sensing members 10 11 are arranged for sensing the position of a float sliding within the members 1 to 4 that duplicates in a way that can be sensed the position of the level of the liquid for a better understanding of the unit let us consider the cylindrical member 1 by applying a vacuum in the interior of the body 1 through the valve 8 there will be a sucking of liquid through the channel 6 once the vacuum has caused the rise of the liquid in the interior of the cylindrical member 1 up to a level that may be sensed by means of the sensor 11 pressurized air will be applied through the valve 9 the level of the liquid go down because the liquid will be forced into the channel 7 with the descent of the level of the liquid the level sensor 10 will be activated at this moment the valve 9 is deenergized and the valve 8 is again energized making the liquid rise again this operation may be repeated for a desired number of times performing a pumping action without moving members the unit dose for each pumping cycle may be adjusted by change of the distance along the cylindrical member.