In this paper we demonstrate the design of a low-cost optical current sensor. The sensor principle is the Faraday rotation of a light beam through a magneto-optical material, SF2, when a magnetic field is present. The prototype has a high sensitivity and a high linearity for currents ranging from 0 up to 800 A. The error of the optical fibre sensor is smaller than 1% for electric currents over 175 A.

The goal of this paper is to present both the development of an intelligent sensor that can be used to obtain information about the existence of rolling contact fatigue cracks created by wheel-rail interactions and also the data obtained in a real-world study performed for its validation. The design of a bogie-mounted instrumentation system to detect and measure wheel rolling in railway units is introduced, and experimental results are presented. The system is designed to analyse and compare the angular velocity of the wheels of a railway unit. It uses photodiodes to acquire information about rolling conditions and a radio frequency link to send that information to a data logger, which acquires and saves the data for post-processing and analysis.