Patent ID: 9098989
Filing Date: 2015-08-04
Classification: G08B

Abstract:
1. A method for evaluating two scattered light signals in a hazard alarm operating in accordance with a scattered light principle, the method comprising: irradiating particles to be detected with a first light in a first wavelength range and with a second light in a second wavelength range; converting light scattered by the particles into respective first and second non-normalized signals correspondingly from said first and second lights, respectively; normalizing the first and second non-normalized signals to one another and producing two normalized scattered light signals having amplitude curves that approximately coincide for dust- and steam-sized particles; transforming the two normalized scattered light signals as a ratio into a polar angle and a polar distance as polar coordinates of a polar coordinate system; forming a weighted smoke density signal and a weighted dust/steam density signal by weighting the polar distance depending on the polar angle, the polar distance being weighted oppositely in forming the weighted smoke density signal and the weighted dust/steam density signal; and outputting the weighted smoke density signal and the weighted dust/steam density signal for further evaluation of the hazard alarm.