Appendix A. Equation Summary
H
2
O Equations (LI-850 only)
Absorptance
α
ω
for water vapor is computed from
A-6
where
V
w
and
V
wo
are the sample and reference raw detector readings, and
Z
w
is
the zero parameter. The pressure correction for water vapor is an empirical func-
tion
g
w
() of absorptance and pressure
P
:
A-7
The value of
P
o
is 99 kPa. When the pressure correction is not enabled,
g
w
() is
simply 1.0. Water vapor concentration
W
(mmol mol
-1
) is computed from
A-8
where
f
w
(
x
) is a third order polynomial whose coefficients are given on the cal-
ibration sheet.
A-9
CO
2
Equations
The measurement of CO
2
is a bit more complicated than for H
2
O because of the
influence of water vapor. There is a slight direct cross sensitivity in the CO
2
signal
to H
2
O. This is measured at the factory and accounted for in the computation of
absorptance (equation A-10). There is also a band broadening effect that is accoun-
ted for in the computation of concentration (equation A-14).
CO
2
absorptance
α
c
is computed from
A-10
A-2
Using the LI-830 and LI-850 Gas Analyzers
Summary of Contents for LI-830
Page 1: ...Using the LI 830 and LI 850 Gas Analyzers...
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