Rosemount 755A, Инструкция по эксплуатации

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I
NITIAL
S
TARTUP AND
C
ALIBRATION
245364-U Rosemount Analytical April 2000 3-11
Model 755A Oxygen Analyzer
upscale standard gases, but slightly different values calculated to provide correct
readout during subsequent analysis of the sample gas. The calculations are
explained in Section 3.4.2.
3.4.1 O
XYGEN
E
QUIVALENT
V
ALUES OF
G
ASES
For computation of background corrections, the analyzer response to each component
of the sample must be shown. Table 3-2 lists the percentage oxygen equivalent
values for many common 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 3-3, if analyzer response to oxygen is +100%,
the response to xenon would be -1.34%.
O
XYGEN
E
QUIVALENTS OF
G
AS
M
IXTURES
The oxygen equivalent of a gas mixture is the sum of the contribution of the individual
gas components.
Example: At lower range limit, i.e., 0% oxygen, composition of sample is 80% CO
2
,
20% N
2
.
From Table 3-3, the % oxygen equivalents are CO
2
. -0.623 and N
2
, -0.358.
% oxygen equivalent of the mixture =
0.8 x (-0.623) + 0.2 x (-0.358) = (-0.4984) + (-0.0716) = -0.570
3.4.2 C
OMPUTING
A
DJUSTED
S
ETTINGS FOR
Z
ERO AND
S
PAN
C
ONTROLS
During instrument calibration, Adjusted Values may be required in setting the ZERO
and SPAN control to correct for the magnetic susceptibility of the background gas.
Terms used in the equation are defined as:
1. Std. Oxygen equivalent of background gas in the standard. Refer to Table 3-3.
2. Spl. Oxygen equivalent of background gas in the sample. Refer to Table 3-3 for
values.
Calibration and measurement must be made at the same pressure in the detector cell
unless the user makes the compensation referred to in Section 4.2.
Adjusted value = % O
2
in Std +
%O
2
Equivalent of Gas
Analyzer Response to Gas
Analyzer Response to O
2
X 100
[100(Spl-Std)]-100(Spl-Std)
100
% O
2
in Std
100