Calibration Issues
CO2 and H2O Analyzers
Using the LI-6400
18-9
What Can Go Wrong When Setting The Zero
When automatically zeroing the IRGAs, two things are done for each IRGA:
1) a D/A (digital to analog output) channel is set. The resolution of these
channels is fairly coarse (19mV), so to make the zero really zero, 2) an adjust-
ment term is computed. This second step ensures that the IRGAs will always
zero - even if you zero the IRGA without having dry or CO
2
free air in them,
and are outside the range that the D/A portion can handle. It is therefore a
good idea to check the values of these two components to make sure they are
both reasonable (Figure 18-10 on page 18-18).
¥
Not Zero Air
The most common problem results from zeroing the IRGAs with air thatÕs not
really CO
2
-free, or not really dry.
LI-6400
PSH-0001
PORTABLE
PHOTOSYNTHESIS SYSTEM
MODEL
SR. NO.
Connect here
Match Valve ON
Please 1) Close the chamber (no leaf)
2) CO2 scrub full on
3) Desiccant full on
Mch:ON
ÒCONFIG.JoeÓ
CO2R_µml CO2S_µml H2OR_mml H2OS_mml
13.1 5.23 2.234 4.387
AutoCO2 AutoH2O AutoAll Plot Quit
+
Figure 18-4. When connecting to a tank of CO2 free air to zero the IRGAs, connect the flow to the sample inlet,
and have the match valve turned on. The chamber needs to be closed tightly, as well.
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 ...