CIRAS-3 Operation Manual V. 1.09
70
We do not recommend removing a CO
2
cartridge for at least 24 hours after it was inserted and
with the CO
2
regulator assembly fitted to the CIRAS-3 console. If you do, the pressurized
cartridge will make a loud popping noise and the pressure may cause the internal tubing
associated with the gas blender to be removed from the back of the CO
2
regulator or gas mixing
diverter valve
.
Changing a CO
2
Cartridge
This is very easy to do. With the CO
2
cartridge holder still inserted into the CIRAS-3 console, turn the
cartridge holder slowly to the left (counter-clockwise) until you start to hear the gas release (unless it is
already empty). The cartridge will then release from the piercing pin and you can safely remove the
holder from the regulator by continuing to turn the holder counter-clockwise until it is removed. It is also
possible to remove the entire CO
2
cartridge holder and regulator from the CIRAS-3 console if you prefer
as described above.
Insert a new CO
2
cartridge into the holder and screw it into the regulator turning the holder clockwise until
snug. We recommend doing this with the CO
2
regulator fitted to the CIRAS-3 console. If you have the
entire assembly removed from the console, place a new CO
2
cartridge in the holder and put it back into
the console and turn the holder a quarter-turn clockwise to lock it in place and then continue until snug.
You might hear a small hiss sound as the pressurized CO
2
cartridge is getting pierced releasing a very
small amount of gas. This is normal. Continue tightening the holder until snug and do not overtighten.
Checking Stability - Before You Place a Leaf in the Chamber
Now that you can observe live readings you can check the system for stability and leaks. This is usually
done with the leaf chamber empty. This way you can isolate the cuvette gaskets for leaks. Press
Controls (F3)
and enter the CO
2
concentration that you might be working with, let’s say 390 µmol mol
-1
.
For now, use the default H
2
O Reference control option “Fixed % of reference” and 100%. Accept the
change to return to the Numeric View screen. These tests are mainly concerned with stability of CO
2
and
H
2
O. You can quickly check temperature and light later. Close the leaf chamber at this point.
Under the Measured Data group observe the values in the first two columns, CO2r, CO2a, CO2d, H2Or,
H2Oa, H2Od. Allow CO2r (Reference CO
2
) to become stable. With no leaf in the chamber we expect to
see the Analysis CO
2
(CO2a) equal to or nearly equal to CO2r. If this is the case there will be a Zero
differential, CO2d=0.0. Look for the same relationships in the water vapor data, H2Or, H2Oa, H2Od.
