System Setup and Operation
CIRAS-2 Operator's Manual Version 2.04
- 47 -
Boundary Layer Resistance
Enter the correct boundary layer resistance value from the green and white test label found on your
cuvette handle. Methods used to determine boundary layer resistance of automatic leaf cuvettes using a
pseudo-leaf can be found in the
PLC5-6 Auto Cuvette Operation Manual.
Percent of Stomata on Upper Leaf Surface
Adaxial/abaxial stomatal ratio defaults to 50% - you may update this for known species-specific values.
Zero/Diff Bal Mode
1.
Zero
. CO
2
/ H
2
O free air is passed through the analyzer sample cells and the values are
recorded. Under these conditions there is no IR absorption and the readings from the detectors
are at maximum. CIRAS-2 uses this information to correct for most factors that cause IRGA drift.
2.
Diff Bal
. The reference (sample) air is passed through both the reference and analysis sample
cells and the offset values are recorded and applied to subsequent measurements. This
compensates for any differences between the cells and ensures that the reported differences in
concentration are accurate.
Please note:
It is very important that the Zero Absorber Columns (Columns 1 and 2) are fresh and that
the reference CO
2
concentration is steady when the Diff-Bal is performed.
Manual with Warnings
Perform manual Zeroes and Diff Bal if desired. CIRAS-2 will prompt you when it determines a Zero or Diff
Bal is required.
Automatic
Zeroes and Diff Bal are pe
rformed automatically at regular intervals. Leaving „Zero/Diff Bal Mode‟ set to
„Automatic‟ is recommended until you become more familiar with CIRAS-2 operation.
Auto Zero with Stored Diff Bal
This mode allows for working over a range of CO
2
concentrations without the need for Diff Bal. Prior to
recording data, the Diff Bal is performed over the anticipated CO
2
/ H
2
O range at approximately 100 ppm
CO
2
/ 3 mb H
2
O intervals. The values are then stored for use during measurement.
Manual Without Warnings
Perform manual Zeroes and Diff Bal if desired. CIRAS-2 will not display a prompt.
Choice of Zero Mode
– Recommendations
Manual With Warnings
: When CO
2
concentrations are being regularly changed (i.e. CO
2
response) and
greatest accuracy is required. The user can then judge when the CO
2
concentration is steady before
selecting Zero.
Automatic
: Ideal for a series of measurements that are conducted at the same CO
2
concentration.
Auto Zero with Stored Diff Bal
: When CO
2
concentrations are being changed and the quickest response
is required.
Use during A/Ci curves to inform CIRAS-2 of expected range of CO
2
/H
2
O concentrations.