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Thu, 22 Jul 1999 08:10:31 PDT |
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Craig,
Here's my understanding:
On a local level, an increase in temperature results in a decrease in relative
humidity. On the global level, the moisture content is constant. Some
assumptions include the ability of the oven to maintain the conditions, a
fixed pressure, and moisture penetration within the board. Calculations
require use of vapor pressure tables (one source, CRC Handbook).
Based on your conditions, I calculate a local relative humidity of 5.1%
Hope this helps,
Glenn
Ref:
1) http://www.usatoday.com/weather/whumcalc.htm
2) CRC Handbook of Chemistry and Physics
3) Accelerated Testing Handbook, Peck and Trapp
Craig Hillman <[log in to unmask]> Wrote:
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| An environmental question:
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| I have a board operating in a 30C, 70%RH environment. The board
| is operating at 85C. How do I determine the humidity level at the
| board?
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| 1. Is the moisture concentration and the RH lower than ambient
| because of evaporation?
| 2. Is the moisture concentration the same and the RH lower because
| of a higher temperature (and thus higher solubility limit)?
| 3. Is the moisture concentration and the RH higher than ambient
| because the higher temperature results in a higher solubility limit?
|
| Thanks in advance,
| Craig
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