Sonde with rotatable pad for carrying out logging measurements in a borehole

A sonde for carrying out logging measurements in a borehole, comprising a body having an outer diameter smaller than the diameter of the borehole, means for centering said sonde body in the borehole, at least one measuring device comprising a transducer, handling means for displacing said measuring device from a position of contact with the borehole wall to a position spaced apart from said wall and vice-versa, means for rotating said measuring device about the sonde axis, means for detecting the angular position of said measuring device with respect to a reference direction, and connecting means for transmitting the signals delivered by the sonde, wherein said measuring device comprises a shaft whose axis, maintained in a plane parallel to the sonde axis is inclined to said axis by an angle comprised between 0.degree. and 90.degree., and at least one wheel carried by said shaft and freely rotatable thereabout, said wheel delimiting a sealed chamber whose characteristics are accurately known, said transducer being carried by said shaft within said wheel.