Setting the zeros

NOTE: Read "Using CO2 and H2O Scrubbers with LI-COR Gas Analyzers" for important information about the interactions between scrub chemicals and the air. See

  1. Plumb the LI-8100A. See Figure 7‑1 for tank gas and Figure 7‑2 for scrubbers.
  2. If you are using tank gas, use a flow splitter to vent the excess gas to the atmosphere. Turn the instrument pump on and set flow from the tank to 2 to 2.5 lpm. Vent the instrument outlet to the atmosphere to prevent pressurizing the analyzer. If you are using chemical scrubbers, plumb everything and then turn the instrument pump on.
  3. Figure 7‑1. Typical plumbing configuration for setting the instrument zero using a zero gas. Always use dry, CO2-free air.
  4. Figure 7‑2. Typical plumbing configuration for setting the instrument zero using gas scrubbers. Soda lime and Ascarite II® are good CO2 scrubbers. Drierite® and magnesium perchlorate are good water vapor scrubbers.
  5. Monitor CO2 and H2O concentra`tions. Allow 1-2 minutes for the CO2 concentrations to stabilize and 15-20 minutes for the H2O concentration to stabilize near zero.
  6. Calibrate:

In the PC Software:

Configure the Data view to show CO2 (µmol/mol) and H2O (mol/mol); (click a variable to change it).

Go to Utilities > Calibration and go to the Zero tab.

When H2O concentrations are stable, click Zero H2O.

When the CO2 concentration is stable, click Zero CO2.

In the App:

Go to Utilities > Calibration, then tap Perform: Zero.

Under the CO2 tab, tap Send Command when the CO2 reading is stable.

Under the H2O tab, tap Send Command when the H2O reading is stable.