To provide an improved flow measuring system wherein only a single flow-indicating meter and electrode/magnet assembly may be used to provide accurate flow measurements of fluid flow in a large number of conduits having different internal cross-sectional dimensions.

An apparatus for measuring the rate of flow of a fluid in a conduit 304 includes a receptor assembly 300 arranged on the external surface of the conduit; and a removable external connector assembly 310 including an electromagnet 314 for establishing a magnetic field that extends transversely across the conduit, and a plurality of circumferentially arranged electrodes 320 that are insertable into direct contact at their tips with the fluid in the conduit via sealable gland passages (in openings 334) contained in the receptor assembly. A calibration adjustment arrangement 326 is provided for adjusting the calibration factor of a flow signal processing system as a function of the conduit cross-sectional area.