Making Measurements
Leaks
Using the LI-6400
4-45
(reference) was used for both sample and reference measurements. The re-
sults are plotted in Figure 4-10.
The diffusion effect
plotted in Figure 4-10 is equivalent to the
term in the model in Figure 4-9. Normalizing by the gradient
should make this data fall on one curve if the model is correct, and
it does to a reasonable degree (Figure 4-11). Curve fitting yields a diffusion
coefficient
k
of 0.46. (The easiest curve fit is to plot (1/
Flow
) on the X axis,
rather than
Flow
;
k
is then the slope of the line.) Note that the outliers tend to
be the data collected with the smallest gradient, so uncertainties in what the
true gradient was are largest.
Figure 4-10. CO
2
diffusion into a closed, empty LI-6400 chamber with black neo-
prene gaskets as a function of flow rate, for various reference concentrations C
r
.
C
a
(ambient CO
2
) was 400 µmol mol
-1
. Diffusion effects are highest at low flow
rates and large gradients. The lines in the figure connect data of common C
r
.
2
2
2
2
2
2
I
I
I
I
I
I
-15
-10
-5
0
5
0
100
200
300
400
500
600
C
s
- C
r
(µmol mol
-1
)
Flow Rate (µmol s
-1
)
0
250
600
2
1040
1570
I
2066
C
r
µmol mol
-1
CO
2
Diffusion Effect
C
a
= 400 µmol mol
-1
C
s
C
r
Ð
(
)
c
o
c
i
Ð
(
)
C
a
C
s
Ð
(
)
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 ...