The evolution of a deep water current meter, the Argonaut-MD

The Argonaut-MD (mooring deployed) is a single-point, vector-averaging, current meter that measures three-dimensional velocities. The MD, released in 1996, was the first of SonTek´s line of low-power Argonaut acoustic Doppler current meters. The design allows for a relatively small and light package that can be used on mooring deployments of over one year. Doppler current meters typically have difficulty in low-scattering conditions. Insufficient scatterers results in backscatter signals that are near or below a system´s noise levels; however, the MD´s short-range one-cell design provides robust velocity measurements in some of the weakest scattering conditions. In this paper we will show how significant increases in sensitivity for the MD have been accomplished. Acoustic signal to noise ratios have been improved 6 to 12 dB by shifting the acoustic pulse frequency, enhancing the systems analogue electronics and altering transducers. Notably, these modifications have little impact on deployment durations.