Patent ID: 7246530

Claim:
A flow sensor for measuring a flow rate component of a fluid containing electrically charged elements, in a selected direction the flow sensor, comprising: a conduit section for transporting the fluid; first and second controllable magnetizing devices arranged substantially opposite to each other in the conduit section wherein a magnetic axis between said first and second magnetizing devices is substantially perpendicular to the selected flow direction of the fluid in the conduit section; a magnet driver configured to control a polarity of a magnetic field between the first and the second magnetizing devices; an electric sensor arrangement including first and second sensor electrodes provided in the conduit section, the first and second sensor electrodes configured to be wetted by the fluid, the first and second sensor electrodes being spaced apart from one another along a line substantially perpendicular to both the selected flow direction and the magnetic axis; and a voltage sensor configured to register a voltage between the first sensor electrode and the second sensor electrode wherein the flow sensor comprises a direct current supply circuit configured to feed first and second control currents (I ctrl-0 ; I ctrl-1 ) to each of the first and second sensor electrodes in the electric sensor arrangement, said first and second control currents (I ctrl-0 ; I ctrl-1 ) each having a sign and a magnitude, wherein said sign and said magnitude cause a direct-current voltage level at the first and second sensor electrodes relative to a reference potential to be controlled toward a predetermined voltage (DC set ).