The penetrometer includes a chassis, a mast mounted thereon and positioned substantially vertically during a test, a rod string, including a tip penetrating the ground that is positioned at one end of the rod string, an anvil that bears against the rod string at an end opposite the tip, a hammer striking the anvil, elements for raising the hammer along the mast up to a fall height, at which the hammer is released, and elements for measuring the sinking of the tip into the ground. The penetrometer further includes an electronic control unit for controlling the fall height, and configured to select the fall height adopted for the test based on the sinking of the tip measured by the measuring elements during one or more earlier tests, and mechanical elements controlled by the control unit for triggering the fall of the hammer at the height selected by the control unit.