Abstract: A flowmeter with a main conduit having a constriction formed therein through which a main flow passes, and a by-pass conduit which is in fluid connection with the main conduit upstream and downstream of the constriction and in which a by-pass flow passes in response to a pressure drop across the constriction. The constriction includes a conical body which is movable within the main conduit to produce an increasing flow area in response to an increasing pressure drop across the constriction. A by-pass flowmeter is provided in the by-pass conduit which produces signals in proportion to a by-pass flow through the by-pass conduit. A calibrated electronic signal converter converts signals produced by the by-pass flowmeter to signals which correspond to the total flow through the main conduit.