Angular momentum mass flowmeter with optical pickoff

Claim 1

A mass rate flowmeter comprising in combination: (a) a flowmeter housing for receiving a stream of fluid whose mass flow rate is to be measured; (b) angularly restrained rotating turbine and impeller elements coaxially mounted within said housing, said turbine and impeller elements being subject to angular displacement in response to the mass rate of flow of the fluid through said housing; (c) optical means fixedly located within said housing at a pickoff position for measuring said angular displacement between said turbine and impeller elements, said optical means including (1) an input optic fiber for directing an incident beam of radiant energy at a surface of one of said turbine and impeller elements, and (2) an output optic fiber for receiving radiant energy reflected from said element surface; and (d) radiant energy beam interrupting means including (1) a single first reference point carried by said element surface for momentarily deflecting the reflected radiant energy from said output optic fiber during movement past said pickoff position with each revolution of said element surface, and (2) a single second reference point carried by the other of said impeller and turbine elements for momentarily blocking said incident radiant energy beam during movement past said pickoff position with each revolution of said other element, (3) whereby the time interval between the moments of movements of said first reference point and said second reference point past said pickoff position during each revolution of said impeller and turbine elements indicates said angular displacement.