Abstract: The illustrated embodiment shows helical grooves of tapering cross section in the inner walls of the interfitting ends of the conduit sections for producing a rotation of the fluid as it enters and leaves the space between the annular terminal surface of one conduit end and the confronting interior ledge of the other. Because of the rotation any air bubbles are removed during filling of the conduit. For particularly vigorous rotation the annular terminal surface and/or interior ledge may be formed obliquely to the flow axis.

Abstract: A flow meter particularly for receiving respiratory flows for pulmonary function diagnoses has a perforated piezo-ceramic flow resistance element and transducer in a flow tube for providing a highly-sensitive flow measurement with little resistance to the flow. Electric contact plates abut opposite planar faces of the piezo-ceramic material plate and are spaced apart at the periphery of the piezo-ceramic plate by an insulating disk. Frame members carry the piezo-ceramic plate and electric contact plates and are spaced and protected within a housing of the flow meter by soft, floating seal members. Contact lugs connected to the electric contact plates conduct signals from the meter which are a function of the bending of the piezo-ceramic material plate under the differential flow pressures on an upstream and a downstream side of the piezo-ceramic plate.