Detection system to determine the transmissivity of a medium with respect to radiation, particularly the light transmissivity of smoke-contaminated air, for fire detection
US3994603A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 14, 1975 |
| Grant date | Nov 30, 1976 |
| Priority date | — |
| Expiry date | Feb 14, 1995 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B17/113
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
To eliminate sources of error in fire detection apparatus regarding variation of light output from a radiation cell, and to eliminate varying ambient conditions such as dust and dirt contamination of reflectors and transducers, the radiation is directed over at least two paths by reflectors which are located such that the numbers of reflections in the paths and the reflection points are the same, whereas the lengths of the paths are different, and evaluating the difference signal to obtain a measure of the density of the medium through which the paths extend, typically the transmissivity of air which may be contaminated by smoke. In one embodiment, reflectors are located in the corners of a polygon, one of the paths extending across the polygon, and the other path extending essentially circumferentially thereof.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.