TABLE 3 
Vapor pressure from psychrometer readings 
This formula applies if the ventilation speed is 3 meters per 
second or more, 
bulb 
t 2 air temperature 
t' : temperature of the wet bulb 
e $: vapor pressure 
saturation vavor pressure for the tem- 
perature of the wet bulb 
@ 
e=e! = F(t-t') 
The factor F varies slightly with the temperature of the wet 
and with the barometric oressure. The following table gives F 
in millibars per degree Fahrenheits 
tl; oF 32 40 50 60 70 £0 90 | 
980 mb | 0.360 06361" .0.364 0.366 0.368 + =0.37L~—06373, 
990 mb Pass jee" O.sen “YO.a70) C4372 |) 0.378") Voge 
1000 mb 04367 ag3e8 "9 MS7e fo.37h  0ua76 «0,378 ose 
1010 mb | 0.371 04373 043750377 043800382 0.3 84 
1020 mb ee 4376... Oe 79. 0g SBR... 04983). 00886. Ouse ae 
| 
1030 mb | 05378 Ond80  G.382 0,385 0.387 94390 ay aeet 
1040 mb | 0.382 0,384 0,385 04389 0439104393 04396 
Wa 6.360, ..0.362,.,.0,305.° 04367 05369 0,372 Oba 
30 an. yA) On375 |. Oe397 4380 0.382 0384 pe 
ese) in, | 0.385 0,389 0.390 04392 04395 0.397 0.400, 
i ; 
' 
tn ce ce nn rt a ta ne ee ene re ee ea ne ee er NL RRS RS ER EE) LR rr RD MN Fr ae en ot ED 
These values were computed from the formula on page lxx of the 
Smithsonian Meteorological Tables, Fifth revised edition, giving, for 
temperature Fahrenheit 
F = 0,000367 B (1 + 9,00064(t" = 32°)), 
where B is the barometric pressure. 
