These flowmeters use acoustic doppler techniques (Acoustic Doppler Current Profiler = ADCP) to measure the water velocity. From this, the flow rate (the discharge) can be calculated.

• SonTek SL500 and SL1500: Horizontal ADCP’s for continuous measurement of water velocity and (calculated) flow rate.
• SonTek HydroSurveyor: Portable ADCP for measurements from a vessel. For an accurate discharge calculation, the soil profile, as well as the flow profile, are measured simultaneously.