| 摘要 |
The invention relates to a magneto-inductive method for determining the flow rate of a medium flowing through a measuring tube in the direction of the measuring tube axis. In order to be able to detect a coating formation on a measuring electrode early and with a high degree of certainty, a test pulse (U<SUB>p</SUB>) of defined pulse length (t<SUB>p</SUB>) is issued to the measuring electrode; at least one signal in response to the test pulse (U<SUB>p</SUB>) is determined at at least two measuring points in time (t<SUB>1</SUB>, t<SUB>2</SUB>), wherein the measuring points in time (t<SUB>1</SUB>, t<SUB>2</SUB>) lie in a time window (t<SUB>end</SUB>-t<SUB>begin</SUB>), which is so selected that no predictable disturbance signals occur on the measuring electrode in this time window (t<SUB>end</SUB>-t<SUB>begin</SUB>). On the basis of the response signal determined in the measuring points in time (t<SUB>1</SUB>, t<SUB>2</SUB>), the relaxation time, or the length of time until the reaching of a predetermined state of discharge (U<SUB>i</SUB>), of the measuring electrode is determined; 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<SUB>i</SUB>), of the measuring electrode, a malfunctioning of the measuring electrode ( 3,4 ) is detected, or becomes detectable.
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