Measuring Chlorophyll Fluorescence with the CFM 
 
CIRAS-2 Operator's Manual Version 2.04 
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7.  Close leaf cuvette (for later LED and CFM tuning). 
Operation from External PC 
To operate the CIRAS-2 system from an external PC, it must have 2 available COM ports.  On modern 
computers this you will typically use two USB ports.  Older computers may use at least one standard 9 pin 
serial port.  In order to use the USB port, a “USB to Serial Adapter” is required (supplied by PP Systems) 
and the associated software must be loaded on your PC.  Follow the instructions provided with the “USB 
to Serial Adapter” when loading the software.   
 
To  determine  which  COM  ports  are  available  on  your  PC,  go  to  Start  -  Control  Panel  –  System  - 
Hardware - Device Manager and open “Ports (COM & LPT)”.   
 
 
 
You will need to remember which COM ports are being used when logging in and setting up CIRAS-2 with 
the CFM under Preferences. 
 
After all electrical and pneumatic connections are made as described in the section Connecting the CFM 
to CIRAS-2 and the COM ports have been determined, perform the following to operate the system from 
an external PC: 
 
1.  Connect the CIRAS-2 PC Interface cable (9 pin D - 5 pin Lemo) between the PC serial port (9 Pin) 
on the back of the PC and the connector labeled “RS232” on the CIRAS-2. 
2.  Connect the gray 9 pin – 9 pin D cable with USB to Serial Adapter from the 9 pin socket on the 
back of the UI labeled “Ext Control Port” to the USB port on your PC. 
3.  Switch the “CFM” slide switch to On. 
4.  Switch the “CFM Control” slide switch to Ext PC.