CIRAS-3 Operation Manual V. 1.09
99
Calibration Setup
CO
2
Calibration
For CO
2
recalibration we recommend a certified, accurate tank (< 1.0% accuracy) of compressed gas
containing CO
2
in air (not CO
2
in nitrogen). Generally speaking, it is recommended that your calibration
gas mixture contains a CO
2
concentration slightly above your normal measurement range. For instance,
if most of your measurements are made near CO
2
levels in the range of 390-450 µmol mol
-1
, a calibration
mixture of 500 µmol mol
-1
would be recommended.
1. Ensure that all chemicals are fresh.
2. Connect the CO
2
calibration mixture to the “REF IN” gas port on the CIRAS-3 console as shown
above. We recommend using flexible tubing to easily connect to the gas port and a flow rate of
250-300 cc/min. Be sure to include a vent pipe between your calibration gas mixture and CIRAS-
3 to avoid overpressure.
3. Enter the CO
2
gas concentration of your calibration mixture in the CO2 box and press
Start CO2
Cal
(F2).
4. Monitor the CO2r and CO2a values and when steady, press
Data Steady
(F4). New scaling
factors for both the Reference and Analysis CO
2
IRGAs will be determined and displayed. To
accept the new calibration, press
Accept Cal
(F5) or
Quit
(F1) to abort the calibration. If you
choose to
Quit
the calibration, you will be prompted with “CIRAS-3 Reject new calibration”.
Press
OK
.
Incoming CO
2
or H
2
O
calibration gas mixture
(250-300 cc/min)
Vent Pipe
