Smoke detector with external sampling volume using two different wavelengths and ambient light detection for measurement correction

摘要

In accordance with certain embodiments, a smoke detector determines the presence of smoke particles outside its housing based on measurements of light detected at different wavelengths and corrected based on an ambient light level.

主权项

1. A smoke detector comprising:
a housing; one or more light emitters for emitting, outside the housing, light of a first wavelength and a second wavelength longer than the first wavelength; one or more light detectors for detecting (i) light emitted from the one or more light emitters reflected back to the one or more light detectors, thereby providing measurements of reflected light including the first and second wavelengths, and (ii) an ambient light level outside of the housing; and an evaluation circuit for (i) correcting a measurement of reflected light including the first wavelength based on the detected ambient light level, thereby producing a corrected first-wavelength measurement, (ii) correcting a measurement of reflected light including the second wavelength based on the detected ambient light level, thereby producing a corrected second-wavelength measurement, and (iii) determining the presence of smoke particles outside the housing based on a ratio of the corrected first-wavelength measurement to the corrected second-wavelength measurement.