Design and Analysis of Improved Alarm Delay-Timers

Alarm systems play an important role in industry to notify operators of abnormal or fault situations. In real industrial plants, however, a majority of nuisance alarm signals, including false alarms and missed alarms, interfere with operators' judgment. The technique of delay-timers, a common means to reduce both false alarm rate (FAR) and missed alarm rate (MAR), is widely performed, yet it suffers from a delayed response. In this paper we propose an improved delay-timer annunciation and clearance method to enhance the performance of conventional delay-timers via bypassing some states in state switch under some conditions. Also the improved delay-timer performance indices are calculated by using Markov chains.