Flow Meter Test Tone Amplitude Compensation
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Solution Overview
Problem
Coriolis mass flowmeters experience errors and bias in stiffness estimates during meter verification at elevated temperatures due to current level saturation in the drive amplifier, leading to noise and uncertainty in flow meter calibration.
Innovation Solution
A method is implemented to calculate a maximum sensor current (MSC) based on electrical resistance, which compensates for temperature-induced amplifier saturation by averaging drive currents and calculating a buffer value to determine an optimal test tone level, ensuring accurate meter verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If meter verification is performed at elevated temperatures, then the flow meter can operate in high-temperature environments, but current level saturation in the drive amplifier causes errors and bias in stiffness estimates
Solution Approach 1:
The patent dynamically adjusts the test tone amplitude parameter based on temperature-induced resistance changes in the drive coil. By calculating the maximum sensor current (MSC) using the formula MSC = (V_max - V_emf) / R_T, where R_T is the temperature-dependent resistance, the system adapts the test signal level to prevent amplifier saturation while maintaining measurement accuracy across temperature ranges.
Solution Approach 2:
The system implements a feedback mechanism where the measured drive current is used to verify amplifier saturation conditions. The patent measures multiple drive currents, averages them, and compares against the calculated MSC to detect saturation. This feedback loop allows the system to identify and compensate for temperature-induced saturation effects, maintaining stiffness estimation accuracy.
2Power
If the drive amplifier operates at high current levels, then sufficient power is available for drive and test tones, but voltage clipping occurs introducing noise and bias into stiffness estimates
Solution Approach 1:
The patent calculates the maximum sensor current (MSC) to determine the optimal test tone amplitude, ensuring the test signal is strong enough for accurate verification but not excessive to cause saturation. By using MSC = (V_max - V_emf) / R_T and applying a buffer value based on averaged drive currents, the system applies just the right amount of test signal power to achieve reliable stiffness estimates without introducing clipping noise.
3Measurement precision
If test tone amplitude is increased to improve signal-to-noise ratio, then stiffness measurement precision improves, but amplifier saturation occurs causing voltage clipping and measurement errors
Solution Approach 1:
The patent dynamically adjusts the test tone amplitude parameter based on temperature-induced resistance changes. By calculating MSC using temperature-dependent resistance values and adjusting the test signal level accordingly, the system maintains optimal signal-to-noise ratio for stiffness measurement precision while preventing amplifier saturation and voltage clipping that would introduce measurement errors.
Solution Approach 2:
The system uses feedback from measured drive currents to detect amplifier saturation conditions. By averaging multiple drive current measurements and comparing against the calculated MSC, the system can identify when the amplifier is approaching saturation and adjust the test tone amplitude accordingly, maintaining measurement precision without generating harmful clipping artifacts.
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 stiffness uncertainty and improves the accuracy of flow meter calibration by preventing voltage clipping and maintaining stable process conditions during meter verification.
Implementation Method 1
A drive coil and magnet may be located between the flow tubes and drives the Coriolis flowmeter at resonance
Implementation Method 2
Two pickoff coils and magnets produce a voltage in response to the resonance motion
Implementation Method 3
When meter verification is performed at a temperature higher than room temperature, resistance inside the drive coil increases
Data Source
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AI summary
A method of determining optimal resistance and compensating for temperature variations in determining a test tone is presented. The optimal resistance in a drive circuit amplifier and drive coil and using the optimal resistance to improve the accuracy of a test tone used in the calibration of a flow meter is presented. The optimal resistance is calculated using a linear extrapolation of the resistance change of the circuit with respect to temperature. The optimal resistance is then used to calculate the proper maximum sensor current (MSC) value using an equation derived from Ohm's law, and from the MSC a test tone level is calculated.