Coriolis Mass Flow Meter Dual Tube Zero Point Calibration
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Solution Overview
Problem
Mass flowmeters based on the Coriolis principle with multiple pairs of measuring tubes face zero point errors due to manufacturing tolerances and differing natural frequencies, leading to phase differences and amplitude variations in sensor signals, which are exacerbated by shared exciter and sensor loops.
Innovation Solution
A mass flowmeter design with two pairs of measuring tubes, each with independent electrodynamic exciters and sensors, uses a common exciter signal and sensor loops to minimize signal amplitude differences by adjusting the sensitivity of vibration sensors to maintain tolerance values, ensuring accurate phase differences and reducing zero point errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common exciter loop and sensor loop are used for two pairs of measuring tubes, then device complexity is reduced, but zero point error increases due to phase differences from different natural frequencies
Solution Approach 1:
The patent applies preliminary action by performing zero point calibration before actual measurements. The calibration process excites the measuring tubes at their natural frequencies and adjusts the excitation signals to compensate for phase differences caused by different natural frequencies. This preliminary adjustment eliminates zero point errors before normal operation, allowing the use of common exciter and sensor loops without sacrificing measurement accuracy.
2Object-affected harmful factors
If measuring tubes have different natural frequencies to minimize crosstalk, then vibration isolation improves, but zero point error occurs due to phase differences in sensor signals
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the excitation frequency and phase for each measuring tube pair based on their natural frequencies. The system identifies the natural frequencies of different measuring tube pairs and modifies the excitation parameters accordingly. This allows the tubes to operate at different frequencies to minimize crosstalk while the calibration process compensates for the resulting phase differences in sensor signals, maintaining measurement accuracy.
3Manufacturing precision
If manufacturing tolerances cause different signal amplitudes from inlet and outlet sensors, then sensor sensitivity varies, but phase differences arise when signals are superimposed
Solution Approach 1:
The patent applies feedback by using the sensor signals themselves to determine and correct phase differences. The system monitors the signals from inlet and outlet sensors, detects phase deviations caused by manufacturing tolerances and amplitude variations, and adjusts the excitation signals accordingly during calibration. This feedback mechanism ensures that even with varying sensor sensitivities, the final measurement signals maintain accurate phase relationships.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively minimizes zero point errors by ensuring relative signal amplitude differences between inlet and outlet sensors are within tolerance, maintaining accurate mass flow measurements despite manufacturing tolerances and differing natural frequencies.
Implementation Method 1
The measuring tube pairs each have an electrodynamic exciter for exciting bending vibrations
Implementation Method 2
two vibration sensors for detecting the bending vibrations
Implementation Method 3
a first useful flexural vibration mode that has a first media-dependent useful mode natural frequency f1
Implementation Method 4
In mass flowmeters based on the Coriolis principle, a flow-proportional phase shift between the signals of an inlet-side vibration sensor and an outlet-side vibration sensor is detected
Data Source
Figure 1a~1d
Figure 1e
Figure 2a~2b
AI summary
The invention relates to a Coriolis mass flow meter (100) comprising two measuring tube pairs each having two measuring tubes (110a, 110b, 110c, 110d) which are mounted so as to be capable of oscillating relative to one another and have a bending vibration useful mode of different useful mode natural frequencies f1, f2; each pair having an electrodynamic exciter (140a, 140c) for exciting the bending vibrations of a measuring tube pair; and each pair having a vibration sensor pair having a first inlet-side vibration sensor (142a-1, 142c-1) and a first outlet-side vibration sensor (142a-2, 142c-2) for detecting bending vibrations at two positions of a first measuring tube pair (110a, 110b); an operation and evaluation circuit (160); for driving the exciter (140a, 140c) and for detecting signals of the vibration sensors (142a-1, 142a-2, 142c-1, 142c-2); for determining phase difference-dependent mass flow measurement values; wherein an exciter signal path is designed to transmit the exciter signal to the first and second electrodynamic exciters; wherein inlet-side and outlet-side sensor signal paths are designed to transmit signals of the vibration sensors of both measuring tube pairs in a superimposed manner; wherein the sensor signals having the first useful mode natural frequency f1 have a first relative signal amplitude difference delta1 between the signals of the inlet-side sensors and the signals of the outlet-side sensors, the sensor signals having the second useful mode natural frequency f2 have a corresponding second relative signal amplitude difference delta2, and the amount of a difference deviation D = |delta1 - delta2| of the second relative signal amplitude difference from the first relative signal amplitude difference delta1 is not more than a tolerance value DT.