Abstract: A metering device contains a rotor which defines elongate chamber, there being a shuttle contained within the chamber movable between two terminal end positions. Frusto-conical surfaces defined on the rotor cooperate with annular members defining corresponding seats. One passage extends from one end of the chamber to one frusto-conical surface, and another passage extends from the other end of the chamber to the other frusto-conical surface. Each annual element defines a respective inlet and outlet for fluid and a shuttle is present within the chamber. As the rotor rotates, the shuttle effects a shuttling movement thus measuring dispensed volumes of fluid. A sensor is provided to detect physical contact of the shuttle with the end of the chamber to cause the rotor to advance.