Various methods of measurement technology can be used but only a few make sense and are suitable for application in the stormwater and wastewater sector.
The practically all-purpose solution for filling level measurement
For the detection of liquid levels in basins, reservoirs, pipes and sewers, the ultrasonic probe measurement method offers an optimal solution in most cases.
The principle of ultrasonic measurement is based on continual ultrasonic impulses that are emitted from the sensor and reflected off the surface of the medium. The sensor receives the reflected sound waves and calculates the distance, as the interval between emission and reception of the signal is proportional to the filling level.
The ultrasonic sensor with integrated transducer is reliable and precise, even under difficult conditions. The sensor can measure liquids within a range of 0.07 up to 4 metres; a maximum cable length of up to 1.000 metres offers great flexibility for fitting activities.
With this measuring technique there is a strong dependence of the speed of sound on the temperature, therefore the ultrasonic measuring instruments we use are equipped with integrated temperature compensation at the connection.
HydroScreen fine bar screen with ultrasonic measurement and proximity switch
A major advantage of the ultrasonic sensor is the contactless and, therefore, very low-maintenance filling level measurement mode.
The optimal accessibility of the compact and powerful transmitter means it can be connected quickly, thus ensuring simple and fast installation and commissioning.
The dust-tight and waterproof IP68 housing guarantees continuous maintenance-free operation. Depending on requirements, safe operation is offered by ATEX approval in Ex zones 0, 1 and 2.
The ultrasonic measuring principle may not be suitable for media that tend to foam. In these cases, the installation of pressure sensors is recommended.
Information for planners and operators:
- Reflections can falsify the results of ultrasonic and radar measurements.
- Direct sunlight can cause a temperature drift which may lead to measurement deviations of up to 100%. The sensors must be protected from direct sunlight and equipped with temperature drift compensation.
- Contamination of sensors can also lead to incorrect measurements with ultrasound and radar equipment. Even cobwebs with water drops can lead to the failure of a measuring instrument. A humid environment causes corrosion which can lead to malfunction of the measuring equipment if left unprotected.
- Certain measuring methods, such as ultrasound, have to maintain specific distances before the medium can be measured. The use of mirrors can help but regular cleaning is vital.
- The measurement of flow rates or water level heights can never be accurate in wastewater. Even under laboratory conditions, experience has shown that the measuring accuracies specified by the manufacturers cannot be achieved. Deviations from flow rate measurements have resulted in deviations of up to ± 5 %, no matter how accurate the recalibration.
