Sensitivity fault indication technique implemented in smoke dete

Details Sensitivity fault indication technique implemented in smoke dete Sensitivity fault indication technique implemented in smoke dete

1996-08-12

1998-01-13

Hofsass, Jeffery

Communications: electrical

Condition responsive indicating system

With particular system function

340511, 340512, 340516, 340630, 250574, 356438, G08B 2900

Patent

active

057084149

ABSTRACT:
Self-contained smoke detector systems each have internal self-diagnostic capabilities and function as components of an automatic fire alarm communication system implemented with a conventional two-wire alarm initiating circuit. Each system includes a microprocessor-based self-diagnostic circuit that periodically checks sensitivity of radiation sensor electronics to smoke obscuration level. By setting tolerance limits on the amount of change in voltage measured in clean air, the system can provide an indication of when it has become either under-sensitive or over-sensitive to the ambient smoke obscuration level. An algorithm implemented in software stored in system memory determines whether and provides a sensitivity fault condition signal indicating that for a time (such as 27 hours) the clean air voltage has strayed outside established sensitivity tolerance limits. The sensitivity fault condition signal includes multiple time displaced pulses, each of which having a duration and a magnitude that cooperate to diminish the probability of approximately concurrent sensitivity fault condition signals produced by multiple smoke detector systems causing the alarm initiating circuit to generate a false alarm signal.

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