Patent ID: 7340963

Claim:
A method for magneto-inductive determination of flow rate of a medium flowing through a measuring tube in the direction of the measuring tube axis, wherein a magnetic field passes through the measuring tube essentially perpendicularly to the measuring tube axis, a measurement voltage is induced in at least one measuring electrode arranged essentially perpendicularly to the axis of the measuring tube, and the induced measurement voltage delivers information concerning the volume flow of the medium in the measuring tube, the method comprising the steps of: issuing a test pulse (U p ) of a defined pulse length (t p ) to the measuring electrode; determining at least one signal in response to the test pulse (U p ) at at least two measuring points in time (t i , t 2 ); selecting the measuring points in time (t 1 , t 2 ) to lie in a time window (t end -t begin ), which is such that no predictable disturbance signals occur on the measuring electrode in said time window (t end -t begin ); determining the relaxation time (T), or the length of time until reaching of a predetermined state of discharge (U i ), of the measuring electrode on the basis of the response signal determined in the measuring points in time (t 1 ,t 2 ); and detecting a malfunctioning of the measuring electrode on the basis of the determined relaxation time, or on the basis of the length of time until the reaching of the defined state of discharge (U i ), of the measuring electrode.