Cross Duct Type

The DSL-340 is an optical instrument designed to measure the concentration of dust or particulate matter suspended in the exhaust gas passing through a duct, stack, or flue; typically, the exhaust gas from an industrial combustion process or air filtration system.

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 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 particulate concentration in the stack, and this can be used to present as a reading in mg/m³.

Unlike the standard transmission technique, DDP has immunity to gradual reductions in the absolute intensity of the light signal and therefore, has the advantage that it is significantly less susceptible to drift with time, temperature or dirtying optics, than traditional opacity monitors using the standard transmission technique.

The light source in the Transceiver is a long life, stabilised green LED which offers long life and stable intensity. The transmitted light beam is pulsed to give complete immunity to ambient light levels. The intensity of the transmitted light is monitored at source so that any variations in the emitted light level are compensated in the received signal. The Transceiver has on board temperature measuring to provide stability over temperature.

The DSL-340 is available with or without an Operator Interface (control unit) so for the most cost effective monitoring solution the DSL-340 can operate as a “stand-alone” instrument consisting of the Transceiver head (TRX) and Reflector head, with all electrical connections (including outputs such as the alarm relays, 4-20mA and Modbus) being made inside the TRX head. As a stand-alone instrument the DSL-340 is set-up and controlled using the supplied utility software, installed on a PC or laptop, and connected via the USB connector on the TRX. When supplied with an Operator Interface (OI) all power supply and output connections are made in the OI rather than the TRX.

The DSL-340 has no moving parts, is of rugged design and has an excellent reliability record. Regular maintenance simply involves cleaning the optical surfaces which are easily accessible due to our latched head design. Both the TRX and Reflector heads are supplied with an air purge body, which when connected to a high volume source of clean air, keeps the contaminated stack gas away for the lens surfaces. An Aluminium air purge body is available for use on standard installations and a more advanced Stainless Steel air purge body is available for more demanding installations.