Electrode Switching for Drift Elimination in Magnetic Inductive Flow Measurement
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Solution Overview
Problem
Magnetic inductive flow measurement devices using permanent magnets suffer from measurement errors due to electrostatic and electrochemical charges, which cannot be calculated out with statistical methods, leading to inaccuracies in flow rate measurements.
Innovation Solution
The use of a switch to short-circuit and then open the electrodes, allowing the dissipation of electrostatic and electrochemical charges, with the potential difference after opening used to measure the flow rate, and a control unit to manage the switching and signal evaluation, ensuring accurate signal measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If permanent magnets are used to generate a static magnetic field for energy-efficient operation, then energy consumption is reduced, but measurement errors occur due to electrostatic and electrochemical charges causing drift in the induced voltage
Solution Approach 1:
The patent applies periodic action by cyclically short-circuiting the electrodes at defined intervals. The switch closes for a first period (0.3-1 second) to discharge electrostatic and electrochemical charges, then opens for a second period (1-3 seconds) to measure the flow-related voltage. This periodic switching eliminates the drift error while maintaining the energy efficiency of permanent magnets, as the magnet continuously generates the magnetic field without requiring power input during the measurement phase.
2Productivity
If electrodes are continuously connected to measure the induced voltage, then flow velocity can be continuously monitored, but electrostatic and electrochemical charges accumulate causing measurement drift
Solution Approach 1:
The periodic switching between short-circuit and measurement states allows the system to maintain continuous monitoring capability while periodically eliminating charge accumulation. The cycle repeats continuously, ensuring that measurement functionality is always available while drift errors are systematically removed at regular intervals.
Solution Approach 2:
The patent discards the contaminated voltage signal that includes drift components by short-circuiting the electrodes during the first period. This allows electrostatic and electrochemical charges to dissipate. During the second period, the system recovers a clean measurement signal that reflects only the flow-related induced voltage, free from drift errors.
3Measurement precision
If the electrodes are short-circuited to eliminate charge accumulation, then measurement accuracy is improved, but the measurement process is interrupted
Solution Approach 1:
The periodic action principle structures the measurement process into alternating phases of charge elimination and signal measurement. By optimizing the duration of each phase (first period: 0.3-1 second for short-circuiting, second period: 1-3 seconds for measurement), the system achieves high measurement accuracy while minimizing the time lost to calibration cycles. The measurement phase occupies the majority of each cycle, ensuring continuous operational capability.
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 method provides a cost-effective solution with increased accuracy by eliminating measurement errors caused by electrostatic and electrochemical charges, allowing for precise flow rate calculations.
Implementation Method 1
According to Faraday's law, this results in a separation of the moving charges within the magnetic field. The at least two electrodes are typically located on opposite sides of the measuring tube and measure a voltage that, ideally, is proportional to the flow velocity of the charge carriers
Implementation Method 2
connecting the at least two electrodes of the measuring device to a switch which is designed to short-circuit the electrodes
Implementation Method 3
the switch is designed to short-circuit the electrodes... the electrodes are short-circuited during a first period... the electrostatic and electrochemical charges occur at the electrodes of the measuring device, particularly near their surfaces. However, the charges can be dissipated (neutralized) by the switch according to the invention, which short-circuits the electrodes
Data Source
Figure 1A~1B
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AI summary
The invention relates to a measuring apparatus for measuring the flow velocity of an electrically conductive medium in a volume permeated by a magnetic field, having a means for producing the magnetic field, at least two electrodes and an evaluation unit which evaluates a signal from the electrodes and calculates the flow velocity, wherein the at least two electrodes are connected to a switch which is designed to short-circuit the electrodes.