RSS-2-300WL Non-Contact Flow Meter
1
Introduction
Geolux RSS-2-300WL ow meter uses radar technology to provide precise contactless
measurement of surface ow velocity and precise distance (level) measurement from the sensor to
the water surface. Fully contactless radar technology enables quick and simple sensor installation
above the water surface and requires minimum maintenance.
Surface velocity measurement functionality is achieved by transmitting an electromagnetic wave
in 24 GHz frequency range (K-band) and measuring the frequency shift of the electromagnetic
wave reected from the owing water surface. The frequency shift is caused by the Doppler effect
of the moving surface on the electromagnetic wave. As the relative speed between the radar
sensor and the water surface increases, the detected frequency shift also increases, thus enabling
the ow meter to precisely determine the surface velocity.
Water level is measured by measuring the distance from the sensor to the water surface, which
is proportional to the frequency difference between the transmitted and the received signal. The
radar periodically transmits a linear chirp ranging in frequency from 77 GHz to 81 GHz. As the
distance between the radar and the water surface increases, so does the difference between the
transmitted and received frequency, enabling the level meter to precisely determine the distance
between the sensor and the water surface. The radio signal modulation and detection algorithms
used in the sensor allow very precise measurements that are not dependent on air temperature,
humidity, or other parameters of the environment.
The ow meter is able to detect water surface velocity ranging from 0.02 m/s to 15.0 m/s with
precision of 0.001 m/s while the distance can be measured in range from 0.2 m to 15 m or 30
m with resolution of 0.5 mm and accuracy of ±2 mm. An integrated tilt sensor measures the
inclination angle of the sensors and the surface velocity measurement is automatically cosine-
corrected according to the measured mounting tilt angle.
The ow meter is able to measure water ow at distances ranging from 0.2 m up to either 15 m or
30 m, depending on the device version: WL-15-1 is the 15 m version of the device, and WL-30-1 is
the 30 m version.
Calculation of the ow (discharge) is done internally in the sensor combining surface velocity
measurement and level measurement with congured cross section of the river or channel.
Conguration of the measurement parameters like channel prole cross section, material of
the edges and the location of the sensor above the water can be easily set using Geolux PC
conguration application - Geolux Instrument Congurator. When parameters are set properly,
the sensor will calculate ow with an accuracy of approximately ±1% compared to ADCP
measurement for the same location. Measurements of the surface velocity and water level will also
be available in parallel to the ow readings on the sensor digital communication interfaces.
