Patent ID: 7265544

Claim:
A method for obtaining an interference-free-measurement from a flowmeter, comprising: providing a flowmeter including a measuring tube through which a flowable medium flows; arranging externally on the measuring tube a magnetic arrangement for generating a magnetic field through which the flowable medium passes when flowing through the measuring tube; arranging diametrically at the measuring tube at least two measuring electrodes for detecting the measurement voltage induced by the flowable medium; connecting the at least two measuring electrodes to an interference-voltage eliminating unit; configuring the interference-voltage eliminating unit for eliminating common-mode interference by differentiation; configuring the interference-voltage eliminating unit for eliminating unequal interference voltages by providing comparing means for comparing the current voltage values U+(n) and U−(n) of each individual measuring electrode with the associated preceding voltage value U+(n−1) and U−(n−1); and outputting a measurement for further signal processing only when the comparison produces an equal, essentially proportional change in the voltage values U+(n) to U+(n−1) and U−(n) to U−(n−1) at each measuring electrode ( 4 a : 4 b ), which corresponds to an interference-free measurement.