Diagnostics are used to indicate whether your instrument is operating correctly. The LI-7500 and LI-7500A Open Path CO2/H2O Analyzers output integers between 0 and 255 that correspond to as many as 5 diagnostic values. The diagnostic values of the LI-7200 Enclosed CO2/H2O Analyzer and LI-7700 Open Path CH4 Analyzer are integers between 0 and 65535 that indicate up to 10 and 16 diagnostics, respectively. A detailed explanation of the diagnostic values for the LI-7500A and LI-7200 and how to decipher them are described in a technical tip at http://www.licor.com/env/newsline/2012/11/. A similar explanation for the LI-7700 is located in the Data Files section of the LI-7700 instruction manual.
In the EddyPro® software, the diagnostic values of the LI-7500/7500A/7200/7700 are configured for processing in the Raw File Description of the Metadata File Editor, as shown in the LI-7700 example in Table 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 Table 2 (no records flagged).
Table 1. Setting the LI-7700 diagnostic value in EddyPro.
Table 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-7500/7500A/7200/7700 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. Table 3 shows how EddyPro handles each diagnostic value of the LI-7500/7500A/7200/7700 when flagged. 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.
Table 3. Action of EddyPro on diagnostics from the LI-7500/7500A/7200/7700 if flagged.
For the LI-7500 and the LI-7500A/7200 with earlier versions of embedded software (below V6.0.0), Automatic Gain Control (AGC) is reported in the raw data outputs separately from the diagnostic values. For the LI-7500A/7200 with later versions of embedded software (V6.0.0 or above) and the LI-7700, Relative Signal Strength Indicator (RSSI) is part of the raw data outputs. If AGC or RSSI is set as a diagnostic value in the Raw File Description of the EddyPro metadata file, EddyPro will either give you erroneous processed results or stop working due to incorrect QA/QC. AGC and RSSI should be set up as regular variables instead of specific diagnostic values in EddyPro.