Magnetic extensometers are used to monitor failures and settlements, often associated with the construction of embarkments, embankments and barriers. An extensometer is normally equipped with a series of measuring points (magnet rings). Checking their position by means of a probe, it is possible to know the lowering of every section between two rings and the lowering in comparison to the reference point. The magnetic rings are connected to the soil by steel springs, and they move as a result of compaction or thrusts of the soil. Readings are made lowering the probe through the access tube; this way it is possible to measure the position of the magnet rings after the beddings. When the probe enters the magnetic field area of a ring, it closes a circuit and activates a visual and acoustic signal. The operator can then register the depth to which the probe is located by measuring the value on the centimeter cable.