Rotor rotational velocity measurement arrangement comprises a microphone and evaluation electronics in which a Fourier transform is applied to the rotor sound signal to determine its angular velocity

摘要

Measurement arrangement for measuring the rotational velocity of a two or more bladed rotor (2) comprises a sound recorder or microphone (6) the output signal of which is fed to an evaluation unit (8) in which a Fourier transform program is stored for processing the microphone output signal. The transformed signal corresponds to the rotational velocity and is output from the measurement arrangement. The invention is based on the fact that the blades of a rotor, e.g. a helicopter rotor or propeller blade give off a sound signal that contains the angular frequency of the blades as the base frequency within its frequency spectrum.