Self-adjusting smoke detector with self-diagnostic capabilities

US5798701A · kind A · utility

Assignee

• SLC Technologies · US

Inventors

• Brian Andrew Bernal · Portland, US
• Daniel Croft · Beaverton, US
• Kirk R. Johnson · Rogers, US
• Douglas H. Marman · Ridgefield, US
• Mark A. Peltier · Sherwood, US

Key dates

• Filing date: Feb 27, 1997
• Grant date: Aug 25, 1998
• Expiry date: Feb 27, 2017

Classification

• Technology area (CPC G): Physics
• CPC primary: G08B29/185
• WIPO field: Control
• WIPO sector: Instruments

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 com…