Railway Applications
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Fiber Optic Sensors on the Railway
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SENSOR LINE has contributed a fiber optic railway sensor concept to the possible solutions for the overwhelming EMI problems that railway vehicle detection systems are anticipated to face in the nearest future. Modern propulsion and braking systems are being introduced but can not be fully utilised due to insufficiencies of the existing railway track equipment in general. Even some devices far less sensible than sensors are said to be literally disassembled by the strong magnetic fields of eddy-current brakes used with the new German ICE-3 train. And future engines are going to disturb the frequency range now used for detection purposes, too.
General advantages of fiber optic road traffic sensors also apply to railway wheel load sensors without any restrictions:
- The signals delivered are static (present as long as load applied)
- Sensor failure can be detected at once (especially before there is a vehicle which might not be detected)
- There is virtually no noise limiting the amplification of small signals
But the biggest advantage is (of course)
- These sensors are not affected by whatever electrically or magnetically is happening on the track
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The sensors developed by SENSOR LINE are designed to be installed between the rail and the sleeper substituting the elastomer plate (rail pad) which is used for many types of track work at that place. Therefore installation can happen very quickly. One only has to loosen the screws (respectively the bolt nuts) of the sleeper and the adjacent ones, lift the rail a little, replace the elastomer plate with the sensor and fasten the screws again. The remaining work is only cabling so the track itself is not affected any more and it might only happen that the work must be interrupted for a moment when a train is passing. There is no adjustment or calibration required.
Installed in this unique way the sensor causes minimal interference to all kinds of track maintenance. It is furthermore protected against environmental influences including game bite. Burying the cables will make the sensor remarkably difficult to be discovered by saboteurs and thieves, the latter will also find that there are no parts of further value incorporated.
Along with the fact that the sensor structure is very simple and easy to manufacture in large quantities these are advantages promising noticeable cost reductions in purchase as well as in operation.
Examples of possible applications are
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Track Switches |
These are relatively simple sensors which must only generate at least one signal when a train is present. They are used for example to control automatic level crossings. For such purposes the simplest kind of fiber optic railway sensors is sufficient.
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Gravity Shunting |
The art of gravity shunting is the art of decelerating a car that is descending from a hump in a way that it will arrive at some given remote point of the track with some given low speed. Being able to do so requires information not only about the car's current speed but also about its weight. Using SENSOR LINE's fiber optic rail pad sensors both kinds of information can be obtained at the same time and with the same measurement setup thanks to their analogous response to the wheel load.
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