Dry Cabinet, Hygrometers and Humidity Control Packs - some findings

[dynoto]

Hi guys, just wanna share my mini-research on the dry cabinet.

The story is, recently i just got myself icabi hd-20 which comes with an analog hygrometer.

I'm not sure how accurate the hygrometer is (pretty sure it isn't), so i decided to get a separate precision hygrometer just to make sure the RH Levels are accurate. I couldn't really find hygrometer that is tailored to dry cabinets, most of them are just general purpose with 5% accuracy, pretty wide variance.

Fortunately, there are another type of industry with same type of people who took great attention to humidity, particularly cigar collectors ... and there are lots of products that is catered for maintaining humidity levels for cigar storage :bsmilie:

after some googling around, i got myself this precision hygrometer from amazon called "Caliber IV"

i know some may think why i'm going this length instead of just buying a more expensive dry cabinets to begin with.
my hypothesis is that even the most expensive dry cabinets with their own built in hygro (digital / analog) may not be 100% accurate, and the best way to make sure is to cross-match the readings from various hygros

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also, during my research i found this company called Boveda that sells 2-way dry pack (absorb/release moisture depending on the humidity rating).
they selling humidity packs (that is down to 1% accuracy :bigeyes with various humidity levels from low 20% to high 70% ... so i'm thinking it can also be used as an alternative to dry cabinets (serious, i'm not joking)

(i got the 75% rh pack to test my hygrometer accuracy just to double check)

 

[shierwin]

The Salt Test ... simple, cheap, good and accurate...

https://www.stevejenkins.com/blog/2...grometer-humidity-sensor-using-the-salt-test/

 

[Octarine]

And the magic word of "sufficient accuracy". There is little use to maximum measurement accuracy if the dry cabinet is not airtight and the difference between 40% and 45% RH does not matter for fungus growth.

 

[shierwin]

For the expenses in getting the dry box,dry packs plus Caliber IV and etc odds and ends, and time spent, the sum total could have gotten you a good powered dry cab.... unless you have to be very very precise in the RH of the cab.

 

[anuar ahmad]

and all those findings/hypothesis on precise RH is to critically store your equipment away never to be used again or something else?
most other days, my equipment are with me at work or at play and would be in the cabinet at most 2-3 days when I alternate its usage... so precision not critical for me.
I just ensure it is within the recommended RH range by having another hygrometers at the top and bottom shelves and glad all of my equipment is still fungus free.

 

[dynoto]

The Salt Test ... simple, cheap, good and accurate...

:think: from what i read is, salt causes corrosion ... especially when used for çalibrating digital sensors it could damage the transistors

And the magic word of "sufficient accuracy". There is little use to maximum measurement accuracy if the dry cabinet is not airtight and the difference between 40% and 45% RH does not matter for fungus growth.

but if dry cabinet meter stays reads at 35%, using typical cheap hygrometer with 5% variance it could mean 30%~40% ph level though
thats why i think lower accuracy reading gives a better peace of mind :sweat:

For the expenses in getting the dry box,dry packs plus Caliber IV and etc odds and ends, and time spent, the sum total could have gotten you a good powered dry cab.... unless you have to be very very precise in the RH of the cab.

hmm, but good drycabs how precise are they in terms of measurement? i see those that has built in monitor

 

[kandinsky]

:think: from what i read is, salt causes corrosion ... especially when used for çalibrating digital sensors it could damage the transistors

An engineering company that makes such sensors quotes it as a usable method, I'd think there's no risk/little of corrosion unless you did it wrongly or if there's accidental contact. Unless you spray the salt mixture into the air, it's not going to get on the hygrometer...

Since its inception in 1962, OMEGA has grown from manufacturing a single product line of thermocouples to an established global leader in the technical marketplace, offering more than 100,000 state-of-the-art products for measurement and control of temperature, humidity, pressure, strain, force, flow, level, pH and conductivity. OMEGA also provides customers with a complete line of data acquisition, electric heating and custom engineered products.

https://www.omega.com/temperature/Z/pdf/z103.pdf

 

[Octarine]

:think: from what i read is, salt causes corrosion ... especially when used for çalibrating digital sensors it could damage the transistors

Please read again. Nobody says you should immerse the hygrometer into the wet salt. The salt with its hygroscopic character will create a defined, known humidity level. This will be your reference to determine the deviation by your hygrometer. The test will take a few hours maximum with the small volume of air inside the bag or plastic box you should use.

but if dry cabinet meter stays reads at 35%, using typical cheap hygrometer with 5% variance it could mean 30%~40% ph level though
thats why i think lower accuracy reading gives a better peace of mind :sweat:

ph level is a different thing, we talk about RH [emoji6] Then again: is the difference between 30% and 40% relevant if the recommendation is 'below 45%'? That's what I meant with' sufficient accuracy'. To quote another senior member here: "Your camera is not made of tofu." So worry less, shoot more.

hmm, but good drycabs how precise are they in terms of measurement? i see those that has built in monitor

Compare the cabinets. Some have an open system, some have a closed loop system to regulate the RH level. One thing is the same: the hygrometer. It's irrelevant whether the display is analog or digital, they are household devices and will not deliver accuracy of a lab, simply because that's not required.
If you are so worried, adjust the RH closer to 30% and done. (The myth of low RH damaging the equipment has been busted already.)

 

[dynoto]

An engineering company that makes such sensors quotes it as a usable method, I'd think there's no risk/little of corrosion unless you did it wrongly or if there's accidental contact. Unless you spray the salt mixture into the air, it's not going to get on the hygrometer...

thanks for the insight! this is really helpful

Please read again. Nobody says you should immerse the hygrometer into the wet salt. The salt with its hygroscopic character will create a defined, known humidity level. This will be your reference to determine the deviation by your hygrometer. The test will take a few hours maximum with the small volume of air inside the bag or plastic box you should use.


ph level is a different thing, we talk about RH [emoji6] Then again: is the difference between 30% and 40% relevant if the recommendation is 'below 45%'? That's what I meant with' sufficient accuracy'. To quote another senior member here: "Your camera is not made of tofu." So worry less, shoot more.


Compare the cabinets. Some have an open system, some have a closed loop system to regulate the RH level. One thing is the same: the hygrometer. It's irrelevant whether the display is analog or digital, they are household devices and will not deliver accuracy of a lab, simply because that's not required.
If you are so worried, adjust the RH closer to 30% and done. (The myth of low RH damaging the equipment has been busted already.)

haha oops, yeah i mean Rh not Ph lol keep mixing those two together.

issit? :bigeyes: damn, sorry i'm outdated. i thought when Zeiss state in their website never lower than 30% i quite panick :sweat: