Magnetic-flux-based plumb line coordinometer for horizontal displacement monitoring of dam

Abstract Monitoring the horizontal displacement of plumb lines is essential for guaranteeing the safety of dams. A magnetic-flux-based plumb line coordinometer, which is immune to environmental changes in dust concentration and humidity, is proposed. Firstly, the theoretical relationship between the displacement and the measured magnetic field is derived from the magnetic circuit theory, and the dimensions of the sensor have been optimized. Secondly, the effect of plumb line eccentricity on the displacement measurement is studied and a structure with ferromagnetic guide is proposed to reduce this effect. Finally, a plumb line coordinometer device is fabricated to measure displacements in two orthogonal directions, and a decoupling algorithm is proposed to obtain displacements in two directions. Based on the experimental results, the coordinometer can measure displacement in two orthogonal directions with a maximum error of 0.09 mm within the 60 mm measurement range. The developed plumb line coordinometer has been installed in a hydroelectric power plant for on-site testing, and the displacement measurement results are in good accordance with the optical method and artificial observation.