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AQUATRAN Model 3/40 Operator's Manual
Individual Zero Processing
Adjusting the ReZero frequency will compensate for small shifts in the baseline zero. It may also be
necessary to compensate for individual variations such as seal permeation and leakage in the Test
Cartridge. This is done with Individual Zero Processing.
During individual zero processing an impermeable barrier made of aluminum foil (referred to as a foil) is
mounted in the Test Cartridge. Any water vapor that is picked up on the carrier gas side is thus due to
factors other than permeation through the barrier.
Note: When using a Test Cartridge that is not designed to utilize a Mounting Foil a "Test Loop" or other
suitable method is employed. See Figure 3-1.
The instrument uses the Individual Zero value obtained during the Individual Zero phase to automatically
correct the Water Vapor Transmission Rate measurements made during the Test phase.
Whenever you test a Very Good barrier you should perform individual zero processing. The settings for the
Individual Zero fields are explained below.
None
Beginning/End
Use Last
Purging the Sample
Most mounted package samples contain a significant volume of gas on the Carrier side of the barrier
material. Before the package cassette is loaded and clamped into a Test Cell this volume contains water
vapor from the ambient environment. The water vapor in this volume must be removed before the carrier
gas stream can safely by measured by the water vapor Sensor. Inadequate purging of the Test Cell can
result in "Failed" tests and a reduction in water vapor sensor life.
The process of reducing the residual water vapor on the Carrier side of the test cell to a safe level is
referred to as "Purging the Sample". The AQUATRAN Model 3/40 provides the capability to include a
"Purge State" at the beginning of the Test phase.
When a Purge state is initiated the "High Purge" valve is activated to increase the Carrier Gas flow to all
Test Cells. The increased Carrier Gas flow purges the test cells of ambient water vapor in less time than
would be required at the normal rate.
Note: When you use Individual Zero processing, the Purge state will only occur during the Test Phase.
MOCON, Inc.
When Individual Zero mode is set to "None" an Individual Zero phase
will not be performed. The default Individual Zero mode is "None".
When using these options, the individual zero value for the Test Cell is
measured. This value is used to correct the measured transmission
rate to improve the accuracy of the reported results. The "Beginning"
and "End" settings indicate when the Individual Zero phase will be
performed at the Beginning or at the End of the test.
In this mode the latest individual zero value measured is used to make
the correction. This mode is useful when making many tests on the
same type of material and the user is confident that seal permeation
and leakage is not a problem and every sample barrier is mounted the
same.
Revision D
Preparing for a Test
3-3
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