Dewpoint Temperatures?

Question

When finding dewpoint, why do you use warm water instead of very cold water?

Please explain.

Thank you!

Answer 1

You do not want to use very cold water because in order to calculate the dewpoint temperature one wets the wick of the wet bulb thermometer and slings it. The evaporation of the water on the wick cools the thermometer to what is known as the wet bulb temperature. You don't want to start with water that may be colder than the wet bulb temperature, or you will get an erroneous reading.