A method of (and an associated device for) applying or measuring the force applied to a sample tube is disclosed. The method includes the steps of driving a plurality of gripping fingers from an open position to a gripping position against a tube, while measuring the movement of first and second coaxial gears driving the fingers before the fingers grip the tube, stopping the movement of the first coaxial gear when the fingers grip the tube, and allowing and measuring a further limited movement of the second coaxial gear after the fingers grip the tube.