Capacitive Sensor Guard Electrode Interruption Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current capacitive sensing systems require complex and costly methods to detect interruptions in sense or guard electrodes, which is a challenge particularly in safety-relevant applications like automotive systems.
Innovation Solution
A capacitance measurement circuit with a periodic signal voltage source, a sense current measurement circuit, and a remotely controllable switch member that provides an additional electrical path between the guard electrode and a reference potential, allowing for the detection of guard electrode interruptions using a voltage signal indicative of the capacitance between the sense and guard electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex interruption measurement circuits and additional hardware are used to detect electrode interruptions, then detection reliability is improved, but device complexity and cost increase
Solution Approach 1:
The capacitive sensor system performs self-diagnosis by utilizing its own existing electrodes and measurement circuits. The guard electrode is periodically connected to reference potential through a switch, and the resulting capacitance changes are measured by the existing measurement circuit, allowing the system to detect its own interruptions without external diagnostic equipment
Solution Approach 2:
The existing capacitive sensor components (sense electrode, guard electrode, measurement circuit) are made to serve dual functions: normal sensing operation and interruption diagnosis. The same hardware infrastructure is used for both sensing and self-diagnosis, eliminating the need for separate diagnostic hardware
2Reliability
If complex interruption measurement circuits are implemented, then interruption detection capability is improved, but manufacturing cost increases
Solution Approach 1:
The system uses its own existing hardware infrastructure for self-diagnosis, eliminating the need for additional expensive diagnostic equipment. The measurement circuit already present in the capacitive sensor is reused for interruption detection, reducing manufacturing costs
Solution Approach 2:
The diagnostic function replicates the normal sensing measurement process but applies it to detect interruptions. By using the same measurement principles and hardware for both sensing and diagnosis, the system avoids the cost of separate diagnostic circuitry
3Measurement precision
If additional hardware is added for interruption detection, then detection accuracy is improved, but hardware complexity increases
Solution Approach 1:
The capacitive sensor system uses its own existing electrodes and measurement circuits for self-diagnosis. The guard electrode, already present for sensing purposes, is temporarily connected to reference potential to enable interruption detection without requiring additional hardware components
Solution Approach 2:
The switch periodically connects the guard electrode to the reference potential for diagnostic measurements. This periodic switching enables continuous monitoring capability while using the same hardware for both normal operation and diagnosis, avoiding the need for separate continuous diagnostic hardware
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 solution enables a simpler and less costly detection of guard electrode interruptions, maintaining operational availability of the capacitive sensor with quasi-continuous monitoring and reducing the need for additional hardware, while ensuring reliable detection of sensor interruptions.
Implementation Method 1
a capacitance measurement circuit (26) for determining a sense current of a capacitive sensor (12)... a periodic signal voltage source (28) that is configured for providing an alternating measurement voltage with reference to a reference potential (30)
Implementation Method 2
A capacitive sensor generally comprises at least one antenna electrode, to which is applied an oscillating electric signal and which thereupon emits an electric field into a region of space proximate to the antenna electrode
Implementation Method 3
The capacitive coupling is generally determined by applying an alternating voltage signal to a capacitive antenna electrode and by measuring the current flowing from said antenna electrode
Data Source
AI summary
A capacitance measurement circuit for determining a sense current of a capacitive sensor which includes at least one electrically conductive sense electrode and at least one electrically conductive guard electrode. The measurement circuit includes at least one switch member that is remotely controllable by a switch remote control unit, wherein the at least one switch member in at least one closed state is configured to provide an additional electrical path between the at least one guard electrode and a reference potential.