Method for operating a magnetic-inductive flowmeter and magnetic-inductive flowmeter

A method for operating a magnetic-inductive flowmeter, wherein the magnetic-inductive flowmeter includes at least one measuring tube for guiding a flowing medium, at least one magnetic field generating device for generating a magnetic field passing through the measuring tube perpendicular to the direction of flow of the medium, at least one pair of electrodes for tapping an electrical voltage induced in the medium in the measuring tube, and at least one control and evaluation unit, the method comprising:

• recording, using the control and evaluation unit, the electrode signal of the electrode voltage during a magnetic field alignment as measurement data;
• filtering the measurement data by a low-pass filter so that a first low-pass filtered evaluation signal is present;
• determining a first flow parameter from the low-pass filtered evaluation signal, which is compared with a first limit value stored in the control and evaluation unit;
• filtering the measurement data by a high-pass filter so that a high-pass filtered evaluation signal is present;
• determining a second flow parameter from the high-pass filtered evaluation signal, which is compared with a second limit value stored in the control and evaluation unit;
• separately subjecting the low-pass-filtered evaluation signal and the high-pass-filtered evaluation signal to a same evaluation;
• and
• assigning a two-phase flow to the flowing medium if at least one of:
• (i) the first flow parameter exceeds the first limit value;
• and (ii) the second flow parameter exceeds the second limit value.