Vibronic measuring system

A vibronic measuring system configured to measure at least one flow parameter of a flowing fluid measured substance, the measuring system comprising:

• a transducer including:
• a tube assembly configured to conduct the flowing measured substance, the tube assembly including at least one tube, which:
• defines a lumen enclosed by a tube wall and extends from a first tube end to a second tube end with a tube length;
• and
• is configured to be flowed through by the measured substance in a flow direction from the first tube end to the second tube end while enabled to vibrate;
• an exciter assembly configured to convert electrical power into mechanical power as to excite and maintain forced mechanical vibrations of the tube assembly;
• and
• a sensor assembly configured to detect mechanical vibrations of the tube assembly and to generate vibration signals respectively representing vibration movements of the tube assembly;
• and
• an electronics unit electrically connected to the exciter assembly and to the sensor assembly, the electronics unit configured to at least intermittently feed an electrical drive signal into the exciter assembly,
• wherein inherent in the tube assembly is a plurality of vibration modes respectively having an associated modal damping and an associated resonance frequency determined thereby, in which vibration modes the at least one tube performs damped vibration movements respectively having one or more vibration antinodes and two or more vibration nodes, such that:
• vibration movements of the at least one tube in a fundamental vibration mode, which is a first-order flexural vibration mode, have exactly one vibration antinode and two vibration nodes, and
• vibration movements of the at least one tube in a harmonic mode, which is 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 includes a vibration exciter, which is mechanically connected to the at least one tube and is configured to convert electrical power with a temporally-variable electrical current into mechanical power such that, at a drive point of the vibration exciter on the at least one tube mechanically connected thereto, a temporally-variable drive force acts on the at least one tube,
• and the at least one vibration exciter is positioned and aligned such that a drive offset, which is 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, is not more than 3 mm and/or less than 0.5% of the tube length,
• wherein a vibration node of vibration movements of the at least one tube in a second-order or higher-order vibration mode, which vibration node is formed between two vibration antinodes of said vibration movements of the at least one tube in said second-order or higher-order vibration mode, is within the reference cross-sectional area,
• wherein the sensor assembly includes a first vibration sensor, which is positioned on the at least one tube at a distance from the vibration exciter in the flow direction and is configured to detect vibration movements of the at least one tube and convert the vibration movements into a first vibration signal representing said vibration movements, and
• wherein the sensor assembly includes a second vibration sensor, which is positioned on the at least one tube at a distance from the vibration exciter in the flow direction and is configured to detect vibration movements of the at least one tube and convert them into a second vibration signal representing the vibration movements,
• wherein the electronics unit is configured to feed the electrical drive signal to the vibration exciter, at least intermittently, with a sinusoidal first current component having a first frequency and a first amplitude as to excite first used vibrations, which are mechanical vibrations of the at least one tube forced by the vibration exciter and having a first used frequency, which is a vibration frequency corresponding to the first frequency, such that:
• the first frequency deviates from a resonance frequency of an odd-order vibration mode by less than 1% of the resonance frequency and/or by less than 1 Hz wherein the resonance frequency of said odd-order vibration mode corresponds to or depends on an associated first modal damping of the odd-order vibration mode;
• and
• the first or second vibration signals generated by the first and second vibration sensors each include a first signal component, which is a sinusoidal signal component having a frequency corresponding to the first used frequency, and
• wherein the electronics unit is configured to feed the electrical drive signal to the vibration exciter, at least intermittently, with a sinusoidal second current component having a second frequency and a second amplitude to generate second used vibrations, which are mechanical vibrations of the at least one tube forced by the vibration exciter and having a second used frequency, which is a frequency corresponding to the second frequency, such that:
• the second frequency deviates from a resonance frequency of an even-order vibration mode by less than 1% of said resonance frequency and/or by less than 1 Hz wherein the resonance frequency of said even-order vibration mode corresponds to or depends on an associated second modal damping of the even-order vibration mode;
• and
• the first or second vibration signals generated by the first and second vibration sensors each include a second signal component, which is a sinusoidal signal component having a frequency corresponding to the second used frequency, and
• wherein the electronics unit is configured to determine, both based on a difference between a phase angle of the first signal component of the first vibration signal and a phase angle of the first signal component of the second vibration signal and based on at least one of the second signal components and/or of the second current component, measured values representing the at least one flow parameter of the measured substance.