A linear, unidirectional anemometer of rapid response

Abstract

A heated wire dissipating constant power causes temperature changes in the air moving past it which vary approximately inversely as the wind speed. These temperature changes are detected by a thermometric bridge and, by means of a circuit with feedback control, an electrical signal is constructed which is linearly related to the velocity. The resulting anemometer is sensitive only to the normal velocity component and, by combining two such anemometers, changes in sign of this component can be accommodated. Four fine wires (0.0005 in. tungsten or nickel) are used but they can be replaced if damaged without affecting the calibration. The time constant of the instrument is about 0.3 s at a wind speed of 0.5 ms-1 and decreases somewhat at higher speeds.