CIRAS-3 Operation Manual V. 1.09  102  support@ppsystems.com 
 
TIP 
You must always perform a MAX C prior to using “Approximate reference air” for CO
2
 Reference under 
Settings (See Settings (F2) on page 73
).  This will ensure that you are within 30 µmol mol
-1
 of your CO
2
 
reference set value and stable. 
 
Store Diff Bal 
For response curves, we recommend using Auto Zero, stored Diff Bal.  Prior to using this option, you 
MUST first perform a “Store Diff Bal” prior to starting a response script.  This process allows you to store 
“Zero” and “Diff Bals” in advance to avoid disruptions during a response.  Press Store Diff Bal (F4) to 
begin the process. 
 
To begin, enter the minimum and maximum ranges for both CO
2
 and H
2
O.  For instance, if the working 
CO2 range is 200-1000, enter 200 for CO2 min and 1000 for CO2 max.  Press the Tab key to advance to 
each setting.  Make sure the desiccants are fresh and the PLC3 leaf cuvette head is closed prior to 
starting the Stored Diff Bal process.  When complete and ready, press Start (F2).  The process is 
automated taking approximately 20 minutes to complete beginning with an initial Zero before proceeding 
through 6 levels.  The status bar for each level will be highlighted when complete as shown below.