Abstract
An instrument based on the light extinction method was developed to measure the mass concentration of elementary carbon particles (dry soot) in diesel exhaust. The instrument uses a laser diode with 635nm wavelength as light source, and measurement tube with 770mm light length. The features of the instrument are raw gas direct sampling, 0.1second response time and wide detection range of 0.15 to 1000mg/m^3. The soot mass concentrations change dynamically depending on the variation in engine load and speed were measured
