DH Instruments COMPASS FOR MOLBOX, Руководство пользователя

Страница: 143 / 226

COMPASS

for molbox™ User’s Manual
Page 129
© 1998-2003 DH Instruments, Inc .
FEATURE DESCRIPTION
Prompt for manual valve
isolation for zero set
points
(check box)
Checking this option causes COMPASS to pause test execution and prompt for
manual valve operation when a zero flow set point is encountered in the test
sequence. A prompt to open the valves occurs after the flow is averaged for that
set point. Use this feature if a manual valve is included in the test system and used
to assure zero flow at the zero set point.
Uncheck this option to avoid a valve operation prompt at zero flow set points.
Allow flow adjustments
for leak tests and zero
set points
(check box)
When checked, this feature causes the <Flow Control> form to display prior to a
leak test and when setting zero flow to allow the flow to be adjusted. Some DUTs
have a very small natural leak when closed. As a result, if setting zero flow, an
apparent flow is achieved by the leak through the DUT. This leak can be present
only when there is a differential pressure on the DUT. To remove the differential
pressure, the DUTs internal valves can be opened up all the way to allow pressure
equilibrium. This feature should only be used when true manual isolation of flow is
present.
Use DUT Error as DUT
Set Error for zero set
points
(check box)
Use this feature to force the calculation of DUT Set Error to be the same as the
DUT Error at zero set points. This allows the offset of the DUT Set Error to be
logged at zero. By default, this feature is not checked. Tests with zero set points
with or without jogging and flow regulation will still force the new error calculation,
provided that the test defined set point is zero. When using the
[RUN DUT] option,
the error calculation is changed only when the actual set point is 0 flow.
Apply DUT K Factor to
manual entry reference
(check box)
When checked, COMPASS multiplies manually entered reference flow values by
the DUT’s K Factor. Use this option only when the value entered is not already K
Factor corrected. If the DUT does not use a K Factor or the reference does not
require manual entry, no action is taken regardless of the state of the check box.
DUT overrange limit
(numeric entry field,
default 15 %)
There are occasions in Test Definitions in which the target flow must be a flow
value that exceeds the defined flow range of the DUT. This option defines the
maximum acceptable DUT overrange as a % FS of the DUT flow range. Entering a
value that is too small can prevent the actual flow from being set when less
accurate DUTs are used while a value that is too large may cause errors from the
instrument controlling the flow.
This limit can be significant when flow regulation is active and COMPASS is
actively controlling the flow (see Section 9.5.6). For example, if the DUT’s
<Max Flow> entry is 5 slm but 5.5 slm is required due to the current regulation setup,
an overrange limit of 5 % will not allow flow to be properly regulated. Alternatively,
if flow regulation is active but the flow supply is not adequate,
COMPASS will
continue to increase the set command in an attempt to reach the desired flow.
If the supply is inadequate to reach the target flow, the target flow will never be
achieved and
COMPASS will eventually send set point commands well beyond the
upper limit of the DUT in an attempt to reach the target flow. The DUT overrange
limit prevents infinitely high set point commands in this situation.
The <Manual DUT P and T Entry Method> panel selections are used when running a DUT Definition
whose [Correction] tab specifies a density correction (see Section 8.5.3) and no gas pressure or
temperature measuring devices are specified in the System Configuration (see Section 10.2) The panel
selections specify when manual pressure and temperature entries will be made when running the test.
When both pressure and temperature measurement are automated, the features on this panel are not
used. Table 47 covers the operation of the
<Manual DUT P and T Entry Method> panel.