A system for automatically fuelling vehicles, primarily automobiles, that includes a sensor to detect the presence of a person in proximity to the fuelling system. A fuelling robot includes a robot head that can be moved relative to the robot to enable the robot head to be brought by a positioning system from a rest position to a predetermined position in relation to the fuel-tank pipe of the vehicle. The robot head is provided with electrically conductive sheet-metal elements that are connected to an oscillating electric circuit. A sensing circuit senses a change in the frequency of the oscillating circuit that results from a change in the capacitance between the sheet-metal elements, such as when a person is near the fuelling robot. The sensing circuit activates an alarm in response to a predetermined frequency change, to warn a person who is too near the fuelling robot.