Section 3
Theory of Operation
3-13
time the reference cell is scrubbed. The same is true when ambient air is
returned to the reference cell.
It is easier to leave the reference gas alone and scrub the sample cell; this
avoids zero shifts and gain changes. One can then measure the output
voltage V and compute V
r
and C
r
according to equations 3-34 and 3-35.
V
V
V
K
r
= −
−
1
3-34
C
F V
P
P
T
T
r
r
o
o
=
+
+
273
273
3-35
These values can be used as needed to compute C
s
or
∆
C over as long a time
period as C
r
and temperature are stable.
Note
: This is not implemented in
the instrument, but is provided as an aid to those needing this trick.
