Quick notes:
* This model is NOT EPA qualified under the new regulations
* Uses 2 Liquid Crystal Windows to augment the light beam and create a very accurate opacity measurement.
* Utilizes an incandescent source lamp ... 5 vdc (running at 4.63 vdc)
* Does NOT use HART protocol ... requires two people to service instrument (typically)
* This model was released as the OPM2000A when it should have been given a new number (the first
   half of the product run was the OPM2000A that used the old 3 plastic LCW design). 

Description:
The model OPM Opacity/Dust Density Monitor is designed for continuous 
In situ measurement of the optical density (extinction) of stack emissions.
Designed to meet the requirements of the U.S. Environmental Protection 
Agency's (EPA) 40 CFR, Part 60, Appendix B, Performance Specification 1,
the transmissometer's instantaneous and average outputs can be configured to
represent stack exit opacity, dust density, optical density, or extinction.

The OPM is a double pass system that transmits a beam of light across 
the stack to a retroreflector, which in turn bends the light beam back to
the transceiver's optical system.  The OPM uses a patented system of 
glass Liquid Crystal Windows (LCWs) that are transparent when energized and
translucent when deenergized.  Use of glass LCWs directs the light beam without 
mechanical choppers or other moving parts, improving 
measurement stability, reliability, and accuracy.  No moving parts, 
makes the OPM a truly digital, solid state transmissometer. 

The OPM incorporates many self check features to ensure a reliable 
measurement.  The detected signal is compensated for 
variations such as changes in ambient light in the stack, lamp aging effects,
and stray light for improved accuracy.
