Instruction Manual
Instruction Manual
748213-S
April 2002
3-4 Operation Rosemount Analytical Inc. A Division of Emerson Process Management
Model 755R
RANGE % OXYGEN
RECOMMENDED ZERO
STANDARD GAS
RECOMMENDED SPAN
STANDARD GAS
0 to 1 Nitrogen 0.9% O2, balance N2
0 to 2.5 Nitrogen 2.3% O2, balance N2
0 to 5 Nitrogen 4.5% O2, balance N2
0 to 10 Nitrogen 9% O2, balance N2
0 to 25 Nitrogen Air (20.93% O2)
0 to 50 Nitrogen 45% O2, balance N2
0 to 100 Nitrogen 100% O2
Table 3-1. Calibration Range for Various Zero-Based Operating Ranges
a. Oxygen Equivalent Value of Gases
For computation of background correc-
tions, the analyzer response to each
component of the sample must be shown.
Table 3-2 (page 3-6) lists the percentage
oxygen equivalent values for many com-
mon gases.
The percentage oxygen equivalent of a
gas is the instrument response to the
given gas compared to the response to
oxygen, assuming that both gases are
supplied at the same pressure .
In equation form:
To select a random example from Table
3-2, if analyzer response to oxygen is
+100%, the response to xenon would be
-1.34%.
The oxygen equivalent of a gas mixture is
the sum of the contribution of the individ-
ual gas components.
Example: Zero Based Range
At lower range limit, i.e., 0% oxygen, composition of sample is 80% CO
2
, 20% N
2
.
From Table 3-1 (page 3-4), the % oxygen equivalents are CO
2
. -0.623 and N
2
, -0.358%.
% oxygen equivalent of mixture =
0.8 x (-0.623) + 0.2 x (-0.358) = (-0.4984) + (-0.0716) = -0.570% Oxygen
b. Computing Adjusted Settings for Zero and Span Controls
During instrument calibration, adjusted values may be required in setting the ZERO and SPAN controls
to correct for the magnetic susceptibility of the background gas.
The quantities are defined as follows:
BGGst = Oxygen equivalent of background gas in standard gas (see Table 3-2, page 3-6)
BGGs = Oxygen equivalent of background gas sample (see Table 3-2, page 3-6)
OP = operating pressure. Unless special pressure corrections are to be made, the zero stan-
dard, span standard and sample gases must all be admitted at the same pressure.
%O2 Equivalent of Gas =
Analyzer Response to Gas
Analyzer Response to O
2
X 100%