Column for measuring longitudinal dimensions (1) comprising: a supporting frame (2), a carriage (3) capable of moving along a measuring axis (z) along the supporting frame, a probe tip (44) connected to said carriage and designed to be brought into contact with the piece to be measured, a motorized driving device of the carriage comprising a cable or belt (40) for moving said carriage along said measuring axis and a driving motor (5), a system for measuring the position of said carriage (3) along said measuring axis. The driving motor drives an upper driving pulley through a reducing gear and a friction element. The motor, the reducing gear and the friction element are all integrated inside the pulley. Advantages: gain of space. Reduction of the number of parts. Reduction of the constraints applied by the driving belt on the carriage.