The Vectron

The Vectron is a new pulse-coherent Doppler sonar system that has been developed to allow remote measurement of turbulent velocities at mid-water depth (O 10 m distant from the instrument transducers) to meet the measurement and monitoring needs of the in-stream tidal generating industry. Multiple sonar units (based on the Nortek AD2CP hardware platform) are networked together and the instrument is configured with a modular philosophy that allows a great deal of flexibility in acoustic sampling schemes. Time synchronization between the essentially independent instruments is achieved through a low latency Ethernet switch using a master Precision Time Protocol (PTP) clock. Pulse-to-pulse coherent sampling is achieved by taking advantage of bistatic beam geometries that isolate a small sample interval (at 7 m from the central transducer). Velocity ambiguity is overcome using a completely new technique based on multiple computations of the pulse-topulse correlations. A prototype system was deployed from a wharf in Parrsboro (Nova Scotia) where turbulent flows with mean velocities up to about 2 m/s were observed. Velocity power spectra are presented and compared to reference observations from a nearby single-point flowmeter.