Measuring Vibrations

When researchers measure the vibrations of a structure, they usually measure its acceleration using special instruments called accelerometers.

Accelerometer
(20 mm diameter and 12mm long)
mounted on a steel block.

These extremely sensitive electronic instruments can detect tiny movements of a very stiff structure, like a concrete dam, when there is hardly any wind blowing on it at all (Suprisingly, dams do move in the wind).

Here is one placed inside the gallery of a concrete dam. It is protected in a plastic bag to stop moisture affecting the electronics. Electrical signals from the accelerometers run along the cables back to the monitoring and recording equipment (Show Me)