Monitoring Solutions

- Model D-R 290 - Compliant Continuous Opacity Monitoring System



Designed for cost effective stack opacity monitoring, the D-R 290 meets all the requirements of the U.S. EPA (40 CFR Part 60).


The D-R 290 mounts on a stack or duct and projects a beam of light from an optical head on one side to a reflector on the other. The light is reflected back through the gas (double pass for greater sensitivity) to the optical head. A detector in the optical head determines opacity by comparing the ratio of the energy level of the reflected light to the energy level of the projected light.

A Super Wide Band Diode (SWBD) generates the transmitted light. Due to the SWBD's broadband nature, it is not influenced by other light sources (like sunlight), and it's measurement results are not influenced by temperature or other factors. The SWBD also has a long life span compared to traditional halogen lamps.

The optical head incorporates automatic zero and span compensation by use of an internal reflector (representing zero opacity), and a neutral density filter (representing a known span value), which interrupt the measurement beam periodically. During this period, the dirt accumulation on the window is measured, and the zero and span signals are automatically compensated. All electronic components utilize microprocessor design for long term, trouble free reliability.

The windows of the optical head and reflector are kept clean through the use of a purge blower system. This system blows clean ambient air in front of the window to keep flue dust and heat away from the mounting pipes. Incoming air is filtered using economical automotive filters. In most applications, the filters only need to be changed once every three months.

A microprocessor-based controller is included for remote display and control of the opacity monitor. This unit provides a digital display for up to 10 selected ranges (5 each for opacity and optical density), corrected for stack exit conditions, and uncorrected for path light measurement. This readout can be integrated over a wide range of time periods.

  • In-situ, continuous, measuring principle
  • Long life, solid state light source
  • Optimal evaluation of measuring signals due to wide spectrum of Super Wide Band Diode (SWBD) - more stable than conventional LED systems
  • High performance microprocessor technology
  • LCD display in opacity or optical density, and calibration capable in mg/m3
  • Auto zero and span check with window soiling correction
  • Hermetically sealed optics & electronics housing
  • Simple alignment without special tools
  • Advanced purge air system for reduced maintenance
  • Programming via controller or remote bus interface
  • Data available as analog output or bus interface
  • Two analog output signals with switchable ranges

Monitoring Solutions offers a complete package solution to your opacity needs. A Sales Engineer will visit your site to offer an evaluation and review permit and installation requirements. If upgrading an existing opacity unit, a determination will be made for re-use of existing components and the easiest upgrade path specific to the site.

After a sale, Monitoring Solutions Engineers will work with the customer to insure the right components are provided, pre-configured for your stack and installation conditions. Complete drawing documentation and O&M manuals are provided, and where required Monitoring Solutions can supply a site specific QA/QC manual for your new opacity system.

Installation assistance, start-up assistance, and compliance certification complete the system solution offered by Monitoring Solutions.

  • Optic Head (Transceiver)
  • Reflector
  • Stack Controller
  • Remote Controller (19' rack mount panel, or flush mount)
  • Dual Purge Air Blowers with Pressure Switches
  • Weather Enclosures
  • Mounting Hardware and Flanges

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