Patent ID: 7549348

Claim:
A flow meter connectable in-line with a piping system for indicating flow characteristics of a known fluid flowing through the piping system of known internal diameter comprising: a) a flow tube comprising a peripheral wall defining a hollow flow chamber therein and having a fluid inlet at a first end and a fluid outlet at a second end; at least a portion of said flow tube is transparent; b) a piston slidably mounted within said flow chamber and having an indicator associated with said piston; wherein fluid flowing through said flow chamber from said fluid inlet to said fluid outlet acts on said piston to advance said piston toward said fluid outlet and wherein the distance said piston advances toward said outlet end increases with increases in the flow rate of the fluid flowing through said flow chamber; c) a scale including a plurality of scale markings and associated temperature indicia aligned along a longitudinal axis of said flow tube proximate said transparent portion thereof, said scale markings and said associated temperature indicia calibrated to indicate the flow rate through the flow meter that must be obtained for the known fluid at a temperature corresponding to the selected scale marking to obtain a desired flow characteristic of the known fluid flowing through the piping system of known internal diameter at the specified temperature as indicated by alignment of said indicator associated with said piston with said selected scale marking.