CIRAS-3 Operation Manual V. 1.09  193  support@ppsystems.com 
 
H
2
O Calibration 
For H
2
O calibration, an air supply of known water vapor concentration is required (mb).  Refer to H2O 
Calibration on page 100 for instructions.  Typically this is achieved using a commercially available 
humidity generator or water vapor generator.  If you do not have a device for H
2
O recalibration, please 
contact PP Systems and we will be happy to recommend some.  PP Systems can also perform H
2
O 
recalibration services at our factory. 
PLC3 Leaf Cuvettes 
Cuvette Gaskets 
The most common part requiring routine inspection and replacement are the leaf cuvette gaskets.  This is 
also the place where leaks are often discovered leading to fluctuations in CO
2
 and H
2
O readings.  Over 
time, plant material can cause the gasket material to crack or even deform requiring replacement.   
 
Leaf gaskets can easily be removed using a fine screwdriver to pry them out of their respective channels 
in the cuvette head.  Open the leaf cuvette head as shown above and using a fine screwdriver and gently 
pry the worn gasket material from the head.  Take care to remove all debris, old gasket material or 
anything else that will prohibit you from clean replacement of the new gaskets.  Peel the new gasket from 
the white backing and carefully place it in the appropriate location on the cuvette head and seal it in 
place.  We recommend applying a very light smear of silicone grease to preserve the gaskets and to 
provide a good seal. 
 
Lower head gasket