A vibronic sensor (1) comprises: an oscillator (10) with at least one first measuring tube (10.1, 10.2; 20.1, 20.2; 30.1, 30.2) for guiding a medium; a first electrodynamic
exciter (15; 25; 35) for exciting the oscillator (10) to bending vibrations of the at least one first measuring tube (10.1, 10.2; 20.1, 20.2; 30.1, 30.2), wherein the first electrodynamic
exciter (15; 25; 35) comprises a first
excitation coil (15.1; 25.1; 35.1) and a first excitation
magnet (15.2; 25.2; 35.2); which cooperate to excite the bending vibrations; at least one second electrodynamic
exciter (18; 28, 29; 38) for exciting the oscillator (10) to bending vibrations of the at least one first measuring tube (10.1, 10.2; 20.1, 20.2; 30.1, 30.2); wherein the at least one second electrodynamic exciter (18; 28, 29; 38) includes at least one second
excitation coil (18.1; 28.1, 28.2; 38.1) and at least one second excitation
magnet (18.2; 28.2,29.2; 38.2) comprises; which cooperate to excite the bending vibrations; at least one inlet-side electrodynamic sensor arrangement (12a) for detecting the bending vibrations of the at least one first measuring tube (10.1, 10.2; 20.1, 20.2; 30.1, 30.2); and at least one outlet-side electrodynamic sensor arrangement (12b) for detecting the bending vibrations of the at least one first measuring tube (10.1, 10.2; 20.1, 20.2; 30.1, 30.2); a measuring and operating circuit configured to drive the electrodynamic exciters with excitation signals; and to detect sensor signals from the electrodynamic sensor arrangements in order to determine a
mass flow
rate measurement and / or a density measurement, as well as to determine a value of a monitoring parameter which depends on a state of the measuring tube; characterized in that the first excitation
magnet comprises a first hard magnetic material,and the second excitation magnet comprises a second hard magnetic material, wherein the first hard magnetic material is stronger and less stable over the long term at high temperatures than the second hard magnetic material, wherein the measuring and operating circuit is configured to drive the first electrodynamic exciter with an
excitation current of a first excitation frequency corresponding to a
natural frequency of a
bending vibration of the at least one measuring tube, to drive the second electrodynamic exciter with an
excitation current of a second excitation frequency which causes an excitation of a
bending vibration of the measuring tube out of
resonance, to determine the
mass flow rate and / or the density value based on the vibrations of the at least one measuring tube at the first excitation frequency, and to determine the value of the monitoring parameter based on the vibrations of the measuring tube at the second excitation frequency.