Magnetic-Inductive Flowmeter Parasitic Field Detection
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Solution Overview
Problem
Magneto-inductive flowmeters operating with harmonic alternating magnetic fields face interference from parasitic magnetic fields, which can falsify flow measurements, and existing methods do not effectively detect or compensate for these parasitic fields.
Innovation Solution
The method involves forming pairs of measured values using different current values and determining the correspondence between these values and the permeability function, signaling non-correspondence as an indication of a parasitic magnetic field presence, utilizing existing current and measured values without additional equipment, and employing materials with hysteresis to ensure accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic field conductor with high permeability is used to guide magnetic flux, then the magnetic field generation is improved, but the permeability becomes a non-linear function of magnetic field strength causing measurement errors
Solution Approach 1:
The patent uses the non-linear permeability characteristic itself as a detection mechanism. By measuring the actual magnetic flux density and comparing it with expected values based on the known non-linear permeability function, the system generates feedback about parasitic magnetic fields. This feedback loop allows the system to detect and compensate for interference without requiring linear material properties.
Solution Approach 2:
The patent changes the operating parameters by using multiple different magnetic field strengths (different current values) to excite the electromagnet. By operating at different points on the non-linear permeability curve and observing how the system responds, the method can distinguish between expected non-linear behavior and unexpected parasitic field effects. This parameter variation enables detection despite the non-linearity.
2Ease of operation
If harmonic alternating magnetic fields are used for flow measurement, then the measurement process is simplified, but parasitic magnetic fields cause falsified measurements
Solution Approach 1:
The system maintains the simple harmonic alternating field operation but adds a feedback mechanism that continuously monitors the actual magnetic flux density. When parasitic fields cause deviations from expected values, the feedback detects these anomalies and triggers compensation or error signaling, preserving operational simplicity while restoring measurement accuracy.
Solution Approach 2:
The patent introduces an intermediary detection step that measures the magnetic flux density as an intermediate parameter. This intermediary measurement acts as a mediator between the simple harmonic field operation and the final flow measurement, allowing the system to identify and correct parasitic field effects without changing the fundamental measurement approach.
3Measurement precision
If multiple current values are used to detect parasitic magnetic fields, then detection accuracy is improved, but the measurement process becomes more complex
Solution Approach 1:
The patent makes the existing electromagnet multi-functional by using it both for generating the measurement magnetic field and for detecting parasitic fields. The same hardware components (electromagnet, magnetic field conductor, flux density sensor) serve dual purposes: normal flow measurement and parasitic field detection. This eliminates the need for separate detection equipment and reduces overall system complexity.
Solution Approach 2:
The method merges the measurement function and detection function into a single integrated process. By combining multiple current value measurements with the normal operational measurements, the system achieves parasitic field detection without adding separate measurement systems. The data from operational measurements is reused for detection purposes, reducing complexity through functional integration.
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 allows for reliable detection and compensation of parasitic magnetic fields, ensuring accurate flow measurements by identifying shifts in magnetic flux densities and electric field strengths, thereby improving measurement reliability and reducing interference.
Implementation Method 1
According to Faraday's law of induction, an electric field strength is generated in a flowing, electrically conductive medium perpendicular to the flow direction of the medium and perpendicular to the magnetic field when a magnetic field is applied
Implementation Method 2
The magnetic field conductor achieves its ability to guide the magnetic flux generated by the electromagnet through its greater permeability compared to its surroundings
Implementation Method 3
If the magnetic field conductor comprises a material with hysteresis, the magnetic flux density in the medium may be affected by the hysteresis behavior of the material
Data Source
AI summary
The invention describes a method for operating a magnetic-inductive flowmeter with a magnetic field generation device for generating a magnetic field which permeates a flowing medium and with a measuring device for determining measured values which represent the field strength of the electrical field induced in the flowing medium by the magnetic field, wherein the magnetic field generation device comprises at least one electromagnet and a magnetic field conductor which is at least partially penetrated by the magnetic field, and the permeability of the magnetic field conductor is a non-linear function of the magnetic field strength. The invention specifies a method of the type described above in which the presence of a parasitic magnetic field is detected, specifically by virtue of the fact that the electromagnet is energized at least with a first current value and a second current value, the measuring device determines a first measured value when the electromagnet is energized with the first current value and determines a second measured value when the electromagnet is energized with the second current value, a first measured value pair is formed from the first current value and the first measured value and a second measured value pair is formed from the second current value and the second measured value, the correspondence of the measured value pairs and of the function of the permeability is determined, and the non-correspondence of the measured value pairs and of the function of the permeability is signalled, wherein the non-correspondence is at least partially caused by the presence of a parasitic magnetic field in the magnetic field conductor.