Instruction Manual
NivuFlow 550
page 26
rev. 00 / 12.04.2017
Functional Principle
12 Operating Range
The NivuFlow 550 is a non-portable measurement system for flow measurement. The equip-
ment is conceived preferably for measurements in clear to heavily polluted aqueous liquids
with various compositions.
The system can be used in part filled flumes, channels and pipes featuring various shapes and
dimensions.
You can find an overview on connectable sensors in chapter „9.2 Connectable sensors“. The
use of several sensors supports the more accurate detection of flow velocities on a common
measurement place.
Note to the Radar measurement method
The measurement method used to determine the surface velocity is based on the Doppler
principle.
The Radar sensor transmits a signal. The signal hits the waves on the water surface, is
reflected and is re-detected by the sensor. The reflection from the water surface causes a
frequency shift.
The Radar sensor measures the wave movement and computes the liquid’s surface veloc-
ity from this movement. Therefore it is indispensable to have (at least minor) movement of
waves on the medium surface available.
13 Functional Principles
13.1 Flow Velocity Measurement
13.1.1 Surface Radar
The OFR surface radar system is aligned towards the flow direction. It transmits radar waves
and receives the reflections from the waves on the water surface. Due to the difference
between transmitted and received frequencies it is possible to calculate the velocity of the
movement ( Radar-Doppler effect).
The transmitter then uses complex integrated algorithms to compute the parameters below
from the velocity determined from the water surface:
• Flow profile and
• average velocity within the wetted cross section
Fig. 13-1
Measurement using Surface Radar