Making Measurements
Some Simple Experiments
Using the LI-6400
4-11
2
Dry the incoming air
Once the chamber humidity is on target, and the flow rate is stable, turn the
desiccant knob to full scrub. Observe what happens to reference humidity,
flow rate, and sample humidity (
H2OR_mml
,
Flow_µml
, and
H2OS_mml
).
Reference humidity should go to zero, flow will decrease, and H2OS_mml
will remain unchanged. Also, keep an eye on how quickly or slowly
CO2S_mml
gets to itÕs new value.
Question #5:
What does it mean if the reference humidity (
H2OR_mml
)
doesnÕt get within 0.5 mmol mol
-1
of zero? (Answer on page 4-53.)
Question #6:
Will the sample cell CO
2
(
CO2S_µml
) increase or decrease
during this step? Why? (Answer on page 4-53.)
3
Moisten the incoming air
Now turn the desiccant knob to full bypass, and watch the flow increase, ref-
erence humidity increase, and the sample cell water mole fraction remain un-
changed. The sample cell CO
2
will go the
other
direction from how it
changed in the previous step (not to give the answer to Question #6 awayÉ).
4
Change to constant RH
Return the desiccant knob to midway, and after the flow rate stabilizes, note
the value of
RH_S_%
. Now change to constant RH control, and target that
value of
RH_S_%
.
5
Turn on the coolers
Turn on the temperature controllers (
f4
level 2), and set the block temperature
for a target about 5¡C below itÕs present value (display line
h
). But, before
you do this, try another question:
Question #7:
What will cooling the chamber do to flow rate (owing to the
constant RH control mode) and why? (Answer on page 4-53.)
6
Watch RH and flow
As the air temperature drops in the chamber, watch the flow compensate for
the changing RH. Notice that it is not quite as tight a control as when we were
controlling on a constant mole fraction; RH will drift off target a little bit as
the temperature changes. (Why? Read about it in
7
Change to constant VPD
Note the current value of
VpdA
(display line
d
), the vapor pressure deficit
based on air temperature. Then change to controlling to a constant VPD,
based on Tair, and target that value. (See
Содержание LI-6400
Страница 1: ...Using the LI 6400 Portable Photosynthesis System ...
Страница 15: ...Part I The Basics ...
Страница 16: ......
Страница 174: ...Making Measurements Answers to Questions 4 56 Using the LI 6400 4 ...
Страница 175: ...Part II Useful Details ...
Страница 176: ......
Страница 200: ...Standard Tools Power ON Hooks 5 24 Using the LI 6400 5 ...
Страница 214: ...Real Time Data Real Time Graphics 6 14 Using the LI 6400 6 ...
Страница 234: ...Environmental Control Light Control 7 20 Using the LI 6400 7 ...
Страница 244: ...Light Sensor Considerations Gallium Arsenide Phosphide GaAsP Sensor 8 10 Using the LI 6400 8 ...
Страница 288: ...Data Logging Making Your Own AutoPrograms 9 44 Using the LI 6400 9 ...
Страница 289: ...Part III Working With Files ...
Страница 290: ......
Страница 312: ...The LPL File System Troubleshooting 10 22 Using the LI 6400 10 ...
Страница 340: ...Downloading Files Using a Data Capture Program 11 28 Using the LI 6400 11 ...
Страница 375: ...Part IV Configuration Issues ...
Страница 376: ......
Страница 420: ...Defining User Variables Old Style vs New Style 15 18 Using the LI 6400 15 ...
Страница 454: ...Using an Energy Balance Further Reading 17 12 Using the LI 6400 17 ...
Страница 455: ...Part V Maintenance Troubleshooting ...
Страница 456: ......
Страница 572: ...Troubleshooting Useful Information 20 46 Using the LI 6400 20 ...
Страница 587: ...Diagnostics and Utilities Sys Utility Programs Using the LI 6400 21 15 EBVpd t C guess EBSatVap _EBvap_kPa ...
Страница 593: ...Part VI Programming ...
Страница 594: ......
Страница 622: ...Programming with LPL Compiler Directives 22 28 Using the LI 6400 22 ...
Страница 846: ...Index I 16 Using the LI 6400 ...