Hanging Pendulums are used for accurate and long term monitoring of horizontal structural movements of large structures such as dams, bridges and other tall buildings. The upper end of a steel wire is anchored to the structure under observation. A weight suspended from the lower end is free to move in an oil tank, the oil serving to damp oscillations of the wire. Displacements relative to the wire may be measured using a portable optical readout unit or for remote reading, an automatic x- y coordinator. Measurements can be made at one or several elevations along the wire, taking readings of two perpendicular components of horizontal movement at each elevation.
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