Troubleshooting

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 or the data logger configuration.

  • If connecting to a PC with the CarbonWare app, is it using the correct serial port?
  • Typically, only valid serial ports are listed. You can try them one at a time or check the port number assignment in you computer Device Manager. To find the serial port number, open the Device Manager (press the Windows key , type Device Manager, then press Enter). Click Ports (COM & LPT). Look for USB Serial Port (COM#). The serial port numbers are shown beside the ports.
  • Power supply inadequate?
  • If connecting to a PC with the USB cable, do not extend the cable. Voltage drops over a long cable can cause problems with the power supply (not enough power) or digital communication.

Measurement issues

Flux diagnostics

Before computing any results, the LI-720 filters implausible values from the 10 Hz raw data. A diagnostic code is provided for every computed result. The diagnostic code can reveal more about what was wrong with a particular measurement, details about environmental conditions for the time period, and information about the LI-720 performance over that time period. Some diagnostic codes are simply for your information - there is nothing to do besides know what the code indicates. Other codes may indicate that service is required. A few are reserved. A diagnostic code of 0 indicates normal operation.

Decoding the diagnostic

The diagnostic code is a 16-bit binary value encoded as a decimal value. It is included as the last parameter in output groups 0 and 1. The decimal value ranges from 0 to 65535 (corresponding to bit positions 0 through 15). It encodes up to 16 issues.

You can decode the diagnostic from decimal to binary using the calculator included with your computer operating system (Windows and macOS; select programmer mode). Enter the diagnostic value and observe the positions of the 0s and 1s in the binary results. Associate the 1s with the descriptions in Table 7‑1.

Figure 7‑1. You can decode the decimal diagnostic using a converter such as the calculator included with your computer operating system. Then, associate the binary 1s with conditions described in Table 7‑1.
Table 7‑1. A diagnostic code is included with each flux result. A diagnostic is triggered if the threshold was exceeded for more than 10% of samples in a measurement period.
Bit
Position		 DEC Description Threshold
- 0 Normal operation No issues reported
0 1 Sonic temperature - vertical t_sonic
<-25 or >50 °C
1 2 Sonic signal quality - horizontal  
2 4 Sonic signal quality - vertical  
3 8 Temp/RH sensor 1 = error; 0 = OK
4 16 Temperature ta <-25 or >50 °C
5 32 RH sensor RH >100 or <0%
6 64    
7 128 Lamp temperature t_src
<-25 or >50 °C
8 256 Source RH scrub quality RH_src >4%
9 512 Ambient pressure 1 = error; 0 = OK
10 1024 Ambient pressure P<45 or > 115
11 2048 Signal strength (RSSI) <80%
12 4096 Level sensor 1 = error; 0 = OK
13 8192 Compass 1 = error; 0 = OK
14 16384 Detector temperature detector temperature
<-25 or >50 °C
15 32768 PAR sensor reading PPFD
<-20 or >3000
16 65536 H2O out of range H2O <10 or >60
17 131072 CO2 out of range CO2 <-10 or >1500
18 262144 Missing sonic data frames -
19 524288 Data storage invalid Invalid JSON detected on startup
20 1048576 GPS and RTC 0 = GPS good; 1 = no update during interval
21 2097152 Flux QC flag >40% of high speed data flagged as bad