Variable Frequency Magnetic Flowmeter Noise Bias Reduction
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Solution Overview
Problem
Magnetic flowmeters face challenges in high-precision applications due to process noise effects from electronic, mechanical, and electromagnetic sources, leading to biased flow measurements.
Innovation Solution
A magnetic flowmeter with a variable frequency pulsed current source is used to generate a magnetic field, which reduces signal bias by varying the pulse frequency and sampling phase to minimize noise interference, and calculates an average flow measurement based on multiple frequencies and phases to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic flowmeter uses a constant frequency pulsed current source to generate a magnetic field, then the flow measurement can be performed with a simple and stable excitation signal, but the measurement becomes biased due to noise interference at specific frequencies
Solution Approach 1:
The patent applies dynamics by transitioning from a constant frequency pulsed current source to a variable frequency pulsed current source. The excitation frequency is continuously varied over time, which prevents the flow measurement system from being consistently affected by noise at any single frequency. This dynamic adjustment of the excitation parameter resolves the contradiction by maintaining measurement capability while avoiding fixed-frequency noise interference.
Solution Approach 2:
The patent implements parameter changes by modifying the frequency parameter of the pulsed current source. Instead of operating at a fixed frequency, the system varies the excitation frequency across a range of values. This parameter change allows the measurement to escape from noise-dominated conditions at specific frequencies, thereby improving measurement accuracy while maintaining the pulsed operation mode.
2Measurement precision
If the pulse frequency is varied to reduce noise bias, then measurement accuracy improves, but the complexity of the current source increases
Solution Approach 1:
The patent applies periodic action by implementing a systematic frequency variation scheme where the excitation frequency follows a predetermined periodic pattern. This approach reduces noise bias through frequency diversity while maintaining a manageable level of complexity by using structured, repeating frequency sequences rather than arbitrary or chaotic variations.
Solution Approach 2:
The variable frequency pulsed current source is designed to automatically adjust its operating frequency according to a predetermined schedule without requiring manual intervention or complex real-time analysis. This self-service capability reduces the operational complexity while still achieving the goal of noise reduction through frequency variation.
3Measurement precision
If multiple frequencies and phases are used to calculate average flow measurement, then noise-induced bias is reduced, but the signal processing complexity increases
Solution Approach 1:
The patent merges multiple flow measurements obtained at different frequencies and phases into a single averaged flow rate value. By combining these multiple measurements through averaging, the system reduces the impact of noise-induced bias while maintaining relatively simple signal processing. The merging of multiple data streams into a consolidated result achieves noise reduction without requiring complex individual processing of each measurement.
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 effectively reduces noise-induced bias in flow measurements, providing more accurate and precise flow rate data in noisy environments without requiring complex signal processing or operator configuration.
Implementation Method 1
Magnetic flowmeters (or mag meters) measure flow by Faraday induction, an electromagnetic effect. The meter energizes a coil to generate a magnetic field across a pipe section, and the magnetic field induces an electromotive force (EMF) across the process flow.
Implementation Method 2
Magnetic flowmeters (or mag meters) measure flow by Faraday induction, an electromagnetic effect. The meter energizes a coil to generate a magnetic field across a pipe section, and the magnetic field induces an electromotive force (EMF) across the process flow.
Data Source
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AI summary
An apparatus comprises a pipe section for process flow, a coil for generating a magnetic field across the pipe section, a current source for energizing the coil to generate the magnetic field, and an electrode for sensing an electromotive force induced across the process flow by the magnetic field. The current source energizes the coil at a plurality of different pulse frequencies. A processor calculates a function of the electromotive force at the plurality of different pulse frequencies, and generates a flow output based on the function.