Development of optical smoke concentration meter with high precision

Optical smoke concentration meter is a kind of normal measurement instrument for combustion Lab and standard measurement bin. First, the function mechanism of various kinds of disturbances and noises in smoke concentration measurement are comprehensively analyzed, and a scheme of optical smoke concentration with dual optical path is presented herein, which is based on the infrared light-extinction principle. Such technologies as dual optical path design, infrared light modulation and cross-correlation detection, are adopted for noise rejection. Furthermore, a PC software implementation about lock-in amplifier is applied to enhance the SNR and precision of measurement greatly. Finally, a test instrument is developed and the test results show the scheme presented herein is valid to improve the measurement precision remarkably.