PP Systems CIRAS-3 - Page 74

CIRAS-3 Operation Manual V. 1.09 74 support@ppsystems.com
Settings
Zero, Diff Bal mode
Manual. You will be prompted when to perform a Zero or Diff Bal.
Automatic. Zeros and Diff Bals will be performed automatically every 31
minutes. We recommend this mode if small ∆CO
2
and ∆H
2
O is anticipated and
for less experienced users. A Diff Bal cycle will also take place when there is a
large change in CO
2
(100 µmol mol
-1
) or H
2
O (5 mb) concentration.
Auto Zero, stored Diff Bal. This option can be useful and is highly
recommended for situations where large step changes in chamber CO
2
and
H
2
O are intended, such as occurs with CO
2
in A/Ci curves. Prior to using this
option, you must perform a Stored Diff Bal (See Store Diff Bal on page 102
).
CO2 Reference
Approximate reference air. The CO
2
supplied to the leaf chamber from
CIRAS-3’s internal CO
2
source will generally be within 30 µmol mol
-1
from the
actual set value within the control range of 0-2000 µmol mol
-1
. Prior to using
this option, you should perform a Max C (See
Find Max C on page 100) for
optimal accuracy and control. For response curves or in situations that require
frequent, large changes in CO
2
levels, this option is recommended because it
settles near the set value very quickly (within 1-2 minutes).
Exact reference air. The CO
2
supplied to the leaf chamber from CIRAS-3’s
internal CO
2
source will be within 2 µmol mol
-1
from the actual set value within
the control range of 0-2000 µmol mol
-1
. If working at the same CO
2
level
throughout a measurement sequence or for long periods, this option is ideal.
Fixed analysis air. Allows CO
2
control on the analysis gas (feedback from the
leaf) as it is measured by the Analysis side IRGA.
Ambient (remove chemicals). This option is frequently used to supply the
natural outdoor CO
2
to the leaf chamber. Several considerations are involved
whenever the stable internal CO
2
source (CO
2
cartridge) is not used. If this
option is selected, the CO
2
regulator should be empty but in place and the soda
lime must be removed from the CO
2
/H
2
O control column as shown below.
Humidity control can still be available if the H
2
O Absorber column is filled with
Drierite.
CO
2
regulator in place (with no
CO
2
cartridge inserted)
Empty CO
2
absorber column for
ambient measurement of CO
2
Note, H
2
O control is still
available with Drierite in this
absorber column