CIRAS-3 Operation Manual V. 1.09 75 support@ppsystems.com
(chamber humidity)
Fixed % of reference. This option is most common. Typically, we recommend
setting this to 75% of reference (you can change this at any time). If ambient
conditions where you work are typically humid (60+ %RH) set Fixed % of
reference to produce a chamber humidity less than ambient. The %RH in the
leaf chamber is calculated and displayed so you can make necessary
adjustments based on that. If ambient air in your surroundings is typically dry,
set to 100% of reference (the system’s reference air is usually slightly more
humid than ambient because of the soda lime reaction). Anticipate that
transpiration water vapor from the leaf will increase chamber humidity, and
maintain chamber RH <70%. At times you may see a warning in the instrument
status bar (lower left) that leaf chamber humidity >70%. If this message does
not go away, you should reduce the incoming %RH until you get below 70%.
Fixed reference mb. Allows you to choose a specific saturation partial
pressure value of chamber air, from 0 mb to dewpoint, depending on the state
of saturation of the ambient air.
Constant VPD . Automatically adjusts chamber humidity to maintain a
consistent leaf-to-air vapor pressure deficit between the absolute range 0-100
mb (0-10 kPa). The target VPD that can be achieved will be dependent on
dynamic leaf physiological factors and not only on how dry you make the
incoming reference air.
Ambient (remove chemicals). To supply water vapor unaltered from the
surrounding environment to the leaf chamber. Several considerations are
involved whenever stable, internally generated water is not used.
Please Note. It is very easy to increase the humidity of the air above ambient if
required. Please contact PP Systems for the application note that was
prepared for this feature.
2
regulator in place (with no
CO
2
cartridge inserted)
Empty CO
2
absorber column for
ambient measurement of CO
2
Empty H
2
O absorber column for
ambient measurement of H
2
O
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