Wet bulb temperatures can be determined by checking with
your local weather station or by investing in an aspirated
psychrometer, a sling psychrometer, or an electronic
humidity meter. Wet bulb psychrometers consist of two
thermometers exposed to the same airstream. The end of
one thermometer is covered by a wetted wick. As the water
in the wick evaporates, the temperature of the thermometer
decreases to the wet bulb temperature. The other thermometer
is exposed directly to the airstream and measures
the dry bulb temperature. The difference between a sling
psychrometer and an aspirated psychrometer is the way the
airstream is provided. A sling psychrometer is mounted on
a swiveled handle and whirled rapidly, while an aspirated
psychrometer uses a small fan to provide air movement.