Anemometer

Anemometer, an instrument for measuring the velocity or pressure of the wind. Robinson's anemometer, which is the form usually employed at meteorological stations, consists of two horizontal arms crossing each other at right angles, to the ends of which are fixed hemispherical metal shells, so arranged that when the whole is supported on a pivot at the centre, the action of the wind will produce rotation, which is directly proportional to the wind velocity. Osler's anemometer registers wind pressure thus: A pencil, moved by clockwork across a sheet of paper, is made to diverge correspondingly with the pressure of the wind on a metal plate, acting through metal springs on the pencil.