Abstract: A measuring instrument comprises a column (10) on which is mounted a carriage (11) with a drive cursor (12) and a measuring cursor (20) sliding on the drive cursor (12) and carrying a measuring contact (24) and a measuring device (40). A measuring force device (25) is arranged between the two cursors and determines, thanks to a lever (26) a rest position and two measuring positions vertically upwardly or downwardly offset or corresponding to a predetermined measuring force on the member to be measured. A motor (15) displaces the drive cursor (12) and the position detector (36) permits measuring the relative position between the two cursors. A control unit (35) controls the speed and direction of rotation of the motor (15) as a function either of the signals (44) received from the position detector (36) or from two external contacts (42, 43).