Calibration Issues
CO2 and H2O Analyzers
Using the LI-6400
18-11
Setting the CO
2
Span
To check the span of the CO
2
analyzer, youÕll need a known concentration of
CO
2
. Generally, this is provided by a tank of compressed gas (CO
2
in
air
, not
nitrogen) that has been certified, or (even better) that has been measured using
a correctly calibrated gas analyzer. The concentration should be at or above
where you work most of the time, so 400 or 500 µmol mol
-1
is fine
4
.
Setting the CO
2
IRGA gain is a process by which the user can manually (us-
ing the arrow keys
-¯
) adjust the values of
G
cr
and
G
cs
(these items are de-
fined in Equations (14-8) and (14-9) on page 14-6).
■
■
■
■
Checking/Setting the CO
2
Span
Look at Figure 18-6 on page 18-12.
1
Select
"IRGA span"
from the Calib Menu
2
Set the flow from the tank.
See the comments under step 1 on page 18-7.
3
Attach to the IRGA.
You have a choice here, as shown by Figure 18-6: Attach to the sample inlet
on the sensor head, and have Match ON,
-or-
Use a Y connector to split the flow, and attach to both sample and reference
ports simultaneously, and have Match Off.
4
Adjust the span settings as needed
When
CO2Rµml
is highlighted, you are adjusting the CO
2
reference IRGAÕs
span factor. The sample IRGA is
CO2Sµml
.
The span values should be close to 1.0, as described in
4.
At the factory, we use our 1500 µmol mol
-1
tank for setting spans.
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 ...