Dual spectrum frequency responding fire sensor
US4785292A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 11, 1987 |
| Grant date | Nov 15, 1988 |
| Priority date | — |
| Expiry date | Feb 11, 2007 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF23N2229/08
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
Apparatus for sensing the ex(i)stence of a fire and providing a warning, if desired, with improved discrimination against the possibility of false alarms. Dual channel detectors are used, one detector being set to respond to incident radiation having a wavelength in the range of 0.8 to 1.1 microns while the other wavelength range is significantly displaced therefrom, being selected for wavelengths in the range from 14 to 25 microns. Reliability of true signal detection is further improved by the provision of separate flame flicker bandpass filters in the respective channels, these bandpass filters being set for different passbands. Circuits providing ratio discrimination, threshold detectors and delay circuitry are combined with the dual spectrum detectors and disparate flicker frequency filters to achieve improved performance. In addition, the dynamic range of instrument sensitivity is substantially increased by utilizing preamplifiers with wide gain variability controlled by automatic gain control circuits in the dual channel circuitry.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.