Patent ID: 8714027

Claim:
A method for operating a magneto-inductive flow measuring system, wherein the magneto-inductive flow measuring system has a measuring tube, the measuring tube has a lumen for conveying an at least slightly electrically conductive, measured substance, and the magneto-inductive flow measuring system has a first and a second electrode electrically interacting with the measured substance, comprising the steps of: applying an input voltage in a first diagnostic operation, between the first and second electrodes, wherein the input voltage produces an electrical current essentially within the lumen; providing the flow measuring system additionally with a third and a fourth electrode electrically interacting with the measured substance; determining an output voltage falling between the third and fourth electrodes essentially due to the electrical current; determining an input impedance present between the first electrode and the second electrode; and detecting, by means of a relationship formed between the output voltage and the input voltage and/or the input impedance, an accretion in given cases present on an inner wall of the measuring tube and/or on the first, second, third and/or fourth electrode, especially one deposited from the measured substance; wherein: a thickness (ε) of the accretion and/or a ratio K of the conductivity of the measured substance to the conductivity of the accretion are determined, especially determined by means of said relationship; and by means of the output voltage, a state of the flow measuring system and/or a chemical and/or physical property of the measured substance is determined.