Portable weigh-in-motion rail device

Portable weigh-in-motion rail device is prepared for identification of parameters of loads exerted by vehicles on the railway track. The system developed by Adaptronica Sp. z o. o. allows for weighing trains in motion.

Portable weigh-in-motion rail device makes use of the measurement of rail strain caused by the passing train. The device uses portable transducers (patent-pending application), attached to the rail foot in a non-destructive manner. The main components of the measurement system are schematically presented in Fig. 1.

Fig. 1 Scheme of the main components of the portable weigh-in-motion rail device

The characteristic feature is that the additional preparation of the ballast and sleeper before the system installation is not required. The installation process of the detectors is fast. Closing the rail line is not necessary.

An important advantage of the system is the use of portable detector installed to the rail foot by clamping elements which significantly reduces the installation time and cost. The clamping element is designed in such a way that it can be adjusted to all types of rails. Before installation, additional preparation of the track is not required e.g. hardening of the ballast. A view of the portable weigh-in-motion rail device is presented in Fig. 2.

Fig. 2 The detectors installed on the rail

An important feature of the device is the operation without additional limitation on train speed. Usage of four detectors improves stability and measurement precision therefore contributing to improvement of the system reliability.

Portable weigh-in-motion rail device makes it possible to take into account the current state of the track and environmental conditions through self-calibration based on the weight (determined by the manufacturer) of the electric locomotive.

The self-calibration algorithm enables to maintain precision of the measurements in case of track in different technical condition and equipped with different type of sleepers.


Portable weigh-in-motion rail device enables weighing of rail vehicles and particularly allows for determination of bogie axle, linear load identification, detection of car weight and velocity as well as the type of the passing train. By use of two pairs of detectors (one pair per each rail), the device enables determination of the uniformity of the load exerted by each axle on the rail track.

The device may be used for overload and overspeed detection of the rail vehicle.

An additional feature of the device is its use for diagnostic purposes related to the assessment of the condition of the wheels of the rail vehicle.

The recorded measurement results may be subject to archiving. They can be used for statistical purposes.

Principle of operation

The principle of operation of the portable weigh-in-motion rail device is the measurement of rail strain caused by the passing train. The measurement is realized by the use the strain gauge or piezoelectric strain sensor which is glued to the strain detector attached by metal brackets to the rail foot.

During the passage of the train, the time sensor signal is preconditioned by amplification, filtering and sampling before storage.

The basic measurement and diagnostic information related to the weighed rail vehicle are included in the time and amplitude parameters of the recorded measurement signal.

Measured parameters

  • axle load measurement,
  • rail car weight measurement,
  • velocity of the rail vehicle measurements,
  • number of cars detection,
  • axle overload detection,
  • unbalanced axle load detection,
  • determination of rail vehicle type,
  • wheel defects detection.

Basic technical parameters

velocity range of the rail vehicle:5 - 100 [km/h],
axle load range 1000 - 30000 [kg],
velocity measurements precision±3[%] dla σ=95[%],
axle load measurements precision±5[%] dla σ=95[%],
rail car weight measurements precision±5[%] dla σ=95[%],
temperature range of device operation-20ºC……..+70ºC.

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Printable version: PDWSZ_system_eng.pdf