Non-contact discharge radar RQ-30 (RQ-30a)

The RQ-30 is a sensor for continuous discharge measurement of rivers, open channels and canals with known cross-section profile. The sensor uses innovative radar technology to measure velocity, water level and discharge. It enables reliable, non-contact measurement without the need for structural work in the water.

  • General
  • Technical data
  • Documents
  • Video
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  • Non-contact, maintenance free measurement system
  • No structural work is necessary in the water
  • No threat to the systsem through flooding
  • Low power consumption enables operation using solar cells
  • Recognition of flow direction
  • Measuring range from +/- 0.10 to +/- 15 m/s (depending on the flow conditions)
  • Recognition of hysteresis-effects
  • Measurement in backwater situations
  • Measures even where weed growth prevails and sensor is not affected by turbidity
  • Measurement in tidal waters
  • Automatic angle measurement
  • Optional (RQ-30a): analogue outputs from 4 to 20 mA

The RQ-30 enables discharge measuerment for rivers, streams, open channels and canals for which continuous monitoring is desired. Thanks to the non-contact radar technology the measuring equipment is not susceptible to contamination, debris or driftwood in the water. Furthermore, the non-contact measurement warrants very low maintenance and fail-safe operation especially during high water or flooding. The sensor can be simply mounted on bridges, on the roofs of closed canals or channel superstructures.

The non-contact radar technology determines the water surface flow velocity using the Doppler frequency shift method, the water level is established by a travel time measurement. With known cross section profile the discharge Q of the water can then be calculated on basis of the continuity equation: Q = vm · A (h)


Dimensions 338 mm x 333 mm x 154 mmm
Total weight 5,4 kg
Protection IP 67
Power supply  from 6 to 30 V
Power consumption at 12 V standby: approx. 1mA; active: approx. 140  mA
Operating temperature -35 to +60 °C
Miscellaneous integrated lightening protection

Measurement range  from 0 to15 m (standard); 0 to 35 m (extended)
Resolution 1 mm
Radar frequency 26 GHz (K-Band)
Radar opening angle 10 °

Measurement range  from 0,1 to15 m/s
Accuracy +/- 0,01 m/s; +/- 1 % FS
Resolution 1 mm/s
Measurement duration from 5 to 240 s
Measurement interval from 8 s to 5 h
Measurement frequency 24 GHz (K-Band)
Radar opening angle 12 °
Distance to water surface from 0,5 to 35 m
Necessary minimum wave height 3 mm


Analogue output (RQ-30a) 3 x output 4 - 20 mA for water level, velocity and discharge
Digital interface

1 x SDI-12; 1 x RS 485 or Modbus

Transfer rate: 1,2 to 19,2 kBd


Non-contact Discharge Radar RQ-30 Contact-free discharge measurement for channels and open rivers using radar technology ProductLeaflet_RQ_30_EN.pdf 

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Non-contact discharge radar RQ-30 (RQ-30a)
Non-contact discharge radar RQ-30 (RQ-30a)
Non-contact discharge radar RQ-30 (RQ-30a)
Discharge measurement at Rhine river, Vorarlberg
Non-contact discharge radar RQ-30 (RQ-30a)
Discharge measurement with RQ-30
Non-contact discharge radar RQ-30 (RQ-30a)
Illustration of discharge measurement with RQ-30 Doppler Radar
Non-contact discharge radar RQ-30 (RQ-30a)
Dimensions of RQ-30