LI-COR LI-6400, Руководство пользователя

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Making Measurements
Matching the Analyzers
Using the LI-6400 4-39
As the message indicates, a bad leak in the chamber or a stuck match valve
can cause the reference - sample differences to be this large. Badly zeroed
and/or spanned IRGAs can cause this to happen as well.
See page 20-21 for troubleshooting help.
When To Match
¥ When you start
Remember to match before getting very far with the first leaf of the day.
¥
When rates are low
With low photosynthesis or transpiration rates, sample - reference differences
will be small, and any offsets will be important.
¥
After large concentration changes
If the IRGAs are well zeroed and spanned, matching once at any concentra-
tion will suffice for all other concentrations. More typically, however, the IR-
GAs may not be so well zeroed and spanned, so matching will be a function
of concentration.
¥
Periodically
How often? That depends most on temperature changes, so itÕs hard to pre-
scribe a definite time. Start with 30 minutes or so, and adjust as needed. Use
of the coolers to stabilize temperatures will help to minimize zero drift and
thus reduce the need for matching.
Logging Match Adjustments
The adjustment factors that are computed when a match occurs can be stored
each time you log data (Figure 4-8).
"Flow" "PARi" "PARo" "Press" "CsMch" "HsMch" "Status"
172.8 1026 1311 98.07 -2.2 0.04 111115
215.7 1070 1354 98.07 -1.2 0.03 111115
233.3 1062 1337 98.07 -0.8 0.02 111115
199.4 1164 1450 98.07 -0.6 0.01 111115
200.2 1160 1440 98.07 -0.5 -0.01 111115
199.7 1113 1374 98.06 -0.6 0.00 111105
Figure 4-8. The default log file format includes the adjustment factors that are set when
the IRGAs are matched. This provides a record of what happened.