Patent ID: 6983661

Claim:
An electromagnetic flow sensor for measuring an electrically conductive fluid flowing in a pipe, comprising: a flow tube, designed to be inserted into the pipe, for conducting the fluid, the flow tube being electrically nonconductive at least on a fluid-contacting inner side; an electrode arrangement comprising at least two measuring electrodes disposed on the flow tube for picking up a voltage induced in the fluid; and a magnetic field system likewise disposed on the flow tube, said magnetic field system including at least a saddle-shaped first field coil and at least a saddle-shaped second field coil for producing a magnetic field cutting the fluid during operation of the flow sensor, a ferromagnetic first pole piece for said saddle-shaped first field coil and a ferromagnetic second pole piece for saddle-shaped second field coil for directing the magnetic field towards the fluid, and at least a ferromagnetic first return path, extending around the flow tube upstream of the two field coils, and at least a ferromagnetic second return path, extending around the flow tube downstream of the two field coils, for directing the magnetic field around the flow tube, said ferromagnetic first pole piece being magnetically coupled to said ferromagnetic first return path by means of at least a ferromagnetic first coupling element and to said ferromagnetic second return path by means of at least a ferromagnetic second coupling element, and said ferromagnetic second pole piece being magnetically coupled to said ferromagnetic first return path by means of at least a ferromagnetic third coupling element and to the said ferromagnetic second return path by means of at least a ferromagnetic fourth coupling element, wherein each of said ferromagnetic coupling elements comprises at least one essentially trough-shaped cover segment which receives a first winding section of the respective associated saddlle-shaped field coil, lying essentially on a first periphery of the flow rube, or a second winding section of the respective associated saddle-shaped field coil, lying essentially on a second periphery of the flow tube.