Case Study: FMU90 Transmitter And FDU92 Sensor Provides Filter Control In Wastewater

The Prosonic S FMU90 and FDU92 ultrasonic system measures the difference in water level between two sides of a filtration system.

Sewage treatment plants in Denmark.

This large wastewater treatment plant uses all kinds of instrumentation from different suppliers. Endress+Hauser has proven to be a reliable partner and is an important supplier due to the high quality and reliability of instruments.

In the inlet of the plant, the raw sewage water is filtered through 3 automated systems. The filtration systems are equipped with an endless mesh, which captures the solid materials. As the mesh is being filled with sewage materials, the automated system rolls the mesh a step up and dumps the waste into a container. To control the automation, a Prosonic FMU90 transmitter with two FDU92 ultrasonic sensors measures the difference in water level between the two sides of the filter.

The customer is very pleased with the ultrasonic system from Endress+Hauser, and has not experienced any problems.

The compact Prosonic FMU90 is used for continuous, non-contact level measurement in fluids and coarse bulk materials. Additionally, the sensors can be used for flow measurement in open channels and measuring weirs.

In ultrasonic level measurement the operating principle is based on the measurement of the travel time of a sound signal transmitted from and received by the same sensor after reflection from the liquid or solids surface. The travel time of a sound pulse is a direct measure of the height of the material in a silo or tank. The distance in air traveled by the pulse in feet is equal to the travel time in seconds multiplied by the speed of sound in feet per second. Signal process techniques, including temperature compensation and rejection of false echoes returned by tank obstructions, are used to maintain the integrity of the level information.