LI-COR LI-8100A - H 2 O Span; Setting Zero: CO 2 and H 2 O; Using a Calibrated Tank of Zero Gas

User Calibration
5-3
H
2
O Span
For known water vapor concentrations, a convenient standard to use is a dew point
generator such as the LI-COR LI-610 Portable Dew Point Generator. To avoid
condensation problems, choose a dew point temperature that is about 3 to 5 °C
below the ambient temperature. Also, since water vapor sorbs and desorbs from
surfaces, minimize the sorbing surface area (minimize tubing lengths), and allow
plenty of time for the reading to stabilize. It is important not to rush through water
vapor calibrations; give the surfaces plenty of time to equilibrate to large changes
in water vapor concentration.
Setting Zero: CO
2
and H
2
O
Using a Calibrated Tank of Zero Gas
1. Plumb the LI-8100A.
A. Attach a tank of dry, CO
2
-free gas to the LI-8100A air inlet.
B. Vent the instrument outlet to the atmosphere.
C. Turn off the pump, if it is on, and set flow from the tank at 0.5 l/min.
2. Monitor CO
2
and H
2
O concentrations.
When concentrations are stable, proceed to step 3. Allow 1-2 minutes for the
CO
2
concentrations to stabilize and 15-20 minutes for the H
2
O concentration
to stabilize near zero.
3. Calibrate.
Windows Software
A. Select Calibration from the Utilities menu.
B. Click on the Zero tab.
i. Verify that the CO
2
concentration in the main window is still stable.
ii. Click on the Zero CO
2
button.
iii. Click Yes to perform the calibration.
C. On the Zero tab:
i. Verify that the H
2
O concentration in the main window is stable.
ii. Click on the Zero H
2
O button.
iii. Click Yes to perform the calibration.
D. Click on Close to exit the calibration screen.
Software for Apple iOS
A. Select Calibration from the Utilities menu.
B. Tap the Zero button.
i. Enable CO
2
.
ii. Verify that the CO
2
concentration is stable.
iii. Tap the Send Command button.