A FLOW SENSOR AND METHOD FOR MEASURING A FLOW RATE COMPONENT OF A FLUID CONTAINING ELECTRICALLY CHARGED ELEMENTS

摘要

The invention relates to measurement of a fluid flow, wherein a flow rate component of the fluid is measured along a selected direction. A magnetic field whose polarity varies over time is applied to the fluid, which presumed to contain electrically charged elements. First and second sensor electrodes ( 120, 121 ) are arranged to be wetted by the flowing fluid. The electrodes ( 120, 121 ) are spaced apart from one another along a line being substantially perpendicular both to the selected flow direction and a magnetic axis of the magnetic field. A DC-level drift of the sensor electrodes ( 120, 121 ) is prevented by supplying a control current (I_ctrl-0; I_ctrl-1) to each of the sensor electrode ( 120, 121 ), which has such sign and magnitude that a direct-current voltage level at the sensor electrodes ( 120, 121 ) relative areference potential is controled towards a predetermined voltage (DC_set).