Patent ID: 7287435

Claim:
An inductive flow meter for electrically conductive liquids, having a flow channel section ( 1 ) of essentially circular cross section that is electrically insulating at least on its inner side; having at least one pair of electrodes ( 2 , 3 ) that are situated diametrically opposite one another and are electrically coupled to the electrically conductive liquid; and having a magnetic field generation system ( 7 ) that is formed either from a magnetic closed circuit ( 20 ) with a field coil and with pole shoes ( 7 P) that surround the flow channel section ( 1 ) over a specific axial length (b) and at a specific angle of wrap (2φ 0 ), or by a field coil arrangement ( 7 L) that surrounds the flow channel section ( 1 ) over a specific axial length (b) and at a specific angle of wrap (2φ 0 ), and which system generates a magnetic field that penetrates the flow channel interior in the region upstream and downstream of the measuring electrodes ( 2 , 3 ) as well as between the measuring electrodes and is oriented substantially perpendicular to the connecting straight line between the measuring electrodes and perpendicular to the flow channel longitudinal axis (Z), and whose field lines respectively penetrate the flow channel inner wall in a restricted fashion on active area arrangements (Fa, Fb, Fc, Fd, Fe, Ff) that are positioned between the measuring electrodes ( 2 , 3 ) and extend circumferentially in accordance with said angle of wrap (2φ 0 ) and axially in accordance with said axial length (b); characterized in that, in a developed presentation of the flow channel inner wall, bounding straight lines (T 1 , T 2 ) that are laid tangentially against the active area arrangements (Fa, Fb, Fc, Fd, Fe, Ff) and touch the active area arrangements at two points from outside, converge in pairs in the direction of the respective location of the measuring electrodes ( 2 , 3 ), and there are located between the respective two points of contact concave regions (K) in which the boundary lines of the active area arrangements have no points of contact of any sort with the tangential bounding straight lines.