DH Instruments PPC2 AF - Setting Pressures for Leak Check;Purge Function; Typical Use of the Leak Check;Purge Function

3. OPERATION
Page 39 © 1998 DH Instruments, Inc.
After a five (5) second wait the display is :
1. Current measured pressure and pressure
units.
2. Current reference pressure transducer and
range.
3. Indication that PPC2 AF has opened the
SPLT exhaust valve and is waiting for
pressure to go to zero gauge. This indication
flashes.
89.63 psi a H3
Purging
Once the pressure reaches less than 3 psi (20 kPa) gauge or 16 psi (110 kPa)
absolute, PPC2 AF opens its internal vent valve and returns to the main run
screen in its normal vented condition.
When the SPLT exhaust valve opens at pressure during the purge routine, any liquid
contaminant collected will be released through the SPLT exhaust tube. If measurable
amounts of liquid contamination are exhausted from the SPLT exhaust valve, it is
recommended that the purge function be repeated until no noticeable amount of
liquid contamination is observed exhausting from the SPLT exhaust valve.
The internal volume of the SPLT is about 20 cc. The SPLT will not operate
effectively if the volume of liquid contaminants connected is greater than
about 10 cc. Even if an SPLT is being used, precautions should be taken to
reduce potential liquid contamination from the device or system under test
as much as possible before making the test connection.
Do not plug the SPLT exhaust valve. The purge routine can not be completed
with the SPLT exhaust valve plugged and the SPLT's protective function will
not be effective.
If the SPLT is electrically connected to the PPC2 AF, its exhaust valve will
always be open when the PPC2 AF vent valve is open. It may be closed
manually using the DRIVER function (see Section 3.3.4.)
3.2.8.4 SETTING PRESSURES FOR LEAK CHECK/PURGE FUNCTION
The direct pressure control keys are active when in the LEAK CHECK screen and
can be used to adjust pressure as desired (see Section 3.1.2.2) keeping in mind
that the VENT key will cause the PURGE function to execute.
Pressing the ENTER key from the leak check screen will cause the regular set
pressure screen for automated pressure control to appear (see Section 3.2.3.1).
An automated pressure control command can then be executed. Press the LEAK
CHECK function key when desired to resume LEAK CHECK/PURGE function.
3.2.8.5 TYPICAL USE OF THE LEAK CHECK/PURGE FUNCTION
The most common use of the LEAK CHECK/PURGE function is at the beginning
of a test just after the device or system under test has been connected to the
PPC2 AF TEST port. Generally, the purge process should be completed before
leak checking is performed. This may not be the case when the PPC2 AF will be
used to apply only ascending pressures.