Troubleshooting
IRGA Problems
Using the LI-6400
20-19
Occasional Instability
This problem is characterized by an occasional jump in the IRGA reading, for
no apparent reason. Before deciding there is an electronic problem, eliminate
a couple of other possibilities:
¥
Insects?
Flying insects can fairly easily get into the sample cell when the chamber is
open, or even into the match valve. Those that find the sample cell are des-
tined to eventually encounter the mixing fan and become debris, but prior to
that, you will be seeing the effects of insect respiration on your measure-
ments. So, if you see periodic spikes in the sample CO
2
(such as 5 or 10
µmol mol
-1
every minute or so), you may have acquired a guest.
¥
Leaks?
¥
Connections?
See if there is any relationship between the jumps and movement of the cable.
There could be a faulty connection at work. Before doing this, set up a strip
chart to monitor the IRGAs. That makes it easier to detect a jump.
Stalled Chopper Motor
The chopper motor is the motor that spins the filter wheel in the IRGA/sensor
head. This motor should begin to run shortly after the IRGAs are powered on.
If the chopper motor does not run, the ÒIRGAs Not ReadyÓ message will be
displayed in New Measurements mode. The typical chopper motor failure is
due to the bearings. So, prior to itÕs demise, there may be increased audible
noise coming from the motor, and even subsequent electronic noise in the
IRGA signals.
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Determining if the Chopper Motor is Running
1
Turn off the pump and chamber fan
In New Measurements mode, turn off the pump (
2 F2 N
) and chamber fan
(
3 F3 O
[the letter, not the number]), so you can hear the chopper motor.
2
Put the LI-6400 to sleep
Go to the Utility Menu, and select ÒSleep ModeÓ. Listen for a motor in the
sensor head (NOT the console) to wind down once you press
Y
indicating itÕs
OK to sleep.
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 ...