how to calculate the relative humidity directly from wet and dry temperatures. kindly give the formula?

Question

for measurement purpose, i need the equation which should directly realtes the dry bulb, wet bulb and % of realtive humidity

thanks in advance
kanagaraj

Answer 1

take a look here http://www.faqs.org/faqs/meteorology/temp-dewpoint/

es0 = reference saturation vapor pressure (es at a certain temp,
usually 0 deg C)
= 6.11 hPa

T0 = reference temperature (273.15 Kelvin, Kelvin = degree C +
273.15)

Td = dew point temperature (Kelvin)

T = temperature (Kelvin)

lv = latent heat of vaporization of water (2.5 * 10^6 joules
per kilogram)

Rv = gas constant for water vapor (461.5 joules* Kelvin / kilogram)

e = es0 * exp( lv/Rv * (1/T0 - 1/Td))
es = es0 * exp( lv/Rv * (1/T0 - 1/T))

RH= e/es * (100%) = relative humidity !!!!

Answer 2

i am afraid you have to know absolute humidity..

or if the pressure is 1 atm, you can use psychrometric chart ;)