Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1975-02-18
1976-08-24
Smith, Alfred E.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250227, 340237S, 356207, G01N 2126
Patent
active
039768910
ABSTRACT:
A photoelectric detector in which partial light beam obfuscation caused by dirty windows is balanced out by providing two beams of light passed through the gaseous medium in which smoke or the like is to be detected, the beam windows being subject to substantially equal accumulation thereon over a period of time of soot or the like which causes the windows to become dirty or clouded. The windows are so spaced that the respective beams pass different distances through the smoke. The relative beam intensities as received are compared by connecting photoresponsive devices in a bridge circuit. A meter is connected to the bridge and preferably calibrated to read directly in Ringlemann numbers.
REFERENCES:
patent: 3447370 (1969-06-01), Tanzman
patent: 3619624 (1971-11-01), Sorenson
patent: 3652850 (1972-03-01), Briggs
patent: 3677652 (1972-07-01), Little
patent: 3772525 (1973-11-01), Goodwin
patent: 3784307 (1974-01-01), Jackson et al.
patent: 3805066 (1974-04-01), Chijuma et al.
patent: 3809913 (1974-05-01), Prellwitz
Baldwin George H.
Electra-Tronics, Inc.
Nelms D. C.
Smith Alfred E.
Yeager Arthur G.
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