Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1997-02-27
1998-08-25
Hofsass, Jeffery A.
Communications: electrical
Condition responsive indicating system
Specific condition
340629, 340630, 250574, G08B 1710
Patent
active
057987017
ABSTRACT:
A smoke detector (10) has internal self-adjustment and self-diagnostic capabilities. It includes a microprocessor-based alarm control circuit (24) that periodically checks the sensitivity of a smoke sensing element (20) to a smoke level in a spatial region (12). The alarm control circuit and the smoke sensor are mounted in a discrete housing (25) that operatively couples the smoke sensor to the region. The microprocessor (30) implements a routine (50) stored in memory (32) by periodically determining a floating adjustment (FLT.sub.-- ADJ) that is used to adjust the output (RAW.sub.-- DATA) of the smoke sensing element and of any sensor electronics (40) to produce an adjusted output (ADJ.sub.-- DATA) for comparison with an alarm threshold. The floating adjustment is not greater than a maximum value (ADJISENS) or less than a minimum value (ADJSENS). Except at power-up or reset, each floating adjustment is within a predetermined slew limit of the immediately preceding floating adjustment. The floating adjustment is updated with the use of averages (NEW.sub.-- AVG) of selected signal samples taken during data gathering time intervals having a data gathering duration that is long in comparison to the smoldering time of a slow fire. The adjusted output is also used for self-diagnosis.
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Bernal Brian A.
Croft Daniel P.
Johnson Kirk R.
Marman Douglas H.
Peltier Mark A.
Hofsass Jeffery A.
Mannava Ashok
SLC Technologies Inc.
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