Design Of On-line Smoke Detecting System Based On Optics

Fire smoke concentration is a key parameter in fire science research.And thus the accurate measurement of it is of vital importance to the fire hazard precaution, analysis on fire smoke composition as well as safety evaluation of upholstery materials.To address this long-lasting demand, an on-line optical detecting system is developed. Based on in-depth research of the national standards for measuring fire smoke concentration and large quantity of literatures both in and out the country in this field, the system matches the relevant parameters and requirements. It is implemented under light extinction principle and measured by double light with proper optical mechanism configuration and circuit design in order to effectively avoid bigger errors caused by single optical path measuring system.By adopting alternative and comparative measuring principles, i.e., time sharing and alternative testing of reference light path and measure light path can successfully eliminate the effects caused by the circuit system and the instability of electrophotonic detector. The system analysizes and calculates different parts of the signal circuit including preamplifier, instrument amplifier, analog to digital conversion circuit and low pass filter, hence achieves better linearity, operation bandwidth, noise immunity in the signal circuit.The characteristics of this system is the following:using optical attenuation changing system which is automatic; using semi-conductive laser as probe source which is cheap and therefore reduces cost; using electrophotonic detector whose operating wavelength ranging from 530nm to 850nm, so change laser source can be flexible.