A fluid metering device may meter the flow of fluid. The device may have a main chamber and a piston configured and oriented to reciprocate within the main chamber. The piston may be configured and oriented to define a first and a second sub-chamber whose volumes vary inversely as a function of the position of the piston during its reciprocation. The fluid metering device may have a first inlet valve configured to controllably regulate the flow of fluid into the first sub-chamber, a first outlet valve configured to controllably regulate the flow of fluid out of the first sub-chamber, a second inlet valve configured to controllably regulate the flow of fluid into the second sub-chamber, and a second outlet valve configured to controllably regulate the flow of fluid out of the second sub-chamber. A valve controller may be configured to control each of the values in a manner that causes fluid to flow through the each of the sub-chambers at an average rate that substantially tracks a control signal which is delivered to the valve controller.