Logging CH4 data in .ghg data files

When using the LI-7700 to measure gas exchange with the eddy covariance method, data from the LI-7700 are recorded in .ghg files and processed with EddyPro on the SmartFlux System along with CO2/H2O measurements provided by an LI-7500A/RS/DS or LI-7200/RS.

Note: We recommend that you always run the most up-to-date software for the best performance. Software updates are available from licor.com/7700software.

Configuring the LI-7700 output rate and time setting

Launch the LI-7700 application, connect to the LI-7700, set the PTP time to automatic, and set the output rate to 10 Hz. Higher output rates may be needed in some circumstances.

Click OK, then close the LI-7700 application.

Connecting the LI-7700 with the eddy covariance system

Launch the CO2/H2O analyzer application (called LI-7x00 A RS DS 8.x), select the LI-7500A/RS/DS or LI-7200/RS from the list, and click Connect.

Be sure to configure the LI-7500A/RS/DS or LI-7200/RS for eddy covariance measurements.

Click the LI-7700 button, or under Site Setup > LI-7700 , click settings () to open the connection window.

Select the LI-7700 from the list or enter an IP address in the LI-7700 Hostname field (for networked device on different subnet mask as computer) and click Connect. Click Apply or OK.

Entering LI-7700 information

Under Site Setup > CH4 Analyzer, specify the separation between the sonic anemometer and the LI-7700 sample volume and select variables to log. See Collect data on the gas analyzer position

Important: At least one separation must be different from 0. Values are measured at the site and are relative to the sonic anemometer. Entering wrong values will result in incorrect flux calculations.

  • Northward Separation (cm) (mandatory): North/south distance between the LI-7700 and the anemometer. Positive values if north and negative values if south of the anemometer.
  • Eastward Separation (cm) (mandatory): East/west distance between the LI-7700 and the anemometer. Positive values if east and negative values if west of the anemometer.
  • Vertical Separation (cm) (mandatory): Vertical distance between the LI-7700 and the anemometer. This value is negative if the center of the LI-7700 sample volume is below the center of the reference anemometer sample volume and positive if the gas sample is above.

Selecting variables

Under the Site Setup window, click the default button () to select the recommended variables for processing. Or, click Select All to log all variables. When you start logging data the selected variables for the LI-7700 will be logged with the dataset. Check the Log LI-7700 status records (.status) to collect LI-7700 STATUS records. This is for diagnostic purposes.

Verifying the connection

Verify the connection under the dashboard of the LI-7500A/RS/DS or LI-7200/RS software. The software dashboard indicates a successful connection by listing the LI-7700 or an error (). If there is an error, the software provides guidance to resolve the issue.

Turning on data logging

Data logging is controlled in the bottom of the Site Setup window. To start datalogging:

  • Click to activate data logging,
  • Insert a suitable USB drive into the USB port.
  • Power on the LI-7550 (a USB drive must be in the USB port).