AQUATRAN 3/38 Operator’s Manual
Preparing for a Test
MOCON, Inc.
Revision G
3-3
The Sample Conditioning Time
When you condition a sample in the test cell, carrier gas and test gases are routed to the test cell as they
are during testing. However, the carrier gas is not routed to the water vapor sensor. This conditioning period
allows a sample barrier to acclimate to the conditions within the test cell.
When you use individual zero processing the sample will be conditioned twice, once with no water vapor
present in the Test Gas before individual zero testing and once using water vapor before the transmission
rate test.
A Very Good barrier material may take a long time to reach equilibrium, conditioning can be used to limit the
number of transmission rate values that appear on a printed report.
The amount of time in hours that the sample is conditioned can be specified. After the specified conditioning
period the system will automatically begin testing or individual zero processing.
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 edge leaks in the test cells. This is done with
Individual Zero Processing.
During individual zero processing the Permeant Driving Force is deliberately reduced to negligible levels.
The Permeant Driving Force is reduced by inserting a blocking foil in the cell. Any water vapor that is picked
up on the carrier gas side is thus due to factors other than permeation.
The instrument automatically subtracts this Individual Zero value from the water vapor transmission rate
value to produce a very accurate result.
Whenever you test a Very Good barrier you should perform individual zero processing. The settings for the
Individual Zero fields are explained below.
Individual Zero - Off/On
When set to Off an Individual Zero phase will not be performed. When
set to On an Individual Zero phase is performed as specified by the
Individual Zero Mode control. The default mode is off.
Beginning/End
When using these options, the individual zero value for the cell is
measured. This value is subtracted from the measured transmission
rate to give a corrected transmission rate value. The “Beginning” and
“End” settings indicate when the Individual Zero phase will be
performed at the Beginning or at the End of the test.
Last Individual Zero
In this mode the latest individual zero value measured is used. This
value is subtracted from the measured transmission rate to give a
corrected transmission rate value. The mode is useful if making many
tests on the same type of material and the user is confident that edge
leakage is not a problem and every sample barrier is mounted the
same.
