Research on weak signal detection in laser transmissiometer for dust measurements

ZHANG Tao
（FPI（Hangzhou） Stock Corporation， Hangzhou 310015， China）

Abstract： Aiming at monitoring dust concentration on-site， an on-site laser dust concentration monitor was designed. In a typical continuous emission monitoring system（CEMS），measuring range of laser dust concentration monitor is up to 15 m，but the output optical power of LD is below 20 mW. To get the ultra-weak reflected light from strong noisy background，a digital averager was designed to refine "nW" level light signal.  The performance of prototype was tested at different measuring range and different extinction. The results indicate that，using digital averager to detect dust concentration on-site，measuring range reaches desired 15 m and the linearity is better than 2%.
Key words： laser dust concentration monitor； dust concentration detection； weak signal detection； digital averager