D.7 MONITORING CRACKS

The devices we have installed on the floor of the rotunda in the south-west gallery and on the wall linking the two stretches of this gallery are called fissurometers or crack meters.

We use these devices for monitoring the cracks in the wall in these parts of the galleries, as they record data on a continuous basis. The refurbishing work in the south-west gallery, opening to the public, and greater activity in the research tasks in this area require a more thorough control of this kind of damage.

We have deployed a device in the rotunda in the south-west gallery in order to monitor its development. We have placed two devices on the wall that divides the gallery, one vertically and the other horizontally, which means we can monitor the crack’s evolution in both directions.

As regards the measuring devices, we are working with both string pot sensors and potentiometers. The former record the change of frequency on a cable when adjusting its voltage. It is the same phenomenon as the one involved in playing a guitar or a piano.