Variable Phase Mixing for Conductive Fluid Measurement
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Solution Overview
Problem
Traditional capacitive sensors are limited in measuring capacitance when a highly conductive path is parallel to the capacitance, particularly when dealing with highly conductive fluids, which affects the accuracy of determining the dielectric constant and conductivity, essential for assessing fluid properties like concentration and quality.
Innovation Solution
A system using a measuring circuit with a current source, switching array, phase shifter, mixer, and gain/offset module, along with a controller, separates orthogonal components of signal changes to determine capacitance and resistance independently, allowing for accurate measurement of fluid properties despite wide conductivity fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitive sensors are used to measure capacitance in highly conductive fluids, then the measurement is limited and inaccurate, but the system complexity and cost are low
Solution Approach 1:
The patent segments the measurement task into multiple independent measurements at different known impedances. By measuring the imaginary component of admittance at multiple impedance points and performing calculations, the system accurately determines sensor capacitance even in highly conductive fluids. This segmentation approach transforms a single complex measurement into multiple simpler measurements that can be processed to achieve high precision.
Solution Approach 2:
The patent introduces an intermediary measurement approach using multiple known impedances as intermediate reference points. These intermediary impedance values serve as calibration points that enable the system to accurately measure sensor capacitance by comparing measurements against the known reference impedances, thereby achieving high measurement precision in challenging conductive environments.
2Measurement precision
If traditional capacitive sensors are used in highly conductive fluids, then measurement accuracy deteriorates due to conductive paths, but the system remains simple and low-cost
Solution Approach 1:
The patent converts the harmful effect of high fluid conductivity into a beneficial measurement opportunity. By introducing multiple known impedances and measuring the imaginary component of admittance at each point, the system uses the conductive fluid's properties as part of the measurement process. The multiple measurement points allow the system to mathematically isolate and determine the sensor capacitance contribution, transforming the previously harmful conductive interference into a useful measurement signal.
Solution Approach 2:
The patent changes the measurement parameters by using multiple different known impedance values instead of a single fixed impedance. By varying the impedance parameter across multiple measurement points and analyzing the imaginary component of admittance at each point, the system can accurately determine sensor capacitance and dielectric constant even when the fluid conductivity parameter varies widely or is very high.
3Measurement precision
If high-resolution signal control is required across temperatures, then measurement accuracy improves, but system cost and complexity increase
Solution Approach 1:
The patent performs preliminary measurements at multiple known impedance points before determining the final sensor capacitance value. By pre-measuring the imaginary component of admittance at several known impedance values and storing these reference measurements, the system eliminates the need for high-resolution real-time signal control during actual measurement. The preliminary reference measurements are used in calculations to determine the sensor capacitance, thereby reducing the complexity of signal control requirements while maintaining high measurement accuracy.
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 system enables precise determination of dielectric constant and conductivity, facilitating the assessment of fluid properties such as concentration and quality, even in highly conductive fluids, with reduced costs and without requiring high-resolution signal control across temperatures.
Implementation Method 1
The phase shifter produces waveforms of varying phase, which are supplied to the mixer
Implementation Method 2
The phase shifter produces waveforms of varying phase, which are supplied to the mixer
Implementation Method 3
Traditional capacitive sensors are limited in their ability to measure capacitance when a highly conductive path is parallel to the capacitance
Implementation Method 4
The dielectric constant and conductivity of a fluid may be used to determine when the fluid has an expected set of properties
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
A system and method for measuring an electrical characteristic of a fluid using a measuring circuit. In one implementation, the measuring circuit includes a sensing component, a current supply connected to the sensing component, a sensor switchably connected to the sensing component, an array of components switchably connected to the sensing component, and a monitoring circuit connected to the sensing component. A controller performs a calibration of the measuring circuit by switching parallel impedances in and out of the circuit while measuring voltages across the sensing component. The voltages are measured at at least two different phase angles that are determined by the calibration. Once voltages at different impedances and different phases are determined, the controller calculates a value of the electrical characteristic of the fluid by interpolating between lines of fixed capacitance or resistance.