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VIBRONIC MEASURING SYSTEM

20230341246 · 2023-10-26

    Inventors

    Cpc classification

    International classification

    Abstract

    A measuring system includes a vibration-type transducer including a tube and measuring system electronics electrically coupled to a vibration exciter and a sensor assembly, wherein at a drive point, the vibration exciter is positioned such that a drive offset is no more than 3 mm and/or less than 0.5% of the tube length, and wherein a vibration node of a second or higher order, lies within the reference cross-sectional area, and wherein the measuring system electronics is configured to both provide a drive signal with a sinusoidal current having a frequency such that the frequency deviates from a resonant frequency of a vibration mode of a second order naturally intrinsic to the tube by less than 1% of the resonant frequency and/or by less than 1 Hz, and to perform a self-diagnosis of the measuring system based on a corresponding signal component of at least one vibration measurement signal.

    Claims

    1-59. (canceled)

    60. A vibronic measuring system for measuring and/or monitoring at least one measured variable, which is at least one of a mass flow, a volumetric flow, a flow rate, a density and a viscosity of a flowing measured substance, which measured substance is a gas, a liquid or a dispersion, the measuring system comprising: a transducer comprising: a tube assembly configured to conduct the measured substance; an exciter assembly configured to convert electrical power into mechanical power as to excite and maintain forced mechanical vibrations of the tube assembly; a sensor assembly configured to detect mechanical vibrations of the tube assembly and to generate vibration measurement signals respectively representing vibration movements of the tube assembly; and an electronics unit electrically coupled to the transducer, including the exciter assembly and the sensor assembly, via electrical connecting lines and configured to control the transducer and to evaluate the vibration measurement signals generated by the transducer, wherein the electronics unit includes at least one microprocessor, wherein the tube assembly includes a first tube that is at least sectionally curved and/or at least sectionally straight, which first tube: extends from a first tube end to a second tube end with a tube length of greater than 100 mm; includes a lumen defined by a tube wall that extends from the first tube end to the second tube end; and is configured to be flowed through by the measured substance at least in a flow direction from the first tube end to the second tube end, wherein, inherent in the first tube, is a plurality of vibration modes respectively having a corresponding resonance frequency, in which modes the first tube can perform or performs vibration movements respectively having one or more vibration antinodes and two or more vibration nodes, such that the vibration movements of the first tube in a fundamental, first order vibration mode have exactly one vibration antinode and two vibration nodes and such that vibration movements of the first tube in a harmonic, second order or higher order vibration mode have two or more vibration antinodes and three or more vibration nodes, wherein the exciter assembly includes an electrodynamic vibration exciter mechanically connected to the first tube and configured to convert electrical power with a time-variable electrical current into mechanical power such that, at a drive point of the vibration exciter on the first tube mechanically connected thereto, a time-variable drive force acts on the first tube such that a line of action of the drive force is perpendicular to a normal of a drive cross-sectional area of the first tube, wherein the vibration exciter is positioned and aligned such that a drive offset, which is a smallest distance between the drive cross-sectional area of the first tube enclosed by an imaginary circumferential line of the first tube passing through the drive point, and a specified reference cross-sectional area of the first tube is not more than 3 mm and/or less than 0.5% of the tube length, viz. especially less than 0.2% of the tube length, viz. especially is equal to zero with an intact or original transducer, wherein a vibration node, formed between two vibration antinodes of vibration movements of the first tube in a second order or higher-order vibration mode, deviating from the first order vibration mode, of the vibration movements is within the reference cross sectional area, wherein the electronics unit is configured to energize the vibration exciter via electrical power fed into the vibration exciter via an electrical drive signal having a time-variable electrical current such that the first tube performs forced mechanical, flexural vibrations at one or more vibration frequencies specified by the drive signal, wherein the sensor assembly includes: an electrodynamic or optical first vibration sensor, which is positioned on the first tube and at least partially mechanically connected to the first tube at a distance from the vibration exciter of more than 10 mm and/or more than one fifth of the tube length in the flow direction, wherein the first vibration sensor is configured to detect and convert vibration movements of the first tube into a first vibration measurement signal representing the vibration movements, which first vibration measurement signal is an electrical or optical signal, such that the first vibration measurement signal contains one or more sinusoidal signal components respectively having a frequency corresponding to a vibration frequency of vibration movements of the first tube; and an electrodynamic or optical second vibration sensor, which is positioned on the first tube and at least partially mechanically connected to the first tube at a distance from the vibration exciter of more than 10 mm and/or more than one fifth of the tube length in the flow direction, wherein the second vibration sensor is configured to detect and convert vibration movements of the first tube into a second vibration measurement signal representing the vibration movements, which second vibration measurement signal is an electrical or optical signal, such that the second vibration measurement signal contains one or more sinusoidal signal components respectively having a frequency corresponding to a vibration frequency of vibration movements of the first tube, wherein the electronics unit is configured to receive and evaluate the first and second vibration measurement signals so as to determine and output measured values representing the at least one measured variable, wherein the electronics unit is further configured to: provide the drive signal at least intermittently with a sinusoidal first current having a first frequency such that: the first tube predominantly performs at least partially first used vibrations, viz. mechanical vibrations forced by the energized vibration exciter at a first used frequency, viz. a vibration frequency corresponding to the first frequency, such that the first used frequency deviates from a first resonance frequency, which is a resonant frequency of the fundamental vibration mode, by less than 1% of the first resonance frequency and/or by less than 1 Hz, and/or such that the first used frequency deviates from a second resonance frequency, which is a resonant frequency of the second-order vibration mode, by more than 5% of the second resonance frequency and/or by more than 10 Hz, and/or such that the first used vibrations are suitable for causing, in the flowing measured substance, Coriolis forces that depend upon the mass flow; and each of the first and second vibration signals respectively includes a first signal component, viz. a sinusoidal signal component having a signal frequency corresponding to the first used frequency; and determine measured values representing the at least one measured variable, including mass-flow measured values representing a mass flow of the measured substance and/or density measured values representing a density of the measured substance, based upon at least one of: the signal frequencies of the first signal components; an amplitude of at least one of the first signal components; and a phase angle of at least one of the first signal components, wherein the electronics unit is further configured: during a test interval that lasts more than 10 millisecond (ms) and/or is time-limited and/or recurrently started, to provide the drive signal at least intermittently with a sinusoidal second current having a second frequency such that: the second frequency, for two or more vibration periods and/or a period of more than 10 ms, deviates from the second resonance frequency of the second order vibration mode by less than 1% of the second resonance frequency and/or by less than 1 Hz; and the first tube at least partially performs, simultaneously with the first used vibrations and/or stationarily, viz. for two or more vibration periods and/or a period of more than 10 ms with a constant non-zero vibration amplitude, second used vibrations, viz. mechanical vibrations forced by the vibration exciter at a second used frequency, viz. a frequency corresponding to the second frequency, whereby each of the first and second vibration signals respectively includes a second signal component, viz. a sinusoidal signal component having a signal frequency corresponding to the second used frequency; and to perform a self-diagnosis of the measuring system, viz. checking a functionality of the measuring system and/or calibrating the measuring system and/or determining whether a fault of the measuring system is present, based on at least one of: the signal frequency at least one of the two second signal components; an amplitude of at least one of the two second signal components; and a phase angle of at least one of the two second signal components.

    61. The measuring system according to claim 60, wherein the first used frequency deviates from the first resonance frequency of the fundamental vibration mode by less than 1% of the first resonance frequency and/or by less than 1 Hz.

    62. The measuring system according to claim 60, wherein the first used frequency deviates from a third resonance frequency, which is a resonant frequency of a third-order vibration mode inherent in the first tube, viz. a third-order flexural vibration mode, in which vibration mode the vibration movements of the first tube have exactly three vibration antinodes and two vibration nodes, by less than 1% of the third resonance frequency and/or by less than 1 Hz, viz., especially corresponds to the resonance frequency, fr3.

    63. The measuring system according to claim 62, wherein a first vibration node of vibration movements of the first tube in the third-order vibration mode is located in the first tube end, and wherein a second vibration node of the third-order vibration mode is located in the second tube end.

    64. The measuring system according to claim 60, wherein the harmonic mode corresponds to a second-order vibration mode, viz., a second-order flexural vibration mode, in which second-order vibration mode the vibration movements of the first tube have exactly two vibration antinodes and three vibration nodes.

    65. The measuring system according to claim 64, wherein a vibration node, formed between two vibration antinodes of the vibration movements of the first tube in a second-order vibration mode, which is located at half the tube length, of the vibration movements is within the reference cross-sectional area; and/or wherein a main inertia axis of the first tube, which is perpendicular to the vibration direction of the vibration movements of the first tube in the second-order vibration mode, is within the reference cross-sectional area of the at least one tube.

    66. The measuring system according to claim 60, wherein at least one of: the drive offset corresponds to a distance between an area centroid of the drive cross-sectional area of the first tube and an area centroid of the reference cross-sectional area of the first tube; a line of action of the drive force is perpendicular to a normal of a drive cross-sectional area of the first tube; an intersection line of two, mutually orthogonal symmetry planes of the first tube is within the reference cross-sectional area; and a main inertia axis of the first tube, which is perpendicular to the drive force, is within the reference cross-sectional area of the first tube.

    67. The measuring system according to claim 60, wherein the electronics unit is configured to provide at least intermittently the second current of the drive signal simultaneously with the first current, such that an amplitude of the first current is adjusted to not be less than an amplitude of the second current and/or such that an amplitude of the second current is adjusted to more than 40% of an amplitude of the first current; and/or wherein the electronics unit is configured to adjust the second frequency as a function of the first frequency such that the second frequency is within a frequency setting interval, of which an upper interval limit and/or a lower interval limit and/or a center frequency corresponds to a specified multiple of the first frequency, wherein the specified multiple is a multiple of the first frequency corresponding to more than 230% of the first frequency and/or less than 300% of the first frequency.

    68. The measuring system according to claim 60, wherein the electronics unit includes a digital first phase-locked loop configured to adjust the first frequency and a digital second phase-locked loop configured to adjust the second frequency.

    69. The measuring system according to claim 68, wherein the electronics unit is configured to adjust a capture range of the second phase-locked loop using an output signal of a loop filter of the first phase-locked loop and/or based upon the first frequency.

    70. The measuring system according to claim 60, wherein the electronics unit is configured to perform the self-diagnosis of the measuring system to do at least one of: determine whether and/or to what extent a fault of the measuring system is present, which fault causes at least one of: reduces a functionality of the measuring system; causes a malfunction of the measuring system; reduces an integrity of at least one of the first and second vibration measurement signals or of measured values obtained therefrom; and causes a measurement error of measured values obtained therefrom; determine whether or to what extent the tube assembly is damaged in comparison to a reference state determined in advance; determine whether and/or to what extent a fault of the measuring system is present due to one or more vibration properties of the tube assembly that are changed, in comparison to a reference state determined therefor in advance, due to damage to the tube assembly; determine whether and/or to what extent damage to the tube assembly is present due to erosion on an inner side, facing the lumen, of the tube wall and/or due to a formation of deposits on the inner side of the tube wall; and determine whether and/or to what extent a measurement error is present in the determination of the measured values due to damage to the tube assembly.

    71. The measuring system according to claim 60, wherein the electronics unit is configured to perform the self-diagnosis of the measuring system to determine whether a present fault of the measuring system can be ascribed to an irreversible change of one or more flow properties of the tube assembly due to a reduction in a flow cross-section of the tube assembly due to a blockage of one or more tubes of the tube assembly and/or due to a deposit on an inner side of the tube wall of one or more tubes; and/or wherein the electronics unit is configured to perform the self-diagnosis of the measuring system to determine whether a present fault of the measuring system can be ascribed to an irreversible change of one or more vibration properties of the tube assembly due to at least one of: a reduction in a wall thickness of the tube wall of one or more tubes; a plastic deformation of one or more tubes; a deposit on the inner side of the tube wall of one or more tubes; and a crack in the tube wall of one or more of the tubes.

    72. The measuring system according to claim 60, wherein the electronics unit is configured to determine at least one of: a modal deflection of the first used vibrations corresponding to a difference of the signal amplitudes of the first signal components by determining, based upon at least one of the vibration measurement signals, deflection values representing the modal deflection of the first useful vibrations; the modal deflection of the first used vibrations corresponding to a difference of the signal amplitudes of the second signal components by determining, based upon at least one of the vibration measurement signals, deflection values representing the deflection of the second used vibrations; and a deflection ratio corresponding to a ratio of the modal deflection of the first used vibrations and the modal deflection of the second used vibrations by determining, based upon at least one of the vibration measurement signals, deflection ratio values representing the deflection ratio.

    73. The measuring system according to claim 60, wherein the electronics unit is configured to determine at least one of: a modal damping of the first used vibrations corresponding to a ratio of the signal amplitude of one of the first signal components, or of a sum or a difference of the signal amplitudes of the first signal components, and a signal amplitude of the first current by determining, based upon the drive signal and at least one of the vibration measurement signals, damping values representing the damping of the first used vibrations; a modal damping of the second used vibrations corresponding to a ratio of the signal amplitude of one of the second signal components, or a sum or a difference of the signal amplitudes of the second used signal components, and a signal amplitude of the second current by determining, based upon the drive signal and at least one of the vibration measurement signals, damping values representing the damping of the second used vibrations; and a damping ratio corresponding to a ratio of the modal damping of the first used vibrations and the modal damping of the second used vibrations by determining, based upon the drive signal and/or at least one of the vibration measurement signals, damping ratio values representing the damping ratio.

    74. The measuring system according to claim 60, wherein the electronics unit is configured to determine, based upon the drive signal and at least one of the vibration measurement signals, damping values representing a modal damping of the second used vibrations by comparing one or more of the damping values to a damping reference value determined in advance.

    75. The measuring system according to claim 74, wherein, for performing the self-diagnosis of the measuring system, the electronics unit is configured to, at least one of: compare one or more of the damping values to the damping reference value determined in advance or via an intact measuring system and, in case of a deviation of one or more of the damping values from the damping reference value, to output a fault alarm message representing the deviation; determine, based upon several of the damping values, at least one of a change trend, a change rate, and a change velocity of the damping of the second used vibrations as to determine an increasing fault with decreasing damping of the second used vibrations and/or to output a fault alarm message representing an increase of a fault; and determine and output a scatter measure, viz. an empirical variance and/or a span, for the damping of the second used vibrations of the first tube and/or to compare the scatter measure to one or more damping reference values specified therefor.

    76. The measuring system according to claim 60, wherein at least one of: the electronics unit is configured to determine the resonance frequency of the first vibration mode of the first tube, viz to determine, based upon the drive signal and/or at least one of the vibration measurement signals, frequency values representing the resonance frequency; the electronics unit is configured to determine the resonance frequency of the second vibration mode of the first tube, viz., to determine, based upon the drive signal and/or at least one of the vibration measurement signals, frequency values representing the resonance frequency; and the electronics unit is configured to determine a resonance frequency ratio corresponding to a ratio of the resonance frequency of the first vibration mode and the resonance frequency of the second vibration mode, viz., to determine, based upon the first and second frequencies of the drive signal and/or based upon the signal frequencies of the first and second signal components of at least one of the vibration measurement signals, frequency ratio values representing the resonance frequency ratio.

    77. The measuring system according to claim 60, wherein the electronics unit is configured to determine, based upon the drive signal and/or at least one of the vibration measurement signals, frequency values representing the resonance frequency of the second vibration mode, viz., to compare one or more of the frequency values to one or more reference values specified therefor, and/or to use several of the frequency values to determine a scatter measure for the resonance frequency of the second vibration mode.

    78. The measuring system according to claim 77, wherein the electronics unit is configured to determine and to output, based upon a plurality of frequency values, a scatter measure for the resonance frequency of the second vibration mode and/or, for performing the self-diagnosis of the measuring system, to compare the scatter measure to a reference value specified therefor and, in the case of a deviation of the scatter measure from the reference value, to output a message representing the deviation.

    79. The measuring system according to claim 78, wherein the electronics unit is configured to determine, based upon the drive signal and/or at least one of the vibration measurement signals, frequency ratio values representing a ratio of the resonance frequency of the first vibration mode and the resonance frequency of the second vibration mode, viz., to compare one or more of the frequency ratio values to one or more reference values specified therefor, and/or to use several of the frequency ratio values to determine a scatter measure for the resonance frequency ratio of the first tube.

    80. The measuring system according to claim 79, wherein: the electronics unit is configured, for performing the self-diagnosis of the measuring system, to compare one or more of the frequency ratio values to at least one frequency ratio reference value determined therefor in advance, and to output, in the case of a deviation of one or more of the frequency ratio values from the frequency ratio reference value, a message representing the deviation declared as a fault alarm; and/or the electronics unit is configured to determine, based upon a plurality of frequency ratio values, and to output, a scatter measure of an empirical variance and/or a span, for the resonance frequency ratio of the first tube and/or, for performing the self-diagnosis of the measuring system, to compare the scatter measure to a reference value specified therefor and, in the case of a deviation of the scatter measure from the reference value, to output a message representing the deviation.

    81. The measuring system according to claim 60, wherein the electronics unit is configured to determine, based upon the vibration measurement signals, phase difference values representing a phase difference of the second signal components, viz., a difference between a phase angle of the second signal component of the first vibration measurement signal and a phase angle of the second signal component of the second vibration measurement signal, viz., to compare one or more of the phase difference values to a phase difference reference value determined therefor in advance and/or to use several phase difference values to determine a scatter measure for the phase difference of the second signal components.

    82. The measuring system according to claim 81, wherein: the electronics unit is configured, for performing the self-diagnosis of the measuring system, to compare one or more of the phase difference values to at least one phase difference reference value determined therefor in advance, and to output, in the case of a deviation of one or more of the phase difference values from the phase difference reference value, a message representing the deviation as a message declared as a fault alarm; and/or the electronics unit is configured to determine, based upon a plurality of phase difference values, and to output, a scatter measure of an empirical variance and/or a span, for the phase difference of the second signal component and/or, for performing the self-diagnosis of the measuring system, to compare the scatter measure to a reference value specified therefor and, in the case of a deviation of the scatter measure from the reference value, to output a message representing the deviation.

    83. The measuring system according to claim 60, wherein the electronics unit is configured to determine, based upon at least one of the vibration measurement signals, deflection ratio values representing a ratio of the deflections of the first used vibrations and the deflections of the second used vibrations, viz., to compare one or more of the deflection ratio values to one or more reference values specified therefor, and/or to use several of the deflection ratio values to determine a scatter measure for the deflection ratio of the first tube.

    84. The measuring system according to claim 83, wherein: the electronics unit is configured, for performing the self-diagnosis of the measuring system, to compare one or more of the deflection ratio values to at least one deflection ratio reference value determined therefor in advance, and to output, in the case of a deviation of one or more of the deflection ratio values from the deflection ratio reference value, a message representing the deviation as a message declared as a fault alarm; and/or the electronics unit is configured to determine, based upon a plurality of deflection ratio values, and to output, a scatter measure of an empirical variance and/or a span, for the deflection ratio of the first tube and/or, for performing the self-diagnosis of the measuring system, to compare the scatter measure to a reference value specified therefor and, in the case of a deviation of the scatter measure from the reference value, to output a message representing the deviation.

    85. The measuring system according to claim 60, wherein the electronics unit is configured to provide the second current with a specified current amplitude.

    86. The measuring system according to claim 60, wherein the electronics unit is configured, for performing the self-diagnosis of the measuring system, to recurrently compare the signal amplitude of at least one of the second signal components to an amplitude reference value dependent upon the signal amplitude of the second current and/or specified therefor, viz., a reference value corresponding to a signal amplitude of the at least one second signal component determined at the specified current amplitude of the second current, viz., to determine whether or to what extent the signal amplitude deviates from the amplitude reference value.

    87. The measuring system according to claim 60, wherein: the first signal components of the first and second vibration measurement signals follow a change in a mass flow of the measured substance conducted in the first tube with a change in a phase difference of the first signal components, viz., a difference between a phase angle of the first signal component of the first vibration measurement signal and a phase angle of the first signal component of the second vibration measurement signal; and the electronics unit is configured to generate, based upon the phase difference of the first signal components, mass-flow measured values representing the mass flow.

    88. The measuring system according to claim 81, wherein the electronics unit is configured, for performing the self-diagnosis of the measuring system, to check or to calibrate, based upon the second signal components of at least one of the vibration measurement signals, viz., based upon a phase angle of at least one of the second signal components and/or based upon a phase difference of the second signal components, a mass-flow-to-phase-difference characteristic curve function of the transducer, according to which the phase difference of the first signal components depends upon the mass flow, and/or a mass-flow-to-measured-value characteristic curve function of the measuring system, according to which mass-flow measured values determined based upon the phase difference of the first signal components depend upon the mass flow.

    89. The measuring system according to claim 88, wherein the electronics unit is configured, for performing the self-diagnosis of the measuring system, to check the mass-flow-to-phase-difference characteristic curve function of the transducer, viz., a scale zero point of the mass-flow-to-phase-difference characteristic curve function, based upon a phase difference of the second signal components, viz., a difference between a phase angle of the second signal component of the first vibration measurement signal and a phase angle of the second signal component of the second vibration measurement signal, viz., to determine whether or to what extent a drift of the mass-flow-to-phase-difference characteristic curve function is present.

    90. The measuring system according to claim 89, for performing the self-diagnosis of the measuring system, for checking a scale zero point of the mass-flow-to-phase-difference characteristic curve function of the transducer, which corresponds to a phase difference of the first signal components measured when the measured substance is at rest or to a mass-flow measured value determined when the measured substance is at rest, and/or a measurement sensitivity, which corresponds to a change in the phase difference of the first signal components related to a change in the mass flow, viz., for determining whether and to what extent an irreversible change in the scale zero point is present.

    91. The measuring system according to claim 60, wherein: the electronics unit is configured to follow a change in a density of the measured substance conducted in the first tube with a change in the first frequency of the drive signal; and the electronics unit is configured to generate, based upon the first frequency of the drive signal and/or based upon the signal frequency of the first signal component of at least one of the vibration signals, density measured values representing the density.

    92. The measuring system according to claim 60, wherein the electronics unit is configured, for performing the self-diagnosis of the measuring system, to calculate, based upon the second signal components of at least one of the vibration measurement signals, viz., based upon the signal frequency thereof, and/or based upon a signal amplitude of at least one of the second signal components and/or based upon a phase angle of at least one of the second signal components, one or more characteristic number values for at least one measuring system characteristic number, which characterizes an operating state of the measuring system such that the measuring system characteristic number depends upon one or more parameters of a system function of the measuring system provided between the second current component of the drive signal and the second signal component of the at least one vibration measurement signal.

    93. The measuring system according to claim 92, wherein the electronics unit is configured, for performing the self-diagnosis of the measuring system, to respectively compare one or more characteristic number values for the measuring system characteristic number to one or more reference values determined for the measuring system characteristic number, by a manufacturer of the measuring system and/or during the production and/or a start-up of the measuring system and/or as a function of the drive signal, viz., one or more reference values representing a reduced functionality of the transducer and/or one or more reference values representing a malfunction of the transducer and/or one or more reference values representing a defective transducer, viz., to evaluate and/or quantify a deviation of one or more of the characteristic number values from one or more of the reference values.

    94. The measuring system according to claim 93, wherein the electronics unit is configured to determine a condition of whether one or more characteristic number values for the measuring system characteristic number are greater than the at least one reference value for the measuring system characteristic number, viz., when one or more characteristic number values for the measuring-system characteristic number are greater than one or more reference values representing a reduced functionality of the transducer and/or greater than one or more reference values representing a malfunction of the transducer and/or greater than one or more reference values representing a no longer intact transducer, to output a message representing the condition, wherein the message is declared as a fault alarm.

    95. The measuring system according to claim 92, wherein the electronics unit includes a non-volatile electronic data memory configured to store digital data without an applied operating voltage, viz., to store one or more reference values determined in advance for the measuring system characteristic number.

    96. The measuring system according to claim 95, wherein one or more reference values, determined in advance by a manufacturer of the measuring system and/or during production of the measuring system and/or during operation of the measuring system, for the measuring system characteristic number, viz., one or more reference values representing a reduced functionality of the transducer, and/or one or more reference values representing a malfunction of the transducer, are stored in the electronic data memory.

    97. The measuring system according to claim 96, wherein the electronics unit is configured to respectively compare one or more characteristic number values for the measuring system characteristic number to one or more reference values, stored in the data memory, for the measuring system characteristic number.

    98. The measuring system according to claim 60, wherein the electronics unit is configured to provide the drive signal with the second current during a test interval lasting more than 10 ms and/or is time-limited and/or recurrently started, such that the second current is non-volatile or stationary, viz., for two or more vibration periods and/or a period of more than 10 ms, has a substantially constant, non-zero amplitude.

    99. The measuring system according to claim 98, wherein at least one of: the electronics unit is configured to determine during the test interval, based upon the second signal components, viz., based upon the signal frequency and/or signal amplitude of at least one of the second signal components and/or based upon a phase angle of at least one of the second signal component, measured values representing the at least one measured variable; the test interval lasts for more than 100 ms; the electronics unit is configured to automatically, in a time-controlled manner, start and/or end the test interval, recurrently; and the electronics unit is configured to receive and execute one or more commands that start the test interval.

    100. The measuring system according to claim 60, wherein the tube wall comprises a stainless steel, a duplex steel, or a super duplex steel, of a titanium alloy and/or a zirconium alloy and/or a tantalum alloy.

    101. The measuring system according to claim 60, wherein the first tube has an inner tube diameter caliber of more than 0.1 millimeters (mm).

    102. The measuring system according to claim 101, wherein at least one of: the first tube has a caliber-to-tube-length ratio that is more than 0.08 and/or less than 0.25; the tube length of the first tube is more than 200 mm and/or less than 2,000 mm; and the first tube has a caliber greater than 10 mm.

    103. The measuring system according to claim 60, wherein at least one of: aside from the vibration exciter, the exciter assembly does not include any other vibration exciter connected to the first tube; the vibration exciter is positioned and aligned such that the drive offset is less than 0.5 mm or such that the area centroid of the drive cross-sectional area of the first tube corresponds to or coincides with the drive reference point; each of the first-order and second-order vibration modes of the first tube respectively includes a first vibration node located in the first tube end of the at least one tube and a second vibration node located in the second tube end of the at least one tube; the first tube is curved sectionally in the shape of a circular arc, and/or in a V-shape, such that the first tube includes a central vertex arc segment and/or such that exactly one main inertia axis of the first tube is within the reference cross-sectional area of the first tube; and the first tube is straight sectionally such that the three main inertia axes of the first tube are within the reference cross-sectional area of the first tube, and/or a center of mass is within the reference cross-sectional area of the first tube.

    104. The measuring system according to claim 60, wherein the tube assembly includes a second tube, which is at least sectionally curved and/or at least sectionally straight, and/or is structurally identical to the first tube and/or is at least sectionally parallel to the first tube.

    105. The measuring system according to claim 104, wherein: the second tube extends with a tube length from a first tube end to a second tube end and includes a lumen, which is enclosed by a metallic tube wall, which extends from the first tube end to the second tube end; and the second tube is configured to be flowed through by measured substance at least in the flow direction from the first tube end to the second tube end, simultaneously with the first tube while enabled to vibrate.

    106. The measuring system according to claim 104, wherein a plurality of vibration modes respectively having an associated resonance frequency are inherent in the second tube, in which modes the second tube performs vibration movements respectively having one or more vibration antinodes and two or more vibration nodes, such that vibration movements of the second tube in the second-order vibration mode are in opposition to the vibration movements of the first tube in the second-order vibration mode, and/or such that vibration movements of the second tube in the first-order vibration mode are in opposition to the vibration movements of the first tube in the first-order vibration mode.

    107. The measuring system according to claim 106, wherein: a resonance frequency of the first-order vibration mode of the first tube is equal to a resonance frequency of the first-order vibration mode of the second tube; and a resonance frequency of the second-order vibration mode of the first tube is equal to a resonance frequency of the second-order vibration mode of the second tube.

    108. The measuring system according to claim 104, wherein: the first vibration sensor is disposed both on the first tube and on the second tube, viz., mechanically connected both partially to the first tube and partially to the second tube; and the first vibration sensor is configured to differentially detect vibration movements in opposition, both of the first tube and of the second tube, and to convert the vibration movements into the first vibration measurement signal such that the vibration measurement signal represents vibration movements in opposition of the first and second tubes.

    109. The measuring system according to claim 104, wherein: the second vibration sensor is disposed both on the first tube and on the second tube, viz., mechanically connected both partially to the first tube and partially to the second tube; and the second vibration sensor is configured to differentially detect vibration movements in opposition, both of the first tube and of the second tube, and to convert the vibration movements into the second vibration measurement signal such that the vibration measurement signal represents vibration movements in opposition of the first and second tubes.

    110. The measuring system according to claim 104, wherein: the tube assembly includes an inlet-side flow divider configured as a line-branching unit and including at least two flow openings; and the tube assembly includes an outlet-side flow divider, which is structurally identical to the first flow divider and/or configured as a line-merging unit including at least two flow openings.

    111. The measuring system according to claim 110, wherein each of the first and second tubes of the tube assembly is respectively connected to each of the first and second flow dividers as to form fluidically parallel flow channels, such that: the first tube opens with its first tube end into a first flow opening of the first flow divider and with its second tube end into a first flow opening of the second flow divider; and the second tube opens with its first tube end into a second flow opening of the first flow divider and with its second tube end into a second flow opening of the second flow divider.

    112. The measuring system according to claim 104, wherein the vibration exciter is mechanically connected both partially to the first tube and partially to the second tube.

    113. The measuring system according to claim 104, wherein at least one of: the vibration exciter is configured to act differentially on the first and second tubes, such that the first and second tubes simultaneously perform opposite, forced mechanical vibrations of equal frequency; the vibration exciter is configured to convert electrical power with a time-variable electrical current into mechanical power such that a time-variable drive force acts on the second tube at a drive point formed by the vibration exciter on the second tube mechanically connected thereto, viz. simultaneously and/or oppositely to the drive force acting on the first tube at the drive point formed by the vibration exciter on the first tube mechanically connected thereto; and the vibration exciter is configured to simultaneously convert electrical power fed by the electrical drive signal into forced mechanical vibrations of the first and second tubes, such that the first and second tubes simultaneously perform forced mechanical vibrations at the first frequency and/or at the second frequency.

    114. The measuring system according to claim 60, wherein: the vibration exciter includes a vibration coil having an air coil and an armature; and/or each of the first and second vibration sensors is respectively includes a plunger coil having an air coil and an armature.

    115. The measuring system according to claim 60, wherein the vibration exciter includes a magnetic armature, including a permanent magnet and a coil flooded by the magnetic field of the armature, viz., an air coil.

    116. The measuring system according to claim 115, wherein: the magnetic armature is mechanically connected to the first tube to form the drive point; and/or the coil is electrically connected to the electronics unit and is configured to receive the drive signal and to conduct the first and second currents thereof.

    117. The measuring system according to claim 60, further comprising an electronics protective housing configured for the electronics unit, which electronics protective housing is fastened to a transducer protective housing of the transducer and/or is metallic.

    118. The measuring system according to claim 60, further comprising a metallic transducer protective housing, wherein the transducer protective housing and tube assembly are fastened to one another detachably.

    Description

    [0088] Shown in detail are:

    [0089] FIG. 1 a perspectival side view of an exemplary embodiment of a vibronic measuring system;

    [0090] FIG. 2 a schematic, in the manner of a block diagram, of an exemplary embodiment of a vibration-type transducer suitable for a vibronic measuring system according to FIG. 1, and a measuring system electronics unit electrically coupled thereto;

    [0091] FIG. 3 a schematic, in the manner of a block diagram, of a further exemplary embodiment of a vibration-type transducer suitable for a vibronic measuring system according to FIG. 1, and a measuring system electronics unit electrically coupled thereto;

    [0092] FIG. 4a a schematic of a tube assembly of a vibration-type transducer suitable for a vibronic measuring system according to FIG. 1, with a tube excited to vibrate to first useful vibrations;

    [0093] FIG. 4b a schematic of Coriolis vibrations of the tube, excited in a tube assembly according to FIG. 4 due to useful vibrations and dependent upon the mass flow;

    [0094] FIG. 5 a schematic diagram of first-order, second-order, or third-order vibration modes inherent in a tube of a tube assembly according to FIG. 4;

    [0095] FIGS. 6, 7 schematics of the tube assembly according to FIG. 4 with tube excited to second useful vibrations;

    [0096] FIGS. 1 or 2 and 3 schematically show exemplary embodiments or embodiment variants for a vibronic measuring system used to measure and/or monitor at least one, especially time-variable, measured variable of a fluid, e.g., at least intermittently flowing and/or at least intermittently two- or multi-phase or inhomogeneous, measured substance FL, wherein the measured variable can, for example, be a flow parameter, such as a mass flow ṁ, a volumetric flow and/or a flow rate, or, for example, a substance parameter, such as a density p and/or a viscosity η, of the measured substance FL. The measuring system is especially provided or configured to be integrated into the course of a process line conducting a fluid FL used as a measured substance, viz., for example, a gas, a liquid, or a dispersion, and to be at least intermittently flowed through during operation by the fluid FL supplied or discharged via the process line. Moreover, the measuring system is provided to determine, viz., especially to calculate and/or output, measured values X.sub.M, and optionally also digital measured values, (chronologically successively) quantifying the at least one physical measured variable. The process line may, for example, be a tube line, viz., for example, a tube line of a filling plant, a refueling device, or another industrial plant.

    [0097] As shown respectively in FIGS. 1, 2, and 3, or readily apparent from their combination, the measuring system comprises a vibration-type transducer 10, viz., a transducer with a tube assembly formed by means of at least one (first) or several tubes for conducting the measured substance, an exciter assembly (31) for converting electrical power to excite and maintain forced mechanical vibrations of the at least one tube, and a sensor assembly (41, 42) for detecting mechanical vibrations of the tube assembly and for providing vibration measurement signals (s1, s2), e.g., electrical or optical vibration measurement signals, respectively representing vibration movements of the tube assembly, viz., especially of the one or more tubes thereof. In addition, the measuring system furthermore comprises a measuring system electronics unit 20, which is electrically coupled to the transducer 10, viz., both to the aforementioned exciter assembly of the transducer and to the aforementioned sensor assembly of the transducer, viz., for example, by means of corresponding electrical connecting lines, especially, formed by means of at least one microprocessor (.Math.C) and/or arranged in an electronics protective housing (200) and/or used as a transmitter for controlling the transducer, viz., especially to cause the aforementioned mechanical vibration of the at least one tube and to evaluate vibration measurement signals supplied by the transducer, viz., for example, to determine the aforementioned measured values.

    [0098] According to a further embodiment of the invention, the measuring system furthermore comprises a support frame 100, especially a bending- and/or torsion-resistant support frame, wherein, as is also schematically shown in FIGS. 1, 2, or 3, said support frame 100 and the tube assembly are fastened to one another - for example, by material bonding or also detachably. In order to protect the transducer or its components from harmful environmental influences, to avoid undesired sound emissions by the vibrating tubes, or to collect measured substance escaping from a leak-tight tube assembly, the aforementioned support frame 100 can also be designed, as quite customary in vibronic measuring systems of the type in question, as a transducer protective housing that surrounds the tube assembly, together with the exciter assembly and sensor assembly, e.g., also in such a way that said transducer protective housing is metallic and/or has a compressive strength that is greater than a greatest compressive strength of the at least one tube of the tube assembly and/or is more than 50 bar. In addition, the measuring system electronics unit 20 can also be accommodated, as quite customary in measuring systems of the type in question, within an electronics protective housing 200, which is, for example, fastened to the aforementioned support frame or transducer protective housing of the transducer and/or is metallic.

    [0099] The at least one tube of the tube assembly can be straight at least sectionally, viz., especially hollow-cylindrical, and/or curved at least sectionally, e.g., in such a way that said tube has a central vertex arc segment, viz., especially is substantially V-shaped or has a V-shaped silhouette, and/or that the tube ultimately has a tubular shape located in a single (tube) plane. As indicated in FIG. 2, the at least one tube extends from a first tube end to a second tube end with a tube length corresponding to a length of an imaginary center line of the tube, e.g., of more than 100 mm, and the tube has a lumen, which is enclosed by a tube wall and extends from the first tube end to the second tube end. According to a further embodiment of the invention, the tube length of the tube is more than 200 mm, e.g., also more than 500 mm, and/or less than 2,000 mm - for example, also less than 1,500 mm. In the case of an at least sectionally curved tube, the aforementioned tube length corresponds to an extended or unwound length of the tube, and the tube can be manufactured by bending a tubular, semi-finished product. According to a further embodiment of the invention, the tube wall of the at least one tube comprises a metal, viz., for example, a steel, especially a stainless steel, duplex steel, or super duplex steel, a titanium alloy and/or a zirconium alloy, especially a Zircaloy, and/or a tantalum alloy and/or a nickel-based alloy. Moreover, the at least one tube of the tube assembly can be designed in one piece - for example, in such a way that the tube is produced seamlessly or (at least in the case of a tube wall made of metal) with a single welded seam. According to a further embodiment of the invention, the at least one tube of the tube assembly has a caliber (inner tube diameter) that is more than 0.1 mm, viz., for example, also more than 0.5 mm, and/or the tube wall of the at least one tube has a smallest wall thickness that is not less than 0.5 mm, e.g., also more than 1.5 mm, and this especially such that the wall thickness of the tube wall is substantially uniform. According to a further embodiment of the invention, the tube has a caliber-to-tube-length ratio that is more than 0.08, especially, more than 0.1, and/or less than 0.25, especially, less than 0.2. Incidentally, the at least one tube or each of the tubes of the tube assembly may, however, also assume any other of the geometric shapes and/or dimensions customary in conventional (standard) vibronic measuring systems, viz., for example, 1 mm, 2 mm, 5 mm, 10 mm, 15 mm, or even more, and/or may be produced from further materials customary for this purpose.

    [0100] According to a further embodiment of the invention, the tube assembly of the transducer 10 has at least one second tube 112, as shown schematically in FIG. 3. The tube 112 may be at least sectionally curved and/or at least sectionally straight. Moreover, the tube 112, as indicated in FIG. 3, may, for example, also be designed structurally identically to the tube 111 and/or be arranged in parallel to the tube 111 at least sectionally. The tube 112 likewise extends, like the tube 111, from a first tube end to a second tube end with a tube length and likewise has, like the tube 111, a lumen, which is enclosed by a tube wall, e.g., a metallic tube wall, and extends from the first tube end to the second tube end. Moreover, the tube 112 is likewise designed to be flowed through by measured substance or a partial volume thereof at least in a flow direction from the first tube end to the second tube end, especially simultaneously with the first tube, and, meanwhile, to be allowed to vibrate. In addition, the tube assembly can furthermore have a first, and/or inlet-side, flow divider 21, which is, for example, used as a line-branching unit here, and has at least two flow openings, and a second, and/or outlet-side, flow divider 22, which is, for example, structurally identical to the aforementioned flow divider 21 and/or used as a line-merging unit, and has likewise at least two flow openings, and each of the tubes 111, 112 of the tube assembly can then respectively be connected to each of the first and second flow dividers to form two, fluidically parallel flow channels, e.g., in such a way that the tube 111 opens with its first tube end into a first flow opening 21a of the first flow divider 21 and with its second tube end into a first flow opening 22a of the second flow divider 22, and that the second tube 112 opens with its first tube end into a second flow opening 21b of the first flow divider 21 and with its second tube end into a second flow opening 22b of the second flow divider 22. The tube length of the tube 111 may, for example, be equal to the tube length of the tube 112. Furthermore, the tube assembly may also have further tubes, viz., for example, two further tubes, and therefore, as also shown in, inter alia, the above-mentioned US-A 56 02 345, WO-A 96/08697, US-A 2017/0356777, WO-A 2019/081169, or WO-A 2019/081170, a total of four tubes. Accordingly, both the flow divider 21 and the flow divider 22 respectively have, especially exactly, four flow openings, and each of the tubes of the tube assembly can be respectively connected to each of the flow dividers 21, 22 to form four, fluidically parallel flow paths. In the aforementioned case in which the tube assembly has four tubes, the tubes may, for example, also be designed such that they are structurally identical only in pairs, viz., for example, the tube lengths are selected to be of equal size only in pairs. Moreover, for the case in which the tube assembly has two or more tubes, the wall of each of the tubes may, for example, comprises the same material, as is quite customary in the case of tube assemblies of the type in question or transducers or measuring systems formed therewith; this, for example, also in such a way that the tube wall of each of the tubes of the tube assembly has a wall thickness that is equal to a wall thickness of the other tube or of each of the other tubes and/or that each of the tubes of the tube assembly has a caliber, viz., an inner diameter, that is equal to a caliber of the other tube or of each of the other tubes.

    [0101] As already indicated, the tube assembly or the transducer MW formed therewith is provided especially to be connected via an inlet end 10+, e.g., also enclosed by a first connecting flange, of the tube assembly or of the transducer MW and a corresponding outlet end 10#, e.g., enclosed by a second connecting flange, to the aforementioned process line and to be flowed through during operation by the measured substance FL. Moreover, a sealing surface may respectively be formed at each of the aforementioned connecting flanges. In the aforementioned case in which the tube assembly has at least two tubes and the two flow dividers respectively connected thereto, the inlet end 10+ of the tube assembly is correspondingly formed by means of the flow divider 21, and the outlet end 10# of the tube assembly is correspondingly formed by means of the flow divider 22, and accordingly, the flow divider 21 can have the aforementioned first connecting flange, and the flow divider 22 can have the aforementioned second connecting flange. Moreover, the at least one tube of the tube assembly can furthermore be configured to conduct measured substance FL or a partial volume thereof in its respective lumen, viz., for example, to carry out forced mechanical vibrations, which especially cause a measurement effect corresponding to the at least one measured variable and/or were excited by means of the exciter assembly, about an associated static resting position; this especially such that the at least one tube of the tube assembly is allowed to vibrate and is meanwhile flowed through by measured substance, starting from its first tube end in the direction of its second tube end (flow direction). As is quite customary in the case of transducers of the type in question, the aforementioned forced mechanical vibrations can be at least partially forced flexural vibrations of the at least one tube about an imaginary vibration axis of the tube assembly, viz., for example, a vibration axis imaginarily connecting the first and second tube ends.

    [0102] The aforementioned exciter assembly of the transducer 10 in turn is especially provided or configured to convert electrical power fed thereto (from the measuring system electronics unit 20) into mechanical power in such a way that, as indicated in FIG. 4a or even readily apparent from a combination of FIGS. 2 and 4a, the at least one tube 111 of the tube assembly and/or each of the tubes thereof performs at least intermittently forced mechanical vibrations about a respective static resting position, while the sensor assembly is provided or configured to detect mechanical vibrations of the tube assembly, and not least mechanical vibrations forced by means of the exciter assembly, and/or flexural vibrations of the at least one tube and to provide a first vibration measurement signal s1 and a second vibration measurement signal s2, of which electrical, for example, vibration measurement signals s1, s2, each represent at least partially vibration movements of one or more of the tubes of the tube assembly, e.g., respectively by means of a respective variable electrical voltage corresponding to vibration movements (X.sub.s1, X.sub.s2) of the at least one tube; this especially such that, as shown schematically in FIG. 4b, the vibration measurement signals s1, s2 (or respectively a spectral signal component s1N1 or s2N1 thereof) follow a change in a mass flow of the measured substance conducted in the tube assembly with a change in a first phase difference (Δφ12), viz., a change in a difference between a phase angle of the vibration measurement signal s1 and a phase angle of the vibration measurement signal s2, and/or such that each of the aforementioned vibration measurement signals s1, s2 respectively follows a change in a density of the measured substance conducted in the tube assembly with a change in a respective signal frequency of at least one spectral signal component.

    [0103] The exciter assembly of the measuring system according to the invention has a vibration exciter 31, e.g., an electrodynamic vibration exciter, which is mechanically connected to the at least one tube and is moreover configured to convert electrical power with a time-variable electrical current into mechanical power in such a way that, as indicated in FIG. 2 or readily apparent from a combination of FIGS. 2 and 4a, a time-variable drive force F.sub.exc1 acts on the tube at a drive point formed by means of said vibration exciter 31 on the tube mechanically connected thereto. In this case, an imaginary circumferential line of the tube, which passes through the aforementioned drive point encloses a cross-sectional area of the tube, which is also referred to below as the drive cross-sectional area of the tube. According to a further embodiment of the invention, the vibration exciter 31 is positioned such that, as indicated in FIG. 4a, a line of action of the aforementioned drive force F.sub.exc1 is perpendicular to a normal of the drive cross-sectional area of the tube. According to a further embodiment of the invention, the vibration exciter 31 is of the electrodynamic type, viz., formed by means of a vibration coil having, for example, an air coil and an armature, or the vibration exciter 31 has a magnetic armature, formed, for example, by means of a permanent magnet, and a coil flooded by the magnetic field of the armature, viz., for example, an air coil. The magnetic armature can, for example, be mechanically connected to the at least one tube 111 to form the drive point, and/or the coil can be electrically connected to the measuring system electronics unit 20, for example.

    [0104] In the aforementioned case in which the tube assembly has two tubes, the vibration exciter 31 is configured according to a further embodiment of the invention to simultaneously excite mechanical vibrations of the two tubes 111, 112; this especially such that the vibration exciter 31 acts differentially on the two tubes 111, 112, viz., can introduce or introduces only excitation forces in opposition into the two tubes 111, 112, e.g., in such a way that the first and second tubes 111, 112 simultaneously perform opposite, forced mechanical vibrations of equal frequency. The vibration exciter 31 can accordingly be mechanically connected, for example, both to the tube 111 and to the tube 112, viz., for example, in such a way that the aforementioned drive force acts on both the tube 111 and the tube 112. According to a further embodiment of the invention, the vibration exciter 31 is configured to provide electrical power with a time-variable electrical current into mechanical power such that a time-variable drive force acts on the second tube at a drive point formed by means of the vibration exciter 31 on the second tube mechanically connected thereto, viz., especially simultaneously with and/or oppositely to the drive force acting on the tube 111 at the drive point formed by means of the vibration exciter 31 on the tube 111 mechanically connected thereto. According to a further embodiment of the invention, it is furthermore provided that, apart from the vibration exciter 31, the exciter assembly have no further vibration exciter connected to the tube, as is, for example, also customary in conventional vibronic (standard) measuring systems.

    [0105] The sensor assembly of the measuring system according to the invention in turn has, as also schematically shown in FIG. 2, a first vibration sensor 41, especially an electrodynamic or optical, first vibration sensor, and a second vibration sensor 42, especially an electrodynamic or optical, second vibration sensor. Each of the vibration sensors 41, 42, which, for example, are also structurally identical, are respectively positioned on the tube, viz., especially respectively mechanically connected at least partially to the tube, and are moreover configured to detect vibration movements of the at least tube and to convert them into a first or second vibration measurement signal, e.g., an electrical or optical, second vibration measurement signal, representing said vibration movements; this especially such that each of the first and second vibration measurement signals respectively contains one or more sinusoidal signal components of a respective frequency corresponding to the vibration frequency of vibration movements of the tube. According to a further embodiment of the invention, it is furthermore provided that each of the vibration sensors 41, 42 be respectively positioned at a distance from the vibration exciter 31 in the flow direction, especially of more than 10 mm and/or more than one fifth of the tube length and/or at the same distance; this especially in such a way that the vibration sensors 41, 42, as also customary in conventional vibronic (standard) measuring systems, are positioned at a distance from one another in the flow direction on the tube. According to a further embodiment of the invention, each of the first and second vibration sensors 41, 42 is respectively formed by means of a plunger coil having, for example, an air coil and an armature. In the aforementioned case in which the tube assembly has at least two tubes, each of the vibration sensors 41, 42 can respectively be positioned both on the first tube 111 and on the second tube 112, viz., especially mechanically connected both partially to the first tube and partially to the second tube, and each of the vibration sensors 41, 42 can moreover be configured to detect, especially differentially, vibration movements, viz., especially vibration movements in opposition, both of the first tube and of the second tube and convert them into the first or second vibration measurement signal in such a way that each of the vibration measurement signals represents vibration movements, especially, vibration movements in opposition, of the first and second tubes 111, 112 (FIG. 3); this especially also in the aforementioned case in which the vibration sensors 41, 42 are respectively electrodynamic vibration sensors constructed in the manner of a plunger coil. In the aforementioned case in which the tube assembly has two tubes, each of the first and second vibration sensors is positioned, according to a further embodiment of the invention, both on the first tube and on the second tube, viz., for example, mechanically connected both partially to the first tube and partially to the second tube. Moreover, each of the first and second vibration sensors is configured to detect vibration movements, viz., for example, vibration movements in opposition, both of the first tube and of the second tube and convert them into the respective first or second vibration measurement signal in such a way that each of the first and second vibration measurement signals represents vibration movements of the first and second tubes. The vibration sensors can especially be designed such that vibration movements, not least also vibration movements of the tubes in opposition, can be differentially detected therewith and/or that each of the first and second vibration measurement signals respectively represents vibration movements of the first and second tubes in opposition.

    [0106] Inherent in the at least one tube or in each of the tubes of the tube assembly is, naturally, respectively, a plurality of vibration modes (natural vibration forms) which respectively have an associated resonance frequency (f1, f2, ..., fx) and in which the tube can perform or performs vibration movements respectively having one or more vibration antinodes (SB) and two or more vibration nodes (SK), in such a way that the number of vibration nodes in relation to the number of associated vibration antinodes is respectively greater by exactly one. Vibration movements of the respective tube in a fundamental vibration mode, viz., a first-order vibration mode (f1 mode), viz., for example, a first-order flexural vibration mode, have, as also indicated in FIG. 5, exactly one vibration antinode and, accordingly, two vibration nodes (f1 mode: 1SB, 2SK), while vibration movements of the respective tube in an harmonic mode (deviating from the fundamental vibration mode), viz., a second-order or higher-order vibration mode (f2 mode, f3 mode, f4 mode, ... fx mode), viz., for example, a second-order, third-order, fourth-order, or higher-order flexural vibration mode, accordingly have two or more vibration antinodes and, correspondingly, three or more vibration nodes (f2 mode: 2SB, 3SK, f3 mode: 3SB, 4SK, f4 mode: 4SB, 5SK, ..., fx mode: x.Math.SB, [x+1].SK). In this case, each of the aforementioned vibration modes of the tube, and therefore also the first-order, second-order, or third-order vibration modes (f1 mode, f2 mode, f3 mode), has a first vibration node located in the first tube end of the at least one tube and a second vibration node located in the second tube end of the at least one tube (FIG. 5). In the aforementioned case in which the tube assembly has two (or more) tubes, a plurality of vibration modes respectively having an associated resonance frequency is correspondingly also inherent in the second tube 112, in which vibration modes the second tube (like the tube 111) can perform or performs vibration movements respectively having one or more vibration antinodes and two or more vibration nodes; this, for example, also in such a way that, in the case of a corresponding excitation, vibration movements of the tube 112 in the first-order vibration mode (f1 mode) are opposite, e.g., also in opposition, to vibration movements of the tube 111 in the first-order vibration mode thereof (f1 mode), and/or that, in the case of a corresponding excitation, vibration movements of the tube 112 in the second-order vibration mode (f2 mode) are opposite, viz., for example, also in opposition, to vibration movements of the tube 111 in the second-order vibration mode thereof. According to a further embodiment of the invention, the tube assembly is furthermore designed such that, at least in the case of an original or intact transducer, a resonance frequency f1 of the first-order vibration mode of the tube 111 is equal to a resonance frequency of the first-order vibration mode (f1 mode) of the tube 112 and/or that, at least nominally, viz., in the original or intact transducer, a resonance frequency f2 of the second-order vibration mode of the tube 111 is equal to a resonance frequency of the second-order vibration mode of the tube 112. In the aforementioned case in which the tube assembly has two or more tubes, and also quite customary in conventional vibronic (standard) measuring systems, the tube assembly may, moreover, further have coupling elements used to also adjust vibration properties of the tube assembly, and not least also to tune one or more resonance frequencies of the tubes thereof; this especially such that, as also indicated in FIG. 3, a first coupling element 23, e.g., a plate-shaped, first coupling element, is mechanically connected to each of the tubes and is positioned at a further distance from the flow divider 22 than from the flow divider 21, and that at least one, second coupling element 24, e.g., a plate-shaped, second coupling element and/or a second coupling element structurally identical to the coupling element 23, is mechanically connected to each of the tubes thereof and is positioned at a further distance from the flow divider 21 than from the flow divider 22.

    [0107] In the measuring system according to the invention, the vibration exciter 31 is positioned and aligned such that, as is also shown schematically in FIGS. 4a or 6, and also quite customary in, inter alia, conventional vibronic (standard) measuring systems, a drive offset ΔE, viz., a smallest distance between the aforementioned drive cross-sectional area of the tube 111 and a specified reference cross-sectional area of the at least one tube, is no more than 3 mm and/or less than 0.5% of the tube length, wherein the reference cross-sectional area in turn is selected or defined, viz., for example, is determined with an intact or original transducer, such that a vibration node, which is formed between two vibration antinodes of vibration movements of the at least one tube in a harmonic mode, viz., for example, the second-order vibration mode, and/or is (nominally) located at half the tube length, of said vibration movements is within the reference cross-sectional area. The drive offset ΔE thus virtually also corresponds to a distance between an area centroid (center point) of the drive cross-sectional area of the tube and an area centroid (center point) of the reference cross-sectional area of the at least one tube. According to a further embodiment of the invention, the reference cross-sectional area of the at least one tube is moreover selected such that a main inertia axis, perpendicular to the aforementioned drive force, of said tube and/or an intersection line of two, mutually-orthogonal symmetry planes of said tube are within the reference cross-sectional area. Moreover, the tube assembly and the exciter assembly according to a further embodiment of the invention are designed such that the drive offset ΔE, at least nominally or initially, and therefore in the intact or original transducer, and as also quite customary in, inter alia, conventional vibronic (standard) measuring systems, is only slightly greater than zero, viz., less than 2 mm, e.g., also less than 1 mm, and/or less than 0.2%, of the tube length; in the case of ideal or completely symmetrical tube and sensor assemblies, also such that the drive offset is equal to zero (ΔE = 0), and therefore the area centroid of the drive cross-sectional area of the tube corresponds to or coincides with the area centroid of the reference cross-sectional area as far as possible. In the aforementioned case in which the at least one tube is curved at least sectionally, viz., for example, at least sectionally has the shape of a circular arc and/or is substantially V-shaped, the at least one tube 111 may furthermore also be designed, and the aforementioned reference cross-sectional area may be selected, such that exactly one main inertia axis of the at least one tube is within the reference cross-sectional area of said tube. For the other case in which the at least one tube is straight over the entire length of the tube, the aforementioned reference cross-sectional area in turn may be selected such that each of the three main inertia axes of the at least one tube is within the reference cross-sectional area of the at least one tube or that a center of mass is within the reference cross-sectional area of the at least one tube. According to a further embodiment of the invention, the reference cross-sectional area is selected such that a vibration node of said vibration movements that is formed between the two vibration antinodes of the vibration movements of the at least one tube in the aforementioned second-order vibration mode, viz., especially the second-order flexural vibration mode, and/or a main inertia axis of the at least one tube, which is perpendicular to the vibration direction of the vibration movements of the tube in said second-order vibration mode, is within the reference cross-sectional area of the at least one tube.

    [0108] As already mentioned, the measuring system comprises, in addition to the transducer 10, a measuring system electronics unit 20 electrically coupled thereto, viz., especially both to the exciter assembly thereof and to the sensor assembly thereof. The measuring system electronics unit 20 may, for example, be designed to be programmable and/or remotely parameterizable, viz., for example, correspondingly formed by means of at least one microprocessor and/or at least one digital signal processor (DSP) and/or by means of a programmable logic component (FPGA) and/or by means of a customer-specifically programmed logic module (ASIC). Furthermore, the measuring system electronics unit 20 can be supplied with the electrical energy required during operation by means of internal energy stores and/or from outside the measuring system electronics unit 20 via a connecting cable. The electrical coupling or connection of the transducer 10 to the measuring system electronics unit 20 may take place by means of corresponding electric connecting lines and corresponding cable feedthroughs. In this case, the connecting lines can be formed at least partially as electric conductor wires sheathed at least in some sections by electric insulation - for example, in the form of “twisted pair” lines, ribbon cables, and/or coaxial cables. As an alternative or in addition thereto, the connecting lines can also be formed at least in some sections by means of printed conductors of a printed circuit board, and especially a flexible, optionally varnished, printed circuit board. Moreover, as also shown schematically in FIG. 1, the measuring system electronics unit 20 may, for example, be accommodated in a corresponding, separate, electronics protective housing 200, which is especially impact-resistant and/or also explosion-resistant and/or at least protects against spray water, and can moreover be designed such that, during operation of the measuring system, it can exchange measurement and/or other operating data, e.g., also status messages, such as respectively current measured values or setting and/or diagnosis values used to control the measuring system (FIGS. 2 and 3), with a superordinate electronic (measurement) data processing system (not shown here), e.g., a programmable logic controller (PLC), a process control system (PLS), a remote terminal unit (RTU), or a supervisory control and data acquisition (SCADA) process executed on a personal computer (PC) and/or a workstation, via a data transmission system - for example, a fieldbus system, and/or wirelessly via radio. Accordingly, the measuring system electronics unit 20 may, for example, have such a transmitting and receiving circuit COM, which is fed during operation by a (central) evaluation and supply unit provided in the aforementioned data processing system and remote from the measuring system. For example, the measuring system electronics unit 20 (or its aforementioned transmitting and receiving electronics COM) may moreover be designed such that it can be connected electrically to the aforementioned external electronic data processing system via a two-conductor connection 2L, optionally also configured as a 4-20 mA current loop, and, via said connection, can both obtain the electrical power required for operating the measuring system from the aforementioned evaluation and supply unit of the data processing system and transmit measured values, optionally, digitized measured values, to the data processing system - for example, by (load) modulation of a direct supply current fed by the evaluation and supply unit. Moreover, the measuring system electronics unit 20 may also be designed such that it can be operated nominally at a maximum power of 1 W or less and/or is intrinsically safe. Moreover, the measuring system electronics unit 20 may, for example, also be constructed in a modular manner in such a way that various electronic components of the measuring system electronics unit 20, such as a measurement and evaluation circuit DSV formed, for example, by means of one or more microprocessors and/or by means of one or more digital signal processors, for processing and evaluating the measurement signals provided by the transducer 10, and not least the vibration measurement signals, a driver circuit Exc for controlling the transducer 10 or the exciter assembly thereof, an internal power supply circuit VS for providing one or more internal operating voltages, and/or the aforementioned transmitting and receiving circuit COM used to communicate with the aforementioned superordinate (measurement) data processing system or the aforementioned external fieldbus, are respectively arranged on one or more separate circuit boards and/or are respectively formed by means of one or more separate microprocessors. As can be respectively seen from FIGS. 2 and 3, the aforementioned transmitting and receiving circuit COM may, for example, also be provided for one of the outputs (x.sub.m) of measured values (X.sub.M) determined internally by the measuring system - for example, by the aforementioned measurement and control circuit DSV. Accordingly, the transmitting and receiving circuit COM may moreover be configured to convert received measured values X.sub.m into an output signal x.sub.m providing said measured value X.sub.M, e.g., an output signal complying with an industry standard, viz., for example, DIN IEC 60381-1:1985-11, IEC 61784-1 CPF1 (Foundation Fieldbus), IEC 61784-1 CPF3 (Profibus), IEC 61158, or IEC 61784-1 CPF9 (HART). In order to visualize measured values (X.sub.M) generated internally by the measuring system and/or status messages generated internally by the measuring system, such as an error message or an alarm, on-site, the measuring system may furthermore have a display and operating element HMI, such as an LCD, OLED, or TFT display positioned in the aforementioned electronics housing 200 behind a window provided correspondingly therein, which HMI also communicates at least intermittently with the measuring system electronics unit 20, and a corresponding input keyboard and/or a touchscreen. In the case in which the measuring system has the aforementioned support frame 100, which is particularly designed as a transducer protective housing, the electronics protective housing 200 may, for example, be fastened to said support frame, as also shown schematically in FIGS. 1, 2, and 3 or readily apparent from the combination thereof.

    [0109] In the measuring system according to the invention, the measuring system electronics unit 20 is in particular configured to energize the vibration exciter 31, viz., to feed electrical power into the vibration exciter 31 by means of an electrical drive signal e1 having a time-variable electrical current, in such a way that the at least one tube performs forced mechanical vibrations, viz., for example, flexural vibrations, at one or more vibration frequencies specified by the drive signal e1. Moreover, the measuring system electronics unit 20 is configured to at least intermittently, viz., for example, in normal measuring operation or during a measuring interval, provide the drive signal e1 with a sinusoidal first (useful) current eN1 having a first (AC) frequency f.sub.eN1, in such a way that the at least one tube at least partially, e.g., also predominantly, performs first useful vibrations, viz., mechanical vibrations, forced by the vibration exciter 31 (energized with the (useful) current eN1) or a first drive force (component) F.sub.exe1 generated therewith, at a first useful frequency f.sub.N1, viz., a (vibration) frequency corresponding to the first (AC) frequency f.sub.eN1 (f.sub.N1 = f.sub.eN1) and that, as a result, the vibration signal s1 has a first useful signal component s1N1, and the vibration signal s2 has a first useful signal component s2N1, viz., respectively a sinusoidal signal component with a (signal) frequency f.sub.s1N1 or f.sub.s2N1 corresponding to the first useful frequency f.sub.N1 (f.sub.s1N1 = f.sub.s2N1 = f.sub.N1); this especially such that the first useful frequency f.sub.N1 deviates from a resonance frequency f2 of the second-order vibration mode (f2 mode) by more than 5% of said resonance frequency f2 ( | f2 - f.sub.N1 | > 0.05 f2) and/or by more than 10 Hz ( |f2 - f.sub.N1 | > 10 Hz) and/or such that the first useful vibrations are suitable for causing, in the measured substance flowing through the at least one rube or through the tube assembly formed therewith, Coriolis forces F.sub.c dependent upon the mass flow thereof. Accordingly, the measuring system electronics unit can furthermore be configured to adjust the first (useful) current eN1 of the drive signal, as is quite customary in vibronic measuring systems of the type in question, such that, due to the first useful vibrations excited therewith, Coriolis vibrations dependent upon the mass flow are also forced, and, as a result, the useful signal components s1N1; s2N1 of the vibration measurement signals s1, s2 follow a change in a mass flow of the measured substance conducted in the at least one tube with a change in a phase difference of the first useful signal components of the vibration measurement signals s1, s2, viz., a difference between a phase angle of the first useful signal component s1N1 and a phase angle of the first useful signal component s2N1. In the aforementioned case in which the tube assembly has at least two tubes, the vibration exciter 31 may moreover also be configured correspondingly to simultaneously convert electrical power fed in by means of the electrical drive signal e1 into forced mechanical vibrations of the first and second tubes 111, 112; this especially also such that the first and second tubes 111, 112 perform forced mechanical vibrations at the first useful frequency f.sub.N1 simultaneously, viz., for example, vibrations in opposition. In the aforementioned case in which the vibration exciter 31 is formed by means of a coil electrically connected to the measuring system electronics unit, energizing the vibration exciter 31 means that the coil receives the drive signal e1, viz., the current thereof.

    [0110] The aforementioned (AC) frequency f.sub.eN1 of the useful current components eN1, and therefore the first useful frequency f.sub.N1, may for example correspond to a resonance frequency of the tube assembly, which also depends upon the density of the measured substance FL conducted in the tube assembly, viz., for example, a lowest resonance frequency of the tube 111 or the resonance frequency f1 of the fundamental vibration mode (f1 mode). Accordingly, the measuring system electronics unit 20 according to a further embodiment of the invention is furthermore configured to adjust the first (AC) frequency f.sub.eN1 such that said (AC) frequency f.sub.eN1 or the useful frequency f.sub.N1 deviates from the resonance frequency f1 of the fundamental vibration mode by less than 1% of said resonance frequency f1 ( | f1 - f.sub.N1 | < 0.01 f1) and/or by less than 1 Hz ( | f1 - f.sub.N1 | < 1 Hz), viz., for example, corresponds to the resonance frequency f1 of the fundamental vibration mode (f1 mode), or that the vibration movements of the first useful vibrations ultimately correspond to those of the fundamental vibration mode (f1 mode) of the at least one tube 111. According to another embodiment of the invention, the measuring system electronics unit is configured to adjust the first (AC) frequency f.sub.eN1 such that said (AC) frequency f.sub.eN1 or the useful frequency f.sub.N1 deviates from a resonance frequency f3 of the third-order vibration mode (f3 mode) by less than 1% of said resonance frequency f3 ( | f3 - f.sub.N1 | < 0.01 f3) and/or by less than 1 Hz ( | f3 - f.sub.N1 | < 1 Hz), viz., for example, corresponds to the resonance frequency f3 of the third-order vibration mode (f3 mode), or that the vibration movements of the first useful vibrations thus ultimately correspond to those of the third-order vibration mode (f3 mode) of the at least one tube 111.

    [0111] In order to generate the drive signal e1, the measuring system electronics unit 20, as is quite customary in such measuring systems, can have a corresponding driver circuit Exc, formed, for example, by means of one or more phase locked loops (PLL) used to determine a respective resonance frequency or to adjust the currently required (AC) frequency.

    [0112] The measuring system electronics unit 20, as already indicated, is furthermore especially also provided to receive and evaluate the vibration measurement signals s1, s2 generated by means of the transducer 10, viz., especially to determine and output measured values X.sub.m representing the at least one measured variable. In particular, the measuring system electronics unit 20 is configured to determine, based upon at least the first useful signal components s1N1, s2N1, viz., for example, based upon the (signal) frequency thereof, and/or based upon an amplitude of at least one of the useful signal components s1N1, s2N1 and/or based upon a phase angle of at least one of the useful signal components s1N1 or s2N1, measured values representing the at least one measured variable, viz., for example, mass-flow measured values representing the mass flow of the measured substance and/or density measured values representing the density of the measured substance; this, for example, also in a manner typical for measuring systems of the type in question, and not least also for the measuring systems known from the above-mentioned US-A 2006/0266129, US-A 2007/0113678, US-A 2010/0011882, US-A 2012/0123705, US-A 2017/0356777, US-A 56 02 345, US-A 59 26 096, WO-A 2009/136943, WO-A 2019/017891, WO-A 2019/081169, WO-A 2019/081170, WO-A 87/06691, WO-A 96/05484, WO-A 96/08697, WO-A 97/26508, WO-A 99/39164, or our own, non-published, international patent application PCT/EP2019/082044. According to a further embodiment of the invention, the measuring system electronics unit 20 is accordingly furthermore configured to generate, based upon the aforementioned phase difference of the first useful signal components s1N1; s2N1, mass-flow measured values representing the mass flow, e.g., by means of a phase-difference-to-mass-flow-measured-value characteristic curve function programmed into the measuring system electronics unit, viz., a characteristic curve function of the measuring system electronics unit, and optionally also designed as a (linear) parameter function, according to which a determined phase difference is therewith converted into mass-flow measured values X.sub.m. According to a further embodiment of the invention, the measuring system electronics unit 20 is the measuring system electronics unit is moreover configured to determine the resonance frequency f1 of the first vibration mode (f1 mode) of the at least one tube, viz., for example, to determine, based upon the drive signal e1 and/or on at least one of the vibration measurement signals s1, s2, frequency values X.sub.f1 representing the resonance frequency f1; this, for example, also in order to calculate, based upon such frequency values, the density measured values X.sub.p representing the density - for example, according to a corresponding resonance-frequency-to-density-measured value characteristic curve function of the measuring system electronics unit. Alternatively or additionally, the measuring system electronics unit 20 may also be provided or configured to generate, based upon at least one vibration measurement signal s1, s2, and or upon the drive signal e1, viscosity measured values, viz., measured values representing the viscosity of the measured substance FL - for example, according to a damping-to-viscosity-measured-value characteristic curve function of the measuring system electronics unit. The processing of the vibration measurement signals s1, s2, and possibly also a control of the aforementioned driver circuit(s) Exc, which is quite customary in such measuring systems, may also take place, as is also shown schematically in FIGS. 2 or 3 - for example, also by means of the aforementioned measurement and evaluation circuit DSV.

    [0113] The program codes executed during operation of the measuring system in the measuring system electronics unit 20, viz., for example, in one or more of the aforementioned microprocessors or digital signal processors of the measuring system electronics unit 20, can respectively be stored persistently, for example, in one or more non-volatile data memories (EEPROM) of the measuring system electronics unit 20, viz., memories storing digital data even without an applied operating voltage, and, when said measuring system electronics unit is started up, can be loaded into a volatile data memory (RAM) provided, e.g., integrated into the microprocessor, in the measuring system electronics unit 20 or in the aforementioned measurement and evaluation circuit DSV. For processing in the microprocessor or in the digital signal processor, the vibration measurement signals s1, s2 are of course first to be converted into corresponding digital signals by means of corresponding analog-to-digital converters (A/D), viz., for example, by, respectively, suitably digitizing the respective signal voltage of each of the vibration measurement signals s1, s2, which are electrical here; cf. in this respect, for example, the above-mentioned US-B 63 11 136. Accordingly, corresponding analog-to-digital converters for the vibration measurement signals s1, s2 and/or at least one non-volatile electronic data memory EEPROM, which is configured to store digital data, viz., for example, even without an applied operating voltage, can be provided in the measuring system electronics unit 20, viz., for example, in the aforementioned measurement and evaluation circuit DSV. In order to further improve the accuracy with which the measured values X.sub.m are ultimately determined, the transducer can, as also respectively shown schematically in FIGS. 2 and 3 and as quite customary in such measuring systems, furthermore also have temperature sensors 71 (71, 72) used to detect temperatures within the tube assembly and to provide one or more corresponding temperature measurement signals θ1 (θ1, θ2), and respectively attached, for example, directly to the at least one tube of the tube assembly, and/or strain sensors used to detect mechanical stresses within the tube assembly and to provide one or more corresponding strain measurement signals, and respectively attached, for example, directly to one of the tubes of the tube assembly, and the measuring system electronics unit can furthermore be configured to receive and process the temperature or strain measurement signals, viz., especially to also use them in the determination of the measured values.

    [0114] As already mentioned, vibration-type transducers, and therefore the vibronic measuring systems formed therewith, can be exposed during their service life to a plurality of loads, which cause significant deviations of the transducer or of the measuring system from a reference state determined in advance, e.g., a respective initial delivery state and/or a state during the start-up of the measuring system on-site; this especially also such that the tube assembly experiences such damage, e.g., due to overloads, that the vibration properties of the at least one tube change, or that the transducer is damaged overall because, inter alia, one or more system functions (transfer functions) that are inherent in the transducer or measurement functions correspondingly formed in the measuring system have thereby also correspondingly changed in comparison to a respective (reference) system function of the original transducer or (reference) measurement function of the measuring system. Changes in the vibration characteristics of the at least one tube can be ascribed, for example, to changes in one or more modal flexural stiffness, mass and/or damping, viz., in each case determining one of the aforementioned vibration modes, and result in one or more (natural) vibration forms deviating from their respective equivalent when the transducer is in the reference state; this regularly also in such a way that an original, typically substantially homogeneous or uniform, distribution of the aforementioned (system) parameters of (modal) flexural stiffness, (modal) mass, and (modal) damping is changed, viz., is increasingly unevenly distributed. As a result, such loads lead not only to the natural or resonance frequency of one or more of the aforementioned vibration modes, but especially also the form of the vibration movements of the respective vibration modes being subjected to changes in such a way that the position of one or more of the vibration nodes located between two vibration antinodes of the at least one tube in one or more of the harmonic modes thereof, and therefore also the position of the aforementioned reference cross-sectional area in relation to its respective original position, is changed. Accordingly, the drive offset determined relative to the reference cross-sectional area also experiences changes - for example, in such a way that the drive offset in comparison to the drive offset ΔE determined in the original or intact transducer increases. In addition, during the service life of the measuring system, the at least one vibration exciter, as well as each of the vibration sensors, can also be subjected to changes relevant to the measurement accuracy, e.g., as a result of thermally-induced (over)load or aging - for example, in such a way that an electrical impedance of the transducer is also changed as a result. (Over)loads which can lead to damage to the tube assembly or the transducer as a whole, may, for example, be high (excess) temperatures or temperature shocks, excessively high pressures or pressure surges in the measured substance, excessively high clamping forces exerted on the transducer on the part of the process line and/or excessively strong vibration forces, harmful properties of the measured substance conducted in the transducer, or also material fatigue, and can, inter alia, result in a significant reduction in the wall thickness of the tube wall, e.g., due to corrosion and/or abrasion of the tube wall of the at least one tube caused by the measured substance, or in a significant reduction in a flow cross-section of the tube assembly, e.g., as a result of an at least partial clogging of the tube assembly and/or as a result of a solid deposit on the inner side of the tube wall contacting the measured substance, in a plastic deformation of the at least one tube, or also in crack formation within the tube assembly, viz., for example, the tube wall, and therefore even lead to the transducer possibly no longer being safe.

    [0115] System functions affected by such damage to the transducer may, for example, correspond to one or more (modal) vibration responses of the tube assembly, which are relevant for the measurement of the at least one measured variable, viz., for example, a functional dependence of an amplitude of the aforementioned useful vibrations upon the drive signal, or characterize a functional dependence of an amplitude of the aforementioned Coriolis vibrations upon the drive signal and mass flow, or a measurement function which involves one or more of the aforementioned vibration responses and according to which the measuring system ultimately converts the measured variable to be respectively detected into the respective measured values. Examples of such system functions of the transducer can accordingly, for example, include a mass-flow-to-phase-difference system function, viz., a system function of the transducer according to which the aforementioned phase difference of the first useful signal components of the vibration measurement signals depends upon the mass flow, one or more resonance frequencies of the tube assembly as system functions containing (system) parameters, such as a density-to-resonance-frequency system function, viz., for example, a system function of the transducer according to which the aforementioned resonance frequency f1 depends upon the density, or damping of vibrations as system functions containing (system) parameters, such as a viscosity-to-damping function, viz., for example, a system function of the transducer according to which a damping of the first useful vibrations depends upon the viscosity. Measurement functions of the measuring system which are based upon one or more of the aforementioned system functions of the transducer, e.g., a mass-flow-to-measured-value involving the mass-flow-to-phase-difference system function and the aforementioned phase-difference-to-mass-flow-measured-value characteristic curve function of the measuring system electronics unit, viz., a measurement function of the measuring system according to which mass-flow measured values determined thereby depend upon the mass flow, and/or a density-to-measured-value function of the measuring system involving the aforementioned density-to-resonance-frequency system function of the transducer and the aforementioned resonance-frequency-to-density-measured-value characteristic curve function of the measuring system electronics unit, and/or a viscosity-to-measured-value characteristic curve function of the measuring system involving the aforementioned viscosity-to-damping system function of the transducer and the aforementioned damping-to-viscosity-measured-value characteristic curve function of the measuring system electronics unit may, however, accordingly also be affected.

    [0116] The damage to the transducer or the tube assembly thereof can, especially, result in one or more (system) parameters characterizing system functions or a corresponding measurement function, e.g., a (scale) zero point and/or a (measurement) sensitivity (slope of the characteristic curve function) of the aforementioned phase-difference-to-mass-flow-measured-value characteristic curve function corresponding to a change in the phase difference of the first useful signal components related to a change in the mass flow, being subject to corresponding changes over time, viz., especially having a drift. As a result of such (over)loads of the transducer occurring, possibly also several times and/or recurrently for a longer period of time, the transducer can be damaged in the course of the operating time to such an extent that its functionality or a functionality of the measuring system as a whole is limited to a considerable extent or completely; this, for example, also in such a way that a fault or a malfunction of the measuring system, which possibly also leads to measurement errors in the determination of the measured values, is present as a result, e.g., because an integrity of at least one of the vibration measurement signals or measured values obtained therefrom is significantly reduced, and therefore a measurement accuracy of the measuring system, with which the measuring system ultimately represents the measured variable to be detected in the corresponding measured values, is significantly reduced compared to an initial or nominal measurement accuracy of the original or intact measuring system.

    [0117] In order to be able to as early and reliably as possible detect and possibly report any changes in the transducer, e.g., of its mechanical properties and/or of its electrical properties, or a defect, ascribed thereto, of the transducer or the measuring system formed therewith, it is therefore furthermore provided, e.g., also in the course of a diagnosis of the measuring system (self-diagnosis) performed by the measuring system itself, to actively excite the tube assembly to mechanically vibrate by means of the exciter assembly in such a way that the at least one tube performs vibrations which, as schematically illustrated in FIGS. 6 or 7 or readily apparent from their combination with FIG. 5, correspond to the aforementioned second-order vibration mode (f2 mode), and to correspondingly evaluate the resulting vibration measurement signals by means of the measuring system electronics unit 20, viz., especially to examine them for faults of the measuring system; this especially such that said vibrations corresponding to the second-order vibration mode (f2 mode) are non-volatile or stationary, viz., have a (substantially) constant, non-zero vibration amplitude for two or more vibration periods and/or a period of more than 10 ms (milliseconds). For this purpose, the measuring system electronics unit 20 of the measuring system according to the invention is furthermore configured to at least intermittently provide the drive signal e1, as also respectively indicated in FIGS. 6 or 7, with a sinusoidal second (useful) current eN2 having a second (AC) frequency f.sub.eN2 deviating from the first (AC) frequency f.sub.eN1 by, for example, more than 10 Hz, in such a way that the at least one tube 111 at least partially performs second useful vibrations (different from the first useful vibrations), viz., mechanical vibrations forced by the vibration exciter 31 (energized with the (useful) current eN2) or a vibration exciter 31 energized by a second drive force (component) F.sub.exc2 generated therewith, at a second useful frequency f.sub.N2, viz., a (vibration) frequency corresponding to the second (AC) frequency f.sub.eN2 (f.sub.N2 = f.sub.eN2), whereby each of the first and second vibration signals s1, s2 respectively has a second useful signal component s1N2 or s2N2, viz., a sinusoidal signal component with a (signal) frequency f.sub.s1N2 or f.sub.s2N2 (f.sub.s1N2 = f.sub.s2N2 = f.sub.N2) corresponding to the second useful frequency f.sub.N2. According to a further embodiment of the invention, the measuring system electronics unit 20 is furthermore configured to provide the aforementioned second (useful) current (eN2) with a specified (current) amplitude.

    [0118] In the measuring system according to the invention, the measuring system electronics unit 20 is moreover especially configured to adjust the second (AC) frequency f.sub.eN2 such that it deviates from a resonance frequency f2 of the second-order vibration mode (f2 mode) of the at least one tube 111 by less than 1% ( | f2 - f.sub.N2 | < 0.01 f2), e.g., also by less than 0.1%, of said resonance frequency f2, and/or by less than 1 Hz ( |f1 - f.sub.N2 | < 1 Hz), e.g., also by less than 0.1 Hz; this especially also such that (AC) frequency f.sub.eN2 corresponds to the resonance frequency f2 of the second-order vibration mode (f2 mode) (f.sub.eN2 = f2). Only for the aforementioned (ideal) and therefore non-critical case to be expected at most in an original or a completely intact transducer or measuring system, in which case the drive offset ΔE is actually zero, the second useful vibrations would not be excited in this manner, and the vibration signals s1, s2 would therefore not have the second useful signal component s1N2 or s2N2 or would have it with the amplitude of zero; otherwise (ΔE <> 0), however, as a result of such an energization of the vibration exciter 31 with the second (useful) current eN2, the second useful vibrations are actually also excited, and their vibration movements correspond to those of the second-order vibration mode (f2 mode) of the at least one tube 111. For the aforementioned case that the tube assembly has at least two tubes, the vibration exciter 31 can moreover also be configured to convert electrical power fed in by means of the electrical drive signal e1 into forced mechanical vibrations of the first and second tubes 111, 112 in such a way that the first and second tubes 111, 112 simultaneously perform forced mechanical vibrations at the second useful frequency, viz., for example, forced mechanical vibrations at the first useful frequency f.sub.N1 and at the second useful frequency f.sub.N2. Accordingly, the measuring system electronics unit 20 according to a further embodiment of the invention is furthermore also configured to provide the second useful current e1N2 of the drive signal e1 at least intermittently also simultaneously with the first (useful) current e1N1; this, for example, also in such a way that the (current) amplitude of the first (useful) current e1N1 is adjusted to not be smaller than the (current) amplitude of the second (useful) current e1N2 and/or that the (current) amplitude of the second (useful) current e1N2 is adjusted to more than 40%, e.g., not less than 50%, of the (current) amplitude of the first (useful) current e1N1.

    [0119] Alternatively or additionally, the measuring system electronics unit is furthermore configured to adjust the second (AC) frequency f.sub.eN2 as a function of the first (AC) frequency f.sub.eN1 or as a function of the resonance frequency f1; this, for example, in such a way that the second (AC) frequency f.sub.eN2 is within a frequency setting interval, of which an upper interval limit and/or a lower interval limit and/or a center frequency corresponds to a specified multiple of the first (AC) frequency f.sub.eN1, viz., for example, a multiple of the first (AC) frequency f.sub.eN1 corresponding to more than 230% of the first (AC) frequency f.sub.eN1 and/or less than 300% of the first (AC) frequency f.sub.eN1. According to a further embodiment of the invention, the measuring system electronics unit furthermore comprises a first, e.g., also digital, phase-locked loop (PLL1), used to adjust the (AC) frequency f.sub.eN1, and a second, e.g., digital, phase-locked loop (PLL2), used to adjust the (AC) frequency f.sub.eN2. Moreover, the measuring system electronics unit 20 can furthermore be configured to adjust a capture range of the second phase-locked loop (PLL2) based upon the first (AC) frequency f.sub.eN1 or by means of at least one output signal of the first phase-locked loop (PLL1), viz., for example, an output signal of a loop filter of the first phase-locked loop (PLL1).

    [0120] The measuring system electronics unit 20 of the measuring system according to the invention is moreover also configured to carry out a (self-) diagnosis of the measuring system based upon or by evaluating at least one of the second useful signal components s1N2, s2N2, e.g., based upon their (signal) frequency and/or based upon a (signal) amplitude of at least one the second useful signal components s1N2, s2N2, which (signal) amplitude is possibly also normalized with the (AC) frequency f.sub.eN2in the case of an electrodynamic vibration sensor, and/or based upon a phase angle of at least one of the second useful signal component s1N2, s2N2, viz., for example, to check a functionality of the measuring system and/or to (re)calibrate the measuring system and/or to determine whether a fault of the measuring system is present, e.g., in such a way that a functionality of the measuring system is reduced and/or that a malfunction of the measuring system is present and/or a measurement error is present in the determination of the measured values - for example, because an integrity of at least one of the vibration measurement signals s1, s2 is reduced. The measuring system electronics unit can, for example, also be configured to determine in the course of the aforementioned (self-) diagnosis, e.g., based upon the (signal) frequency of the second useful signal components and/or based upon a (signal) amplitude of at least one of the second useful signal components s1N2 and/or based upon a phase angle of at least one of the second useful signal components s1N2, whether and/or to what extent a fault of the measuring system (🙁) is present due to one or more vibration properties of the tube assembly (FIG. 7) changed in comparison to a reference state (🙂) determined therefor in advance, e.g., as a result of damage to the tube assembly, and possibly, for example, also to determine to what extent damage to the tube assembly is present as a result of erosion (corrosion, abrasion) on an inner side, facing the lumen, of the tube wall or a corresponding reduction in a wall thickness of the tube wall of the at least one tube and/or as a result of the formation of deposits on an inner side, facing the lumen, of the tube wall and/or due to a crack in the tube wall of one or more of the tubes and/or due to plastic deformation of one or more of the tubes, and/or to what extent a measurement error is present in the determination of the measured values due to damage to the tube assembly. The aforementioned reference state of the transducer can, for example, correspond to its respective state at delivery from the manufacturer and therefore be correspondingly determined during a calibration at the manufacturing plant and/or during a start-up of the measuring system, and can be stored in the measuring system electronics unit in the form of corresponding reference values for (system) parameters specifying one or more system functions of the transducer.

    [0121] The aforementioned evaluation of at least one of the second useful signal components s1N2, s2N2 can, for example, be a simple examination of at least one of the vibration measurement signals s1, s2 for the second useful signal component or a detection of said second useful signal component in the vibration measurement signals s1, s2 above a specified (minimum) signal level; it may, however, also comprise a dedicated measurement of the respective (signal) amplitudes or temporal amplitude profiles and/or of the respective phase angles or temporal phase angle profiles and/or of the respective (signal) frequency or temporal frequency profiles of one or more of the second useful signal components s1N2, s2N2. For example, parameter values which respectively characterize the respective vibration response or one or more of the aforementioned system functions can be determined recurrently by means of the measuring system electronics unit based upon the vibration measurement signals s1, s2 and can be compared to reference values correspondingly specified therefor. Alternatively or additionally, one or more characteristic number values for at least one measuring-system characteristic number can be recurrently calculated by means of the measuring system electronics unit based upon the vibration measurement signals s1, s2, which characteristic number values characterize an operating state of the measuring system, e.g., in such a way that a respective characteristic number value respectively corresponds to a relationship of two or more of the aforementioned parameter values or respectively depends upon several such parameter values. A measuring-system characteristic number to be determined can furthermore also be selected such that it represents a measure of the drive offset in such a way that the measuring-system characteristic number indicates whether or to what extent the drive offset deviates from an originally present (initial) drive offset, e.g., as a result of a change in position of the area centroid of the reference cross-sectional area or a corresponding displacement of the reference cross-sectional area, or in such a way that increasing characteristic number values quantify an increasing drive offset, and decreasing characteristic number values quantify a decreasing drive offset. Alternatively or additionally, the measuring-system characteristic number can also be defined, for example, such that it represents a measure of change in how quickly the drive offset changes over time. If a correspondingly specified tolerance measure, viz., for example, a still acceptable tolerance measure, of a deviation between a determined parameter value and/or characteristic number value and a respectively specified reference value or a threshold value representing an impermissibly high deviation is exceeded, an error can thus easily be diagnosed in a timely manner by means of the measuring system electronics unit 20, e.g., in order to then generate and output a system status message or fault message which signals this accordingly and is possibly also declared as an alarm. Vibration responses or (system) parameters characterizing system functions can, for example, be (vibration) amplitude ratios or (vibration) frequency ratios, flexural stiffnesses, ratios of modal flexural stiffnesses, dampings, or ratios of modal damping of the at least one tube. The corresponding reference values for the parameter values and/or characteristic number values, as well as the respective corresponding threshold values can be determined in advance, viz., for example, in the course of a (first) calibration of the measuring system by the manufacturer at the factory or possibly also in the course of a start-up of the measuring system on-site, by means of the measuring system itself, which is still in the original (reference) state, and/or based upon laboratory measurements with structurally identical measuring systems or measuring systems of the same type, and can accordingly be stored in advance in the measuring system electronics unit 20 - for example, in the non-volatile data memory EEPROM thereof. The parameter values respectively determined with the measuring system electronics unit 20 can furthermore also be output, e.g., displayed on-site, and/or passed to the aforementioned (measurement) data processing system.

    [0122] Taking into account the respectively adjusted first and second useful frequencies, a corresponding resonance frequency ratio of the respective vibration modes can, for example, also be determined and be used for (self-) diagnosis as a (system) parameter specifying system functions of the transducers, e.g., in such a way that a temporally changing, e.g., continuously increasing or continuously decreasing, ratio of the resonance frequency f2 to the resonance frequency f1 is used as an indicator of the presence of a fault of the transducer. According to a further embodiment of the invention, the measuring system electronics unit 20 is accordingly configured to determine the resonance frequency f2 of the second vibration mode (f2 mode) of the at least one tube 111, viz., for example, based upon the drive signal e1 and/or frequency values X.sub.f2 representing the resonance frequency f2 of at least one of the vibration measurement signals s1, s2, and/or to determine a resonance frequency ratio f1/f2 corresponding to a ratio of the resonance frequency f1 of the first vibration mode (f1 mode) and the resonance frequency f2 of the second vibration mode (f2 mode), viz., for example, to determine, based upon the first and second (AC) frequencies f.sub.eN1, f.sub.eN2 of the drive signal e1 and/or based upon the signal frequencies f.sub.s1N1, f.sub.s2N1, f.sub.s1N2, f.sub.s2N2 of the useful signal components s1N1, s1N2, s2N1, s2N2 of at least one of the vibration measurement signals, frequency ratio values X.sub.f12 (X.sub.f12 = f.sub.eN1/f.sub.eN2; X.sub.f12 = f.sub.s1N1/ f.sub.s1N2; X.sub.f12 = f.sub.s2N1 f.sub.s2N2) representing the resonance frequency ratio f1/f2. For carrying out the (self-) diagnosis of the measuring system by means of the measuring system electronics unit 20, the recurrently determined frequency ratio values X.sub.f12 can furthermore, for example, be compared to a reference value specified therefor, viz., especially in order to determine whether or to what extent the resonance frequency ratio f1/f2 deviates from said reference value.

    [0123] Taking into account the deflections (amplitude) of the second useful vibrations, a change in the natural vibration form of the second-order vibration mode can furthermore, for example, also be determined and be used for the (self-) diagnosis as a (system) parameter specifying system functions of the transducer.

    [0124] According to a further embodiment of the invention, the measuring system electronics unit 20 is therefore furthermore configured to determine, based upon the vibration measurement signals s1, s2, phase difference values representing at least one phase difference of the second useful signal components, viz., a difference between a phase angle of the second useful signal component s1N2 of the vibration measurement signal s1 and a phase angle of the second useful signal component s2N2 of the vibration measurement signal s2. For carrying out the (self-) diagnosis of the measuring system by means of the measuring system electronics unit 20, the recurrently determined phase difference values can, for example, furthermore be compared to one or more reference values specified therefor, e.g., in order to determine whether or to what extent the phase difference of the second useful signal components or an underlying modal deflection of the second useful vibrations of the at least one tube deviate from the respective reference value. For example, an excessively high and/or temporally continuously increasing phase difference of the second useful signal component can be used as an indicator of the presence of a fault. One or more of the aforementioned reference values for the phase difference of the second useful signal component can, for example, also be set as a function of a phase difference, which is currently already determined for the determination of the mass-flow measured values X.sub.m, of the first useful vibrations. Alternatively or additionally, the phase difference values determined for the second useful vibrations can also be used for carrying out the (self-) diagnosis of the measuring system by means of the measuring system electronics unit 20, in order to determine a phase difference ratio corresponding to a ratio of the aforementioned phase difference of the second useful vibrations and the phase difference, which is used for the determination of the mass-flow measured values X.sub.m, of the first useful vibrations. According to another embodiment of the invention, the measuring system electronics unit 20 is furthermore configured to determine, based upon the vibration measurement signals s1, s2, at least one of the (signal) amplitudes of the first useful signal components s1N1, s2N1, which (signal) amplitude is possibly also normalized with the (AC) frequency f.sub.eN1 in the case of an electrodynamic vibration sensor, and therefore amplitude values respectively representing deflections x1 of the first useful vibrations, viz., especially both amplitude values X.sub.s1N1 representing the (signal) amplitudes of the useful signal components s1N1 and amplitude values X.sub.s2N1 representing the (signal) amplitudes of the useful signal components s2N1, and/or the measuring system electronics unit 20 is configured to determine at least one of the (signal) amplitudes of the second useful signal components s1N2, s2N2, and therefore amplitude values respectively representing deflections x2 of the second useful vibrations, viz., especially both X.sub.s1N2 representing the (signal) amplitudes of the useful signal components s1N2 and amplitude values X.sub.s2N2 representing the (signal) amplitudes of the useful signal components s2N2 -for example, by forming a respective moving average for the (signal) amplitudes of the useful signal components s1N1, s1N2, s1N2 or s2N2 by means of FIR filter and/or by numerical integration of the amplitude values X.sub.s1N1, X.sub.s2N1, X.sub.s1N2, or X.sub.s2N2. Alternatively or additionally, the measuring system electronics unit is furthermore configured to determine a deflection ratio x1/x2 corresponding to a ratio of the (modal) deflection (amplitude) of the first useful vibrations and the (modal) deflection of the second useful vibrations, viz., for example, to determine, based upon at least one of the vibration measurement signals s1, s2, deflection ratio values representing the deflection ratio x1/x2 - possibly by using the aforementioned deflection values X.sub.s1N1, X.sub.s1N2 and/or the aforementioned deflection values X.sub.s2N1, X.sub.s2N2. For carrying out the (self-) diagnosis of the measuring system by means of the measuring system electronics unit 20, the recurrently determined amplitude values, viz., especially the amplitude values X.sub.s1N2, X.sub.s2N2, and/or the correspondingly determined deflection ratio values, can, for example, furthermore be compared to one or more reference values specified therefor, e.g., in order to determine whether or to what extent one and/or more of the (signal) amplitudes or one or more of the modal deflections of the vibrations of the at least one tube, viz., especially the deflections of the second useful vibrations, deviate from the respective reference value. One or more of the aforementioned reference values for the amplitude values X.sub.s1N2, X.sub.s2N2 (or the modal deflections of the vibrations of the at least one tube) can, for example, also be set as a function of an instantaneously adjusted (current) amplitude of the second (useful) current eN2 and/or of one of the instantaneous deflection values X.sub.s1N1 and/or X.sub.s2N1.

    [0125] Taking into account both the deflections of the first or second useful vibrations and the drive force which respectively causes them, it is moreover, for example, also possible to determine a corresponding modal spring stiffness of the respective useful vibrations or a respectively corresponding vibration mode and to use it for the (self-) diagnosis as a (system) parameter specifying system functions of the transducer, e.g., in such a way that an excessively low and/or temporally continuously decreasing (modal) spring stiffness of the second useful vibrations or a temporally changing, e.g., continuously increasing or continuously decreasing, ratio of a (modal) spring stiffness c2 of the second useful vibrations to a (modal) spring stiffness c1 of the first useful vibrations is used as an indicator of the presence of a fault. Alternatively or additionally, taking into account both the deflection velocity of the first or second useful vibrations and the drive force which respectively causes them, it is moreover, for example, also possible to determine a (modal) damping of the respective useful vibrations or the corresponding vibration mode and to use it for the (self-) diagnosis as a (system) parameter specifying system functions of the transducer, e.g., in such a way that an excessively low and/or temporally continuously increasing damping of the second useful vibrations or a temporally changing, e.g., continuously increasing or continuously decreasing, ratio of a (modal) damping d2 of the second useful vibrations to a (modal) damping d1 of the first useful vibrations is used as an indicator of the presence of a fault.

    [0126] According to a further embodiment of the invention, the measuring system electronics unit 20 is furthermore configured to determine a (modal) damping of the second useful vibrations corresponding to a ratio of the (signal) amplitude of one of the second useful signal components s1N2, e.g., also a sum or a difference of the (signal) amplitudes of the second useful signal components, and a (signal) amplitude of the second (useful) current eN2, viz., for example, to determine, based upon the second (useful) current e1N2 and a second useful signal component of at least one of the vibration measurement signals s1, s2, damping values representing the damping d2 of the second useful vibrations. For carrying out the (self-) diagnosis of the measuring system by means of the measuring system electronics unit 20, the recurrently determined damping values can furthermore, for example, be compared to one or more reference values specified therefor, viz., especially in order to determine whether or to what extent the damping of the second useful vibrations of the at least one tube deviates from a reference value (damping reference value) specified therefor. Alternatively or additionally, the measuring system electronics unit can furthermore also be configured to determine a damping ratio d1/d2 corresponding to a ratio of the (modal) damping of the first useful vibrations and the (modal) damping d2 of the second useful vibrations, viz., for example, to determine, based upon the first and second (useful) currents of the drive signal and/or at least the first and second useful signal components of at least one of the vibration measurement signals, damping ratio values representing the damping ratio d1/d2. Accordingly, the measuring system electronics unit 20 is furthermore also configured to determine both the aforementioned (modal) damping of the second useful vibrations and a (modal) damping of the first useful vibrations corresponding to a ratio of the (signal) amplitude of one of the first useful signal components s1N1, e.g., also a sum or a difference of the (signal) amplitudes of the first useful signal components s1N1, s2N1, and a (signal) amplitude of the first (useful) current eN1, viz., for example, to determine, based upon the drive signal and at least one of the vibration measurement signals, damping values representing the damping of the first useful vibrations. For carrying out the (self-) diagnosis of the measuring system, the measuring system electronics unit 20 according to a further embodiment of the invention is furthermore configured to compare one or more of the aforementioned damping values representing the damping of the second useful vibrations and/or one or more of the aforementioned damping ratio values to at least one reference value determined therefor in advance and/or, by means of an intact measuring system, and, viz., for example, also to output, in the case of a deviation of one or more of the damping values from the respective reference value (damping reference value) or in the case of a deviation of one or more of the damping ratio values from the respective reference value (damping ratio reference value), a message representing this, especially, a message declared as a (fault) alarm. According to another embodiment of the invention, the measuring system electronics unit 20 is furthermore configured to determine, based upon the second (useful) current e1N2 and a second signal component of at least one of the vibration measurement signals s1, s2, the spring stiffness c2 of spring stiffness values representing the second useful vibrations. For carrying out the (self-) diagnosis of the measuring system by means of the measuring system electronics unit 20, the recurrently determined spring stiffness values can furthermore, for example, be compared to one or more reference values specified therefor, viz., especially in order to determine whether or to what extent the spring stiffness c2 of the second useful vibrations of the at least one tube deviates from a reference value (spring stiffness reference value) specified therefor. Alternatively or additionally, the measuring system electronics unit can furthermore also be configured to determine a spring stiffness ratio c1/c2 corresponding to a ratio of the (modal) spring stiffness c1 of the first useful vibrations and the (modal) spring stiffness c2 of the second useful vibrations, viz., for example, to determine, based upon the first and second (useful) currents and/or the first and second useful signal components of at least one of the vibration measurement signals, spring stiffness ratio values representing the spring stiffness ratio c1/c2. Accordingly, the measuring system electronics unit 20 is furthermore also configured to determine both the aforementioned (modal) spring stiffness c1 of the second useful vibrations and a (modal) spring stiffness of the first useful vibrations corresponding to a ratio of the (signal) amplitude of one of the first useful signal components s1N1, e.g., also a sum or a difference of the (signal) amplitudes of the first useful signal components s1N1, s2N1, and a (signal) amplitude of the first (useful) current eN1, viz., for example, to determine, based upon the first (useful) current e1N1 and the first useful signal components of at least one of the vibration measurement signals, spring stiffness values representing the spring stiffness c1 of the first useful vibrations. For carrying out the (self-) diagnosis of the measuring system, the measuring system electronics unit 20 according to a further embodiment of the invention is furthermore configured to compare one or more of the aforementioned spring stiffness values representing the spring stiffness c2 of the second useful vibrations and/or one or more of the aforementioned spring stiffness ratio values to at least one reference value determined therefor in advance and/or by means of an intact measuring system, and, viz., for example, also to output, in the case of a deviation of one or more of the spring stiffness values from the respective reference value (spring stiffness reference value) or in the case of a deviation of one or more of the spring stiffness ratio values from the respective reference value (spring stiffness ratio reference value), a message representing this, especially, a message declared as a (fault) alarm.

    [0127] The parameter values determined for one or more of the aforementioned (system) parameters, viz., for example, the resonance frequency ratio f1/f2 of the at least one tube, the deflection ratio x1/x2 of the first and second useful vibrations, the (modal) damping d2 of the second useful vibrations, the damping ratio d1/d2 of the first and second useful vibrations, the (modal) spring stiffness d2 of the second useful vibrations, the spring stiffness ratio c1/c2 of the first and second useful vibrations, etc., viz., for example, spring stiffness values representing the (modal) spring stiffness c2, spring stiffness ratio values representing the spring stiffness ratio c1/c2, damping values representing the (modal) damping d2, damping ratio values representing the damping ratio d1/d2, deflection ratio values representing the deflection ratio x1/x2, phase difference values representing the phase difference of the second useful signal components, etc., can furthermore also be used for recurrently determining a scatter measure of the respective system parameter. Such a scatter measure can, for example, be an empirical variance or a span for the respective (system) parameter or the parameter values respectively determined therefor. The determined scatter measure can likewise be for the (self-) diagnosis, e.g., in such a way that a fault of the measuring system is at most inferred if the respective (system) parameter has a low scatter measure, viz., a scatter measure below a correspondingly specified threshold value, and/or that a (system) parameter having a scatter measure above a correspondingly specified threshold value does not trigger any fault notification, even if a comparison of its parameter values to the respective reference value would initially indicate this. Alternatively or additionally, the scatter measure determined respectively with the measuring system electronics unit 20 can also be output, e.g., displayed on-site, and/or passed to the aforementioned (measurement) data processing system. Alternatively or additionally, the parameter values determined for one or more of the aforementioned (system) parameters, viz., for example, the resonance frequency ratio f1/f2 of the at least one tube, the deflection ratio x1/x2 of the first and second useful vibrations, the damping of the second useful vibrations, the damping ratio d1/d2 of the first and second useful vibrations, etc., can furthermore also be used for the recurrent determination of a temporal change, viz., for example, a change trend and/or a rate of change and/or a change rate and/or a change velocity of the respective (system) parameter. The determined temporal change can likewise be used for the (self-) diagnosis, for example, in such a way that, in the case of decreasing damping of the second useful vibrations or in the case of a change in the resonance frequency ratio f1/f2 and/or damping ratio d1/d2 increasing with a change rate within a specified measuring range, an increasing fault of the transducer is determined, and/or a message representing an increase in a fault, especially, a message declared as a (fault) alarm, is output. The temporal change or change rate or change velocity respectively determined with the measuring system electronics unit 20 can moreover also be output, e.g., displayed on-site, and/or passed to the aforementioned (measurement) data processing system.

    [0128] The (self-) diagnosis according to the invention of the measuring system can, for example, be carried out during a test interval correspondingly reserved for this purpose, e.g., also an occasionally repeated test interval, or a test interval respectively lasting more than 10 ms (milliseconds), advantageously of more than 100 ms, and especially not less than 1 s (second). The test interval can be time-limited, e.g., to respectively less than 1 min, be started nevertheless recurrently, e.g., by a command from outside the measuring system and/or in an automated manner, viz., in a time-controlled and/or event-controlled manner by the measuring system electronics unit itself. For example, the measuring system electronics unit can be configured to start the test interval in the case of a measured substance FL detected as flowing in a stationary manner and/or to end it in the case of a measured substance FL detected as flowing in a non-stationary manner or in the case of rapidly changing measuring conditions and/or rapidly changing measured variables. Accordingly, the measuring system electronics unit according to a further embodiment of the invention is to automatically start and/or end the test interval and/or is to be able to receive and execute one or more commands that start the test interval. According to a further embodiment of the invention, the measuring system electronics unit is furthermore configured to start the test interval during the normal measuring operation or during the excitation of the first useful vibrations in such a way that at least the drive signal e1 with the second (useful) current eN2 is provided; this, for example, also in such a way that the drive signal e1 simultaneously also contains, at least intermittently, the first (useful) current eN1, so that the second useful vibrations are simultaneously excited with the first useful vibrations, and the first and second useful vibrations are therefore at least intermittently superposed on one another during the test interval. According to a further embodiment of the invention, the measuring system electronics unit is moreover configured to determine during the test interval, based upon the second useful signal components s1N2; s2N2, and especially based upon their (signal) frequency and/or based upon a (signal) amplitude of at least one of the second useful signal components s1N2 and/or based upon a phase angle of at least one of the second useful signal component s1N2, measured values representing the at least one measured variable.