Patent ID: 7174256

Claim:
A magnetoinductive flowmeter for measuring the flow volume of a medium travelings through a measuring tube, with a magnet that serves to generate a magnetic field permeating the measuring tube and including a magnetic-field component that extends perpendicular to the direction of flow, with a first measuring electrode and a second measuring electrode for collecting voltage induced in the medium, a reference electrode that is itself in conductive contact with the medium, as well as a preamplifier to which the potentials collected by the two measuring electrodes are fed, wherein a control circuit element is provided for controlling the common-mode input voltage of the preamplifier and/or the potential span of the dynamic range of the preamplifier in such fashion that said common-mode input voltage of the preamplifier corresponds to approximately half the maximum output voltage of the preamplifier, and wherein the control circuit element is connected to the reference electrode for the purpose of controlling the potential of the reference electrode.