Examination of Coil Structure to Reduce Water Influence on Eddy-Current Rail Displacement Sensors

Eddy-current rail displacement sensors are mounted on track inspection vehicles for rail inspection on railroads and can measure rail displacement in a non-contact manner. Currently, there is a problem that if a high dielectric constant such as water is deposited near the sensor, the capacitance between the coil and the rail changes, affecting rail displacement detection. Therefore, we compared the characteristics of a 25-turns coil used in existing sensors and a 3-turns coil with the same Quality factor but fewer turns, and studied a coil structure that is less susceptible to the effects of water.