Capacitive Conductivity Measurement in Motor Vehicle Fluid Containers
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Solution Overview
Problem
Existing methods for determining the electrical conductivity of operating fluids in motor vehicle reservoirs, such as water tanks, are inadequate as they often require direct contact with the fluid, which can lead to contamination and inaccurate readings, especially when distinguishing between distilled and tap water.
Innovation Solution
A method using capacitors attached to the reservoir walls to determine conductivity by applying alternating voltages and analyzing impedance or capacitance phase angles and deviations, allowing non-contact measurement and reliable quality assessment based on predefined criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct contact measurement methods are used to determine electrical conductivity, then measurement capability is achieved, but fluid contamination and measurement accuracy deteriorate
Solution Approach 1:
The patent uses the container wall as an intermediary medium to transmit electrical signals between the measurement electrodes and the fluid. The electrodes are positioned on opposite sides of the container wall, allowing the wall to mediate the electrical field interaction without direct contact between electrodes and fluid, thus preventing contamination while enabling conductivity measurement through impedance analysis
Solution Approach 2:
The patent replaces direct mechanical contact measurement systems with a non-contact electrical field-based measurement system. Instead of inserting electrodes into the fluid, the system uses capacitive coupling through the container wall to measure electrical conductivity, substituting a field-based measurement approach for a contact-based mechanical system
2Object-affected harmful factors
If non-contact measurement methods are used, then fluid contamination is prevented, but measurement reliability and accuracy may worsen
Solution Approach 1:
The patent measures impedance at multiple different frequencies to obtain phase angle information that characterizes the fluid's electrical conductivity. By changing the measurement parameter from single-frequency to multi-frequency impedance analysis, the system achieves reliable conductivity determination through the phase angle maximum method while maintaining non-contact measurement
Solution Approach 2:
The patent uses feedback from the phase angle measurement to determine the presence of a maximum within a specific frequency range. This feedback mechanism allows the system to reliably assess fluid conductivity by detecting the characteristic phase angle behavior that occurs with distilled versus tap water, ensuring measurement reliability without direct contact
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
Enables accurate and reliable determination of fluid quality without direct contact, ensuring the conductivity meets specified requirements for safe vehicle operation, preventing potential damage by issuing alerts or stopping the vehicle if conductivity is insufficient.
Implementation Method 1
Determining and storing a first impedance of the capacitor for the first frequency, a second impedance of the capacitor for the second frequency, and a third impedance of the capacitor for the third frequency
Implementation Method 2
the frequency-dependent capacitance of the capacitor depends on the electrical conductivity of the medium through which the alternating electric field between the first and second electrodes passes
Implementation Method 3
The frequency-dependent impedance of the capacitor depends on the electrical conductivity of the medium through which the alternating electric field between the first and second electrodes passes
Data Source
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AI summary
The present invention discloses methods for determining an electrical conductivity of an operating liquid in an operating liquid container (1) for a motor vehicle, wherein the operating liquid container (1) comprises at least one capacitor (60, 70) which is fastened to a container wall (10, 20, 30) of the operating liquid container (1) and has a first electrode (61, 71) and a second electrode (62, 72) opposite said first electrode. A first method according to the invention determines the electrical conductivity of the operating liquid by means of a frequency-dependent phase progression of the impedance of the at least one capacitor (60, 70). Another method according to the invention determines the electrical conductivity of the operating liquid by means of a frequency-dependent capacitance progression of the at least one capacitor (60, 70). The present invention further discloses an operating liquid container (1) which is designed for carrying out the methods according to the invention.