IB-106-340
1-1
SECTION I. INTRODUCTION
1-1.
COMPONENT CHECKLIST OF TYPICAL
SYSTEM (PACKAGE CONTENTS). A typical
Rosemount Oxymitter 4000 Oxygen Transmitter
should contain the items shown in Figure 1-1. Record
the part number, serial number, and order number for
each component of your system in the table located on
the first page of this manual.
Also, use the product matrix in Table 1-1 at the end
of this section to compare your order number against
your unit. The first part of the matrix defines the
model. The last part defines the various options and
features of the Oxymitter 4000. Ensure the features
and options specified by your order number are on or
included with the unit.
1-2.
SYSTEM OVERVIEW.
a.
Scope. This Instruction Bulletin is designed to
supply details needed to install, start up, operate,
and maintain the Oxymitter 4000. Integral signal
conditioning electronics outputs a 4-20 mA signal
representing an O
2
value and provides a membrane
keypad for setup, calibration, and diagnostics. This
same information, plus additional details, can be
accessed with the HART Model 275 handheld
communicator or Asset Management Solutions
(AMS) software.
b.
System Description. The Oxymitter 4000 is
designed to measure the net concentration of
oxygen in an industrial process; i.e., the oxygen
remaining after all fuels have been oxidized. The
probe is permanently positioned within an exhaust
duct or stack and performs its task without the use
of a sampling system.
The equipment measures oxygen percentage by
reading the voltage developed across a heated
electrochemical cell, which consists of a small
yttria-stabilized, zirconia disc. Both sides of the
disc are coated with porous metal electrodes.
When operated at the proper temperature, the
millivolt output voltage of the cell is given by the
following Nernst equation:
EMF = KT log
10
(P
1
/P
2
) + C
Where:
1. P
2
is the partial pressure of the oxygen in the
measured gas on one side of the cell.
2. P
1
is the partial pressure of the oxygen in the
reference air on the opposite side of the cell.
3. T is the absolute temperature.
4. C is the cell constant.
5. K is an arithmetic constant.
NOTE
For best results, use clean, dry, instrument
air (20.95% oxygen) as the reference air.
When the cell is at operating temperature and there
are unequal oxygen concentrations 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 Oxymitter 4000 to
provide exceptional sensitivity at low oxygen
concentrations.
The Oxymitter 4000 measures net oxygen con-
centration 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.
c.
System Configuration. Oxymitter 4000 units are
available in five length options, giving the user the
flexibility to use an in situ penetration appropriate
to the size of the stack or duct. The options on
length are 18 in. (457 mm), 3 ft (0.91 m), 6 ft
(1.83 m), 9 ft (2.7 m), or 12 ft (3.66 m).
Содержание Oxymitter 4000
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