Fig. 3
From: Inspecting the corrosion state of underground reinforced concrete structures
Concept of the potential mapping in the underground: A Electrochemical sensor protected in the supporting tube during the dragging through the underground and B After turning the lever, the sensor is pushed out from inside the tube towards the underground, and the measurement procedure is started; after the measurement, the sensor goes back to the initial position in the case. The direction of the green arrows shows the turning direction of the lever arm and the direction of the movement of the probe