Water Flow



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.

• Specifications

Flow velocity measurement
Measuring range ± 10 m/s
Accuracy 1% of measured value ± 5 mm/s
Number of measuring cells 9

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 (optional) 0.15 … 10 m
Accuracy ±3 mm, depending on stratification
Measuring principle Piezo-resistive
Measuring range 0 … 10 m
Accuracy ±0.25 % FS
Interfaces 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 POM

Wall bracket (accessory)
Components Bracket, protective cover, and C rail mount
Material Stainless steel
Details 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.


OTT SLD Brochure - AUS

OTT SLD Brochure - AUS

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OTT SLD User Manual

OTT SLD User Manual

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Additional files
OTT SLD Evaluation Questionnaire

OTT SLD Evaluation Questionnaire

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