Hi

For mesuring humidty, I have two digitals thermometers. One is mesuring
the ambient air temperature and the second mesures the temperature of a
wet cotton (which is in contact with the ambient air).

In addition, I have a digital pressure sensor.

But my problem is that I don't know the formula to calculate the
relative humidity from dry temperature, wet temperature and pressure.

Someone know this formula ?

Thank you very much

Alain