System Setup and Operation
CIRAS-2 Operator's Manual Version 2.04
- 53 -
Temperature
Track Ambient
Cuvette temperature (T
c
) control tracks ambient temperature as measured by the sensor in the base of
the cuvette handle (PLC5-6).
Entered Values
If selected, enter a temperature value in the field below. Value must be within the range of 8
o
C below
ambient to 45
o
C.
Please note:
Be aware of possible condensation inside the cuvette if warm air passing
through the system is suddenly cooled by the Peltier unit in the cuvette.
None
Cuvette temperature control disabled.
Which Control Type Should I Use?
For most field work involving a large number of leaves, it is advisable to make the measurements as
rapidly as possible so that measurements are being made on leaves adapted to field conditions.
Therefore, we would recommend selecting
Supply (Ref) Approximate ppm
for CO
2
and either
Supply
(Ref) % Ambient
or
Supply (Ref) Set mb (0-Ambient)
for H
2
O. With most leaf cuvettes, stable readings
should be possible within a one minute time interval using these Control Types.
For A/Ci and light response (A/I) curves in the laboratory and field, we recommend selecting
Supply (Ref)
Approximate ppm
for CO
2
and either
Supply (Ref) % Ambient
or
Supply (Ref) Set mb (0-Ambient)
for
H
2
O.
If performing a Light Response:
1. Set the CO
2
to a high, non-limiting value.
2. Set the light to the highest level required.
3. Wait for equilibrium and then reduce the light intensity in steps.
If performing a basic CO
2
Response:
1. Start off with a low CO
2
concentration and high light intensity until equilibration. This will open the
stomata to their maximum.
2. Increase the CO
2
in steps to the maximum desired value.
If performing both a light response and a CO
2
response on the same leaf, start off with a CO
2
response
followed by the light response, as described above.
Customized Operation of CIRAS-2 with Ambient CO
2
Especially for field work, you may wish to measure gas exchange without actually controlling CO
2
concentrations from CIRAS-2, using instead the naturally fluctuating diurnal CO
2
concentrations in
ambient air. To do this:
Empty all soda lime from Absorber Column 3 and replace the empty column in the manifold. Remove
only
the molecular sieve from Absorber Column 4 and replace. (Both soda lime and molecular sieve remove
CO
2
from the gas stream). Next, attach a length of butyl tubing (supplied) to the AIR IN gas port and
shield it from sources of CO
2
such as your breath and engine exhaust. AIR IN must also be protected
