Evaluate scattered light signals in an optical hazard detector and issue a dust / steam warning or a fire alarm

摘要

The invention relates to a method for evaluating two scattered light signals (IR, BL) of an optical danger detector (1) operating according to the scattered light principle. The particles to be detected are irradiated with light in a first wavelength range and with light in a second wavelength range. The light scattered by the particles is converted into first and second scattered light signals (IR ', BL'). The two scattered light signals (IR ', BL') are normalized to one another in such a way that their amplitude curve for larger particles such as dust and steam approximately coincide. Furthermore, an amplitude ratio (R) is formed between the two scattered light signals (IR, BL) and an amplitude comparison value (90%) is determined which corresponds to a predefinable particle size in the transition region from smoke to dust / vapor. The two scattered light signals (IR, BL) are further processed for fire parameters, depending on the current comparison result (C). According to the invention, in the event that the amplitude ratio (R) exceeds the amplitude comparison value (90%), the first scattered light signal (IR) is evaluated and a dust / vapor density signal (SD) is output. In the other case, the second scattered light signal (BL) is evaluated and a smoke density signal (RS) is output.