Guided Tours
Tour #3: Controlling Chamber Conditions
3-32
Using the LI-6400
3
CO
2
Control - Without a 6400-01
In the absence of a 6400-01 CO
2
Mixer, the LI-6400Õs means of controlling
CO
2
is limited to the soda lime adjustment knob. The following experiment
illustrates how this works.
Experiment #4
Adjusting the Soda Lime
For this experiment, the chamber should be empty and closed.
1
Fixed flow of 500 µmol s
-1
Press
2
f2
F
500
enter
.
2
Soda lime full scrub, desiccant full bypass
This will provide incoming air that is free of CO
2
.
3
Note the reference and sample CO
2
They should both be near zero, and stable. Photosynthesis (
Photo
, line
c
)
should be stable. (If itÕs not zero, itÕs because the sample and reference IR-
GAs arenÕt reading the same thing. Matching, discussed on page 4-34, will
take care of that, but weÕll ignore it for now.)
4
Desiccant full scrub.
Notice the burst of CO
2
that you get. ThatÕs because the desiccant buffers
CO
2
(chemically as well as volumetrically).
5
Soda lime full bypass, desiccant full bypass
Now weÕll let ambient air into the chamber. Watch how
unstable
photosyn-
thesis becomes.
Unlike Step 3 when we were scrubbing all the CO
2
from the air, the reference
(and sample) CO
2
are now fluctuating as unmodified, ambient air enters the
system. If you want to see
real
instability, breathe near the air input on the
right side of the console, and watch what happens to photosynthesis.
Points to Remember
¥ The soda lime scrub setting controls reference CO
2
, from ambient down
to zero.
¥ YouÕll need a buffer volume to make stable measurements.
¥ The desiccant buffers a bit of CO
2
.
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 ...