Interference-Voltage Eliminating Unit for Magnetic-Inductive Flowmeter
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Solution Overview
Problem
Magnetic-inductive flowmeters face significant interference from unequal voltage fluctuations due to inhomogeneous medium characteristics, electrode surface soiling, and temperature/pressure distribution, which cannot be effectively eliminated by conventional methods, leading to inaccurate measurements.
Innovation Solution
A method and device that utilize an interference-voltage eliminating unit with a comparer unit to differentiate and suppress unequal interference voltages by comparing current and preceding voltage values from each measuring electrode, allowing only proportional changes to be considered as interference-free for further processing, and using stored error-free values in case of interference detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional differential amplifiers are used to eliminate interference voltages, then common-mode interference is reduced, but unequal interference voltages from inhomogeneous medium characteristics, electrode soiling, and temperature/pressure distribution remain and cause measurement inaccuracies
Solution Approach 1:
The evaluation electronics are segmented into multiple independent processing channels, each handling signals from individual measuring electrodes. This allows separate evaluation of voltage values from each electrode and enables targeted elimination of interference voltages specific to each electrode, rather than treating all signals uniformly.
Solution Approach 2:
The system performs preliminary evaluation of voltage values from measuring electrodes before final measurement processing. By comparing current voltage values with previously determined interference-free values, the system proactively identifies and eliminates interference voltages before they corrupt the measurement results.
Solution Approach 3:
The system uses feedback by comparing current voltage values U+(n) and U−(n) with previously stored interference-free values U+(n−1) and U−(n−1). This feedback mechanism allows the system to detect changes in interference conditions and dynamically adjust the measurement evaluation to maintain accuracy.
2Object-affected harmful factors
If digital filter means such as temporal attenuation and statistical averaging are applied to reduce interference voltages, then some interference is reduced, but satisfactory measurement results are not achieved and measurement precision remains insufficient
Solution Approach 1:
The system extracts and removes interference voltages specifically from the measured voltage values by comparing them with previously determined interference-free values. This targeted extraction of interference components is more effective than general digital filtering, as it specifically removes the harmful interference while preserving the useful measurement signal.
3Adaptability or versatility
If measuring electrodes are exposed to inhomogeneous medium characteristics, electrode surface soiling, and temperature/pressure distribution, then the flowmeter can operate in practical applications, but unequal interference voltages occur that cannot be eliminated by differentiation
Solution Approach 1:
The system performs preliminary evaluation and comparison of voltage values to identify interference-free measurements before they are used in final calculations. This preliminary action allows the system to maintain practical applicability in harsh environments while ensuring measurement accuracy by pre-filtering out corrupted data.
Solution Approach 2:
The system uses feedback mechanisms to continuously monitor voltage values from each measuring electrode and compare them with previously determined interference-free values. This feedback allows the system to adapt to changing environmental conditions and maintain measurement precision even when electrodes are exposed to inhomogeneous medium characteristics and soiling.
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
This approach efficiently eliminates interference voltages, enabling accurate volume and mass flow measurements and allowing for continued operation with restricted accuracy in case of defective electrodes or disturbed signals, while also facilitating diagnostic analysis of interference causes.
Implementation Method 1
The measuring method is based on Faraday's law of induction. This law of nature says that a voltage is induced in a conductor moving in a magnetic field. When this law of nature is utilized for measuring, the electrically conductive medium flows through a measuring tube in which a magnetic field is generated perpendicularly to the direction of flow.
Implementation Method 2
The voltage induced as a result in the medium is picked up by an electrode arrangement.
Data Source
AI summary
A method and device for obtaining an interference free measurement from a flowmeter. The flowmeter includes a measuring tube through which a flowable medium flows through a magnetic field generated by a magnetic arrangement and at least two measuring electrodes for detecting the measurement voltage induced by the flowable medium. The medium gives rise to interference voltages. The electrodes are connected to an interference-voltage eliminating unit by which common-mode interference is first eliminated by differentiation and unequal interference voltages are subsequently eliminated. In operation, the current voltage value U+(n) and U−(n) of each individual measuring electrode is compared with the associated preceding voltage value U+(n−1) and U−(n−1), and the interference-voltage eliminating unit outputs a measurement for further signal processing only when an equal, essentially proportional change in the voltage values U+(n) to U+(n−1) and U−(n) to U−(n−1) is found at each measuring electrode, which is evaluated as interference-free measurement.