Communication Issues

Printable PDF: LI-7500 CO2/H2O Analyzer Communication Issues

Technical Note/FAQ about communication with the LI-7500.

There are three main types of communication issues: (1) Communication between the White Control Box and the Computer, (2) Communication between the Sensor Head and the White Control Box, and (3) Communication between the White Control Box and the Datalogger. Here are a few suggestions for these communication pathways. Some of them might solve multiple communication issues:

  1. Communication between the White Control Box and the Computer
  2. First - check the LI-7500 Windows Interface Software version you have by starting the Windows program on your computer. The LI-7500 does not need to be connected to do this. Then go to 'Help' on the menu and choose ‘About’. Make sure the latest version is installed. If not, the latest software versions can be found on our website.
  3. NOTE: If a new version of software is downloaded onto the computer or laptop, that any 'icon' or ‘shortcut’ on the desktop is changed to point to this correct version. Otherwise, 'double-clicking' that icon will continue to access the older version.
  4. If utilizing a "USB-to-RS232 Adapter" and have a serial port available on the computer, try plugging the RS232 directly into the computer's serial port using the 9975-015 Cable (shown on page 1-7 in the Manual). Periodically, errors related to the USB-to-RS232 Adapter have occurred.
  5. Communication between the Sensor Head and the White Control Box
  6. Examine the Cable that runs from the White Control Box to the Sensor Head. Sometimes film and/or corrosion can build up inside the connection around the pins. Connecting, disconnecting, and reconnecting this connection to the Head a few times can help remove some of this build-up. Similarly, if the Cable connection is not seated fully against the Head, hot and cold weather changes can cause the cable and wiring to expand and contract, causing the wires to intermittently disconnect.
  7. Also examine the wires that come from the Sensor Head and wire into the Control Box. The metal shield cover inside the Control Box needs to be removed to access and examine these connections. Follow the black cable to see where these connect (also see page B-2 in the Appendix). Weather may cause these connections to intermittently lose connection due to expansion and contraction. Check all the wires that are attached to those green connectors, making sure the colors are correct and the connections are tight. Feel free to pull gently on each of the wires to make sure they are securely connected.
  8. Communication between the White Control Box and the Datalogger (if applicable)
  9. Make sure that all the wires/cables are connected properly inside the White Control Box. Start with the diagram in the Manual in Appendix B which illustrates the connections within the Control Box. There should be five separate green connectors. Make sure all of these are tightly connected. Check the communication cables. Are communication errors only occurring with the SDM cable (and datalogger) or only with the RS-232 Serial Port connection to the computer? Are errors occurring through both sets of communication? It is possible that the errors (or error messages) are only occurring due to one form of communication. If the problem is with the SDM/Datalogger communication, try to connect using a Computer, an RS-232 Serial Cable, and the LI-7500 Windows Software program, and see if these same communication errors continue. This can be quickly done using the 9975-015 Cable (shown on page 1-7 in the Manual). Similarly, if errors only occur through the RS-232 Serial Cable connection to the computer, does the connection to the SDM/Datalogger continue to work? Make sure that all these cables and connections in the Control Box are tight. Check all the wires that go into the green connectors.
  10. Something to try to resolve ALL communication errors:
  11. Inside the White Box there is a little blue 'Reset' button. This can also be seen in the Manual on page 5-3. Press this button while the system is up and running to 'reboot' the instrument.
  12. If able to eventually establish a connection between the LI-7500 Windows Software and the LI-7500 System, go to the 'Diagnostics' Tab on the software. In the white 'Current Configuration' window, click on the small [+] sign next to "EmbeddedSW". This will display the Version of Software that is embedded inside the actual LI-7500 instrument. Communication is possible even with the newest version of Windows software and an earlier version of the Embedded software. The latest Version of Embedded Software is available for download: LI-7500 Open Path CO2/H2O Analyzer Instrument (Embedded) Software V3.0.1