Title: Photoelectric detector for smoke or the like

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.

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Inventors: Parkinson, Thomas F. (Columbia, MO, US)

Application Number: 550626
Filing Date: 1975-02-18
Publication_date: 1976-08-24
Assignee: Electra-Tronics, Inc. (Sarasota, FL)
Primary Class(es): 250/575 250/227.11, 340/630, 356/439
Other Classes:
US Patent Ref:

3447370	Jun, 1969	Tanzman	356/207.
3619624	Nov, 1971	Sorenson	250/575.
3652850	Mar, 1972	Briggs	356/208.
3677652	Jul, 1972	Little	250/573.
3772525	Nov, 1973	Goodwin	250/575.
3784307	Jan, 1974	Jackson et al.	250/575.
3805066	Apr, 1974	Chijuma et al.	340/237.
3809913	May, 1974	Prellwitz	356/207.

Other Refs:
Primary Examiner: Smith, Alfred E.
Assistant Examiner: Nelms, D. C.
Attorney: Baldwin; George H., Yeager; Arthur G.