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DETERMINATION OF COEFFICIENT D
Background
The system value Coefficient D must be used to correct moisture calculations for either or both of the
following operational circumstances:
l Extremely Low Moisture Concentration (<1 ppmv)
If measuring extremely low moisture concentrations (<1 ppmv), Coefficient D is used to cor-
rect for the inherent zero offset between the sample and reference gases caused by the gases
travelling different paths to the analyzer cell.
l Sample and Reference Gases are Dissimilar
If sample is any gas other than air or nitrogen and reference gas is air or nitrogen, Coefficient D
is used to correct for the background interference caused by the chemical and physical differ-
ences between the gases. Table I shows typical interference values for gases other than air. This
information is given for reference only; the actual value of the interference must be determined
using the procedure below.
Using dried sample gas as the reference as shown in figure 3a (Part II) eliminates this interference.
NOTE
Table II: Typical Interference Values for Gases Other Than Air
Sample Gas (100%)
Oxygen
Nitrogen
Carbon Monoxide
Propane
Ethane
Ethylene
Methane
Hydrogen
Isobutane
Butane
Isobutylene
F-22
F-12
Carbon Dioxide
2850 Moisture Analyzer
Indicated
ppmv/v
Vapor (% Concentration)
0.0
Heptane in air (4%)
0.0
Benzene in air (9%)
0.7
Methanol i n air (12%)
0.7
Ethanol in air (1%)
1.3
Perchloroethylene in air (3%)
1.3
1.7
2.6
2.6
2.6
5.0
10.0
7.5
44.0
Indicated
ppmv/v
10
10
150
1
8
C-1
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