Patent ID: 8280637

Claim:
A device for measuring a fluid flow (FF) velocity and direction comprising: a pivotable means adapted to rotate at a pivotable means rotation velocity and direction depending on the fluid flow velocity and direction when in contact with the fluid flow, a modulator coupled to the pivotable means and adapted to rotate in conjunction with the pivotable means, a fiber optical arrangement for providing an incident beam (IB) to the modulator and for receiving a return beam (RB) from the modulator, the incident beam (IB) comprising an incident signal, the return beam (RB) comprising a modulated signal, the modulator modulating the incident signal so as to form the modulated signal depending on the pivotable means rotation velocity and direction, wherein, the modulator comprises an encoder comprising at least a first angular sector, a second angular sector and a third angular sector, each angular sector having a determined attenuation coefficient so that the modulated signal comprises at least a first portion, a second portion and a third portion for each complete rotation of the encoder, the device further comprises a processing means for determining the fluid flow (FF) velocity and direction based on at least the first portion, the second portion and the third portion of the modulated signal, the encoder is an amplitude encoder, the first angular sector, the second angular sector and the third angular sector having substantially the same angle (φ 1 , φ 2 , φ 3 ), ROM, each sector transmitting a determined percentage of the incident beam that is different from the other sector.