Measurement of CO2 Evolution
in a Multiplexed Flask System
App. Note 127
Introduction
The LI-8150 is a robust and simple to use multiplexer
designed to interface up to sixteen soil CO2 flux chambers with the LI-8100A Automated Soil CO2 Flux
System. Here we describe considerations for constructing a multiplexed system for measuring CO2 evolution
in flasks utilizing the LI-8100A and LI-8150. We complete this example by demonstrating a twelve flask
system used to measure respiration of detached fruit.
Flask Volume, Mixing and Flow
Considerations
due to instrument noise increases. For the LI-8100A this
noise is known and its effects have been modeled over a
range of dC/dt for various sampling periods (Figure 1).
A chamber volume should be chosen that over the range
of expected fluxes, ensures dC/dt is large enough to be
outside the influence of instrument noise. In circumstances where there are constraints on chamber size, the
observation length used by the LI-8100A can be adjusted
to improve the estimate of dC/dt, as increasing the
number of data points used in the calculation will decrease the effect of noise (Figure 1).
Volume
The LI-8100A operates as a closed system, determining
CO2 flux from the change in CO2 mole fraction over
time in a fixed volume. In its simplest form (ignoring
dilution due to water vapor and not standardizing the
rate for sample area or mass) the relationship between
carbon flux and the change in CO2 mole fraction with
time takes the following form
F=
PV dC
RT dt
Fractional Error
1.000
0.100
0.010
0.001
0.000
0.001
0.01
0.1
1
dC/dt (µmol mol-1 s-1)
(1)
where F is the flux in μmol s-1, P is pressure in kPa, V is
the system volume in liters, R is the ideal gas constant, T
is temperature in K, and dC/dt is the change in CO2
mole fraction with time (μmol mol-1s-1). At ambient
pressure, system volume is the single largest factor
controlling the relationship between dC/dt and flux.
Given the same flux, changing the gas temperature from
20 to 40 °C will only change dC/dt by about 7%, while
doubling the system volume will cut dC/dt nearly in half
because the increased volume serves to dilute the change
in CO2 mole fraction within the system. As dC/dt
decreases, the potential for error in the measurement
Figure 1. The relationship between potential measurement
error due to instrument noise and the change in CO2 mole
fraction with time. Lines are fit to data modeled over 60
(open boxes), 120 (closed boxes), 180 (open circles) and
300 (closed circles) second sampling periods (i.e.,
observation length minus the deadband).
Figure 2 shows the relationship between dC/dt and the
flux for several chamber volumes at standard temperature
and pressure. This, and the information in Figure 1, can
be used as guides for selecting an appropriate chamber
volume and observation length when designing an
experiment.
Continued on next page
2
Chamber Volume (L)
0.25 0.5
2
1
10
5
10
dC/dt (µmol mol-1 s-1)
10
1
0.1
0.01
0.001
0.001
0.01
0.1
Flux (µmol s-1)
Figure 2. The relationship between the change in CO2 mole
fraction with time and flux for several chamber volumes at
standard temperature and pressure.
Mixing
It is important that the volume of air inside the chamber
be well mixed to ensure that fluxes are calculated using
representative samples of the chamber CO2 mole fraction. If there are pockets of unmixed air inside the
chamber, these can act as sources or sinks for CO2 and
cause errors in the flux measurement. For chamber
volumes less than about four liters the pump inside the
LI-8150 may provide adequate mixing. However, this is
contingent on the geometry of both the chamber and the
sample, and how the sample is positioned within the
chamber. If additional mixing is required, small fans or
baffles can be installed inside the chamber.
Flux (fan on) µmol kg-1 s-1
0.45
0.4
y = 1.0201x - 0.0019
R2 = 0.9831
0.35
0.3
0.25
0.2
0.15
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Flux (fan off) µmol kg-1 s-1
Figure 3. Mixing evaluation on a four liter chamber
connected to the LI-6200. There is little difference between
fluxes measured with the chamber fans on or off indicating
that the pump inside the LI-6200 sufficiently mixed the
chamber volume.
It is possible to determine if there is adequate mixing
inside a chamber by looking at the relationship between
fluxes measured under normal operating conditions and
fluxes measured where mixing is known to be good. In
the example shown in Figure 3 we measured respiration
from navel oranges using a four liter chamber attached to
the LI-6200 Portable Photosynthesis System. Measurements were made in pairs on the same fruit, with either
mixing due only to the pump inside the LI-6200 or with
additional mixing using two fans installed in the chamber. There is little difference in the measured fluxes with
either the fans on or off, indicating that the chamber
volume is sufficently mixed using only the LI-6200
pump.
Flow and chamber conditions between
measurements
When configured as a multiplexed flask system, a plumbing change inside the LI-8150 allows flasks to be continuously flushed with ambient air between sampling periods. This serves as the mechanism by which CO2 and
water vapor are exported from the system between
measurements, preventing condensation and excessively
high CO2 mole fractions from developing in the flask.
The flushing rate is determined by the flow rate, provided by an auxiliary pump, and the flask volume. The
time required to reduce the flask concentration by 63%
(i.e., 1/e) is given by
τ=
V
f
(2)
where τ is the time constant in seconds, V is the chamber
volume in liters, and f is the flow rate through the chamber in l s-1. For applications where condensation inside
the chamber is unlikely, and the chamber CO2 (or other
gas species; ethylene for example is known to influence
respiration rates of fruit) mole fraction has little or no
affect on the processes driving the flux, this is of little
importance; however, the time constant is much more
important in situations where condensation may occur,
or when other gases present in the flask might influence
the CO2 flux.
In these situations it may be useful to model the inchamber mole fraction of the offending gas species to
determine a flow rate appropriate to keep the mole
fraction below problem levels. Where increasing the flow
rate is not feasible, chemically scrubbing the gas species
from the incoming gas stream may be necessary. Ignoring the influence of other gas species, under well mixed
and steady state conditions, the chamber mole fraction
for a particular gas species is controlled by the flux of
3
A.
that species from the sample and the flow rate through
the flask, as given by
Co =
F
+ Ci
f
(3)
where Co is the in-chamber mole fraction of the gas
species in μmol mol-1, F is the flux of the species in μmol
s-1, f is the flow rate through the flask in μmol s-1, and Ci
is the incoming mole fraction in μmol mol-1. When the
flux is positive (net efflux from the sample), increasing
the flow rate (decreasing τ) or decreasing the incoming
CO2 mole fraction will decrease the mole fraction of CO2
in the chamber.
B.
Configuring the LI-8150 and LI-8100A
for multiplexed flask measurements
These instructions describe the changes that are required
in order to adapt a sixteen port multiplexer for flask
measurements. The procedure for modifying an eight
port multiplexer is very similar, and where significant
differences exist, they have been noted. A list of parts
available from LI-COR necessary for these modifications
is included in the appendix.
Plumbing
300-08118
C.
Some plumbing changes are required in order to configure the LI-8150 to continuously flush chambers with
ambient air between sampling periods. Refer to Figure 5
to compare a normal LI-8150 with one modified for use
with a flask system.
1. Remove three of the brass plugs with a small adjustable wrench and one of the steel plugs with a 3/16
inch hex key. These plugs usually seal the inner side
(the side closet to the LI-8150 control panel) of the
solenoid manifolds, as shown in Figure 4A. If
modifying an eight port multiplexer, only remove the
two brass plugs from the right hand upper and lower
solenoid manifolds.
2. Using an adjustable wrench, replace the three brass
plugs with quick-connect elbows (part #300-07474)
and the one steel plug with a quick-connect elbow
(part #300-08118) (Figure 4C). Note that the metal
base of the quick-connect fittings can be turned
independently of the upper plastic portion without
damaging the fitting. It may be helpful to insert a
short piece of Bev-a-line tubing into the fitting to
help hold it in position while tightening the metal
base. For the sixteen port model, in order to add a
quick-connect fitting to the lower left solenoid
300-07474
Figure 4. Solenoid connections used to flush flasks between
sampling periods. The figure shows changes to the
manifolds in a 16-port multiplexer. For an 8-port
multiplexer, replace only the plugs on the two righthand
solenoid manifolds; there is no need to remove the
multiplexer control panel. A. The inside of a 16-port
multiplexer. Remove the three brass plugs (circled in red
and yellow) using a small adjustable wrench, and the steel
plug (circled in green) with a 3/16 inch hex key. Note that
the brass plug on the lower right manifold is not visible in
this image (yellow circle). Remove the control panel and
disconnect the air supply line from the lower left manifold
(arrow). B. A 16-port multiplexer with the four plugs and
control panel removed. Install quick connect fittings in
place of the plugs that were removed as shown in panel C.
C. The multiplexer reassembled with connections for an
auxiliary pump installed. Part number 300-07474 is used in
place of the brass plugs and part number 300-08118 is
used in place of the steel plug.
4
1
2
3
4
5
6
7
8
LI-8100A
ACU
Filter
Flow
Meter
Chamber
LI-8150
Pump
Subsample
Loop
Solenoid Manifold
8
7
6
5
4
3
2
1
Auxiliary
Pump
A. Deactivated Solenoid
Solenoid
Flask
Subsample
Loop
LI-8150
Pump
B. Activated Solenoid
Flow
Meter
LI-8100A
ACU
Quick
Connect
Manifold
Exhaust Line
Figure 5. Flow schematics for the LI-8150 configured for normal operation (top) and configured for flask measurements
(bottom right). The flow path used during measurements is shown with blue arrows and the flow path used to flush flasks
between measurements is shown with red arrows. In both diagrams the solenoids at port 3 are activated and the chamber
connected there is being sampled. The box in the lower left hand corner shows how the flow path changes inside the
solenoid manifold when a solenoid is activated.
5
manifold, the hose connecting the lower left solenoid
manifold to the pump will have to be temporarily
removed. First, remove the two thumb screws that
secure the control panel to the LI-8150 and the
ribbon cable from the side of the control panel, and
set the control panel aside (Figure 4B). Carefully
remove the hose from the quick-connect fitting by
pressing down on the orange ring and pulling out on
the hose. Rotate the fitting out of the way. After the
second quick-connect fitting has been added replace
the hose, seating it firmly in the fitting, and reinstall
the control panel (Figure 4C).
3. Ventilation to the flasks is provided with an 8 L/min
diaphragm pump (part #9981-173) that can be
installed inside the LI-8150. If installing this pump
in a sixteen port multiplexer remove the quickconnect straight union installed on the pump outlet
and replace with a quick-connect “Y” fitting (part
#300-03367) as shown in Figure 6B. If installing in an
eight port multiplexer no modification is needed
(Figure 6A).
A.
6. Locate the main power supply cable inside the
LI-8150 (part #9981-108; Figure 8). One end of this
cable terminates in a four-pin slip connector connected to the main circuit board and the other in a
four-pin Eurofast bulkhead mounted to the side of
the LI-8150 case. Remove the cable by disconnecting
the four pin slip connector from the circuit board
and removing the nut on the outside of the LI-8150
from the Eurofast bulkhead.
A.
B.
C.
B.
Figure 6. A. No modifications are needed to the pump if
installing it in an eight port multiplexer. B. This pump is
being installed in a sixteen port multiplexer, so a quick
connect “Y” union is installed on the outlet, in place of the
straight union the pump comes with.
4. Before installing the pump, attach the pump assembly power cable (part #9981-177). This cable connects to the pump via a three-pin slip connector on
the underside of the pump.
5. Remove the cover plate from the instrument by
loosening the two thumb screws (Figure 7A). Mount
the pump in the LI-8150 case by attaching the
mounting plate to one of the two threaded holes
normally used to attach the cover plate (Figure 7B).
Use one of the three 3/8 inch #6-32 hex cap screws
(part #140-04315) and the 7/64 inch long arm hex
key (provided) to attach the mounting plate to the
LI-8150. Use the remaining two hex cap screws to
attach the pump to the plate.
Figure 7. The pump mounting plate can be installed inside
the LI-8150 case using one of the two threaded holes
normally used to attach the cover plate. A. Loosen the two
thumb screws (indicated with arrows) to remove the cover
plate. B. Use one 3/8 inch long #6-32 hex cap screw to
install the mounting plate in place of the cover. C. Use the
remaining two screws to attach the pump to the mounting
plate.
7. Install the pump assembly power cable into the
multiplexer in place of the power cable removed in
step 6 (Figure 8). When the new Eurofast bulkhead is
installed the nut on the bulkhead needs to be tightened to 72 inch-lbs of torque to ensure a water tight
seal.
8. Cut two (one for an eight port multiplexer) 48 cm
sections of Bev-a-line tubing. The two pieces of
tubing are kept at the same length to help ensure that
flow from the pump is split equally between the two
manifolds. For a 16-port multiplexer insert one end
of each hose into the “Y” fitting (part #300-03367)
installed in step 3, and insert the other end into one
of the quick-connect fittings added to the lower
solenoid manifolds in step 2.
6
Exhaust lines
Install plugs (30008151) in the open
connectors on the
solenoid manifolds
Connect the exhaust
lines to the “out” line
from one of the ports
using part #300-03367
Connect the “in” line
from the same port
to the inlet on the
auxiliary pump
Ambient air line
from pump
Pump
To disconnect power to the pump,
unplug this connector
9981-108 power cable in an
unmodified multiplexer
Figure 8. A sixteen port multiplexer configured for flask measurements. Port 16 has been re-purposed to vent flask exhaust
from the LI-8150 case and supply ambient air to the pump.
For an eight port multiplexer connect the pump
outlet with a single section of Bev-a-line tubing to
the lower right hand solenoid manifold.
9. There are two ways to configure the LI-8150 to vent
exhaust from the flasks.
a. Method 1: Dedicate a port on the multiplexer to
supply air to the auxiliary pump and expel
exhaust from the chambers.
i. Disconnect the two urethane hoses
coming from one set of port connections on
the side of the LI-8150 from the solenoid
manifolds.
ii. Insert 1/4 inch quick connect plugs (part
#300-08151) into the open fittings on the
solenoid manifolds (Figure 8).
iii. Connect the urethane hose from the “IN”
connection of the port to the inlet of the
auxiliary pump using a quick connect
straight union.
iv. For a sixteen port model install a quickconnect “Y” fitting (part #300-03367) on the
end of the “OUT” hose. For an eight port
multiplexer, install a quick connect straight
union (part #300-03123) on the “OUT” hose.
v. Cut two 35.5 cm lengths of Bev-a-line
tubing and connect the upper manifolds to
the “Y” fitting with each length of tubing.
For an eight port model use one length of
tubing to connect the upper right hand
manifold to the “OUT” hose.
b. Method 2: If dedicating a port to vent chamber
exhaust and supply air to the auxiliary pump is
undesirable, the supply/exhaust lines can be
routed out of the LI-8150 by leaving the case
open. If using this method, a filter (part #30108119) should be added before the pump inlet.
Constructing chambers
Flasks can be constructed from any gas tight containers,
provided they meet the volume considerations discussed
above and can be fit with connections for the LI-8150. Be
careful with plastic containers as sorption of water vapor
(and possibly CO2) by the container may affect the
measured fluxes. Here we describe how to use 1.89 L
glass canning jars (Ball Corporation, Daleville, IN) as
sample chambers.
1. With the lid removed from the jar, drill one 12 mm
hole off center in the lid. Drill two 8 mm holes on
7
Soil temperature
thermistor
Female quick-connect
bulkhead (300-07126)
Seal washer
Male quick-connect
bulkhead (300-07127)
Rubber grommet
(196-10534)
Figure 9. Mason jar lid fitted with plumbing
connections and a soil temperature thermistor. Two 8
mm holes are drilled in the lid to install the quick
connect bulkheads and a 12 mm hole is drilled to
install the grommet for the thermistor.
either side of the lid, evenly spaced between the
larger hole and the edge of the lid (Figure 9).
2. Place a seal washer (part #167-07256) on the
threaded portion of a female quick-connect bulkhead fitting (part #300-07126) and install it in one of
the 8 mm holes using the nut and washer provided
with the fitting. Repeat this procedure for the other
8 mm hole using a male quick-connect bulkhead
fitting (part #300-07127) (Figure 11).
3. Insert a rubber grommet (part #196-10534) into the
12 mm hole.
4. Gently push a soil temperature thermistor (part
#8150-203) through the hole in the grommet and
then pull back slightly to seal it. A small amount of
silicone grease (part #210-01958-1) can be used to
ease insertion of the thermistor. To get a good seal
the grommet should fit tightly in the hole and against
the thermistor.
5. Two sections of Bev-a-line tubing are required to
connect each chamber to the LI-8150. Cut the
sections to the desired length and fit one end of each
tube with a female quick-connect (part #300-07126)
and the other end with a male quick-connect (part
#300-07127).
6. Measure and record the length of each tube. This
information is very important and will be required
later when the chamber volume is entered for use in
the flux calculations.
7. Attach the tubes to the fixtures on the lid of each
flask, and then to the selected port on the LI-8150.
8. All ports that are not connected to a chamber, or
used to supply/vent air from the flasks should remain
capped with the black plastic caps supplied with the
LI-8150. If these have been misplaced, replacement
caps can be ordered from LI-COR using part #62008298 and 620-08299. One of each will be needed for
every unused port.
Powering the system
The 8150-770 AC Power Supply can be used to supply
power to the LI-8150 and LI-8100A, as well as the
auxiliary pump used for continuously flushing the flasks.
The 8150-770 is capable of providing up to 4.5 Amps at
12 VDC. When the auxiliary pump is installed as
described in this application note the input voltage to the
LI-8150 should not exceed a nominal 12VDC.
Software Setup
There are some software configuration changes that must
be made to use the LI-8150 and LI-8100A for multiplexed flask measurements. The bulk of these changes
are made under the Chamber tab of the Multiplexer
Configuration window and relate to defining the appropriate volumes and areas for the flux calculations.
1. Under the Setup drop down menu in the main
LI-8100A Windows interface software window, select
Measurement Configuration (Figure 10).
2. Select Port Setup from the Multiplexer Configuration window.
3. In the Chamber tab, select Custom from the Chamber: drop-down menu and enter the chamber
volume in cubic centimeters. Be sure to include the
volume of the tubing used to connect the flask to the
LI-8150 in the chamber volume1.
4. Make sure the closed signal check box is unchecked
and that the chamber offset is set to zero.
5. Select the chamber air temperature source from the
Temp Source dropdown menu. If the temperature
source is measured by a different port, skip this and
recompute with the correct temperature later. If
measurements are made at near ambient temperatures a measurement of chamber air temperature
may not be required.
1To
calculate the volume of Bev-a-line IV, multiply the length of
tubing used (in centimeters) by 0.0792. This will give volume in
cm3.
8
Select Setup, then Measurement
Configuration to access the
Multiplexer Configuration window
Select Custom from the Chamber
pulldown menu, and enter the
chamber volume, including hoses
Uncheck this box, as the flask will
not be providing a closed signal
Select the source of the chamber
air temperature measurement. If
the source is measured on a
different port, leave this set to
Chamber
For the Soil Area (cm2) field, enter
the mass or area for which the fluxes
will be calculated. For a mass-based
flux, enter the mass in decigrams to
get a flux in µmol kg-1 s-1
Chamber Offset (cm) will always be
zero
Figure 10. Software configuration for connecting a flask to the LI-8150. In this example port 1 has been configured for a 1.89
L flask connected by two one meter sections of Bev-a-line tubing, and containing a 208.63 g orange. Chamber air
temperature was measured with a thermistor connected to V2. A volume correction can be made for the sample volume by
entering a negative value for Extension Tube Volume (cm3).
6. Soil Area (cm3) is where the sample area or mass is
entered, depending on what basis fluxes will be
calculated on. If a mass is entered in decigrams the
final computed flux values will be in μmol kg-1 s-1,
though they will still be labeled with the units μmol
m-2 s-1.
7. Extension Tube Volume (cm3) can be used to make
a correction for the flask volume occupied by the
sample by entering the sample volume here as a
negative number.
8. Under the Observation tab, Observation Delay
and Purge Time should both be set to zero. While
the flasks are continuously being purged between
measurements, this is not the same as the purge time
set in the software and is not under control of the
LI-8100A. The values entered for the Deadband
and Observation Length will be contingent on
measurement conditions. Typically at moderate flux
rates an observation length of two or three minutes
works well. The deadband will depend on flask
geometery and the flow rate during measurement, as
well as the final CO2 concentration from the previous measurement, as there is some chamber-tochamber carry over; see the LI-8100A Automated
Soil CO2 Flux System and LI-8150 Multiplexer
Instruction Manual for determining an appropriate
deadband length. Keep in mind that the observation
length includes the deadband period.
9. The settings under Data Logging, V2, V3, and V4
will be contingent on the experimental setup. Refer
to the LI-8100A Automated Soil CO2 Flux System
and LI-8150 Multiplexer Instruction Manual for
information about setting the parameters under
these tabs.
10. Repeat steps three through nine for all ports where a
chamber is connected.
11. Select Port Sequence from the Multiplexer Configuration window and define the order in which the
flasks will be sampled.
12. Select Repeat from the Multiplexer Configuration
window and define the sampling frequency.
13. The instrument configuration can be saved from the
Presets window.
9
0.5
0.45
0.4
0.35
0.3
0.25
9:30
7:30
5:30
3:30
1:30
23:30
21:30
19:30
17:30
15:30
A.
9:30
Chamber CO2 concentration
(µmol mol-1)
0.15
13:30
0.2
11:30
A twelve flask system was constructed following the
methods outlined above and used to measure CO2 efflux
from navel oranges. Flask air temperature was monitored
during the measurements with an 8150-203 soil temperature thermistor installed in each flask as described
above. Fluxes were calculated on a fresh weight basis and
a volume correction was used to account for the flask
volume occupied by the fruit. The flux measurements
were made over a 3 minute period (observation length =
3 min). Due to significant carryover of CO2 from one
flask to the next (Figures 11 and 12) the first 60 seconds
of each measurement were ignored in the flux calculations (deadband = 60 sec).
Flux (µmol kg-1 s-1)
A measurement example using a
twelve flask system
Figure 11. Chamber CO2 mole fraction during
measurement of navel orange respiration. Data shown are
for one flask over one three minute measurement. The
initial decrease in CO2 mole fraction is due to mixing of the
high mole fraction air trapped in the measurement loop
from the previous measurement with the air in the flask.
Chamber Temp. (°C)
Time (seconds)
Flux (µmol kg-1 s-1)
Time of Day
B.
dC/dt (µmol mol-1 s-1)
Flux (µmol kg-1 s-1)
Time of Day
C.
Deadband length (seconds)
Figure 12. The change in CO2 mole fraction with time
calculated for various deadband lengths using the data
shown in Figure 13. dC/dt is calculated as the slope of a
straight line fit to the CO2 mole fractions. Due to carryover
of CO2 in the measurement loop, an appropriate estimate
of dC/dt cannot be made without excluding the first 60
seconds of data.
Chamber Temp. (°C)
Figure 13. Navel orange respiration measured with a
multiplexed flask system. A. Respiration rates for ten
oranges measured over a 24 hour period. The number
given for each symbol indicates the port where the flask
was connected. B. The fluxes for port 2 (solid circles)
plotted with chamber airtemperature (open circles). C. The
fluxes shown in panel B plotted as a function of
temperature.
10
In total, ten navel oranges were monitored over a 24 hour
time course. Flux rates were similar for all ten oranges
measured with the multiplexed flask system, as shown in
panel A of Figure 13. The rates declined steadily
throughout the measurement period for all samples, and
tracked a decline in chamber air temperature (Figure
13B). The decrease in respiration rate was well correlated
(r2 = 0.7893) with chamber air temperature over the
measurement period (Figure 13C), and is likely due to
decreased metabolic activity within the fruit as it cooled
(based on chamber air temperature Q10=7.8).
Conclusions
The LI-8150 multiplexer is a highly adaptable instrument. When configured for multiplexed flask measurements it provides a means of rapidly sampling CO2 fluxes
from multiple samples, and tracking fluxes over long
time courses. While in the example shown we monitored
respiration of detached fruit, similar systems have been
applied in monitoring insect respiration (Nestel et al.
2007), respiration of isolated soil samples (Jones and
Kielland 2002, Haney et al. 2008), and monitoring
carbon fluxes from attached leaves and fruit (Araki et al.
1998, Kitano et al. 1997).
References
Araki, T., M. Kitano, M. Hamakoga, and H. Egughi.
1998. Analysis of growth, water balance and respiration
of tomato fruits under water deficit by using a multiple
chamber system. Biotronics 27:61-68.
Haney, R., W. Brinton, and E. Evans. 2008. Soil CO2
respiration: Comparison of chemical titration, CO2
IRGA analysis and the Solvita gel system. Renewable
Agri. And Food Sys. 23:171-176.
Jones, D. and K. Kielland. 2002. Soil amino acid turnover
dominates the nitrogen flux in permafrost-dominated
taiga forest soils. Soil Bio. & Biochem. 34:209-219.
Kitano, M., T. Araki, M. Hamakoga and H. Eguchi. 1997.
On-line measurements of CO2 and H2O gas fluxes, sap
flux and expansive growth in an intact tomato fruit.
Biotronics 26:85-94.
Nestel, D., E. Nemny-Lavy and V. Alchanatis. 2007. Gasexchange patterns of Mediterranean fruit fly pupae
(Diptera: Tephritidae): a tool to forecast developmental
stage. Florida Entomologist 90:71-79.
Figure 14. Multiplexed flask system as described in this document. Note that the LI-8100A Analyzer Control Unit is
required, as well, but not pictured above.
11
Appendix: A list of parts available from LI-COR used to construct a
multiplexed flask system
LI-COR Part number
Quantity
LI-8150 Multiplexer
LI-8150-16 or LI-8150-8
1
LI-8100A Analyzer Control Unit
LI-8100A
1
AC to DC Power supply
8150-770-01
1
Chamber sensor interface
8150-661
One per flask or one for every three Soil
temperature thermistors2
Soil temperature thermistor
8150-203
One per flask
Flask Sampling Kit
8150-670-16 or 8150-670-8
1 (includes all items below)
Rubber grommet
196-10534
One per flask
Silicone grease
210-01958-1
1
Diaphragm pump
9981-173
1
Flask pump power cable
9981-177
1
Pump mounting plate
9881-204
1
#6-32 x 3/8" Hex cap screw
140-04315
3
Bev-a-line tubing (15m)
8150-250
Two to four
Male quick connect
300-07124
Two per flask
Female quick connect
300-07125
Two per flask
Quick-conn couple bulkhead
300-07126
One per flask
Quick-conn plug bulkhead
300-07127
One per flask
Seal washer
167-07256
Two per flask
Quick connect elbow (1/8 NPT)
300-08118
One if modifying an LI-8150-16
Quick connect elbow
300-07474
Two if modifying an LI-8150-8, or three if
modifying an LI-8150-16.
Quick connect “Y”
300-03367
Two if modifying an LI-8150-8 and venting
the exhaust through one of the ports.
Quick connect straight union
300-03123
Three if modifying an LI-8150-8 and venting
the exhaust through one of the ports. Two
are included with the pump.
Quick connect plug
300-08151
Two if using a port to supply ambient air
and vent exhaust.
Filter
301-08119
One if not using a port to supply ambient air.
These items included with either Flask Sampling Kit
Description
2 Three soil temperature thermistors can be measured by a single chamber sensor interface, but the temperature data will have to be linked to the correct
chamber in post processing. There will also be a time delay between the flux and temperature measurement equal to the observation length times the
number of ports between where the sensor interface box is connected and where the flask containing the thermistor is connected.
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to their respective owners.
979-15612, Rev. 2, 7/15
Printed in USA.