Laser Doppler Anemometer - LDA

Backscatter, two-component four-beam fibre-optic LDA system (by Dantec Dynamics A/S, Skovlunde, Denmark ). Particularly, the LDA system consists of a 5 W water-cooled argon-ion laser (version Innova 70, by Coherent Inc., Santa Clara, CA, USA ), a 2D fibre flow transmitter (by Dantec Dynamics A/S, Skovlunde, Denmark , which comprises a transmitter providing colour separation and frequency shifting of the laser beam; fibre manipulators for optimum coupling of the laser light into optical fibres; a probe head with a fibre-optical connection to the transmitter; and back-scatter receiving optics including colour filters, colour separation, and photodetectors), a probe with a diameter of 85 mm (by Dantec Dynamics A/S, Skovlunde, Denmark, with a focal length of 310 mm and a beam spacing of 60 mm), and a signal processor (version 58N40 FVA - Flow Velocity Analyzer enhanced, by Dantec Dynamics A/S, Skovlunde, Denmark). The accuracy of velocity measurements is ±2%. Through an AD/DA-Analog to Digital/Digital to Analog board (Keithley Metrabyte model DAS 50/4), the laser Doppler data can be correlated with up to four 12 bit channels of auxiliary inputs coming from four transducers. The entire system is assisted by a process computer.