ANEMOMETER (from Gr.
Anemometers may be divided into two classes, (1) those that measure the velocity, (2) those that measure the pressure of the wind, but inasmuch as there is a close connexion between the pressure and the velocity, a suitable anemometer of either class will give information about both these quantities.
The Robinson anemometer, invented (1846) by Dr Thomas Romney Robinson, of Armagh Observatory, is the best-known and most generally used instrument, and belongs to the first of these.
Unfortunately, when Dr Robinson first designed his anemometer, he stated that no matter what the size:of the cups or the length of the arms, the cups always moved with one-third of the velocity of the wind.
The other forms of velocity anemometer may be described as belonging to the windmill type.
Probably a sphere would prove most useful for a pressure anemometer, since owing to its symmetrical shape it would not require a weathercock.
Lind's anemometer, which consists simply of a U tube containing liquid with one end bent into a horizontal direction to face the wind, is perhaps the original form from which the tube class of instrument has sprung.
The great advantage of the tube anemometer lies in the fact that the exposed part can be mounted on a high pole, and requires no oiling or attention for years; and the registering part can be placed in any convenient position, no matter how far from the external part.
Approximately II% should be added to the velocity recorded by a tube anemometer for each 1000 ft.
Robinson published a number of papers in scientific journals, and the Armagh catalogue of stars (Places of 5345 Stars observed from 1828 to 1854 at the Armagh Observatory, Dublin, 1859), but he is best known as the inventor (1846) of the cup-anemometer for registering the velocity of the wind.
As to anemometer pressures, it should be observed that the recorded pressure is made up of a positive front and negative (vacuum) back pressure, but in structures the latter must be absent or only partially developed.
Is as great as on small surfaces, such as anemometer plates.
The intensity of pressure was less than on a similiarly exposed anemometer plate.