An anemometer is an instrument for measuring the force or velocity of wind.
There are various types:
A cup anemometer, like that shown in the photo here,
is used to measure the wind speed from the speed of rotation of a windmill
which consist of 3 or 4 hemispherical or conical cups, each fixed to
the ends of horizontal arms attached to a vertical axis.
A Byram anemometer is a variety of cup anemometer.
A counting anemometer has cups or a fan whose rotation
is transmitted to a counter which integrates directly the air movement
A hand anemometer is small portable anemometer held
at arm's length by an observer making a wind speed measurement.
A pressure tube anemometer (Dines anemometer) is
an instrument that derives wind speed from measurements of the dynamic
wind pressures. Wind blowing into a tube develops a pressure greater
than the static pressure, while wind blowing across a tube develops
a pressure less than the static. This pressure difference is proportional
to the square of the wind speed.