A Laser Doppler Anemometer system designed to measure two components of the velocity vector in fluids is presented. The scheme followed is the differential technique with backward scattering configuration. The scheme uses three laser beams crossing at the point of measure. Two of the beams pass through frequency shifters in order to displace the zero reference of each velocity component. The bursts reflected by the particles in the fluid are detected and mixed on the surface of an APD, which is used as an optical detector. The system can work in real time with a rate of 30 measurements per second. It has been designed to detect velocities up to 3 m/s which is a current limit in hydrodynamic experiments. The error committed is about 1% and both signs of the velocity are distinguished.

Peer Reviewed