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.
Summary of Contents for LI-6400
Page 1: ...Using the LI 6400 Portable Photosynthesis System ...
Page 15: ...Part I The Basics ...
Page 16: ......
Page 174: ...Making Measurements Answers to Questions 4 56 Using the LI 6400 4 ...
Page 175: ...Part II Useful Details ...
Page 176: ......
Page 200: ...Standard Tools Power ON Hooks 5 24 Using the LI 6400 5 ...
Page 214: ...Real Time Data Real Time Graphics 6 14 Using the LI 6400 6 ...
Page 234: ...Environmental Control Light Control 7 20 Using the LI 6400 7 ...
Page 244: ...Light Sensor Considerations Gallium Arsenide Phosphide GaAsP Sensor 8 10 Using the LI 6400 8 ...
Page 288: ...Data Logging Making Your Own AutoPrograms 9 44 Using the LI 6400 9 ...
Page 289: ...Part III Working With Files ...
Page 290: ......
Page 312: ...The LPL File System Troubleshooting 10 22 Using the LI 6400 10 ...
Page 340: ...Downloading Files Using a Data Capture Program 11 28 Using the LI 6400 11 ...
Page 375: ...Part IV Configuration Issues ...
Page 376: ......
Page 420: ...Defining User Variables Old Style vs New Style 15 18 Using the LI 6400 15 ...
Page 454: ...Using an Energy Balance Further Reading 17 12 Using the LI 6400 17 ...
Page 455: ...Part V Maintenance Troubleshooting ...
Page 456: ......
Page 572: ...Troubleshooting Useful Information 20 46 Using the LI 6400 20 ...
Page 593: ...Part VI Programming ...
Page 594: ......
Page 622: ...Programming with LPL Compiler Directives 22 28 Using the LI 6400 22 ...
Page 846: ...Index I 16 Using the LI 6400 ...