Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1979-07-27
1981-05-05
Caldwell, Sr., John W.
Communications: electrical
Condition responsive indicating system
Specific condition
250574, 340629, G08B 1710
Patent
active
042662206
ABSTRACT:
A self-calibrating obscuration smoke detector is provided along with a method for the operation thereof. A light source and a photodetector are mounted in spaced relation to one another with the output of the photodetector being a function of the amount of light sensed by the detector from the light source. The photodetector analog output is converted into digital signals by an A/D converter and digital signals are then delivered to a digital processor adapted to periodically calibrate the detector and to perform sampling operations between calibrations. Other sensing devices may be connected to the system with automatic self-calibrating capabilities with respect thereto.
By using a pair of photodetecting cells directly visible to separate light sources or indirectly visible to a single source, a thermally stable system is provided where one cell provides a reference output for the other cell.
REFERENCES:
patent: 3774186 (1973-11-01), Enemark
patent: 3906474 (1975-09-01), Lehsten
patent: 4170419 (1979-10-01), Van Tyne et al.
Caldwell Sr. John W.
Myer Daniel
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