Shielding Electrode for Capacitive Liquid Measurement
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Solution Overview
Problem
Existing electrical measuring assemblies for capacitive measurement of liquids face inaccuracies due to stray capacitances caused by temperature variations and water diffusion in the insulation, leading to defective measurements.
Innovation Solution
A shielding electrode is arranged between the inner and insulating elements to suppress stray capacitances, ensuring that variations in the insulation's permittivity do not affect the capacitance measurement between the inner and outer electrodes, with active shielding achieved through potential synchronization using an operational amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating element is used to electrically insulate the inner electrode from the outer electrode, then electrical insulation is achieved, but stray capacitances occur between the inner electrode and outer electrode that vary with temperature and water diffusion, leading to measurement errors
Solution Approach 1:
A shielding electrode is introduced as an intermediary component between the insulating element and the inner electrode. This shielding electrode acts as a mediator that blocks the capacitive coupling path through the insulating element, preventing stray capacitances from affecting the measurement while maintaining the electrical insulation function of the insulating element.
Solution Approach 2:
The harmful stray capacitance effect is extracted and isolated from the measurement circuit by introducing the shielding electrode. The shielding electrode captures and contains the stray capacitance between the insulating element and inner electrode, separating it from the measurement path between the inner and outer electrodes.
2Measurement precision
If temperature compensation is applied to eliminate temperature-dependent capacitance variation, then temperature effects are reduced, but measurement accuracy is still compromised by varying stray capacitances from insulation changes
Solution Approach 1:
The shielding electrode serves as a protective intermediary that isolates the measurement circuit from insulation variations. By placing the shielding electrode between the insulating element and the inner electrode, it mediates and blocks the transmission of stray capacitance variations to the measurement path, ensuring stable measurements even when insulation properties change.
3Measurement precision
If a shielding electrode is arranged between the inner electrode and the insulating element, then stray capacitances are suppressed and measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The shielding electrode is positioned as an intermediary layer between the insulating element and the inner electrode, creating a capacitive shield that blocks stray electric field lines. This intermediary structure effectively suppresses stray capacitances without requiring fundamental redesign of the basic electrode configuration.
Solution Approach 2:
The shielding electrode is electrically connected to the inner electrode, creating an equipotential surface that extends the inner electrode's potential to the region adjacent to the insulating element. This equipotential connection ensures that no potential difference exists between the shielding electrode and inner electrode, eliminating stray capacitance effects.
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 configuration allows for high-accuracy measurement of liquid quality by isolating the inner electrode from insulation-related interference, enabling continuous or periodic monitoring of liquids with reduced error influences.
Implementation Method 1
a shielding electrode is arranged between the inner electrode and the insulating element, which shields the inner electrode from the insulating element
Implementation Method 2
the capacitance to be measured is constituted between the centrally-arranged inner electrode and the surrounding outer electrode
Implementation Method 3
active shielding achieved through potential synchronization using an operational amplifier
Implementation Method 4
electrical measuring assembly for the capacitive measurement of a liquid
Implementation Method 5
an increase in the electrical permittivity ε of the oil or fat occurs, which is also described as dielectric conductivity
Data Source
AI summary
To increase the measuring precision of an electric measuring assembly (1) for capacitively measuring a liquid, an inner electrode (2) and an outer electrode (3) arranged concentrically to the inner electrode is provided, in which a shielding electrode (5) is arranged between the outer electrode (3) and the inner electrode (2). The potential of the shielding electrode (5) can be actively adjusted to the potential of the inner electrode (2) by a corresponding electric connection such that electric fields which are caused by dielectric displacements in parasitic capacitances are effectively shielded from the inner electrode (2) and thus from the capacitance to be measured. For this purpose, a two-part design of the inner electrode (2) is provided with sections (6) and (7) which can be moved axially relative to each other.