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The DSL-320 Opacity Monitor is an optical instrument designed to measure the visible opacity of exhaust gas in a duct, stack or flue.

The DSL-320 uses the double pass light transmission measurement technique, with a folded beam Transceiver/Reflector arrangement. A light beam emitted from the Transceiver (TRX) passes across the duct, stack or flue to a Reflector, which then returns the light to the Transceiver where the intensity of the received light is measured. Increased particulate or smoke density in the stack gas attenuates the transmitted light and causes the intensity of the received light to fall. This reduction in intensity is measured and presented as % opacity. The higher the level of particulate or smoke present, the more light lost and therefore, the greater the opacity.

  • In situ measurement directly in exhaust gas flow
  • Measurement reading as % Opacity
  • Modulated green LED source for long lifetime stability and immunity to ambient light
  • Rugged 316 stainless steel construction
  • In-situ zero and calibration check facility
  • Choice of interface options enabling easy integration
  • Free utility software for PC based set-up control and data logging
  • Optional Operator Interface with different mounting configurations
  • Simpler installation than single pass opacity monitors
  • Better accuracy over shorter path lengths than single pass opacity monitors
  • Rugged design with no moving parts so low maintenance
  • Latched head and lid design to enable ease of access for installation and maintenance

Optional accessories

  • Operator interface (OI)
  • ​90-260 Vac model available
  • ​Mounting flange installation kit
  • ​Laser alignment tool to assist with installation
  • Air purge blower kit (110 Vac / 230 Vac / 415 Vac)
  • Compressed air purge kit
  • Reference filters for routine calibration check of the instrument

For further information and technical specifications about this product please contact us via phone or email and a member of our team will be happy to help

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