Why is the dew-point method of calculating relative humidity not particularly accurate?

Question

Why is the dew-point method of calculating relative humidity not particularly accurate?

Answer 1

i think the main problem is the computation of relative humidity it self (RH). Usually and it is more often that RH is measured directly using Hygrometer. Hygrometer as an isntrument surely has some errors in it's measurement. Once it is not accurate predicts the RH then we wont get a good measurement of dew point.

especially if you use Capacitive RH Hygrometer, that is the most commonly used to measure atmospheric humidity. These type of sensors have a typical accuracy of about 2% to 5% at RH between 10% and 90%. For very low or very high humidity, accuracy can be lower.. and it will impact the dew point accuracy too.