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Description and specifications
December 2022
proportional to the inverse lograrithm of the oxygen concentration. Therefore,
the output signal increases as the oxygen concentration of the sample decreases.
This characteristic enables the transmitter to provide exceptional sensitivity at low
oxygen concentrations.
The Rosemount OCX8800 oxygen sensor measures net oxygen concentration in
the presence of all the products of combustion, including water vapor. Therefore,
it may be considered an analysis on a wet basis. In comparison with older
methods, such as the portable apparatus, which provides an analysis on a dry gas
basis, the wet analysis will, in general, indicate a lower percentage of oxygen. The
difference will be proportional to the water content of the sampled gas stream.
The combustibles sensor is a catalytic sensor consisting of two resistance
temperature devices (RTDs). One RTD is the reference element covered with an
inert coating. The other RTD element is active, coated with a catalyst. As the
sample gases flow by the sensor, the combustible gases oxidize on the surface of
the active element. The oxidation that occurs produces heat and a temperature
rise in the active element. The temperature difference produces a resistance
relationship between the two elements that is directly proportional to the
concentration of combustibles in the sample gases.
The catalyst is specifically designed to detect carbon monoxide (CO), but the
sensor responds to other combustible gases. The sensor is calibrated using CO;
thus the output should be expressed in terms of CO. However, as the sensor
detects other combustible gases, the output cannot just be labeled CO. The
response of the sensor to other combustible gases gives an output that is
equivalent to the sensor detecting CO.
The term COe is used in this Manual to describe the sensor output. This term
indicates that the sensor is calibrated in terms of CO and that the sensor output is
equivalent to CO but not specific to CO.
Dilution air is provided to the COe sensor to ensure that there is adequate oxygen
to fully oxidize any combustible gases regardless of the concentration of oxygen
in the process.
1.2.3
System configurations
Transmitters are available in four lengths, giving you the flexibility to use a
penetration appropriate to the size of the stack or duct. The length options are 18
in. (457 mm), 3 ft. (0.91 m), 6 ft. (1.83 m), or 9 ft. (2.7 m). Probes are available in
three material options: 316L stainless steel, Inconel 600, and ceramic to
accommodate higher temperatures.
The electronics are contained in a separate housing from the sensors. When the
transmitter is configured with the integral electronics option, the electronics and
sensor housings are mounted as a unit at the stack mounting flange. When the
transmitter is configured with the remote electronics option, the electronics
housing is separated from the sensor housing. The electronics housing may be
mounted up to 150 ft. (45.7 m) from the sensor housing.
The electronics control both sensor temperatures and provide output signals in
one of two ways:
12
Manual
00809-0500-4880
Emerson.com/Rosemount
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