Calculating Dew-point from RH & Temp

If I remembers it correctly ??

Due point is the temperature at which the moisture present in the air at room temperature is sufficient to saturate it.
As quantity of unsaturated moisture in the air is not changing till the due point, by decreasing temperature, vapour pressure remains constant. Hence

RH = unsaturated vapour pressure at room temp./ saturated V.P.at room temp.
= saturated v.P. at due point/saturated V.P. at room temp.

The experimental values of Saturated vapour pressure at different temperatures are given in the tables.

 

I got a table in an old booK for saturated vapour pressure, see if this can help you..

Temp. in deg C -- SVP in mm of Hg
-10--2.1
-5--3.1
0--4.6
5--6.5
10--9.2
20--17.5
30--31.7
40--55.1
50--92.3
60--149.2
70--233.5
80--355.1
90--525.8
100--760
110--1074.5
120--1489
150--3569
200--11647

Inbetween the two given temperatures it is calculated by finding the rate of increase in that range x increase in temp.
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