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Instruction Manual Rev B
Transmissometer/retro reflector
The OPM3000 is a precision, double-pass, dual beam Transmissometer that consists of a transceiver
(transmitter/receiver) mounted on one side of a stack or duct and a passive reflector mounted on the opposite
side. The light source, photo detectors, and all measurement/reference optics used in opacity measurement are
housed in the transceiver.
The function of the reflector is to return the measurement beam to the detector in the transceiver, creating a
double pass across the process stream. The reflectors, optical parts and electronics will vary based on path
lengths.
Optional Air Purge Weather Cover System
The transceiver and reflector may be mounted in weather covers. The weather covers are fairly compact to
allow movement around them even on a three-foot walkway or platform. They protect the stack-mounted
components from dirt, moisture; stack temperatures within the specified ambient temperature limits, and
errant air currents around the stack.
The air purge system constantly circulates air past the optical window. The airflow is directed through the hose
to an air plenum on the stack side of the optical window. The airflow in the air plenum area results in reduced
pressure and increased velocity. This venturi effect tends to continually draw the air around the optical window
into the purge air stream, thereby keeping the lens clean for long periods.
Alignment system
The OPM3000 includes a built-in through-the-lens alignment system. The alignment target can be viewed
through a window on the transceiver. Adjustments to changes in alignment are provided by a 3-point alignment
system, which is integral to the air plenum.
Cabling
The standard cabling used between the stack-mounted units and the control unit is at a minimum 2-pair, #22
AWG, twisted, shielded cable. More pairs or larger pairs than 20 AWG is acceptable.
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