Connecting an Original LI-8100 to an LI-78xx Trace Gas Analyzer

The LI-78xx Trace Gas Analyzers can be connected with into an existing LI-8100A system to measure flux of trace gases, in addition to CO2 with the network connection. The process is described here. The connection uses an Ethernet cable between the Trace Gas Analyzer and LI-8100 to enable time synchronization, which is critical for flux data analysis.

The original LI-8100 did not have an external weather tight Ethernet port, but with a few modifications, you can install one in place of its RS-232 port. Purchase the following components from LI-COR.

Part Number Description
392-10711 External Ethernet Port
6400-26 Internal Ethernet Card
616-07455 PC Card Adapter
392-09436 External Ethernet Cable
208-02330 Loctite Threadlocker Blue 242 (can be purchased from most hardware stores)

Use a 19 mm socket or wrench (a crescent wrench is fine if you are careful). Use a torque wrench for reassembly if you have one available.

To install the components:

  1. Power off the LI-8100.
  2. Remove the external RS-232 port. Use a 19 mm socket to remove the locking nut. It may require some force to break the Loctite seal.
  3. Open the LI-8100’s internal access panel by removing the four thumbscrews.
  4. Pull the RS-232 connector into the LI-8100, put the locking nut back on, and leave it there.
  5. You will need to access it later to connect a computer to the LI-8100 while the Ethernet port is being used to communicate with the LI-78xx analyzer.
  6. Install the external Ethernet port.
  7. Apply a small amount of Loctite on the locking nut of the 392-10711 Ethernet port. Install the port into the open hole where the RS-232 port was, making sure that the key (small indent) on the connector is in the upper right corner as shown. Use a 19 mm socket to torque to 8.1 Nm (72 lb.-in.). If you do not have a torque wrench, tighten it snugly.
  8. Connect the internal Ethernet cable.
  9. Under the right side of the access panel, there are two Compact Flash card slots. Insert the 616-07455 PC card adapter into either of these slots. Insert the 6400-26 internal Ethernet card into that (yours may look different than the picture below). Connect the internal Ethernet cable to that card.
  10. Connect the 392-09436 Ethernet cable to the external Ethernet port. Connect the other end to the LI-78xx trace gas analyzer.
  11. Power on the LI-8100.

Follow the rest of the instructions in the application note here.