The flow is measured with an Acoustic Doppler Current Profiler (ADCP) from Nortek AS. The instrument sends pulses through the water and determines the flow rate at various points in the waterway.
The water level is measured with a pressure sensor, which is mounted in the discharge station together with the ADCP. The measured water pressure is compensated for the local air pressure.
The discharge station is powered by an internal battery. This is charged by a solar panel at the top of the tube and is therefore 100% self-sufficient. No external cabling is therefore required during the installation.
The data will be transferred with one or multiple ‘Low Power Wide Area Network’ (LPWAN) techniques. The advantage of this technique is that range (distance to transmission tower) is large and energy consumption low.
The discharge from this compact unit is calculated on a central server. Results can then be forwarded in various ways, or they can be made available on a personal dashboard that fits all of your data needs.
The current is measured with the Aquadopp Profiler. That is an Acoustic Doppler Current Profiler, also known as ADCP. The ADCP contains two ‘transmitter-receivers’ that send a pulse into the water. The sound is concentrated in a narrow beam and is reflected by floating particles in the water, such as algae or fine sediment. The movement of the particles, on which this pulse reflects, changes the sound. How much the sound changes depends on the speed of these particles. The change we observe as a result of this is called the Doppler effect.
The sensor receives the reflected sound and compares it with the initial condition. The difference is a measure of the speed of the particles and provides insight into the flow of the water.
By using digital signal processing it is possible to measure the current at different distances from the sensor. The ADCP is a so-called ‘two-dimensional’ (2D) sensor. Thanks to sensor technology, we can measure flow velocities in a horizontal surface. This surface is divided into a number of fixed sections. These sections are called “cells.” The sensor always determines the average flow rate in a cell.
Discharge measurements also provide valuable information about water levels. A special pressure sensor is integrated into each discharge station for this purpose.
Together, the shape and the water level of a waterway determine the flow area. The shape of a ditch, river or canal is regularly measured and then regarded as a fixed value.
The alternating water level is measured using a pressure sensor. This pressure sensor is mounted next to the Aquadopp Profiler. The pressure that this sensor registers is decisive for determining the height of the water column.
The pressure sensor measures differential pressure. On one side there is water, on the other side a thin tube leads to the outside air. As a result, variation in air pressure has no influence on the altitude measurement.
Proven network techniques that guarantee an uninterrupted flow of discharge data are part of the station design.
Each discharge station contains a modem facility with which we upload the measurement data into the data network. In this case, a so-called ‘Low Power Wide Area Networks’ (LPWAN) is used. These data transport systems are based on radios that use as little energy as possible. This makes it possible to equip the measuring stations with solar panels and thus make them as self-sufficient as possible.
By only sending the essential measurements and compressing them as efficiently as possible, a measurement can be transmitted every 10 minutes. For channels and pumping stations, a higher data frequency for every minute can be desireable. This is possible by installing a larger solar panel with LPWAN techniques.
The measured data is sent to a central server (Virtual Private Server). Here, the discharge is calculated and the results are made available to the customer. Because all data from measuring stations is integrally processed via a server, it is easy to serve customers with different data types and formats.
To further increase the overview, it is possible to set up a personal discharge dashboard. This gives the customer an immediate graphical overview of measurements.
Permanent support? That’s possible. River Insight offers remote monitoring: the ability to monitor systems 24/7 – including a data validation service.
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