VIBRONIC MEASURING SYSTEM

Abstract

The measuring system comprises a vibration-type transducer (10) and electrically coupled measuring system electronics unit (20) for controlling the transducer and evaluating vibration measurement signals provided by the transducer. The exciter arrangement has a vibration exciter (31) which is positioned and aligned such that a drive offset (ΔE) is no more than 0.5% of the tube length. The measuring system electronics (20) are configured to supply electrical power to the vibration exciter (31) by means of an electrical drive signal (e1) having a temporally-variable electrical current and to provide the drive signal (e1) at least intermittently with a sinusoidal (second useful) current (eN2) having a (second) (AC) frequency, in order to monitor a quality of the measured substance based upon a corresponding (second) useful signal component (s1N2; s2N2) of at least one of the vibration measurement signals (s1, s2).

Claims

1. A vibronic measuring system, especially, a Coriolis mass flow measuring device or Coriolis mass flow/density measuring device, for measuring and/or monitoring at least one measured variable, especially a flow parameter, i.e., especially a mass flow and/or a volumetric flow and/or a flow rate, and/or a substance parameter, i.e., especially a density and/or a viscosity of a fluid measured substance, especially, a gas, a liquid, or a dispersion, which measuring system, especially designed as an in-line measuring device and/or a measuring device of compact design, comprises: a transducer (10) with a tube assembly for conducting the flowing measured substance, with an exciter assembly for converting electrical power into mechanical power used to excite and maintain forced mechanical vibrations of the tube assembly and with a sensor assembly for detecting mechanical vibrations of the tube assembly and for providing vibration measurement signals respectively representing vibration movements of the tube assembly; as well as a measuring system electronics unit (20), which is electrically coupled to the transducer (10), i.e., both to the exciter assembly thereof and to the sensor assembly thereof, especially, by means of electrical connecting lines and is formed, especially, by means of at least one microprocessor and/or is arranged in an electronics protective housing, for controlling the transducer and for evaluating vibration measurement signals provided by the transducer; wherein the tube assembly has at least one tube (111), which especially is at least sectionally curved and/or at least sectionally straight, and/or a first tube, which tube extends from a first tube end to a second tube end with a tube length of, especially, more than 100 mm, and has 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, and which tube is configured to be traversed by the measured substance at least in a flow direction from the first tube end to the second tube end and, meanwhile, to be allowed to vibrate, and wherein, inherent in the tube, is a plurality of vibration modes (natural vibration forms) respectively having an associated resonance frequency (f1, f2, . . . , fx), in which modes the tube can perform or performs vibration movements respectively having one or more vibration antinodes and two or more vibration nodes, in such a way that vibration movements of the tube in a fundamental vibration mode, i.e., a first-order vibration mode (f1 mode), i.e., especially a first-order flexural vibration mode, have exactly one vibration antinode and two vibration nodes and that vibration movements of the tube in a harmonic mode, i.e., a second-order or higher-order vibration mode (f2 mode, . . . fx mode), i.e., especially a second-order or higher-order flexural vibration mode, have two or more vibration antinodes and three or more vibration nodes; wherein the exciter assembly has a vibration exciter (31), especially, an electrodynamic vibration exciter, which is mechanically connected to the tube and is configured to convert electrical power with a temporally-variable electrical current into mechanical power in such a way that, at a drive point formed by means of the vibration exciter on the tube mechanically connected thereto, a temporally-variable drive force acts on the tube, especially in such a way that a line of action of the drive force is perpendicular to a normal of a drive cross-sectional area of the tube, wherein the vibration exciter (31) is positioned and aligned such that a drive offset (ΔE), i.e., a smallest distance between a drive cross-sectional area of the tube enclosed by an imaginary circumferential line of the tube passing through the drive point, and a specified reference cross-sectional area of the at least one tube, especially determined with an intact or original transducer, is not more than 3 mm, e.g., less than 2 mm, and/or less than 0.5% of the tube length, i.e., especially less than 0.2% of the tube length, i.e., 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 at least one tube in a (second-order or higher-order) vibration mode (deviating from the first-order vibration mode) and especially (nominally) located at half the tube length, of said vibration movements is within the reference cross-sectional area, and wherein the measuring system electronics unit (20) is configured to energize the vibration exciter (31), i.e., to feed electrical power into the vibration exciter (31) by means of an electrical drive signal (e1) having a temporally-variable electrical current, in such a way that the tube performs forced mechanical vibrations, especially, flexural vibrations, at one or more vibration frequencies specified by the drive signal (e1); wherein the sensor assembly has a first vibration sensor, especially, an electrodynamic or optical first vibration sensor, which is positioned on the tube at a distance from the vibration exciter, especially, in the flow direction, of more than 10 mm and/or more than one fifth of the tube length, i.e., especially at least partially mechanically connected to the tube and which is configured to detect vibration movements of the tube and convert them into a first vibration measurement signal representing said vibration movements, especially, an electrical or optical first vibration measurement signal, especially in such a way 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 tube, wherein the sensor assembly has at least one second vibration sensor, especially, an electrodynamic or optical second vibration sensor, which is positioned on the tube at a distance from the vibration exciter, especially, in the flow direction, of more than 10 mm and/or more than one fifth of the tube length and/or at a distance from the first vibration sensor in the flow direction, i.e., especially, at least partially mechanically connected to the tube and which is configured to detect vibration movements of the tube and convert them into a second vibration measurement signal representing said vibration movements, especially, an electrical or optical second vibration measurement signal, especially in such a way 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 tube, and wherein the measuring system electronics unit is configured to receive and evaluate the first and second vibration measurement signals, i.e., especially to determine and output measured values representing the at least one measured variable; wherein the measuring system electronics unit is configured both to provide the drive signal (e1) at least intermittently with a sinusoidal first (useful) current (eN1) having a first (AC) frequency, in such a way that the tube performs at least partially, especially, predominantly, first useful vibrations, i.e., mechanical vibrations forced by the (energized) vibration exciter, at a first useful frequency, i.e., a (vibration) frequency corresponding to the first (AC) frequency, especially in such a way that the first useful frequency deviates from a resonance frequency, f1, the fundamental vibration mode, by less than 1% of said resonance frequency, f1, and/or by less than 1 Hz, and/or that the first useful frequency deviates from a resonance frequency, f2, of the second-order vibration mode by more than 5% of said resonance frequency, f2, and/or by more than 10 Hz, and/or that the first useful vibrations are suitable for causing, in the flowing measured substance, Coriolis forces that depend upon the mass flow, and that each of the first and second vibration signals (s1; s2) respectively has a first useful signal component (s1N1; s2N1), i.e., a sinusoidal signal component having a (signal) frequency corresponding to the first useful frequency, and to determine, based upon at least the first useful signal components (s1N1; s2N1), especially, based upon their (signal) frequency and/or based upon an amplitude of at least one of the first useful signal components (s1N1; s2N1), and/or based upon a phase angle of at least one of the first useful signal components (s1N1; s2N1), measured values representing the at least one measured variable, especially, mass-flow measured values representing the mass flow of the measured substance and/or density measured values representing the density of the measured substance; and wherein the measuring system electronics are configured both to provide the drive signal (e1) at least intermittently, especially, during a test interval that lasts no less than 1 s (second) and/or is time-limited and/or recurrently started, with a sinusoidal second (useful) current (eN2) having a second (AC) frequency, in such a way that the second (AC) frequency, especially for two or more vibration periods and/or a period of more than 10 ms, deviates from a resonance frequency, f2, of the second-order vibration mode by less than 1%, especially, by less than 0.1%, of said resonance frequency, f2, and/or by less than 1 Hz, especially, by less than 0.1 Hz, and that the tube performs, at least partially, especially simultaneously with the first useful vibrations, and/or stationarily, i.e., for two or more vibration periods and/or a period of more than 10 ms, second useful vibrations having a constant, non-zero vibration amplitude, i.e., mechanical vibrations forced by the (energized) vibration exciter, at a second useful frequency, i.e., a (vibration) frequency corresponding to the second (AC) frequency, whereby each of the first and second vibration signals respectively has a second useful signal component (s1N2; s2N2), i.e., a sinusoidal signal component having a (signal) frequency corresponding to the second useful frequency, as well as, based upon at least one of the second useful signal components (s1N2; s2N2), especially, based upon the (signal) frequency thereof 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), to monitor a quality of the measured substance, i.e., especially, to determine whether a fault of the measured substance, i.e., an undesired change of one or more substance parameters of the measured substance, is present.

2. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit is configured for monitoring the quality of the measured substance, based upon the second useful signal components (s1N2; s2N2), especially, based upon both the second useful signal components (s1N2; s2N2) and the first useful signal components (s1N1; s2N1), to determine whether and/or to what extent a fault of the measured substance is present, especially, as a result of an (undesired) segregation of the measured substance and/or as a result of an (undesired) loading of the measured substance by one or more foreign substances; and/or wherein the measuring system electronics unit is configured to determine whether and/or to what extent, due to a fault of the measured substance, a measurement error is present in the determination of the measured values.

3. The measuring system according to claim 1, wherein the first useful frequency deviates from a resonance frequency, f1, of the fundamental vibration mode by less than 1% of said resonance frequency, f1, and/or by less than 1 Hz.

4. The measuring system according to claim 1, wherein the first useful frequency deviates from a resonance frequency, fr3, of a third-order vibration mode inherent in the at least one tube, i.e., especially a third-order flexural vibration mode, in which vibration mode the vibration movements of the tube have exactly three vibration antinodes and two vibration nodes, by less than 1% of said resonance frequency, fr3, and/or by less than 1 Hz, i.e., especially corresponds to the resonance frequency, fr3.

5. The measuring system according to the preceding claim, wherein a first vibration node of vibration movements of the at least one tube in the third-order vibration mode is located in the first tube end, and a second vibration node of the third-order vibration mode is located in the second tube end.

6. The measuring system according to one of the preceding claims, wherein the harmonic mode corresponds to a second-order vibration mode (f2 mode), i.e., especially a second-order flexural vibration mode, in which second-order vibration mode the vibration movements of the tube have exactly two vibration antinodes and three vibration nodes.

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

8. The measuring system according to one of the preceding claims, wherein the drive offset 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; and/or wherein a line of action of the drive force is perpendicular to a normal of a drive cross-sectional area of the tube; and/or wherein an intersection line of two, mutually-orthogonal symmetry planes of the at least one tube is within the reference cross-sectional area; and/or wherein a main inertia axis, perpendicular to the drive force, of the at least one tube is within the reference cross-sectional area of the at least one tube.

9. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit is configured to provide the second useful current of the drive signal (e1) at least intermittently simultaneously with the first (useful) current, especially in such a way that an amplitude of the first (useful) current is adjusted to not be less than an amplitude of the second (useful) current and/or that an amplitude of the second (useful) current is adjusted to more than 40%, especially not less than 50%, of an amplitude of the first (useful) current; and/or wherein the measuring system electronics unit is configured to adjust the second (AC) frequency as a function of the first (AC) frequency, especially in such a way that the second (AC) 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 (AC) frequency, i.e., especially a multiple of the first (AC) frequency corresponding to more than 230% of the first (AC) frequency and/or less than 300% of the first (AC) frequency.

10. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit has a first phase-locked loop (PLL1), especially, a digital first phase-locked loop, used to adjust the first (AC) frequency and wherein the measuring system electronics unit has a second phase-locked loop (PLL2), especially, a digital second phase-locked loop, used to adjust the second (AC) frequency.

11. The measuring system according to the preceding claim, wherein the measuring system electronics unit is configured to adjust a capture range of the second phase-locked loop (PLL2) by means of at least one output signal of the first phase-locked loop (PLL1), especially, an output signal of a loop filter of the first phase-locked loop (PLL1), and/or based upon the first (AC) frequency.

12. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit is configured to determine a (modal) deflection of the first useful vibrations corresponding to a (signal) amplitude of one of the first useful signal components (s1N1), especially, a difference of the (signal) amplitudes of the first useful signal components (s1N1; s2N1), i.e., especially to determine, based upon at least one of the vibration measurement signals, deflection values representing the deflection of the first useful vibrations; and/or wherein the measuring system electronics unit is configured to determine a (modal) deflection of the first useful vibrations corresponding to a (signal) amplitude of one of the second useful signal components (s1N1), especially, a difference of the (signal) amplitudes of the second useful signal components (s1N1; s2N1), i.e., especially to determine, based upon at least one of the vibration measurement signals, deflection values representing the deflection of the second useful vibrations; and/or wherein the measuring system electronics unit is configured to determine a deflection ratio x1/x2 corresponding to a ratio of the (modal) deflection of the first useful vibrations and the (modal) deflection of the second useful vibrations, i.e., especially, to determine, based upon at least one of the vibration measurement signals, deflection ratio values representing the deflection ratio x1/x2.

13. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit is configured to determine 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), especially, 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), i.e., especially, 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; and/or wherein the measuring system electronics unit is 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), especially, a sum or a difference of the (signal) amplitudes of the second useful signal components (s1N2, s2N2), and a (signal) amplitude of the second (useful) current (eN2), i.e., especially, to determine, based upon the drive signal and at least one of the vibration measurement signals, damping values representing the damping of the second useful vibrations; and/or wherein the measuring system electronics unit is 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 of the second useful vibrations, i.e., especially, to determine, based upon the drive signal and/or at least one of the vibration measurement signals, damping ratio values representing the damping ratio d1/d2.

14. The measuring system according to one of the preceding claims, wherein the measuring system 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 useful vibrations, i.e., especially to compare one or more of the damping values to a reference value (damping reference value) determined therefor in advance.

15. The measuring system according to the preceding claim, wherein the measuring system electronics unit is configured for monitoring the quality of the measured substance, to compare one or more of the damping values to at least one reference value (damping reference value) determined therefor in advance or by means of an intact measuring system and, especially, also to output, in the case of a deviation of one or more of the damping values from the reference value, a message representing this, especially, a message declared as a (fault) alarm; and/or wherein the measuring system electronics unit is configured for monitoring the quality of the measured substance, to determine, based upon several of the damping values, a temporal change, i.e., especially, a change trend and/or a change rate and/or a change velocity, of the damping of the second useful vibrations, i.e., especially to determine an increasing fault in the case of decreasing damping of the second useful vibrations and/or to output a message representing an increase in a fault, especially, a message declared as a (fault) alarm; and/or wherein the measuring system electronics unit is configured to determine, based upon a plurality of damping values, and especially also to output, a scatter measure, especially, an empirical variance and/or a span, for the damping of the second useful vibrations of the at least one tube and/or, for monitoring the quality of the measured substance, to compare said scatter measure to one or more reference values specified therefor.

16. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit is configured to determine the resonance frequency f1 of the first vibration mode of the at least one tube, i.e., especially to determine, based upon the drive signal and/or at least one of the vibration measurement signals, frequency values representing the resonance frequency f1; and/or wherein the measuring system electronics unit is configured to determine the resonance frequency f2 of the second vibration mode of the at least one tube, i.e., especially to determine, based upon the drive signal and/or at least one of the vibration measurement signals, frequency values representing the resonance frequency f2; and/or wherein the measuring system electronics unit is configured to determine a resonance frequency ratio f1/f2 corresponding to a ratio of the resonance frequency f1 of the first vibration mode of the at least one tube and the resonance frequency f2 of the second vibration mode of the at least one tube, i.e., especially to determine, based upon the first and second (AC) frequencies of the drive signal and/or based upon the signal frequencies of the first and second useful signal components (s1N1, s1N2; s2N1, s2N2) of at least one of the vibration measurement signals, frequency ratio values representing the resonance frequency ratio f1/f2.

17. The measuring system according to one of the preceding claims, wherein the measuring system 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 f2 of the second vibration mode of the at least one tube, i.e., especially 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 f2 of the second vibration mode of the at least one tube.

18. The measuring system according to the preceding claim, wherein the measuring system electronics unit is configured to determine, based upon a plurality of frequency values, and especially also to output, a scatter measure for the resonance frequency f2 of the second vibration mode of the at least one tube and/or, for monitoring the quality of the measured substance, to compare said 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 this.

19. The measuring system according to the preceding claim, wherein the measuring system 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 f1 of the first vibration mode of the at least one tube and the resonance frequency f2 of the second vibration mode of the at least one tube, i.e., especially 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 f1/f2 of the at least one tube.

20. The measuring system according to the preceding claim, wherein the measuring system electronics unit is configured for monitoring the quality of the measured substance, to compare one or more of the frequency ratio values to at least one reference value (frequency ratio reference value) determined therefor in advance and, especially, also to output, in the case of a deviation of one or more of the frequency ratio values from the reference value, a message representing this, especially, a message declared as a (fault) alarm; and/or wherein the measuring system electronics unit is configured to determine, based upon a plurality of frequency ratio values, and especially also to output, a scatter measure, especially, an empirical variance and/or a span, for the resonance frequency ratio f1/f2 of the at least one tube and/or, for monitoring the quality of the measured substance, to compare said 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 this.

21. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit is configured to determine, based upon the vibration measurement signals, phase difference values representing a phase difference of the second useful signal components, i.e., a difference between a phase angle of the second useful signal component (s1N2) of the first vibration measurement signal (s1) and a phase angle of the second useful signal component (s2N2) of the second vibration measurement signal (s2), i.e., especially to compare one or more of the phase difference values to a reference value (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 useful signal components of the at least one tube.

22. The measuring system according to the preceding claim, wherein the measuring system electronics unit is configured for monitoring the quality of the measured substance, to compare one or more of the phase difference values to at least one reference value (phase difference reference value) determined therefor in advance, and especially also to output, in the case of a deviation of one or more of the phase difference values from the reference value, a message representing this, especially, a message declared as a (fault) alarm; and/or wherein the measuring system electronics unit is configured to determine, based upon a plurality of phase difference values, and especially also to output, a scatter measure, especially, an empirical variance and/or a span, for the phase difference of the second useful signal components and/or, for monitoring the quality of the measured substance, to compare said 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 this.

23. The measuring system according to one of the preceding claims, wherein the measuring system 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 x1 of the first useful vibrations and the deflections x2 of the second useful vibrations, i.e., especially, 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 x1/x2 of the at least one tube.

24. The measuring system according to the preceding claim, wherein the measuring system electronics unit is configured for monitoring the quality of the measured substance, to compare one or more of the deflection ratio values to at least one reference value (deflection ratio reference value) determined therefor in advance, and especially also to output, in the case of a deviation of one or more of the deflection ratio values from the reference value, a message representing this, especially, a message declared as a (fault) alarm; and/or wherein the measuring system electronics unit is configured to determine, based upon a plurality of deflection ratio values, and especially also to output, a scatter measure, especially, an empirical variance and/or a span, for the deflection ratio x1/x2 of the at least one tube and/or, for monitoring the quality of the measured substance, to compare said 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 this.

25. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit is configured to provide the second (useful) current (eN2) with a specified (current) amplitude.

26. The measuring system according to the preceding claim, wherein the measuring system electronics unit is configured for monitoring the quality of the measured substance, to recurrently compare the (signal) amplitude of at least one of the second useful signal components (s1N2) to a reference value (amplitude reference value) dependent upon the (signal) amplitude of the second (useful) current (eN2) and/or specified therefor, i.e., especially, a reference value corresponding to a (signal) amplitude of the at least one second useful signal component (s1N2) determined at the specified (current) amplitude of the second (useful) current (eN2), i.e., especially, to determine whether or to what extent the (signal) amplitude deviates from said reference value.

27. The measuring system according to one of the preceding claims, wherein the first useful signal components (s1N1; s2N1) of the first and second vibration measurement signals follow a change in a mass flow of the measured substance conducted in the tube with a change in a phase difference of the first useful signal components, i.e., a difference between a phase angle of the first useful signal component (s1N1) of the first vibration measurement signal (s1) and a phase angle of the first useful signal component (s2N1) of the second vibration measurement signal (s2); and wherein the measuring system electronics unit is configured to generate, based upon the phase difference of the first useful signal components (s1N1; s2N1), mass-flow measured values representing the mass flow.

28. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit is configured to follow a change in a density of the measured substance conducted in the tube with a change in the first (AC) frequency of the drive signal, and wherein the measuring system electronics unit is configured to generate, based upon the first (AC) frequency of the drive signal and/or based upon the signal frequency of the first useful signal component of at least one of the vibration signals (s1N1; s2N1), density measured values representing the density.

29. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit is configured, especially, for monitoring the quality of the measured substance, to calculate, based upon the second useful signal components (s1N2; s2N2) of at least one of the vibration measurement signals, especially, based upon the (signal) frequency thereof, 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), one or more characteristic number values for at least one measured-substance characteristic number (MK1), which characterizes an operating state of the measuring system, especially, in such a way that said measuring-system characteristic number depends upon one or more parameters of a system function of the measuring system provided between the second useful current component of the drive signal (e1) and the second useful signal component (s1N2; s2N2) of the at least one vibration measurement signal.

30. The measuring system according to the preceding claim, wherein the measuring system electronics unit (20) is configured for monitoring the quality of the measured substance, to respectively compare one or more characteristic number values for the measured-substance characteristic number to one or more reference values determined for the measured-substance characteristic number, especially, by the 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, especially, 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, especially, to evaluate and/or quantify a deviation of one or more of the characteristic number values from one or more of the reference values.

31. The measuring system according to the preceding claims, wherein the measuring system electronics unit (20) is configured to determine whether one or more characteristic number values for the measuring-system characteristic number (MK1) are greater than the at least one reference value for the measuring-system characteristic number, i.e., especially if 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 this, especially, a message declared as a (fault) alarm.

32. The measuring system according to one of the preceding claims, wherein the measuring-system electronics unit (20) has a non-volatile electronic data memory (EEPROM) that is configured to store digital data, especially even without an applied operating voltage, i.e., especially to store one or more reference values determined in advance for the measuring-system characteristic number.

33. The measuring system according to claim 32 in conjunction with one of claims 29 through 31, wherein one or more reference values, especially, determined in advance by the 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, i.e., especially, one or more reference values representing a reduced functionality of the transducer, and/or, i.e., one or more reference values representing a malfunction of the transducer, are stored in the electronic data memory.

34. The measuring system according to the preceding claim, wherein the measuring-system electronics unit (20) 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.

35. The measuring system according to one of the preceding claims, wherein the measuring system electronics unit is configured to provide the drive signal (e1) with the second (useful) current (eN2) during a test interval that especially lasts more than 10 ms and/or is time-limited and/or recurrently started, at a sinusoidal having a second (AC) frequency; especially in such a way that the second (useful) current (eN2) is non-volatile or stationary, i.e., has a (substantially) constant, non-zero amplitude for two or more vibration periods and/or a period of more than 10 ms (milliseconds).

36. The measuring system according to the preceding claim, wherein the measuring system electronics unit is configured to determine during the test interval, based upon the second useful signal components (s1N2; s2N2), 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; and/or wherein the test interval lasts for more than 100 ms (milliseconds), especially, not less than 1 s (second); and/or wherein the measuring system electronics unit is configured to automatically, especially, in a time-controlled manner, start and/or end the test interval, especially recurrently; and/or wherein the measuring system electronics unit is configured to receive and execute one or more commands that start the test interval.

37. The measuring system according to one of the preceding claims, wherein the tube wall consists of a steel, especially, a stainless steel, duplex steel, or super duplex steel, of a titanium alloy and/or a zirconium alloy, especially, a Zircaloy, and/or a tantalum alloy.

38. The measuring system according to one of the preceding claims, wherein the tube has a caliber (inner tube diameter) that is more than 0.1 mm, i.e., especially more than 0.5 mm.

39. The measuring system according to the preceding claim, wherein 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; and/or wherein the tube length of the tube is more than 200 mm, especially, more than 500 mm, and/or less than 2,000 mm, especially, less than 1,500 mm; and/or wherein the tube has a caliber greater than 10 mm, especially, greater than 15 mm.

40. The measuring system according to one of the preceding claims, wherein, apart from the vibration exciter (31), the exciter assembly does not have any further vibration exciter connected to the tube; and/or wherein the vibration exciter (31) is positioned and aligned such that the drive offset is less than 0.5 mm, i.e., especially zero, or that the area centroid of the drive cross-sectional area of the tube corresponds to or coincides with the drive reference point, and/or wherein each of the first-order and second-order vibration modes of the tube respectively 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; and/or wherein the tube is curved sectionally, especially, in the shape of a circular arc and/or V, especially in such a way that the tube has a central vertex arc segment and/or that exactly one main inertia axis of the at least one tube is within the reference cross-sectional area of the at least one tube; and/or wherein the tube is straight sectionally, especially, over the entire tube length, especially in such a way that the three main inertia axes of the at least one tube are within the reference cross-sectional area of the at least one tube, and/or a center of mass is within the reference cross-sectional area of the at least one tube.

41. The measuring system according to one of the preceding claims, wherein the tube assembly has at least one second tube (112), which is, especially, 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.

42. The measuring system according to the preceding claim, wherein the second tube extends with a tube length from a first tube end to a second tube end and has a lumen, which is enclosed by a tube wall, especially, a metallic tube wall, and extends from the first tube end to the second tube end, and wherein the second tube is designed to be traversed by measured substance 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.

43. The measuring system according to one of claims 41 through 42, wherein a plurality of vibration modes (natural vibration forms) respectively having an associated resonance frequency is inherent in the second tube, in which modes the second tube can perform or performs vibration movements respectively having one or more vibration antinodes and two or more vibration nodes, especially, in such a way that vibration movements of the second tube in the second-order vibration mode (f1 mode) are opposite, especially, in opposition, to the vibration movements of the first tube in the second-order vibration mode (f2 mode), and/or that vibration movements of the second tube in the first-order vibration move (f1 mode) are opposite, especially, in opposition, to the vibration movements of the first tube in the first-order vibration mode.

44. The measuring system according to claim 43, 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 (f1 mode) of the second tube and wherein 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.

45. The measuring system according to one of claims 41 through 44, wherein the first vibration sensor is positioned both on the first tube and on the second tube, i.e., especially is mechanically connected both partially to the first tube and partially to the second tube, and wherein the first vibration sensor is configured to detect, especially differentially, vibration movements, i.e., especially vibration movements in opposition, both of the first tube and of the second tube and convert them into the first vibration measurement signal in such a way that the vibration measurement signal represents vibration movements, especially vibration movements in opposition, of the first and second tubes.

46. The measuring system according to one of claims 41 through 45, wherein the second vibration sensor is positioned both on the first tube and on the second tube, i.e., especially is mechanically connected both partially to the first tube and partially to the second tube, and wherein the second vibration sensor is configured to detect, especially differentially, vibration movements, i.e., especially vibration movements in opposition, both of the first tube and of the second tube and convert them into the second vibration measurement signal in such a way that the vibration measurement signal represents vibration movements, especially vibration movements in opposition, of the first and second tubes.

47. The measuring system according to one of claims 41 through 46, wherein the tube assembly has a first, and/or inlet-side, flow divider (21), which is, especially, used as a line-branching unit and has at least two flow openings, and wherein the tube assembly has a second, and/or outlet-side, flow divider (22), which is, especially, structurally identical to the first flow divider (21) and/or used as a line-merging unit, and has at least two flow openings.

48. The measuring system according to claim 47, wherein each of the first and second tubes of the tube assembly is respectively connected to each of the first and second flow dividers, especially, to form fluidically parallel flow channels, in such a way that the first tube opens with its first tube end into a first flow opening of the first flow divider (21) and with its second tube end into a first flow opening of the second flow divider (22) and the second tube opens with its first tube end into a second flow opening of the first flow divider (21) and with its second tube end into a second flow opening of the second flow divider (22).

49. The measuring system according to one of claims 41 through 48, wherein the vibration exciter (31) is mechanically connected both partially to the first tube and partially to the second tube.

50. The measuring system according to one of claims 41 through 49, wherein the vibration exciter (31) is configured to act differentially on the first and second tubes, especially in such a way that the first and second tubes simultaneously perform opposite forced mechanical vibrations of equal frequency; and/or wherein the vibration exciter (31) is configured to convert electrical power with a temporally-variable electrical current into mechanical power such that a temporally-variable drive force acts on the second tube at a drive point formed by means of the vibration exciter on the second tube mechanically connected thereto, especially simultaneously and/or oppositely to the drive force acting on the first tube at the drive point formed by means of the vibration exciter on the first tube mechanically connected thereto; and/or wherein the vibration exciter (31) is configured 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, especially in such a way that the first and second tubes simultaneously perform forced mechanical vibrations at the first useful frequency and/or at the second useful frequency.

51. The measuring system according to one of the preceding claims, wherein the vibration exciter (31) is formed by means of a vibration coil having, especially, an air coil and an armature; and/or wherein each of the first and second vibration sensors is respectively formed by means of a plunger coil having, especially, an air coil and an armature.

52. The measuring system according to one of the preceding claims, wherein the vibration exciter (31) has a magnetic armature, formed especially by means of a permanent magnet, and a coil flooded by the magnetic field of the armature, i.e., especially an air coil.

53. The measuring system according to the preceding claim, wherein the magnetic armature is mechanically connected to the at least one tube to form the drive point; and/or wherein the coil is electrically connected to the measuring system electronics unit and is configured to receive the drive signal (e1) and to conduct the first and second (useful) currents (eN1, eN2) thereof.

54. The measuring system according to one of the preceding claims, further comprising: an electronics protective housing (200) for the measuring system electronics unit (20), which electronics protective housing is, especially, fastened to a transducer protective housing of the transducer and/or is metallic.

55. The measuring system according to one of the preceding claims, further comprising: a transducer protective housing, which is especially metallic, wherein the transducer protective housing and tube assembly are fastened to one another, especially, detachably.

Description

[0076] The invention as well as advantageous embodiments thereof are explained in more detail below based upon exemplary embodiments shown in the figures of the drawing. Identical or identically acting or identically functioning parts are provided with the same reference signs in all figures; for reasons of clarity or if it appears sensible for other reasons, reference signs mentioned before are dispensed with in subsequent figures. Further advantageous embodiments or developments, especially, combinations of partial aspects of the invention that were initially explained only separately, furthermore emerge from the figures of the drawing and/or from the claims themselves.

[0077] In the figures:

[0078] FIG. 1 a perspectival side view of an exemplary embodiment of a vibronic measuring system;

[0079] FIG. 2 shows 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;

[0080] FIG. 3 shows 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;

[0081] FIG. 4a shows 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;

[0082] FIG. 4b shows 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;

[0083] FIG. 5 shows 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; and

[0084] FIGS. 6, 7 show a schematic of the tube assembly according to FIG. 4 with tube excited to second useful vibrations.

[0085] FIG. 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 temporally-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 m, a volumetric flow and/or a flow rate, or, for example, a substance parameter, such as a density p and/or a viscosity 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, i.e., for example, a gas, a liquid, or a dispersion, and to be at least intermittently traversed during operation by the fluid FL supplied or discharged via the process line. Moreover, the measuring system is provided to determine, i.e., 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, i.e., for example, a tube line of a filling plant, a refueling device, or another industrial plant.

[0086] As shown respectively in FIGS. 1, 2, and 3, or readily apparent from their combination, the measuring system comprises a vibration-type transducer 10, i.e., 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, i.e., 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, i.e., both to the aforementioned exciter assembly of the transducer and to the aforementioned sensor assembly of the transducer, i.e., for example, by means of corresponding electrical connecting lines, especially, formed by means of at least one microprocessor (pC) and/or arranged in an electronics protective housing (200) and/or used as a transmitter for controlling the transducer, i.e., especially to cause the aforementioned mechanical vibration of the at least one tube and to evaluate vibration measurement signals supplied by the transducer, i.e., for example, to determine the aforementioned measured values.

[0087] 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 FIG. 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.

[0088] The at least one tube of the tube assembly can be straight at least sectionally, i.e., especially hollow cylindrical, and/or curved at least sectionally, e.g., in such a way that said tube has a central vertex arc segment, i.e., 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 consists of a metal, i.e., 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, i.e., 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 one of the geometric shapes and/or dimensions customary in conventional (standard) vibronic measuring systems, i.e., 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.

[0089] 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 traversed 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, i.e., for example, two further tubes, and therefore, as also shown in, inter alia, the above-mentioned U.S. Pat. No. 5,602,345, 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, i.e., 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, consist of 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 have 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 have a caliber, i.e., an inner diameter, that is equal to a caliber of the other tube or of each of the other tubes.

[0090] 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 traversed 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, i.e., 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 traversed 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, i.e., for example, a vibration axis imaginarily connecting the first and second tube ends.

[0091] The aforementioned exciter assembly of the transducer 10 in turn is especially provided or configured to convert electrical power fed thereinto (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 (412), i.e., 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.

[0092] 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 temporally-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 temporally-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, i.e., 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, i.e., 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.

[0093] 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, i.e., 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, i.e., 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 temporally-variable electrical current into mechanical power such that a temporally-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, i.e., 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.

[0094] 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, i.e., 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, i.e., 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, i.e., 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, i.e., 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, i.e., 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.

[0095] 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, i.e., a first-order vibration mode (f1 mode), i.e., 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), i.e., a second-order or higher-order vibration mode (f2 mode, f3 mode, f4 mode, . . . fx mode), i.e., 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, i.e., 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, i.e., 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.

[0096] In the measuring system according to the invention, the vibration exciter 31 is positioned and aligned such that, as is also shown schematically in FIG. 4a or 6, and also quite customary in, inter alia, conventional vibronic (standard) measuring systems, a drive offset ΔE, i.e., 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, i.e., 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, i.e., 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, i.e., 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, i.e., 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, i.e., 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.

[0097] As already mentioned, the measuring system comprises, in addition to the transducer 10, a measuring system electronics unit 20 electrically coupled thereto, i.e., 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, i.e., 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, 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, i.e., 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.

[0098] In the measuring system according to the invention, the measuring system electronics unit 20 is in particular configured to energize the vibration exciter 31, i.e., to feed electrical power into the vibration exciter 31 by means of an electrical drive signal e1 having a temporally-variable electrical current, in such a way that the at least one tube performs forced mechanical vibrations, i.e., 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, i.e., 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, i.e., mechanical vibrations, forced by the vibration exciter 31 (energized with the (useful) current eN1) or a first drive force (component) F.sub.exc1 generated therewith, at a first useful frequency f.sub.N1, i.e., 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, i.e., 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 (|f.sub.2−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, i.e., 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, i.e., 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, i.e., the current thereof.

[0099] 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, i.e., 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 few 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), i.e., 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 few such that said (AC) frequency few 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), i.e., 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. 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.

[0100] 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, i.e., 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, i.e., 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, i.e., 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, U.S. Pat. Nos. 5,602,345, 5,926,096, 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, not prepublished, 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, i.e., 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, i.e., 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, i.e., 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 respectively shown schematically in FIG. 2 or 3, for example, also by means of the aforementioned measurement and evaluation circuit DSV.

[0101] The program codes executed during operation of the measuring system in the measuring system electronics unit 20, i.e., 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, i.e., 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), i.e., 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 U.S. Pat. No. 6,311,136. 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, i.e., 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, i.e., especially to also use them in the determination of the measured values.

[0102] As already mentioned, during operation, the measured substance or the (measured-substance) quality thereof can significantly change temporally or be subject to significant fluctuations; this, especially, also in such a way that, due to deviations of the (measured-substance) quality from a specification specified therefor, the vibration properties of the at least one tube conducting the measured substance change to an extent significantly reducing the measurement accuracy. Changes to the vibration characteristics of the at least one tube can be attributed, for example, to changes of one or more modal masses and/or dampings determined by the quality of the measured substance, i.e., a respective mass and/or damping determining the aforementioned vibration modes, or the respective distribution thereof, and result in the (natural) vibration forms of one or more of the vibration modes of the at least one tube differing significantly from the respective counterpart thereof at normal (measured-substance) quality, i.e., a quality within the specification; this regularly also in such a way that a density, typically substantially homogeneous or uniform, and viscosity of the measured substance that is present in a normal measured substance are distributed increasingly unevenly and the aforementioned (system) parameters of modal mass and modal damping of one or more of the vibration modes are correspondingly changed as a result. As a result, not only do changes in the quality of the measured substance lead to the resonance frequency of one or more of the aforementioned vibration modes changing, but such changes also regularly lead to the form of the vibration movements of the respective vibration modes being subject to changes in such a way that the position of one or more of the vibration nodes located between two vibration antinodes of the vibration movements 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 relative to its respective original position and/or to the vibration nodes, is changed. Accordingly, the drive offset determined relative to the reference cross-sectional area or the vibration node also experiences changes, for example, in such a way that the drive offset in comparison to the drive offset ΔE determined in the normal measured substance increases. Examples of such fluctuations in the (measured-substance) quality or deviations of the (measured-substance) quality from the (measured-substance) specification include a temporally changing loading of the measured substance with a foreign substance, such as solid particles and/or gas bubbles in a liquid, a formation of condensate in a gaseous measured substance, an outgassing of a liquid measured substance or, in the case of a measured substance formed as a dispersion, a temporally changing concentration of individual phases and/or components of the measured substance and/or an occasional segregation of components of the measured substance.

[0103] System functions affected by such changes in the (measured-substance) quality or deviations of the (measured-substance) quality from the specification can, for example, correspond to one or more (modal) vibration responses of the tube assembly that are relevant to the measurement of the at least one measured variable, i.e., for example, a functional dependence of an amplitude of the aforementioned useful vibrations from the drive signal or a functional dependence of an amplitude of the aforementioned Coriolis vibrations from the drive signal and mass flow. Examples of such system functions of the transducer can accordingly, for example, include a mass-flow-to-phase-difference system function, i.e., 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, i.e., for example, a system function of the transducer according to which the aforementioned resonance frequency f1 depends upon the density, or dampings of vibrations as system functions containing (system) parameters, such as a viscosity-to-damping function, i.e., for example, a system function of the transducer according to which a damping of the first useful vibrations depends upon the viscosity. Accordingly, however, one or more measurement functions of the measuring system can also be affected, according to which function the measuring system ultimately converts the measured variable to be detected in each case into the respective measured values which are based upon one or more of the aforementioned system functions of the transducer. Examples of such measurement functions of the measuring system include, inter alia, a mass-flow-to-measured-value function 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, i.e., 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 also 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. The changes in the (measured-substance) quality or deviations of the (measured-substance) quality from the specification in question can, especially, also lead to one or more system functions or (system) parameters characterizing a corresponding measurement function, for example, a (scale) zero point and/or a sensitivity (slope of the characteristic curve function) of the aforementioned phase-difference-to-mass-flow-measured-value characteristic curve function, which corresponds to a change in the phase difference of the first useful signal component related to a change in the mass flow, being subject to corresponding temporal changes, i.e., for example, having corresponding fluctuations, and to a measurement accuracy of the measuring system, with which the latter ultimately represents the measured variable to be detected, in the corresponding measured values, being significantly reduced as a result in relation to a measurement accuracy of the measuring system in the case of the normal measured substance.

[0104] In order to be able to detect and possibly report any changes in the quality of the measured substance or the deviation thereof from the specification as early and reliably as possible, it is therefore furthermore provided 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 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, i.e., especially, to examine them for an impermissible change in the quality of the measured substance; this especially such that said vibrations corresponding to the second-order vibration mode (f2 mode) are non-volatile or stationary, i.e., 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 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), i.e., 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, i.e., 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 Si, s2 respectively has a second useful signal component s1N2 or s2N2, i.e., 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.

[0105] 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).

[0106] For the aforementioned case that the tube assembly has at least two tubes, the vibration exciter 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, i.e., 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.

[0107] 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, i.e., 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 has a first phase-locked loop (PLL1), e.g., also a digital first phase-locked loop, used to adjust the (AC) frequency f.sub.eN1, and a second phase-locked loop (PLL2), e.g., a digital second phase-locked loop, 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, i.e., for example, an output signal of a loop filter of the first phase-locked loop PLL1.

[0108] The measuring system electronics unit 20 of the measuring system according to the invention is also configured, based upon or by evaluating at least one of the second useful signal components s1N2, s2N2, for example based upon the (signal) frequency thereof and/or based upon a (signal) amplitude of at least one of the second useful signal components s1N2, s2N2 and/or based upon a phase angle of at least one of the second useful signal components s1N2, s2N2, to monitor the quality of the measured substance, i.e., for example, to determine whether and/or to what extent a fault of measured substance is present. According to a further embodiment of the invention, the measuring system electronics unit 20 is configured, based upon the at least one of the second useful signal components s1N2, s2N2, to determine whether and/or to what extent a fault of the measured substance influencing vibration characteristics of the second-order vibration mode, i.e., an undesired change of one or more substance parameters of the measured substance, is present, i.e., for example, to determine whether a fault of the measured substance as a result of an (undesired) segregation of the measured substance and/or as a result of an (undesired) loading of the measured substance by one or more foreign substances. In addition, the measuring system electronics unit 20 may also be configured, based upon the at least one of the second useful signal components s1N2, s2N2, to determine whether and/or to what extent, due to a fault of the measured substance, a fault of one or more of the aforementioned system functions or measurement functions of the measuring system, and therefore a measurement error in the determination of the corresponding measured values, is also present.

[0109] 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 measured-substance 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 a state of the measured substance, for example, 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 and/or that the measured-substance characteristic number decreases with decreasing (measured-substance) quality.

[0110] 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 dampings of the at least one tube. The corresponding reference values for the parameter values as well as the respectively corresponding threshold values can be determined in advance, i.e., 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 and/or based upon laboratory measurements with structurally identical measuring systems or measuring systems of the same type, based upon different measured substance of a respectively known measured-substance quality, 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.

[0111] 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 monitoring the quality of the measured substance as a (system) parameter specifying system functions of the transducer, for example, in such a way that a temporally-changing, for example, 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, i.e., 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), i.e., 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 monitoring of the quality of the measured substance 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, i.e., especially, in order to determine whether or to what extent the resonance frequency ratio f1/f2 deviates from said reference value.

[0112] Taking into account the deflections 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 monitoring of the quality of the measured substance as a (system) parameter specifying system functions of the transducer. 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, i.e., 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 monitoring of the quality of the measured substance 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, for example, 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 deviates 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 monitoring of the quality of the measured substance 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, and therefore amplitude values respectively representing deflections x1 of the first useful vibrations, i.e., 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, i.e., especially, both amplitude values 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 of the first useful vibrations and the (modal) deflection of the second useful vibrations, i.e., 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 monitoring of the quality of the measured substance by means of the measuring system electronics unit 20, the recurrently determined amplitude values, i.e., 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, for example, 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, i.e., 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 a 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.

[0113] Taking into account both the deflection velocities 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 monitoring of the quality of the measured substance as a (system) parameter specifying system functions of the transducer, for example, in such a way that an excessively high and/or temporally continuously increasing (modal) 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 of the measured substance, i.e., for example, an excessively high deviation of the quality of the measured substance from the specification and/or an excessively rapid change of the (measured-substance) quality. Additionally, taking into account both the deflections of the first or second useful vibrations and also 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 the respectively corresponding vibration mode and to use if for monitoring the quality of the measured substance as a (system) parameter specifying system functions of the transducer, for example, in such a way that a temporally-changing and/or an excessively high (modal) damping of the second useful vibrations in the case of a simultaneously sufficiently high and temporally-constant (modal) spring stiffness of the second useful vibrations indicates the presence of a fault of the measured substance and/or that an excessively low and/or continuously decreasing (modal) spring stiffness of the second useful vibrations or a temporally-changing, for example 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, possibly also in the case of an excessively high (modal) damping of the second useful vibrations, indicates the presence of a mechanical fault of the tube assembly or of the transducer formed therewith.

[0114] 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, i.e., 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 monitoring of the quality of the measured substance 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, i.e., 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, i.e., 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, i.e., 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 monitoring of the quality of the measured substance, 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, i.e., 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 for a reduced (measured-substance) quality. According to a further 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, spring stiffness values representing the spring stiffness c2 of the second useful vibrations. 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, i.e., 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, i.e., 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 monitoring of the quality of the measured substance by means of the measuring system electronics unit 20, the recurrently determined spring stiffness values or spring stiffness ratio values can furthermore, for example, be compared to one or more reference values specified therefor, i.e., for example, 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. In a further embodiment of the invention, the measuring system electronics 20 is furthermore configured for the case that, based upon the comparison to the reference value, an excessively low and/or temporally continuously decreasing (modal) spring stiffness of the second useful vibrations or a temporally-changing, for example 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 determined, to output a message indicating a damaged measuring system, for example, also a message declared as a (fault) alarm for the measuring system, i.e., especially, also no (fault) alarm for a reduced (measured substance) quality.

[0115] The parameter values determined for one or more of the aforementioned (system) parameters, i.e., 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., i.e., 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 used for the monitoring of the quality of the measured substance, for example, 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, i.e., 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 message, 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, i.e., 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, i.e., 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 monitoring of the quality of the measured substance, for example, in such a way that, in the case of increasing 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 outside a specified measuring range, an increasing deviation of the quality of the measured substance is detected and possibly correspondingly reported. 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.

[0116] The monitoring according to the invention of the quality of the measured substance can, for example, be carried out during a test interval correspondingly reserved for this purpose, for example, also an occasionally repeated test interval or a test interval respectively lasting for 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, i.e., in a time-controlled and/or event-controlled manner by the measuring system electronics unit itself. 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 e2 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.