We address potential problems in this section.

Gas analyzer will not power on or repeatedly powers on and off

  • Adequate power supply? If the Power LED cycles on and off, the power supply is not sufficient to start up the instrument. The instrument requires between 8 and 34 VDC. Power draw may briefly be up to 15 watts during start up. Steady-state power draw is between 4 and 8 watts, depending upon the ambient temperature. Hot and cold temperatures cause the instrument to draw more power.
  • Loose connection? Make sure the power cable connector is tight. Also check the cable for damage and check the connections to the power supply.
  • Blown fuse? Check the fuse, as described in Changing the SmartFlux 3 System fuses. Note that a blown fuse usually indicates some other problem. If the fuse blows repeatedly, carefully check the wiring.

Problems with the SmartFlux 3 System

System powers on/off unpredictably or not powering the anemometer

  • Check connections in the power supply and correct any faulty connections.
  • Check connections on the SmartFlux System power wiring harness and tighten any loose fittings.
  • Check the power wires. The positive wire should go to the Power IN (+) terminal and the negative wire should go to the Power IN (–) terminal on the SmartFlux 2 module.
  • If the Power IN LED is lit, but Power OUT LED is not lit, then a 3A fuse inside the SmartFlux 2 module may have failed.
  • Check the VIN value in the GHG windows interface software (under Diagnostics). Some sonic anemometers have an upper voltage limit of 15 VDC. In this case, supplying an incoming 24 VDC to the SmartFlux System could damage the sonic anemometer. The same voltage provided to the SmartFlux System will be provided to a sonic anemometer powered through the Power Out terminals.

System not visible on the network (cannot connect)

  • Check the Ethernet Activity LED light on the SmartFlux 2 or 3 System. If it is blinking rapidly, this indicates the system is communicating over the network.
  • Check the Ethernet cable and connections to the SmartFlux 2 or 3 system and in the rest of your EC system.
  • Check the power supply connections and correct any faulty connections.
  • Reboot the SmartFlux 2 or 3 System by pressing the reset button.
  • Reboot the gas analyzer.

System not connected to the sonic anemometer

  • If you have renamed the SmartFlux 2 or 3 System, does it have a valid name? The SmartFlux System name can only include upper and lower case letters (A to Z; a to z), numbers (0 to 9), the dash character (-), and the period (.). All other characters are invalid and will prevent the system from working as expected. One indicator of this is that the sonic anemometer status is displayed as disconnected in the gas analyzer software main window.
    • Invalid names: Flux_Site_01 (invalid underscore _ characters); Micromet@TheSwamp (invalid @ character).
    • Valid names: smart03-00901 (the default name).
  • For manually configured anemometers, check to see that the sonic anemometer is set to the proper baud rate.
  • Check the return signal LED lights next to the sonic anemometer data port. If they are flashing or solid, this indicates that the SmartFlux System is communicating with the sonic anemometer.
  • Check the connections on the sonic data input plug wiring and tighten any loose fittings.
  • Check the power supply to the anemometer.
  • Reboot the SmartFlux System by clicking the Reboot button in the analyzer software (on the SmartFlux tab) or the reset button on the SmartFlux System.

USB flash drive not working properly

We recommend using a USB drive from LI-COR because it has been tested with the SmartFlux System. If you use a different USB drive, it should be industrial grade. If the USB LED blinks slowly (one time per second), this indicates an error. Try the following:

  • Press the reset button on the SmartFlux System to re-boot the system.
  • Unmount and re-mount the flash drive.
  • Check to see if space remains on the USB drive. Remove files to free up some space.

Fluxes not being computed, are unreasonable, or raw data not time-aligned

  • Check the time keeping settings for the system. Connect with the gas analyzer using the desktop software and verify that the PTP time keeping is On and set to Automatic for the gas analyzers.
  • Be sure that the GPS antenna is installed outside of the enclosure and with a clear view of the sky. It must receive signals from GPS satellites in order to set the time.
  • Check the results folder and look for the EddyPro log on the USB drive.
  • Try processing data using EddyPro desktop.

Results are not identical to EddyPro desktop results

  • Configuration settings are not the same. Review the configurations and ensure that they are identical.
  • North Offset/Magnetic declination are set differently.
  • Software versions not compatible. Although we attempt to test every possible scenario, there are cases that may lead to slight offsets in flux results. We fix bugs as they are identified. Ensure that you are running the most up-to-date version of EddyPro and the SmartFlux System embedded software. Contact LI-COR technical support ( if you are unable to resolve the issue.

SmartFlux Status server errors

The SmartFlux status server communicates with the win-GHG appliction on a timed basis. Occassionally, you may just need to wait 15 seconds to a few minutes for the status to update. If the IRGA and a LI-7500RS or LI-7200RS are behind a cellular modem, you must check the Modem Connection box to instruct the application to retrieve status information. If the box is clear while the IRGA is behind a modem, the server will report that it is unable to contact the server.

Unable to connect or instrument not visible in software

Firewall rules prohibiting the connection? Create an exception that allows the gas analyzer through the firewall. If you are using the Windows® firewall, follow the instructions provided by Microsoft® at If you are using another firewall, refer to documentation provided with that software.

Issues with gas analyzer measurements

Bad CO2 or H2O readings

  • Signal strength OK? Under the Diagnostics page, check the values of Signal Strength. Even if the signal strength looks acceptable, you may need to clean the optical windows.
  • Are the diagnostic flags (PLL, etc.) OK? Under Diagnostics, check the diagnostics.
  • Zero and Span OK? Go to the Calibration page and make sure the current values of zero and span are near 1.
  • Calibration coefficients correct? Make sure all of the coefficients on LI-7500DS > Calibration > Coefficients match the calibration sheet for the head. You can get your calibration information from the LI-COR web site. The Band Broadening coefficient should be 1.15.

Absorptances make sense, densities don't

If the absorptance value seems correct (rough rule of thumb: absorptance = 0 when density = 0, CO2 absorptance is about 0.1 with a mole fraction of about 400 ppm, and H2O absorptance is about 0.1 with a mole fraction of about 20 mmol/mol), but the displayed values of density or mole fraction are obviously bad, then the problem is in one of the following: calibration coefficients, span parameter, pressure value, and the band broadening value (CO2 only).

Readings very noisy

The variability in absorptance values should be low, with only the 4th decimal place changing once in a while. If density or mole fraction is still noisy, watch the temperature and pressure values to see if they are the source of the noise (or change to a hand entered, constant value to try this). Check the calibration coefficients and band broadening value (if the problem is with CO2) to make sure they are correct.

DSI box status LED blinking

The status LED will blink if one of the diagnostic errors is triggered. One of the most common causes is dirt on the optical windows. Clean the windows (see Cleaning the gas analyzer optical path for details) and see if the blinking stops. If this doesn't resolve the error, to connect to the instrument using the Windows Interface software and check the diagnostics (click Diagnostics > Status). Address any issues and restart the instrument. If a diagnostic error remains triggered after restarting the instrument, contact LI-COR technical support.