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Dry and wet bulb humidity measurement formula

[2011-11-27]

Vapor pressure and relative humidity formula:
Water vapor pressure and relative humidity requirements, although the best ventilated psychrometer, but also can be used without ventilation psychrometer. Calculated by the psychrometer water vapor pressure and relative humidity of the formula:
1 Degree from the ventilated psychrometer water vapor pressure calculation:
(1) does not freeze when the wet bulb
e = E'w-0 .5 (t-t ') P/755
(2) wet bulb freezes
e = E'i -0.44 (t-t ') P/755
t: dry bulb readings (º C)
t ': wet bulb readings (º C)
E'w: t '(º C) water saturation vapor pressure
E'i: t '(º C) the saturated vapor pressure of ice
e: The vapor pressure of demand P: atmospheric pressure
 
2. Never calculated the degree of ventilation psychrometer water vapor pressure:
(1) does not freeze when the wet bulb
e = E 'w-0.0008P (t-t')
(2) wet bulb freezes
e = E 'i-0.0007P (t-t')
Here the meaning of symbols used above. Pressure units are mmHg or unified with the mb.
 
3. Requirements relative humidity:
H = e / Ew × 100
Where H is the relative humidity demand (%), Ew for the t (º C) the saturated vapor pressure (even below 0 º C does not use Ei).
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