Coaxial Sensor for Simultaneous Fluid Conductivity and Dielectric Measurement
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Solution Overview
Problem
Current devices are unable to directly and simultaneously measure the conductivity and dielectric constant of high impedance hydrocarbon-based fluids, such as lubrication oils and kerosene, with the required accuracy and cost-effectiveness, especially in real-time applications, and struggle with detecting small quantities of contaminants like water or drill mud.
Innovation Solution
A sensor system utilizing a single pair of coaxial electrodes with unique geometry and a Microcontroller/DSP for signal processing, enabling direct measurement of both conductivity and dielectric constant using low-cost commercial ICs, and allowing real-time adaptation of measurement parameters to improve resolution and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single pair of coaxial electrodes is used to measure both conductivity and dielectric constant, then device complexity is reduced and cost is lowered, but measurement precision and accuracy deteriorate due to the high impedance nature of hydrocarbon fluids
Solution Approach 1:
The patent transforms the measurement approach by changing from direct DC measurement to AC impedance spectroscopy across multiple frequencies. This parameter change enables accurate measurement of high-impedance hydrocarbon fluids by measuring impedance magnitude and phase angle at multiple frequencies, then calculating conductivity and dielectric constant through mathematical transformation of these AC parameters.
Solution Approach 2:
The patent replaces traditional electrical measurement circuitry with a microcontroller-based digital signal processing system. Instead of using complex analog circuits for impedance measurement, the invention uses a microcontroller to generate AC drive signals, measure voltage and current waveforms, and compute impedance parameters digitally, thereby simplifying the hardware while maintaining measurement precision.
2Adaptability or versatility
If multiple electrodes are used to measure both conductivity and dielectric constant simultaneously, then measurement capability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent makes a single pair of coaxial electrodes perform multiple functions by measuring both conductivity and dielectric constant simultaneously. Through AC impedance spectroscopy at multiple frequencies, the same electrode configuration extracts multiple fluid parameters, eliminating the need for separate electrode systems for different measurements and achieving multi-functionality with minimal hardware.
Solution Approach 2:
The patent combines conductivity measurement and dielectric constant measurement into a single integrated system using one electrode pair. By merging these measurement functions and processing impedance data at multiple frequencies, the system achieves simultaneous multi-parameter measurement, reducing the number of components and simplifying the overall device architecture.
3Ease of manufacture
If standard commercially available ICs are used for measurement, then manufacturing cost is reduced, but measurement resolution and accuracy for high impedance fluids deteriorate
Solution Approach 1:
The patent introduces an intermediary microcontroller system between the electrodes and the measurement ICs. This intermediary performs AC signal generation, waveform acquisition, and digital signal processing to extract impedance parameters, thereby adapting standard low-cost ICs to handle high-impedance hydrocarbon fluid measurements that would otherwise be beyond their capability.
Solution Approach 2:
The patent replaces direct analog measurement circuits with a microcontroller-based digital measurement system. The microcontroller generates precise AC drive signals, acquires voltage and current waveforms through ADC, and computes impedance parameters through digital signal processing, enabling the use of standard commercially available ICs while achieving the resolution and accuracy required for high-impedance fluid measurements.
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 system provides accurate and cost-effective simultaneous measurement of conductivity and dielectric constant, enabling effective monitoring of fluid condition and detecting small changes in contaminants, suitable for real-time applications in hydrocarbon-based fluids.
Implementation Method 1
The present invention provides a sensor, system of measurement, and method of measurement of conductivity and dielectric constant of a fluid
Implementation Method 2
measurement of both the conductivity and dielectric constant
Data Source
AI summary
A sensor, a system of direct measurement using that sensor, and a method of direct and simultaneous measurement of conductivity and dielectric constant of a fluid, particularly high impedance, hydrocarbon-based fluids. The sensor has a cell that holds the fluids to be measured between a single pair of coaxial, bare metal electrodes connected through interface circuitry to measurement circuitry preferably implemented in one or several IC's. The sensor has a mutually compatible electrode geometry that provides both the correct cell constant for measurement of conductivity of hydrocarbons fluids (typical range 0-100,000 pS/cm), and a bulk capacitance (for use in dielectric constant measurement) in the range of measure of readily available low cost commercial IC's (having a typical capacitance measurement span of <10 pF, with a total bulk capacitance at the chip of <20 pF). The cell conductivity constant for use with hydrocarbon-based oils having a conductivity in the range of 1 to 500,000 pS/M is preferably less than or equal to about 0.1. The cell bulk capacitance with hydrocarbon fluids inside the sensor results in a bulk capacitance of at least about 4 pF. In one embodiment, the electronic circuitry is a Microcontroller/DSP that both generates synchronous drive signals at various frequencies, for both conductivity and dielectric constant measurements while directly digitizing and numerically processing the sensor output.