- Author
- Loepfe, M. | Ryser, P. | Tompkin, C. | Wieser, D.
- Title
- Optische Eigenschaften von Brand- und Nichtbrandaerosolen. [Optical Characteristics of Flaming and Non-Flaming Aerosols.]
- Coporate
- Cerberus AG, Mannedorf, Switzerland
- Book or Conf
- University of Duisburg. International Conference on Automatic Fire Detection "AUBE '95", 10th. Proceedings. [Internationale Konferenz uber Automatischen Brandentdeckung.] April 4-6, 1995, Duisburg, Germany, Luck, H., Editors, 394-403 p., 1995
- Keywords
- fire detection | fire detection systems | aerosols | optical properties | optical measuring instruments | light scattering | size distribution | test methods | scattering cross sections
- Abstract
- Optical detection principles play an important role in automated smoke detection systems. Significant properties of an aerosol can be determined from angle and polarization dependent light scattering experiments. A simple instrument was built to continuously monitor the polarized scattering cross sections of air borne aerosols. Two solid state diode lasers with orthogonal polarization vectors serve as light sources. They emit at 690 nm and are modulated with 4 kHz and 5 kHz respectively. Fourteen receivers are arranged on one half of an annulus of 30 cm in diameter. Each detector measures simulteneously the scattered light intensities for both polarizations. After demodulation and separation of the two signals by a lock-in technique, the signals are filtered, amplified and sampled with a time resolution of one second. The flat and open mechanical outline of the apparatus is best suited for direct measurements on the ceiling of a fire laboratory without interfering the natural aerosol convection. Comparisons between aerosols from standard fires conforming to the European norm EN54 and aerosols not originating from combustion processes (water vapor, oil mist) were carried out. Back calculation of the aerosol size distribution from measured data will be demonstrated for latex test aerosols.