Triplicated monitoring system for fault detection - has 2 out of 3 channel system with capability to minimise effect of signal tolerance variation

摘要

A monitoring system using triplicated channels operating on a two out of three basis is designed to provide reliable signalling of an alarm condition. Theinfluence of individual signal tolerance errors does not affect the system sensitivity. Each of the three channels has an electronic switching stage (1,2,3) each of which generates a magnitude difference signal 1a-b1, 1b-c1 and 1a-c1 between the input signals. The signals are compared with a generated tolerance variation (delta x, ab, delta x, bc, delta x, be). Outputs are generated over AND gates (2). The system may be incorporated into matrix switching alarm systems for plant monitoring.