Humidity up in Dry Cabinet when air on is on


Oct 30, 2012
69
0
6
Singapore
#1
I brought a Digi-cabi DHC-040 2 weeks back, and humidity was stable at 50% where I set. I didn't quite believe as it seems too good to be truth, so I got a digital meter from DIY shop to double check the reading.

The reading stays at 50% on both the meter until I on my air conditioning, the humidity reads between 55%-57% on the second meter I placed in the cabinet, while the cabinet meter still reading 50%. Everything will return to normal about 30minute after I off my aircon. These happened for the pass 3 night.

Anyone encounter similar situation before? Anyone can explain why is this happening? I do however believe that both meter are not faulty because I did see both meter display 70% humidity when measuring outside air.:)
 

Rashkae

Senior Member
Nov 28, 2005
19,105
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#2
The key word is "relative".
 

ed9119

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Staff member
Mar 11, 2002
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www.walkeast.com
#3
air con + a warm running peltier unit might have caused a little bit of condensation when you opened the cabinet door

these measurements need to be taken a few hours apart ....

its hard to comment further without understanding your room environment
 

Last edited:

Octarine

Moderator
Staff member
Jan 3, 2008
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Pasir Ris
#4
Both meters are not calibrated. Just because they display the results in a digital way does not mean they are accurate.
 

Oct 30, 2012
69
0
6
Singapore
#5
The key word is "relative".
air con + a warm running peltier unit might have caused a little bit of condensation when you opened the cabinet door

these measurements need to be taken a few hours apart ....

its hard to comment further without understanding your room environment
I do think it is about "relative", but don't know how to explain further.

I do not think it is condensation since the air in the room should get drier when the room is cooling down ( typical air conditioning in HDB flat ). I also take extra precaution on the second night by doing nothing and not opening the door, but just take reading through the glass door. I realize the reading remain high at around 56% until i turn off my aircon the next morning ( I check the reading first thing when I wake up ).

Theoretically, the humidity in the cabinet should remain unchanged at 50%, since there the are no air exchange. So I start to think if it is possible that one of the meter is setup to measure relative and not actual humidity, thus causing this difference.

Seriously, I am not complaining but just curious and these tickles me since I am in engineering but can't explain it. On the other hand, if our cabinet meter is set up to display relative humidity, then will this cause error to most cabinet that were place in rooms where air condition varies day and night?
 

Oct 30, 2012
69
0
6
Singapore
#6
Both meters are not calibrated. Just because they display the results in a digital way does not mean they are accurate.
I am thinking if both meter are not calibrated, then they may not be be accurate and the reading may be slightly different but shouldn't be 5-6% apart. Well, I may be wrong and one of the meter may be faulty.

By the way, shouldn't the cabinet's meter be calibrated before delivery?
 

Oct 30, 2012
69
0
6
Singapore
#7
One more interesting fact is the reading in both meter remain constantly at the same valve throughout the whole day.
 

Octarine

Moderator
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Jan 3, 2008
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#8
I am thinking if both meter are not calibrated, then they may not be be accurate and the reading may be slightly different but shouldn't be 5-6% apart. Well, I may be wrong and one of the meter may be faulty.
By the way, shouldn't the cabinet's meter be calibrated before delivery?
Not required. For the storage of consumer electronics the inaccuracy of a 5% can be tolerated. So these meters are produced with standard settings and some lose batch testing - in the same fashion as the consumer articles. Calibrated meters are checked individually, that's the reason for the higher price.
 

Octarine

Moderator
Staff member
Jan 3, 2008
12,538
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Pasir Ris
#9
The reading stays at 50% on both the meter until I on my air conditioning, the humidity reads between 55%-57% on the second meter I placed in the cabinet, while the cabinet meter still reading 50%. Everything will return to normal about 30minute after I off my aircon. These happened for the pass 3 night.
I suspect: When you turn on the air-con, it's cooling and drying the air in the room. If the door of the dry cab is closed, the inside air is "trapped" with it's content of absolute humidity. Due to the metal of the cabinet it's getting cooled but not dried. With constant absolute amount of humidity and decreasing temperature the Relative Humidity goes up. Easy to observe in daily weather in the evening and night, mainly in the (remaining small) areas with open greenery and trees: dew and mist.
 

Oct 30, 2012
69
0
6
Singapore
#10
I suspect: When you turn on the air-con, it's cooling and drying the air in the room. If the door of the dry cab is closed, the inside air is "trapped" with it's content of absolute humidity. Due to the metal of the cabinet it's getting cooled but not dried. With constant absolute amount of humidity and decreasing temperature the Relative Humidity goes up. Easy to observe in daily weather in the evening and night, mainly in the (remaining small) areas with open greenery and trees: dew and mist.
Good explanation, this is surely the more logical reason. :thumbsup:
 

daredevil123

Moderator
Staff member
Oct 25, 2005
21,661
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48
lil red dot
#11
I do think it is about "relative", but don't know how to explain further.

I do not think it is condensation since the air in the room should get drier when the room is cooling down ( typical air conditioning in HDB flat ). I also take extra precaution on the second night by doing nothing and not opening the door, but just take reading through the glass door. I realize the reading remain high at around 56% until i turn off my aircon the next morning ( I check the reading first thing when I wake up ).

Theoretically, the humidity in the cabinet should remain unchanged at 50%, since there the are no air exchange. So I start to think if it is possible that one of the meter is setup to measure relative and not actual humidity, thus causing this difference.

Seriously, I am not complaining but just curious and these tickles me since I am in engineering but can't explain it. On the other hand, if our cabinet meter is set up to display relative humidity, then will this cause error to most cabinet that were place in rooms where air condition varies day and night?
Actually, I see the reverse when I turn on the airconditioning. Whenever my AC is turned on, the RH will drop around 10-20%.
 

Zenten

Deregistered
Jun 13, 2004
9,845
8
38
#12
I suspect: When you turn on the air-con, it's cooling and drying the air in the room. If the door of the dry cab is closed, the inside air is "trapped" with it's content of absolute humidity. Due to the metal of the cabinet it's getting cooled but not dried. With constant absolute amount of humidity and decreasing temperature the Relative Humidity goes up. Easy to observe in daily weather in the evening and night, mainly in the (remaining small) areas with open greenery and trees: dew and mist.

Eureka !!
 

Zenten

Deregistered
Jun 13, 2004
9,845
8
38
#13
I suspect: When you turn on the air-con, it's cooling and drying the air in the room. If the door of the dry cab is closed, the inside air is "trapped" with it's content of absolute humidity. Due to the metal of the cabinet it's getting cooled but not dried. With constant absolute amount of humidity and decreasing temperature the Relative Humidity goes up. Easy to observe in daily weather in the evening and night, mainly in the (remaining small) areas with open greenery and trees: dew and mist.

Eureka !!
 

blackster

New Member
Apr 19, 2010
93
0
0
#14
Jus set ur dry cabin at 40%-50% then live it as it is, so even if it fluctuate it wont do too much damage.
Next is bring ur came out and worry more bout how to shoot a better picture rather then worrying bout tt extra fluctuation.
 

Jun 7, 2011
939
3
0
#15
daredevil123 said:
Actually, I see the reverse when I turn on the airconditioning. Whenever my AC is turned on, the RH will drop around 10-20%.
Same here.. My dry cabi's RH will drop when my aircon is on.
 

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