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The sensor employs the acoustic Doppler principle to reliably measure flow velocity in a variety of naturally occurring conditions, including during most flood events.

Usage Type: Fixed installation
Measurement technology: Acoustic
Parameters measured: Flow velocity
Product Highlights: Side-Looking-Doppler for continuous discharge measurement in rivers and open channels. Discharge calculation based on velocity - index - method. Integrated vessel filter algorithm, Modbus interface and output of total volume of flow (max. interval 1 day).
Measurement range: ± 10 m/s
Accuracy: ± 1 % of measured value ± 0.5 cm/s

  • Equipped with two horizontal ultrasonic transducers "looking sideways" into the flow (Side Looking Doppler) to measure water velocity.

  • An optional vertical transducer and integrated pressure cell measures the water level.
  • All measurement values are analyzed, verified and processed by an integrated signal processor, before being used in the calculation of discharge.
  • Velocity measurements from up to nine cells are used, along with measured water level, to calculate discharge either internally in the OTT SLD or externally in a data logger.
  • All measurements can be retrieved using SDI-12, RS485 , RS232 or Modbus RTU protocols and are available for storing in a data collection platform, such as the OTT netDL station manager.


Flow velocity measurement



Measuring range

±10 m/s



1% of measured value ± 5 mm/s


Number of measuring cells



Cell size / Blanking



600 kHz

2 … 10 m / 0.5 … 30 m


1.0 MHz

1 … 4 m / 0.3 … 15 m


2.0 MHz

0.2 … 2 m / 0.1 … 8 m


Beam angle / Max. profiling range*



600 kHz

2.4° / 80 m


1.0 MHz

2.4° / 25 m


2.0 MHz

2.1° / 10 m


Minimum coverage

0.15 m (water level option)


Electrical data



Supply voltage

12 ... 16 V DC, typ. 12 V


Power consumption

50 ... 500 mW, depending on measurement cycle


Water level measurement






Measuring range

0.15 ... 10 m



±3 mm, depending on stratification


Pressure cell (optional)



Measuring principle



Measuring range

0 ... 10 m



±0.25 % FS



RS-232, SDI-12 or SDI-12 via RS-485, Modbus (optional)


Environmental conditions



Operating temperature

-5 ... + 35 °C


Storage temperature

-20 ... +70 °C


Length x Ø

45 ... 52.2 cm x 7.5 cm


Housing material



Wall bracket (accessory)




Bracket, protective cover, and C rail mount



Stainless steel



On request


Discharge calculation

Within the unit or externally on a data­logger, e.g. OTT netDL


OTT SLD EasyUse Installation and service software

System setup, commissioning, reviewing and optimizing


OTT Prodis 2 (accessory) Calibration software

Determining correction factors, (velocity-index method and others), optimizing discharge calculation, managing stations


*The beam angle is understood to be the measured angle with regard to the main axis. The maximum profiling range depends on the water profile, salinity, suspended matter content etc.


Related Categories
Aqualab Systems
Water Level Sensors