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激光多普勒風速儀

型號 CA-1350
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型號
CA-1350
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Educational Objectives

l   Doppler Shift

l   Beam Interference

l   Scattering of Light

l   Velocimetry

l   Particle Size

l   Fourier Transformation

l   Modulation Depth

l   Beam Intersection Angle

The working principle of a Laser Doppler Anemometer (LDA) is demonstrated.Two coherent laser beams cross at the measuring spot at which a rotatingacrylic disc with small distortions is placed. Distortions passing the beams’cross point generate scattered light. The frequency of this scattered light isup- and downward Doppler shifted causing a low frequency signal beating. Thisbeating is proportional to the velocity of the distortions in the measuring spot.Scattered light is collected by a lens and focused onto a photo detector. Byfast Fourier transformation the beating frequency is determined and thevelocity of the particles can be deduced. This velocity, definded by theprovided controller, can be compared to the rotation velocity of the disc.