Pendulums are designed to monitor horizontal movements in dams, dam foundations, abutments and to determine the structural movements of bridges, piers, towers and tall buildings.
The direct pendulum consists of a steel wire anchored at the upper end to the structure, with a tensioning weight suspended at the lower end which is free to move in a tank filled by a damping fluid.
The inverted pendulum provides a fixed datum from which structural movements can be measured. It uses the identical wire anchored in firm soil beneath the structure, with a floating unit fixed to its upper end. The floating unit is free to move in a fluid tank keeping the wire vertically. Inverted and direct pendulums are often installed together in the same structure.
Readings can be taken in manual mode with the removable optical coordinometer or automatically with the advanced TEL-310S telecoordinometer. Direct and inverted pendulums are usually installed within gravity or arch dams, but occasionally they are installed in slender structures like skyscrapers or towers to monitor horizontal displacements.