The Rauschenbach dam is a dam in the Free State of Saxony. The dammed waters are the Flöha andWernsbach rivers. It was built between 1960 and 1968 in the upper Flöha valley near Cämmerswalde to supply drinking water. The water is fed into the Central Ore Mountains dam system via the Freiberg district waterworks, and through further transfers it reaches Chemnitz, Dresden and Freiberg. The backwater of the Flöha (Czech: Fláje) extends into the neighboring area of the municipality of Český Jiřetín (Georgendorf) in the Czech Republic. The total reservoir area is 114.58 ha, of which 99.43 ha are on the German side and 15.15 ha on the Czech side. The dam wall of the reservoir is a straight concrete gravity dam. As a special design feature, it has a concrete slab on the bottom of the reservoir(towing slab), to which the dam wall is braced by prestressed steel cables.
Due to lower shear strength parameters than assumed in the static calculations, the so-called drag plate was placed behind the valley fields of the dam wall. It is 87.5 m long, 13.4 m wide and 5.0 m high. It is connected to the dam body and the subsoil via tendons (rock anchors).
The changes in distance between the dam wall and the drag plate in front of it are to be measured. This measuring task is performed by inductive displacement transducers at a total of 5 measuring points. The changes in distance caused by the temperature-related horizontal movements of the dam wall are very small and amount to around 0.2 mm over the course of the year. Larger movements, which are very well recorded by the displacement transducers, only occur during major changes in dam height, such as during the 2013 flood. The output signals of the displacement transducers are continuously recorded and archived as 15-minute average values in a time series database.
Displacement transducer SM403.2.1.KP3X40 at the upper and lower measuring points at the connection between the dam wall and the drag plate
Upper measuring point
Lower measuring point
These measuring tasks have been solved with the inductive displacement transducers of the SM40 series, which are made entirely of stainless steel. The detection and measurement of displacements has been carried out with inductive sensors for many years. The technology is based on the half-bridge principle. The position of the movable core causes a change in inductance in the two coil halves. Integrated electronics convert the change in displacement or angle into a proportional analog output signal.
This simple type of absolute displacement and angle measurement enables the construction of robust, reliable sensors. Packaging in a stainless steel housing and complete encapsulation results in a displacement transducer that is shock-resistant up to 250 g and vibration-resistant up to 20 g, operates between -40 °C and +120 °C and can be immersed up to 5 m.
This customized version of the inductive displacement transducer has a measuring path of 2 mm. The measuring path is converted into an output signal of 4 – 20 mA by the integrated electronics. The attached stainless steel rod ends make it easy to mount the displacement transducers. The inductive displacement transducers can be supplied with an operating voltage between 20 and 32 VDC. The output signal is provided via a PUR cable that is permanently encapsulated with the displacement transducer. The cable length varies between 3 and 16 m, depending on the distance from the measuring point to the measurement data acquisition.
