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Section 1
SYSTEM DESCRIPTION
The Model 1304 Opacity Monitor provides continuous, low maintenance, precision measurement of opacity and
optical density in industrial applications. It is a cost-effective instrument that serves as an aid in operating pollution
and/or process control equipment.
Transmissometer/retro reflector
The Model 1304 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 standard reflector is used for measurement path lengths up to 15 feet.
For longer path lengths, maximum 50 feet, reflectors, optical parts and electronics will vary.
Control Unit
o
The control unit should be mounted in a control room environment i.e., clean, temperature with max/min of +0
o
o
o
to +50
C (+32
to + 122
F). The Model 1304 control unit provides instrument control functions, opacity
readings, alarm and fault indicators, analog outputs, and diagnostics with contact closures.
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 temperatures limits, and errant air currents
around the stack.
The air purge system constantly circulates air past the optical window. The air flow is directed through the hose to
an air plenum on the stack side of the optical window. The air flow 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 Model 1304 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 6-pair, #20
AWG, twisted, shielded cable separation distance approximately 2000FT.. More pairs or larger than 20 AWG is
acceptable for longer distances.
9
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Troubleshooting
