Patent ID: 8069719

Claim:
A flow meter for measuring fluid volume comprising: a housing defining a chamber having a fluid inlet and a fluid outlet, the housing comprising a substantially transparent wall; first and second gears installed within the chamber, the first and second gears being rotatable about respective first and second axes of rotation in response to fluid flow through the chamber, wherein at least one of the first and second gears comprises a distinctive optical characteristic on a top surface adjacent to the substantially transparent wall; and an optical sensor located outside of the chamber and configured to detect an optical property of the top surface of the gears through the substantially transparent wall, wherein the first gear is configured to sweep out a first area of rotation, the second gear is configured to sweep out a second area of rotation, and the first area of rotation and the second area of rotation overlap in an intersection area, and wherein the optical sensor is positioned to detect the top surface of the gears within the intersection area without detecting only fluid during rotation of the gears.