A transmissometer was developed to measure dust concentration at stationary sources employing an LED ( Light Emitting Diode) and a self-compensation system for the degradation of the optical system. The relationship between the optical concentration obtained by the tansmissometer and the mass concentration measured by a gravimetric method were investigated theoretically and experimentally.
The experiments were carried out with four kinds of test dusts. Very good correlations between the optical concentration and the mass concentration were obtained over a wide range of dust concentration, about 10mg/m³-5g/m³. It was found that dust concentration can be measured accurately for a long period with this tansmissometer in which the self-compensation system for optical degradation is very effective. A comparison between the experimental values and calculated results showed good agreement between the phenomenon and the theory of light extinction. It was also found that the effect of dust properties, such as the refractive index and the particle size distribution, can be estimated by calculating parameter K.