Aiming at the problems of low measurement precision and long alarm delay of smog fire alarm widely sold on the market

an improved method based on circuit and optical path is studied.This method for the first time uses the modulation and demodulation of the signal in the measurement and control circuit to modulate the optical signal so as to eliminate the influence of other interfering light.Differential amplification is carried out on voltage signal

absorptivity of light can be improved by increasing the optical path

so as to improve the measurement sensitivity.Through theoretical analysis

circuit design and experiment

it is proved that the detection time can be shortened by 6 ～ 10 seconds.It can improve the detection precision by more than 40 %.