CIRAS-3 Operation Manual V. 1.09  100  support@ppsystems.com 
 
You always have the option to reset the CO
2
 IRGAs back to factory calibration by selecting Factory Cal 
(F6). 
H
2
O Calibration 
For H
2
O recalibration we recommend using an accurate humidity generator or water vapor generator. 
1.  Ensure that all chemicals are fresh. 
2.  Connect the H
2
O 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 H
2
O gas concentration of your calibration mixture in the H2O box and press Start H2O 
Cal (F3). 
4.  Monitor the H2Or and H2Oa values and when steady, press Data Steady (F4).  New scaling 
factors for both the Reference and Analysis H
2
O 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. 
You always have the option to reset the H
2
O IRGAs back to factory calibration by selecting Factory 
Cal (F6). 
TIP 
Make sure that the flow rate from your CO
2
 or H
2
O calibration gas mixture is at least 250 cc/min.   
Otherwise atmospheric air could be drawn into the vent pipe leading to errors in calibration.