Patent ID: 6634238
Filing Date: 2003-10-21
Classification: G01F

Abstract:
A method of operating an electromagnetic flowmeter having a flow tube connected into a fluid-conveying line, said method comprising the steps of:causing the fluid to flow though the flow tube; causing a first excitation current of predeterminable strength, said first excitation current being generated by means of a measuring and control circuit of the electromagnetic flowmeter, to flow through a first field coil mounted on the flow tube for producing a first partial magnetic field of predeterminable average strength which cuts through the fluid; causing a second excitation current of predeterminable strength, said second excitation current being generated by means of said measuring and control circuit, to flow through a second field coil mounted on the flow tube for producing a second partial magnetic field of predeterminable average strength which also cuts through the fluid; varying the strength of at least one of the excitation currents in such a manner that the average strengths of the two partial magnetic fields are at least temporarily different from each other; reversing the polarity of one of the two excitation currents in such a manner that the two partial magnetic fields are at least temporarily directed opposite to each other while having different average strengths; inducing a voltage in the moving fluid traversed by the two partial magnetic fields for changing potentials applied to measuring electrodes positioned at the flow tube; and picking off potentials applied to the measuring electrodes for producing a measurement signal derived from the voltage induced in the moving fluid.