Troubleshooting
Pump/Flow Problems
Using the LI-6400
20-13
sponds much faster than do the stomata, so until the stomata can open wider,
CO
2
is consumed within the leaf, and C
i
will be low. (Negative C
i
Õs, of
course, cannot be real).
2
Photosynthesis too high?
If the value of photosynthesis is too high, C
i
will be too low. The primary cul-
prit: mismatched IRGAs.
3
Conductance too low?
If something is making the value of conductance too low, that will drive C
i
down low or negative. Possible reasons:
¥
Poorly matched IRGAs
Is the match valve working ok?
¥
A terrible water calibration
If you zeroed with wet air (bad desiccant?), all subsequent water readings will
be too low, making conductance too low.
¥
Bad leaf temperature measurement or computation
If leaf temperature is too high, conductance will be too low. If you are mea-
suring leaf temperature, is the thermocouple working? Is there good contact?
Is it well zeroed (page 18-19)? If you are computing leaf temperature (energy
balance), do the values seem reasonable? Do you have the right light source
specified?
Pump/Flow Problems
A useful flow diagram for troubleshooting is Figure 20-14 on page 20-44.
CanÕt Achieve High Flow Rates
Maximum flow rates should exceed 700 µmol s
-1
. If you canÕt achieve that
(use fixed flow control, so you can directly ask for the flow rate you want),
then try these steps.
1
Turn off the mixer.
If you are using the 6400-01 CO
2
mixer, shut it off, and try a high flow rate
again. If this fixes the problem, then the flow was low because the mixer cal-
ibration had specified a lower maximum flow in order to raise the upper limit
of CO
2
concentration. Refer to
2
Remove the soda lime tube
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 ...