Safety Interlock Self-Testing for High-Voltage Instrument Backplanes
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Solution Overview
Problem
Conventional safety interlock systems for test and measurement instruments lack failure detection and troubleshooting capabilities, leading to potential safety hazards and difficulties in identifying faults, especially in complex systems.
Innovation Solution
An enhanced interlock system with self-testing capabilities that includes a digital processing unit to monitor and report the integrity of the interlock system, featuring single fault detection and a modular design to simulate the interlock path without engaging dangerous voltages, ensuring compliance with machine safety standards like EN ISO 13849-1:2015, Category 3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a redundant set of contacts is used in the interlock relay to ensure double fault protection, then safety reliability is improved, but the ability to detect single faults is lost and troubleshooting becomes difficult
Solution Approach 1:
A digital processing unit is introduced as an intermediary component that monitors the interlock system. This unit receives signals from the relay contacts and performs logical analysis to detect faults, separating the safety function from the detection function. The digital processor acts as a mediator between the hardware interlock and the user interface, enabling fault detection without compromising the redundant contact design.
Solution Approach 2:
The system implements feedback by having the digital processing unit continuously monitor the state of relay contacts and provide status information back to the user through displays or interfaces. This feedback mechanism allows the system to report on its own health status, enabling detection of single faults while maintaining the redundant contact architecture for safety.
2Ease of manufacture
If a simple hardware interlock design is used, then ease of manufacture is improved, but troubleshooting capability deteriorates in complex systems
Solution Approach 1:
The digital processing unit performs preliminary diagnostic actions by continuously monitoring interlock contact states and detecting faults before they affect system operation. The system proactively identifies potential issues through logical analysis of contact signals, enabling early detection and simplifying subsequent troubleshooting without requiring complex additional hardware.
3Device complexity
If the interlock system does not provide fault indication, then device complexity is reduced, but loss of information about system safety status occurs
Solution Approach 1:
The digital processing unit enables the interlock system to self-report its status through logical analysis of contact signals. The system serves itself by automatically detecting faults and providing status information without requiring external monitoring equipment, thus maintaining simplicity while eliminating information loss about safety status.
Data Source
AI summary
A test and measurement system includes one or more high voltage sources having a voltage high enough to be dangerous to users, an instrument backplane, having one or more backplane double fault protected interlocks, a power signal, and one or more slots configured to accept one or more modules, and one or more processors configured to execute code that causes the one or more processors to: monitor one or more signals from the one or more backplane double fault protected interlocks; and without engaging any of the one or more high voltage sources, determine an operational state and faulted condition of each of the one or more backplane double fault protected interlocks, and check wiring of an interlock pathway between the test and measurement instrument and a user system.