Method of automatic verification of smoke detector operation within calibration limits
US5936533A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 13, 1998 |
| Grant date | Aug 10, 1999 |
| Priority date | — |
| Expiry date | Oct 13, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B29/145
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A self-contained smoke detector system has internal self-diagnostic capabilities and accepts a replacement smoke intake canopy (14) without a need for recalibration. The system includes a microprocessor-based self-diagnostic circuit (200) that periodically checks sensitivity of the optical sensor electronics (24, 28) 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 (204) determines whether and provides an indication that for a time (such as 27 hours) the clean air voltage has strayed outside established sensitivity tolerance limits. The replaceable canopy is specially designed with multiple pegs (80) having multi-faceted surfaces (110, 112, 114). The pegs are angularly spaced about the periphery in the interior of the canopy to function as an optical block for external light infiltrating through the porous side surface (64) of the canopy and to minimize spurious light reflections from the interior of the smoke detector s…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.