Abstract: A dispensing unit for a fluid dispensing machine comprises at least an inlet duct and an outlet duct for fluid products, connected to a variable-volume pumping chamber comprising at least one flexible wall. Two non return valves mounted in counter-phase are located in the inlet and outlet ducts, respectively. The pumping chamber is coupled to actuator means comprising a stepper motor, a screw-nut screw unit and a carriage. The carriage moves the pumping chamber from a zero position in which the chamber has a maximum volume to an upper limit in which the chamber has a minimum volume. An optic sensor defines the zero point of the pumping chamber so as to guarantee precision and repeatability of the dispensing operations.