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Instruction Manual
760007-A
July 2003
Rosemount Analytical Inc. A Division of Emerson Process Management Operation 3-9
Model NGA2000 PMD
Computing Adjusted Values for Calibration Gas List
Before calibrating the Analyzer Module, values in the Calibration Gas List must be adjusted to correct for
magnetic susceptibility of background gas. In the equation that follows, the quantities are defined as fol-
lows:
• BGGst = oxygen equivalent of background gas in standard gas (Table 3-4 on page 3-10).
• BGGs = oxygen equivalent of background gas in sample (Table 3-4 on page 3-10).
• OP = operating pressure. Unless special pressure corrections are to be made, the zero standard, span
standard and sample gases must all be admitted at the same pressure.
Use the following equation to compute the adjusted settings for the Calibration Gas List:
Adjusted percent oxygen for standard gas =
Where:
A = true percent oxygen of standard gas
B = BGGs
C = BGGst
Example:
Background gs in sample is CO
2
, oxygen equivalent = -0.623%.
Zero gas is 100% N
2.
Span standard gas is air: 21% O
2
, 79% N
2
.
Background gas in zero and span standard gases is N
2
, oxygen equivalent = 0.358%.
With N
2 zero standard gas flowing, zero gas value in the Calibration Gas List would be 0.265% O
2
(as de-
termined by the following):
With air flowing, span gas value in the Calibration Gas List would be 21.21% oxygen (as determined by the
following):
(A)[100 + (B-C)]-100[B-C]
100
= 0.265% O
2
0[100+(-0.623-(-0.358))] - 100{-0.623-(-0.358)]
100
= 21.209% O
2
≅
21.21 O
2
21(100 - 0.265) - 100 (-0.265)
100