Overview of SDI-12 and the LI-710

The LI-710 is an SDI-12 device. Communication can be carried out over a device that mediates the SDI-12 communication such as a datalogger with SDI-12 inputs or an SDI-12-to-USB translator.

Wiring the sensor

The LI-710 is powered by over the brown wire (9 to 33 VDC). Data are transferred over the blue DATA wire. The black wire connects to ground.

Figure 3‑1. Wires from the LI-710 connect to power and an SDI-12 data bus.

Common commands

Here we provide a summary of commands that are used by the LI-710.

  • ? – query the sensor address
  • I - get info
  • A – set the sensor address
  • M – measure
  • XT – start collection (trigger).

Use the XT command every 30 minutes to instruct the LI-710 to begin recording for a 30-minute measurement period. This ensures that data are aligned in time for every measurement period, and it prevents drift in the sampling period.

The XT (trigger) command

If you are using the trigger command, results are updated 30 minutes after the trigger is received. When you send the trigger command, the LI-710 starts a new measurement sequence. If a trigger is received once but not received again, fluxes will be computed in hourly intervals thereafter. Once a trigger is supplied, another trigger command is required to start the next measurement interval. We recommend sending the trigger command and retrieving data once every 30 minutes.

Default settings

All LI-710s leave LI-COR with address 0. It can be changed with the A command if needed.

To communicate with the sensor, you will program the datalogger to measure the sensor output every 30 minutes. Send the sensor the M command to collect data. M0 collects the basic data set. M1, M2, or M3 collect different data sets. The LI-710 only requires the M commands, but you can use them with the XT command to trigger each measurement period. The contents of each packet that is returned by the M commands are defined in Data and variables.

Detailed instructions for common dataloggers are in following sections: