Digital Coil Driver for Magnetic Flowmeter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional magnetic flowmeters face challenges in accurately controlling alternating currents through inductive loads, leading to errors in flow measurements due to instability and overshoot, which are not optimized for varying flow tube parameters over time and temperature.
Innovation Solution
A digital coil driver system using Pulse Width Modulation (PWM) command signals to control the H-bridge circuitry, with a microcontroller adapting the current profile based on real-time impedance measurements to minimize overshoot and ensure fast settling times, allowing the magnetic flowmeter to operate optimally across different flow tube configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current supply circuitry is used to drive alternating current through the coil, then the magnetic field is generated, but the current control is unstable with overshoot and measurement errors
Solution Approach 1:
The patent implements a feedback control mechanism where the microcontroller monitors the actual coil current and adjusts the PWM duty cycle accordingly. The current sense resistor Rsense provides real-time current feedback to the microcontroller, which compares the measured current against the desired current profile and dynamically adjusts the H-bridge switch control to eliminate overshoot and maintain stability.
Solution Approach 2:
The patent transitions from static conventional current control to dynamic PWM-based control. The microcontroller continuously adjusts the PWM duty cycle and switching frequency based on real-time conditions, allowing the system to adapt to varying load conditions, temperature changes, and flow tube parameters, thereby eliminating the overshoot and instability inherent in conventional fixed control methods.
2Speed
If the coil driver operates at high frequency for fast response, then the settling time is reduced, but the overshoot increases due to inductive load characteristics
Solution Approach 1:
The patent employs periodic PWM switching at high frequency to drive the coil current. The microcontroller uses periodic pulse trains with adjustable duty cycles to control the H-bridge switches, enabling fast current reversal while maintaining stability through the periodic nature of the control signal. The switching frequency is optimized to achieve fast response without excessive overshoot.
Solution Approach 2:
The patent dynamically changes control parameters including PWM duty cycle, switching frequency, and pulse width based on the desired current profile and actual measured current. The microcontroller adjusts these parameters in real-time to achieve fast settling times while minimizing overshoot, overcoming the trade-off between speed and stability in inductive load control.
3Adaptability or versatility
If the flow tube parameters change over time and temperature, then the operating conditions vary, but conventional fixed control algorithms cannot adapt
Solution Approach 1:
The patent implements a self-adaptive control system where the microcontroller automatically adjusts control parameters based on real-time feedback from current sensing and impedance measurements. The system performs self-diagnosis and self-adjustment without external intervention, adapting to temperature changes, flow tube parameter variations, and different operating conditions to maintain measurement accuracy.
Solution Approach 2:
The patent uses continuous feedback from current sense resistors and impedance measurement circuits to detect changes in flow tube parameters and temperature. The microcontroller processes this feedback information and dynamically adjusts the PWM control signals to compensate for parameter variations, maintaining optimal performance across different operating conditions.
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 digital coil driver system provides precise control of the magnetic field, reducing measurement errors and adapting to changes in flow tube parameters, ensuring high-frequency current reversal with minimal overshoot and fast settling times, thereby enhancing the accuracy and reliability of flow rate measurements.
Implementation Method 1
a coil with first and second coil wires for receiving a coil current to produce a magnetic field in the fluid
Implementation Method 2
magnetic flowmeters are distinguished from these technologies by characterizing a flow based on Faraday's Law, which depends upon electromagnetic interactions rather than mechanical or thermodynamic effects. In particular, magnetic flowmeters rely upon the conductivity of the process fluid, and the electromotive force (EMF) induced as the fluid flows through a region of magnetic field.
Implementation Method 3
An EMF sensor is arranged to sense the EMF and generate an output related to the flow rate
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A magnetic flowmeter (300) for measuring a fluid flow (101) includes flow tube assembly (102) receiving the flow having a coil (104) with first and second coil wires for receiving a coil current to produce a magnetic field in the fluid. This generates an EMF in the fluid representative of the flow (101). An EMF sensor is arranged to sense the EMF and generate an output related to the flow rate. Current supply circuitry (110) provides the coil current to the first and second wires of the coil (104) in response to a command signal. A digital control circuit (308) provides the command signal to the current supply circuitry (110) as a function of a control algorithm. In one aspect, the control algorithm is adapted to changes in electrical parameters of the coil (104). A method of implementing the magnetic flowmeter (300) is also provided.