The DSL-340 uses the innovative Dynamic Detection Principle (DDP) which measures fluctuations in the intensity of a light beam, using a folded beam Transceiver/Reflector arrangement. Increased dust or particulate density in the stack causes the amplitude of these fluctuations to increase. When calibrated against standard reference measurements, the amplitude of this signal relates directly to the dust concentration in the stack and this can be presented as a reading in mg/m³.