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Institute of Measurement Technology
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Bachelor Theses.

Sleeper detection by means of a magnetic field

Thomas Gahleitner

A method for detecting sleepers by measuring a magnetic field has been developed. The sleeper is detected indirectly via the screw with which the rail is fixed to the sleeper. Due to the material dependency of the magnetic-flux-density, a deviation should be measurable if a screw is located near the measuring point or not. To check the feasibility of the method, a computer simulation was carried out. The simulation is based on a linear magnetic model where a magnetic field is simulated with and without a screw.


Figure 1: Prototype of the sleeper detection system.

The bachelor thesis also documents the construction of a prototype, shown in Figure 1, which emits a light signal when a screw is present. Further functionalities, e.g. output on a display, can be added easily as the prototype uses standard electronic components and software. The strength of the magnetic field is recorded and visualized with a characteristic curve shown in Figure 2. It shows the magnetic-flux-density depending on the distance of the screw to the measuring point and illustrates that a threshold can be defined for detecting the edge of the railway sleeper.


Figure 2: Characteristic curve of magnetic flux density B depending on the distance between the screw and the detection device.

Keywords: sleeper detection, magnetic field measurement, railway sleepers, magnetic flux difference

September 21st, 2020