Dew Point Table (Whirling Psychrometer)

1: Dry bulb is ambient temperature.
2: Minus (subtract) wet bulb temperature from dry bulb temperature. Dry-bulb temp (20) - Wet-bulb temp (15) =  20 °C - 15 °C = 5  °C (value will always be positive +)

Result = DP 12

Dew point

The dewpoint temperature is the temperature at which the air can no longer "hold" all of the water vapor which is mixed with it, and some of the water vapor must condense into liquid water. The dew point is always lower than (or equal to) the air temperature.

Terms:

Water Vapor  is the gas phase of water.

Condense is phase change of a gas to a liquid.

Saturated means reaching to maximum capacity.