Calibration Issues
CO2 and H2O Analyzers
18-10
Using the LI-6400
18
¥
Post-Zero Drift
After zeroing the CO
2
and/or H
2
O IRGAs, if you see continued drift before
exiting the zeroing routine, it likely means that you zeroed them too soon, be-
fore they had equilibrated. This is especially true of water vapor.
¥
DidnÕt zero very well
CO
2
should be within 1 µmol mol
-1
of zero after zeroing, and H
2
O should be
within 0.1 mmol mol
-1
of zero. If things are off more than that, go check the
values using
"View,Store Zero & Span"
(page 18-18). It may be that you
had very non-zero air when you zeroed, or else the IRGA has a problem.
Manually Zeroing the IRGAs
Normally, when the IRGA zeroing program is used, the IRGAs are automat-
ically zeroed by pressing
AutoCO2
or
AutoH2O
. It is possible to zero any one
of the four IRGAs separately, and manually (Figure 18-5).
One occasion when this can be a useful tool is in zeroing the water vapor sam-
ple cell. If both cells are connected with a ÒYÓ (as in Figure 18-6 B), have the
match valve off, and zero as described above when the
reference
cells are sta-
ble. Then turn the match valve on, and adjust the H
2
O sample cell to match
the H2O reference value.
CO2S
-
CO2S
¯
H2OS
-
H2OS
¯
Chamber must be closed. To zero...
..CO2 only: SCRUB CO2, BYPASS desiccant
..H2O only: SCRUB desiccant
Mch:off
ÒCONFIG.JoeÓ
CO2R_µml CO2S_µml H2OR_mml H2OS_mml
13.1 5.23 2.234 4.387
+
CO2R
-
CO2R
¯
H2OR
-
H2OR
¯
-104.5
Figure 18-5. Manual zero function keys are on the 2nd and 3rd level, and are accessed by pressing the
labels
key. When one of the manual zeroing function keys is pressed, the value of the D/A channel that controls that
IRGAÕs zero is displayed to the right of the Match Status. This is also the value displayed in the ÒView,Store
Zeros&SpansÓ program in the Zero column (Figure 18-10 on page 18-18).
The 2nd and 3rd level
function keys allow indi-
vidual IRGAÕs to be ad-
justed.
The value of the D/A
channel for the IRGA
last adjusted manually.
Pump:ON
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 ...