Apparatus for sensing movement of an object relative to a fluid

An apparatus for sensing movement of a moving object moving relative to a fluid, the apparatus comprising:

• a housing fixed relative to and having a cover flush with a fluid-engaging surface of the moving object and not projecting from the fluid-engaging surface into the fluid;
• a spring held in the housing inward of a surface of the housing and having a plurality of elastically deformable blades together defining a plane substantially parallel to the fluid-engaging surface and each having an outer end fixed to the housing and an inner end;
• a hub connected to the inner ends of the blades of the spring;
• respective strain gauges on the blades;
• and
• a rigid pin mounted on the hub of the spring, extending perpendicular to the plane through the cover, and projecting from the fluid-engaging surface of the moving object into the fluid such that a transverse force exerted by the fluid on the pin deflects the pin and thereby deforms the blades and the strain gauges and measurably affects an electrical property of the strain gauges.