A small line-size vortex meter comprising a small-diameter flow tube cast with an integral vortex-shedding bar and an external sensor housing. The outer surface of the housing is formed with an approximately circular recess extending towards the flow tube and communicating with the interior of the tube through side-by-side impulse ports located adjacent one end of the vortex-shedding bar. Inserted into the central region of the recess is a sensor body having diaphragms on opposite sides to respond to vortex pressure fluctuations transmitted through the impulse ports to chambers along the sides of the sensor body. The sensor body comprises an oil-filled capsule with the diaphragms serving to transmit the pressure fluctuations to a piezo-electric sensor element which produces corresponding electrical signals.