Coriolis mass flowmeter and method for monitoring a coriolis mass flowmeter

A Coriolis mass flowmeter, comprising:

• at least one oscillatable measuring tube for conveying a medium;
• at least one exciter for exciting bending oscillations of the measuring tube as a function of an excitation signal;
• at least one oscillation sensor for registering the bending oscillations of the at least one measuring tube and for outputting an oscillation dependent sensor signal;
• and
• at least one measuring- and operating circuit for supplying the exciter with an excitation signal and for registering the sensor signal, wherein the measuring- and operating circuit is adapted to perform the following method:
• ascertaining a resonant frequency of a bending oscillation, wanted mode of the Coriolis mass flowmeter;
• ascertaining a density measured value of a medium conveyed in the measuring tube as a function of the resonant frequency;
• exciting a bending oscillation outside of resonance with an excitation signal, which has an excitation signal amplitude and an excitation frequency, which amounts to u times the resonant frequency of the bending oscillation, wanted mode;
• registering a sensor signal and ascertaining a sensor signal amplitude of the bending oscillation outside of resonance;
• ascertaining a value of an integrity function of the measuring tube depending on a ratio of the sensor signal amplitude of the bending oscillation to the excitation signal amplitude of the bending oscillation,
• wherein
• the integrity function depends further on a density dependent term of a transfer function,
• wherein the density dependent term of the transfer function models contributions of a plurality of oscillation modes to the sensor signal, wherein the integrity function by means of the density dependent term of the transfer function is reduced to reference conditions, and/or transformed to an integrity value, which has no cross sensitivities to media density.