Here we describe how to identify and resolve problems that may arise, starting with connection issues and finishing with diagnostic information.

Connection issues

Most connection issues can be resolved by checking the wiring connections, address of the LI-710, or the data logger configuration.

  • No data or unexpected replies?
  • Check the power wires. Be sure the black lead is connected to ground and the brown one is connected to a 9 to 33 VDC supply. When it is on, you can hear the pump running quietly and faint clicks near the sonic transducers. If you don't hear the LI-710 running, investigate the power supply. If it is running, continue with the next steps.
  • Data wire attached?
  • Check the blue data wire. Be sure it is connected to an SDI-12 terminal, and that the terminal is configured to support the SDI-12 protocol.
  • Wrong address applied to sensor or specified in the program?
  • Check the LI-710 address. Using the command-line interface provided in your data logger program, request information by sending "?!", along with the syntax required by your data logger. The LI-710 should respond with information, including the current address. You can send a command to change the address if needed.
  • Address conflicts with multiple LI-710s or other devices?
  • Each SDI-12 device connected to the terminals must have a unique address. Connect each device to the terminals one at a time and query each one for its address. If you find any conflicting addresses, make changes so each one is unique. You may also need to update the data logger programs to reflect the new device addresses.

Power issues

The LI-710 requires 1.5 watts during normal operation. When power is first supplied, it may draw up to 24.6 watts for 20 milliseconds. Some SDI-12 power supplies are current limited and unable to provide sufficient power to satisfy the startup requirements, leading to continuous reboots or the delivery of partial data. If you observe either of the two scenarios, connect the brown (+) and black (-) wires directly to the data logger power supply (9 to 33 VDC) and power it back on.


Diagnostics in the LI-710 can be imagined as three tiers. First, inside the instrument, every measured value (1/10th of a second) is tested for spikes or plausibility. Implausible data points are quietly discarded by the LI-710; you can see how many were discarded in the eighth parameter of group 1 see (Group 1: Results and sample count), and the percent used as the eighth parameter of group 3 (see Group 3: Performance information and diagnostics). A measurement has up to 18,000 wind and water vapor samples. This is the number of points used to compute the results for the 30-minute period. Note, however, that you should rarely be concerned with the number of discrete points used in a calculation.

The second tier of diagnostic information can reveal more about what was wrong with a particular measurement, details about environmental conditions for the time period, and information about the LI-710 performance over that time period. You can use this to identify an issue that can be addressed by servicing the LI-710. This is the diagnostic value recorded as the ninth variable in data Group 0 and Group 1.

A third tier of diagnostic information is the number of data points used in a flux calculation. DataQC is the eighth parameter in Group 3: Performance information and diagnostics.

Diagnostic codes

Diagnostic information is included as the last parameter in output groups 0 and 1. The diagnostic value, which ranges from 0 to 65535 (corresponding to bit positions 0 through 15), encodes one or more of the issues indicated (see Table 9‑1).

Table 9‑1. A diagnostic code is included with each measurement. Some diagnostic codes are simply for your information, others indicate the quality of data, and others are used to identify issues that should be fixed.
Value Description Threshold
0 Normal operation No issues detected
1 Flow out of range Average flow for a 30-minute period is <125 sccm or >330 sccm
2 Reserved Not applicable
4 Reserved Not applicable
8 Low RH sensor voltage Sensor voltage ≤1.6 V for >50% of time for a 30-minute period
16 Cell temperature out of range >65 °C or <-50 °C for >5% of time for a 30-minute period
32 Reserved Not applicable
64 No sonic Set if sonic anemometer is not detected
128 Poor sonic signal Set if poor sonic signals persist for >10% of time for a 30-minute period
256 Rain detected True for >50% of time for a 30-minute period
512 High humidity shutdown >90% cell RH >2 data points or

>90% ambient RH for 100 data points and 50% of the last 100 sonic rain flag data points
1024 Cold temperature shutdown Cell temperature <0 °C for 100 data points
2048 High cell pressure relative to ambient Average cell pressure - average ambient pressure is > 0.4 kPa for a 30-minute period
4096 Low cell pressure relative to ambient Average cell pressure - average ambient Pressure is < -1.5 kPa for a 30-minute period
8192 Reserved Not applicable
16384 Low pump voltage Pump voltage <8 V for >50% of time for a 30-minute period
32768 High pump voltage Pump voltage >20 V for >50% of time for a 30-minute period

Addressing diagnostic codes

Some diagnostic codes are simply for your information - there is nothing to do besides know what the code indicates. For example, if the LI-710 measures freezing temperatures or persistent high humidity, it stop measurements. You can assume that evapotranspiration is near zero in these conditions. The instrument will resume measurements when temperature or humidity comes back to an acceptable range. In these circumstance, the code simply tells you something about measurements from the time period.

Status codes are additive: if multiple codes are active, the displayed value is the sum of the codes. For example, a display code of 17 indicates that cell temperature is out of range (16), and flow out of range (1). If a measurement has an associated status code, consider whether the measurement is valid or if the instrument should be serviced.

Many other diagnostics can be addressed by servicing the LI-710. The following examples show how you can interpret the code and respond to the issues.

  • A code of 32769 decodes to 32768 (high pump voltage) and 1 (flow out of range), indicating a flow obstruction. Check the intake and exhaust for blockages. If there are no blockages, the pump might have failed and need to be replaced.
  • A code of 17665 decodes to 16384 (low pump voltage), 1024 (cold temperature shutdown, 256 (rain detected), and 1 (flow out of range). The code can be triggered by an obstruction in the sonic path such as rain or soiling of a transducer (start by cleaning the transducers).
  • A code of 128 (poor sonic signal) or code 64 (no sonic) might indicate that the sonic transducers are obstructed. This might be resolved by cleaning the transducers, or it might require additional investigation (start by cleaning the transducers).

If your are unable to resolve a code, contact LI-COR or your sales representative.