages
6,333
I think what he meant was what I was going to say. I've put five hygrometers in the same humidor and they vary by 3%. Put the same five somewhere in my house which is at 35% roughly and they vary 10%.
Exactly, calibrate them to 75% with a salt test, and then they're all different once in the humidor.
 

Jared Nomack

Vintage Human
Joined
Feb 12, 2021
Messages
54
...Even though you can't calibrate cheaper hygros, you can always write the +/- difference on the units themselves, after salt testing.
Right. Interestingly, I had a cheapo in the ziplock with each of the calibrations, and they stopped right at 75%


I always wonder how effective calibrating them at 75% is for a humidity that sits at 68%?
Well, you have to calibrate them somewhere, right? The 75% is just used because it's so easy to get a ziplock to stabilize there, at least that's my understanding.


It's not about calibrating it to a certain %, it's about calibrating the hygrometer to see how far off (75%) it is.
Right. I've always had a hard time really understanding relative humidity, it's not a simple thing (and my mind is). I understand it's not linear. And I understand that there is a difference between measuring the amount of water actually in the air vs that compared to what the air could hold. I don't know how these digital units are calibrated, it seems to me there could be a way to engineer them so they are accurate at all temp levels. Kind of like when GPS units went from measuring simple overland miles, to taking into account elevation changes (to give you a real measure of how much ground you covered). But I'm guessing you couldn't buy those for $14 on amazon (yet).

All of these units are, to my thinking, approximations. If they get me within 2-4 points on temp and RH, I can manage that. And I think they do.
 

Mizicke5273

Member
Joined
Dec 29, 2007
Messages
542
Not sure if it has been said yet on this thread, as I skimmed, but I remember a few guys always saying not to worry too much. As long as you are close to your desired %. I've lived by that for the past decade. I don't worry about my coolidors being +/- 5%. So that basically goes with your findings.
 
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