Programmable Bi-Directional Current Generator for Magnetic Flowmeter
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Solution Overview
Problem
Conventional pulsed direct current (DC) magnetic flowmeters face challenges in achieving accurate flow rate measurements due to coil current overshoot and incorrect magnetic field settling, resulting from the inductance of the coil.
Innovation Solution
A magnetic flowmeter with a programmable bi-directional current generator and a profile generator that issues profile commands to control the current profile of the coil current, allowing for precise control of the magnetic field and reduction of current overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional coil drivers generate simple square pulsed current profiles with pre-determined magnitude, then the device complexity is reduced, but the measurement precision deteriorates due to current overshoot and incorrect magnetic field settling
Solution Approach 1:
The patent applies dynamics by transitioning from static, pre-determined square pulsed current profiles to dynamic, programmable current profiles. The programmable bi-directional current generator dynamically adjusts the current magnitude and timing based on real-time feedback from the magnetic field sensor, allowing the system to adapt to changing conditions and eliminate measurement errors caused by fixed profile limitations.
Solution Approach 2:
The patent implements feedback by using a magnetic field sensor to monitor the actual magnetic field strength and feeding this information back to the programmable bi-directional current generator. This closed-loop feedback system enables real-time correction of current overshoot and ensures the magnetic field settles at the correct strength, thereby improving measurement precision without significantly increasing overall system complexity.
2Productivity
If the coil current is reversed instantaneously, then the productivity is improved by faster measurement cycling, but the measurement precision worsens due to inductance causing current overshoot
Solution Approach 1:
The patent applies preliminary action by using the programmable current generator to pre-condition the current reversal process. Instead of instantaneous switching, the system programmatically controls the current profile during reversal, anticipating the inductive effects and adjusting the switching timing and magnitude to prevent overshoot before it occurs, thus maintaining both speed and precision.
Solution Approach 2:
The patent implements parameter changes by dynamically modifying current profile parameters (magnitude, duration, timing) based on the measurement phase. The programmable bi-directional current generator changes current parameters adaptively - using faster switching when appropriate but slowing down or adjusting magnitude during reversal to compensate for inductance, thereby maintaining measurement precision while preserving overall productivity.
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 enables accurate and precise flow rate measurements by ensuring the magnetic field settles to the correct strength, reducing measurement errors and preventing power amplifier saturation.
Implementation Method 1
The coil is configured to produce a magnetic field across the fluid flow in response to a coil current. The magnetic field induces an EMF in the fluid flow that is proportional to the flow rate.
Implementation Method 2
A magnetic flowmeter with a programmable bi-directional current generator and a profile generator that issues profile commands to control the current profile of the coil current, allowing for precise control of the magnetic field and reduction of current overshoot.
Data Source
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AI summary
A magnetic flowmeter (102) includes a flow tube assembly (120) and a programmable bi-directional current generator (132). The flow tube assembly (120) receives the fluid flow (104) and includes a coil (126A/B) and an electromotive force (EMF) sensor (124A/B). The coil is configured to produce a magnetic field across the fluid flow (104) in response to a coil current. The EMF sensor (124A/B) is arranged to sense an EMF across the fluid flow that is proportional to the flow rate, and generate an output indicating the induced EMF. The current generator (132) includes a profile generator (144) that issues profile commands, a power amplifier (142) and a controller (140). The controller (140) is configured to control the power amplifier (142) to generate coil current pulses forming the coil current that travel through the coil (126A/B) in alternating directions. Each coil current pulse has a current profile that is based on a corresponding profile command.