Redundant Contact Monitoring Through Scheduled Switching Verification
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Solution Overview
Problem
Monitoring the functionality of redundantly interconnected contacts in safety-related systems is complex and requires significant space, limiting flexibility and redundancy, as faults in one contact do not necessarily affect the overall function, and enhancing redundancy or using positively driven contacts is not always feasible due to space constraints.
Innovation Solution
A method and apparatus where a controller switches on or off multiple contacts in a defined schedule, allowing each contact to be verified individually for functionality by monitoring the electrical connection, eliminating the need for enhanced redundancy or positively driven contacts, and providing a simple and reliable monitoring system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundantly interconnected contacts are used to minimize risk in safety-related systems, then reliability is improved, but device complexity increases and monitoring becomes more difficult
Solution Approach 1:
The monitoring method utilizes the existing control device and contact structure to perform self-diagnosis. The control device monitors the functionality of redundant contacts by analyzing signals already present in the system, without requiring external monitoring equipment or additional circuits. This self-service approach maintains high reliability while avoiding increased device complexity.
2Measurement precision
If positively driven contacts are used for diagnosis, then measurement precision is improved, but device complexity and mounting space increase
Solution Approach 1:
The monitoring method works with both normally open and normally closed contacts, making it universally applicable to different contact types. The control device performs diagnostic functions using existing contact structures, eliminating the need for specialized positively driven contacts while maintaining precise functionality verification through signal analysis.
3Reliability
If enhanced redundancy is implemented to improve safety, then reliability is improved, but mounting space increases
Solution Approach 1:
The control device receives feedback signals from the redundant contacts and analyzes their functionality. This feedback mechanism allows the system to maintain high reliability with the existing number of contacts by intelligently monitoring their state, rather than requiring additional redundant contacts that would increase mounting space.
4Measurement precision
If complex monitoring circuits are used to detect faults in redundant contacts, then measurement precision is improved, but device complexity and mounting space increase
Solution Approach 1:
The control device performs self-diagnosis of the redundant contacts by analyzing existing signals in the system. This approach achieves accurate fault detection without requiring complex external monitoring circuits, as the control device utilizes its own resources and existing signal paths to monitor contact functionality.
Data Source
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AI summary
For providing a very simple and reliable monitoring of the functionality of contacts together with a high flexibility of selection of the contacts a method for monitoring the functionality of redundantly interconnected contacts is provided, preferably within a load current circuit, wherein said n contacts, n = 2, provide an electrical connection between a power supply and a load, wherein said n contacts are switchable by a controller and wherein each of said n contacts is designed for providing the electrical connection between the power supply and the load all alone. The method is characterized in that the controller switches on said n contacts during n subsequent activations according to a defined schedule according to which at the first of said n subsequent activations one of said n contacts is switched on first and the remaining n-1 contacts are switched on afterwards, so that a verification regarding the functionality of said one of said n contacts is possible, and according to which at each of the n-1 remaining subsequent activations a further one of said n contacts is switched on first with switching on of the remaining n-1 contacts afterwards, so that after said n subsequent activations each of said n contacts has once been switched on first and a verification regarding the functionality of each of said n contacts is possible. Further, a corresponding method for subsequent deactivations and corresponding apparatuses are provided.