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The subject of the paper is the construction of a smart strength sensor for measuring the wheel dynamic load. An element of the railroad is used as a sensor, e.g. part of P49 type rail with a certain length mounted on standard rail clamps at both ends. Two independent strain-measuring full bridges for the tangential forces are mounted on the rail at a certain distance from the both ends. To obtain a high sampling rate of measuring, two bridge transducers have been incorporated in the offered smart strength sensors. The problems with its synchronizing and cross noises reducing have been solved. A smart controller has been incorporated in the sensor. It consists of a microcomputer unit, bridge transducers and driver for local area network, using physical RS485 standard. On a calibration test set the embedded microcontroller allows an automated self-calibration to be done, using an exemplary sensor of Hottinger Baldwin Messtechnil for comparing. During exploitation it permits to estimate the applied force value, its position on the sensor and also the speed of load moving. Embedded networking permits many measured units to be connected in one complex device, controlled by a central computer.