Diagnostic settings for LI-COR gas analyzers

Diagnostics are used to indicate whether your instrument is operating correctly. The LI-7500A/RS/DS Open Path CO2/H2O Analyzers output integers between 0 and 255 that correspond to as many as 5 diagnostic values. The LI-7200/RS Enclosed CO2/H2O Analyzer outputs integers between 0 and 65535, which corresponds with up to 10 diagnostics. The LI-7700 Open Path CH4 Analyzer outputs integers between 0 and 65535 that indicate up to 16 diagnostics.

Detailed explanations of the diagnostic values are provided in the instruction manuals for the instruments.

In the EddyPro® software, the diagnostic values of the gas analyzers are configured for processing in the Raw File Description of the Metadata File Editor, as shown in the LI-7700 example in Figure 4‑1.

The raw diagnostic integer values are first converted to bit values, and then the diagnostic records that are flagged are counted. A portion of an LI-7700 diagnostic output is shown in Figure 4‑2 (no records flagged).

Figure 4‑1. Setting the LI-7700 diagnostic value in EddyPro.
Figure 4‑2. An example of EddyPro outputs for LI-7700 diagnostics.

A QA/QC system is automatically implemented in EddyPro when the diagnostic values of the LI-7500A/RS/DS, LI-7200/RS, and LI-7700 are selected for processing. A diagnostic value that is flagged may or may not affect flux computation. If it does affect the computation, the related record will be discarded. Otherwise, the record will be processed normally.

  • Flags for the LI-7500A/RS/DA are described in Table 4‑1.
  • Flags for the LI-7200/RS are described in Table 4‑2.
  • Flags for the LI-7700 are described in Table 4‑3.

For example, if the diagnostic bit map in the LI-7700 indicates that Bit number 5 is flagged (Instrument is calibrating), the record will be skipped. Bit values are 0 = bad (flagged) and 1 = OK (not flagged).

Table 4‑1. Action of EddyPro on diagnostics from the LI-7500A/RS/DS.
Bit No. Name EddyPro action if flagged
0 to 3 AGC / Signal Strength Calculate AGC / Signal Strength
4 Sync Process normally
5 PLL Skip record
6 Detector Skip record
7 Chopper Skip record
Table 4‑2. Action of EddyPro on diagnostics from the LI-7200/RS.
Bit No. Name EddyPro action if flagged
0 to 3 AGC / Signal Strength Calculate AGC / Signal Strength
4 Sync Process normally
5 PLL Skip record
6 Detector Skip record
7 Chopper Skip record
8 Head pressure Skip record
9 Auxiliary input Process normally
10 Tin Skip record
11 Tout Skip record
12 Head connected Skip record
13 to 15 Not used (always 0) Process normally
Table 4‑3. Action of EddyPro on diagnostics from the LI-7700 if flagged.
Bit No. Name EddyPro action if flagged
0 LI-7550 Connected Process normally
1 Auxiliary thermocouple input 1 failure Process normally
2 Auxiliary thermocouple input 2 failure Process normally
3 Auxiliary thermocouple input 3 failure Process normally
4 Auxiliary thermocouple input 4 failure Process normally
5 Instrument is calibrating Skip record
6 Bottom heater on Process normally
7 Top heater on Process normally
8 Pump on Skip record
9 Motor spinning (lower mirror) Skip record
10 Block temperature unregulated Skip record
11 Laser temperature unregulated Skip record
12 Bad temperature Process normally
13 Reference channel unlocked Skip record
14 No sample signal Skip record
15 Instrument not ready Skip record