A fluid flow sensor uses lift forces exerted on a plate-like airfoil member
to determine the velocity of a fluid flowing past the sensor. The member
has a pair of spaced, low aspect ratio airfoil elements. A central portion
of the airfoil member is coupled to a frame that positions the airfoil
member in the fluid flow with an angle of attack with respect to the fluid
flow direction. The flowing fluid generates velocity related lift forces
on the airfoil member, the magnitude of which decrease along the airfoil
member from the upstream end to the downstream end. The lift forces so
applied deflect the upstream airfoil element to a greater extent than the
downstream airfoil element. Strain gauges are coupled to the airfoil
elements to detect their deflection. The strain gauges are connected in a
bridge configuration to provide a signal indicative of fluid velocity.