Bob,

You are correct.  I was partially asleep.  Where is Dewey when you need him
to say that 'everything is relative'?

Going to be pretty tough to measure absolute humidity in a quick and easy
manner.  

     One item I found suggested avoiding the term "absolute humidity". 

Steve C

-----Original Message-----
From: Robert Kondner [mailto:[log in to unmask]] 
Sent: Friday, March 08, 2013 12:37 PM
To: 'TechNet E-Mail Forum'; 'Steven Creswick'
Subject: RE: [TN] Humidity Measurements: Relative or Absolute

Steve,

  Relative Humidity:  http://en.wikipedia.org/wiki/Relative_humidity
http://www.youtube.com/watch?v=CL5cgXwKUXc

  If the absolute humidity is high (even 30%) but the temperature is also
high, I think the humidity indicators will show low humidity exposure.

 I think  that relative humidity is crucial to component water absorption or
drying. 

 But I wonder if package cracking doing to expansion of gases entrapped in
the package material (plastic) is a function of the absolute vapor content
in that material. 

Bob K.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Friday, March 08, 2013 11:35 AM
To: [log in to unmask]
Subject: Re: [TN] Humidity Measurements: Relative or Absolute

Bob,

I have always considered them to be absolute.  If relative - relative to
what?

Do the cardboard indicators provide a temp range for which they are valid?

Steve C

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Friday, March 08, 2013 11:24 AM
To: [log in to unmask]
Subject: [TN] Humidity Measurements: Relative or Absolute

Hi,

 

As I start looking at humidity measurement devices I started to wonder if
IPC humidity numbers are Relative or Absolute? Does anyone know off hand. I
need to go buy some specs.

 

I would have thought Absolute but the cardboard indicators are temperature
sensitive as are the desiccant drying systems in dry cabinets. 

 

If the temperature is high, say > 100C then a part will "Bake Out"
regardless of the absolut humidity, is that right?

 

Bob K.  



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