LI-COR LI-7500, Instruction Manual

Page: 92 / 155

Section 4
4-10 Calibration
Note this value
Figure 4-2. Note value of Z
co
, shown as Current Value.
6. When the reading has stabilized, click Zero to set the CO
2
zero. After a brief delay, the
displayed CO
2
value should be fluctuating around zero. Check the resultant value of Z
co
shown on the Zero CO
2
page (Figure 4-2). It should be near 1 (typically between 0.85
and 1.1). This value will steadily increase as the internal chemicals lose effectiveness.
Zero H
2
O
7. Now is a good time to check or set the H
2
O zero, if you have been flowing dry, CO
2
-free
air through the optical path. Click the H
2
O tab, and note the present value of Z
wo
.
8. Wait for the H
2
O reading to stabilize (3 or 4 minutes).