Model NGA2000 PMD

Instruction Manual

760007-A July 2003

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:

(A)[100 + (B-C)]-100[B-C]

Adjusted percent oxygen for standard gas =

100

 

Where:

A = true percent oxygen of standard gas

B = BGGs

C = BGGst

Example:

Background gs in sample is CO2, oxygen equivalent = -0.623%.

Zero gas is 100% N2.

Span standard gas is air: 21% O2, 79% N2.

Background gas in zero and span standard gases is N2, oxygen equivalent = 0.358%.

With N2 zero standard gas flowing, zero gas value in the Calibration Gas List would be 0.265% O2 (as determined by the following):

0[100+(-0.623-(-0.358))] - 100{-0.623-(-0.358)] = 0.265% O2 100

With air flowing, span gas value in the Calibration Gas List would be 21.21% oxygen (as determined by the following):

21(100 - 0.265) - 100 (-0.265)

100

= 21.209% O2 ≅ 21.21 O2

Rosemount Analytical Inc. A Division of Emerson Process Management

Operation 3-9