Inverted Pendulum

The inverted pendulum is installed to provide a fixed datum from which structural movements can be monitored. It consists of a wire, anchored in stable ground beneath the structure, with a float fixed to its upper end. The float, which is free to move in a water tank, tensions the wire and keeps it vertical.

Displacements relative to the wire may be measured using a portable optical readout unit or for remote reading an x- y co-ordinator.
Measurements are made at one or several elevations along the wire, taking readings of two perpendicular components of horizontal movement at each elevation.

Direct (Hanging) Pendulum

The hanging pendulum uses identical measuring devices. The upper end of the 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.
The wire remains vertical but moves with the structure from which it is suspended. Therefore readings of movement relative to the wire must be corrected for
movements of the reading table.

Automatic Readout System

Soil Instruments have designed their ‘non contact’, automatic remote monitoring pendulum co-ordinator to provide monitoring teams with a simple and effective means of logging the tilt or rotation of structures.

The unit consist of a 12 volt motor and gear box assembly, all housed in a waterproof case, and a precision machined carriage onto which two pairs of accurate infrared transmitters and receivers are mounted.

The carriage is moved along a precision track bed using a lead screw assembly. The infrared beams are broken by the wire as the carriage moves along its path. The use of the remote co¬ordinator does not preclude the use of other mechanical or optical measuring equipment.
Where tilt at a number of elevations is required, these co¬ordinators can be linked to a central data acquisition system and profiles generated from the recorded data.