Three-Layer Capacitance Gap Sensor with Common Guard
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Solution Overview
Problem
Existing gap sensors employing capacitance technology face limitations in measuring smaller gaps due to the need for multiple conductive layers, which restricts thinness and prevents simultaneous measurement of multiple electrodes, and require accurate, speedy three-dimensional gap measurements in applications like aircraft assembly and press die processing.
Innovation Solution
An electronic gap sensor with a three-layer structure and flexible printed board using equipotential driving and charge clamp techniques, allowing simultaneous measurement of multiple electrodes by maintaining all electrodes and guard patterns at a common potential, enabling precise capacitance measurement and improved reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple conductive layers are used for guard patterns on each electrode face, then measurement precision is improved, but device complexity increases and probe thinning is restricted
Solution Approach 1:
The patent merges the guard patterns for multiple electrodes into a single common guard layer. Instead of having separate guard patterns for each electrode face, a single conductive layer serves as a common guard for all electrodes, reducing the total number of conductive layers from six (three pairs of electrode-gold layers) to three (one electrode layer and one common guard layer), thereby enabling probe thinning while maintaining measurement precision
Solution Approach 2:
The common guard layer performs the guarding function for multiple electrodes simultaneously. This single conductive layer serves as a universal guard structure that protects and stabilizes the electrical field for all electrode faces, eliminating the need for individual guard patterns on each electrode and reducing overall device complexity
2Reliability
If multiple conductive layers are used for guard patterns, then measurement reliability is improved, but ease of manufacture deteriorates due to restricted thinning
Solution Approach 1:
The patent combines multiple guard functions into a single conductive layer, reducing the number of fabrication steps. Instead of depositing separate gold layers for each guard pattern, a single common guard layer is formed that serves all electrodes, simplifying the manufacturing process and enabling easier probe thinning while maintaining measurement reliability
Solution Approach 2:
The patent employs a flexible printed board structure with thin conductive layers. The common guard layer is implemented as a thin conductive film on the flexible substrate, allowing the probe to be made thinner and more flexible while maintaining electrical stability and measurement reliability through the equipotential driving technique
3Manufacturing precision
If traditional capacitance sensor structure is used, then manufacturing precision is maintained, but productivity decreases due to inability to simultaneously measure multiple electrodes
Solution Approach 1:
The patent combines multiple electrode measurements into a single integrated structure with a common guard layer. This allows all electrodes to be measured simultaneously rather than sequentially, as the common guard structure enables parallel capacitance measurements for all electrode-gold member pairs, dramatically increasing measurement productivity while maintaining manufacturing precision through the equipotential driving technique
Solution Approach 2:
The patent applies equipotential driving where the common guard layer is driven at the same potential as all electrodes. This creates an equipotential environment that eliminates interference between adjacent electrodes, allowing simultaneous measurement of multiple electrodes without crosstalk, thereby improving productivity while maintaining 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
The solution enables accurate, reproducible, and speedy three-dimensional gap measurements, even in narrow spaces, by stabilizing the measurement process and allowing a larger number of electrodes on a compact probe, enhancing measurement accuracy and efficiency.
Implementation Method 1
gap sensor for detecting, by use of a capacitance measuring technique, gaps
Implementation Method 2
electronic gap sensor with a three-layer structure and flexible printed board using equipotential driving and charge clamp techniques, allowing simultaneous measurement of multiple electrodes by maintaining all electrodes and guard patterns at a common potential
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
A probe (2) is a three-layer substrate having two faces on which paired electrodes (E1, E2) are formed at corresponding positions and guard patterns (Ge) are formed around the electrodes. The guard patterns and all electrodes are driven by a common probe signal (Vp) to an equal potential, thereby commonly guarding the electrodes. Based on a clamp current of each electrode, a capacitance is found to obtain gap data.