Capacitive Proximity Sensor Diagnostics Using a Shielding Electrode
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Solution Overview
Problem
Existing capacitive proximity sensors used in safety-relevant areas face challenges in efficiently testing their functionality without complex simulations, especially in large-scale production, which can lead to dangerous situations if the sensors fail to detect objects correctly.
Innovation Solution
A capacitive proximity sensor arrangement that includes a diagnostic electrode at a floating potential, allowing a predetermined test potential to be applied during a diagnostic mode to simulate an object's presence, and measuring the resulting capacitance change with respect to ground, while also checking the resistance between electrodes to ensure structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex test arrangement with simulated operator body parts is used to test sensor functionality, then measurement precision and reliability are improved, but device complexity and manufacturing costs increase significantly
Solution Approach 1:
The patent uses a diagnostic electrode that creates an artificial capacitance change mimicking the effect of an operator's body part approaching the sensor. Instead of using complex physical simulations, the diagnostic electrode generates an electrical signal copy of what would occur during normal operation, thereby simplifying the test arrangement while maintaining testing accuracy
Solution Approach 2:
The diagnostic electrode serves as an intermediary element between the test system and the sensor electrode. It mediates the testing process by being coupled to the sensor electrode through a series circuit with detectable resistance, allowing the control circuit to indirectly assess sensor functionality through resistance measurements without requiring direct physical contact or complex simulations
2Reliability
If numerous sensor arrangements are tested in large-scale production using complex simulation methods, then reliability is improved, but productivity decreases due to time-consuming tests
Solution Approach 1:
The patent replaces mechanical test arrangements (physical simulation of operator body parts) with an electrical testing system. The diagnostic electrode and control circuit create and measure electrical signals to assess sensor functionality, eliminating the need for mechanical simulations and significantly reducing test time while maintaining reliability
Solution Approach 2:
The diagnostic electrode is pre-configured in the sensor arrangement to enable rapid testing. During production, the control circuit can immediately activate the diagnostic electrode and measure the series circuit resistance without requiring setup or calibration, allowing for quick pass/fail decisions that increase productivity
3Productivity
If simple testing methods are used to maintain productivity, then manufacturing efficiency is improved, but sensor reliability may be compromised due to insufficient functionality verification
Solution Approach 1:
The control circuit measures the resistance of the series circuit formed by the diagnostic electrode, sensor electrode, and connecting components. This feedback measurement provides direct information about sensor functionality - if the resistance is within expected parameters, the sensor is functioning correctly. This simple feedback mechanism ensures reliability without complex testing procedures
Solution Approach 2:
The diagnostic electrode serves multiple functions: it tests sensor functionality, verifies electrode integrity, and can detect manufacturing defects. This multi-functional approach ensures comprehensive reliability verification through a single simple testing operation, eliminating the need for multiple separate tests that would reduce productivity
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 method allows for a simple and efficient electronic testing of the sensor's functionality, reducing costs and ensuring the correct operation of the sensor, even in complex configurations, by simulating an object's presence and checking electrode integrity.
Implementation Method 1
a shield electrode (6) arranged between the at least one sensor electrode (1) and the ground plane (2) and with a control circuit (4) connected to the at least one sensor electrode (1), the shield electrode (6) and ground (2) is coupled, the potential of the shield electrode (6) being tracked by the control circuit (4) to the potential of the at least one sensor electrode (1)
Implementation Method 2
the control circuit (4) having a measuring circuit for measuring the capacitance of the at least one sensor electrode (1) with respect to ground (2)
Implementation Method 3
In a first diagnostic operating mode, test potential is applied to the diagnostic electrode (8) and a resulting change in the capacitance of the sensor electrode (1) measured with respect to ground (2) is detected
Implementation Method 4
the sensor electrode (1) or at least one of the sensor electrodes (1) being provided with two connections coupled to the control circuit (4) at two spaced locations and in one second diagnostic operating mode, the resistance between the two connections is checked
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
A capacitive proximity sensor arrangement comprises at least one sensor electrode (1), which is arranged at a distance from a ground plane (2), and a shielding electrode (6) which is arranged between the sensor electrode (1) and the ground plane (2). A control circuit (4) is connected to the sensor electrode (1), the shielding electrode (6) and the ground plane (2), and ensures that the potential of the shielding electrode (6) follows the potential of the sensor electrode (1). The control circuit has a measurement circuit for measuring the capacitance of the sensor electrode (1) in relation to ground. A diagnostic electrode (8) is arranged adjacent to and at a distance from the sensor electrode (1) and at a distance from the shielding electrode (6). In a normal operating mode, the control circuit (4) connects the diagnostic electrode (8) to the sensor electrode (1) or leaves it at a floating potential. In a diagnostic operating mode, the control circuit (4) applies a predefined test potential to the diagnostic electrode (8) and records a resulting change in the capacitance of the sensor electrode.