Emerson Process Management OXYMITTER 4000 - Manual (Page 33)

Instruction Manual
IB-106-340C Rev. 4.1
July 2004
Rosemount Analytical Inc. A Division of Emerson Process Management Description and Specifications 1-3
Hazardous Area Oxymitter 4000
When the cell is at operating temperature
and there are unequal oxygen concentra-
tions across the cell, oxygen ions will travel
from the high oxygen partial pressure side
to the low oxygen partial pressure side of
the cell. The resulting logarithmic output
voltage is approximately 50 mV per decade.
The output is proportional to the inverse
logarithm of the oxygen concentration.
Therefore, the output signal increases as
the oxygen concentration of the sample gas
decreases. This characteristic enables the
Hazardous Area Oxymitter 4000 to provide
exceptional sensitivity at low oxygen
concentrations.
The Hazardous Area Oxymitter 4000 meas-
ures net oxygen concentration in the pres-
ence 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.
c. System Configuration
Hazardous Area Oxymitter 4000 units are
available in three length options, giving the
user the flexibility to use an in situ penetra-
tion appropriate to the size of the stack or
duct. The options on length are 457 mm
(18 in.), 0.91 m (3 ft), and 1.83 m (6 ft).
The electronics control probe temperatures
and provide an isolated output, 4-20 mA,
that is proportional to the measured oxygen
concentration. The power supply can accept
voltages of 90-250 VAC and 48/62 Hz; no
setup procedures are required. The oxygen
sensing cell is maintained at a constant
temperature by modulating the duty cycle of
the probe heater portion of the electronics.
The electronics accepts millivolt signals
generated by the sensing cell and produces
the outputs to be used by remotely con-
nected devices. The output is an isolated
4-20 mA linearized current.
HAZARDOUS AREA
OXYMITTER 4000
IMPS 4000
(1 TO 4 PROBES)
(MUST BE INSTALLED
IN A SAFE AREA
OR BE X- OR Z-PURGED
BY THE CUSTOMER)
REMOTE MOUNTED
SPS 4000
(1 PROBE)
(MUST BE INSTALLED
IN A SAFE AREA)
26310002
Figure 1-2. Hazardous Area Oxymitter 4000
Autocalibration System Options
The Oxymitter 4000 transmitter is available
with an integral or remote electronics pack-
age. Two calibration gas sequencers are
available to the Hazardous Area Oxymitter
4000, but they must be installed in a non-
hazardous, explosive-free environment: the
IMPS 4000 and the SPS 4000 (Figure 1-2).
Systems with multiprobe applications may
employ an optional IMPS 4000 Intelligent
Multiprobe Test Gas Sequencer. The IMPS
4000 provides automatic calibration gas
sequencing for up to four Hazardous Area
Oxymitter 4000 units and accommodates
autocalibrations based on the CALIBRA-
TION RECOMMENDED signal from the
Hazardous Area Oxymitter 4000, a timed
interval set up in HART or the IMPS 4000,
or whenever a calibration request is
initiated.
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