DH Instruments PPC3 - 7 Internal; 1 Config; 2 Control Ref

3. OPERATION
Page 75 © 2002-2007 DH Instruments, a Fluke Company
3.5.7 <7INTERNAL>
 PURPOSE
To view, set, adjust, and maintain various aspects of PPC3’s internal operation.
 OPERATION
To access the internal selections press [SPECIAL],
<7internal>. The display is:
1config 2control ref
3baro 4purge 5lo vnt
The INTERNAL menu choices include:
<1config> To run an automated routine that readjusts internal pressure control
coefficients (see Section
3.5.7.1).
<2control ref> To view or manually set the EXHAUST port condition (see Section
3.5.7.2).
<3baro> View the real time output of the on-board barometer, if present
(see Section
3.5.7.3).
<4purge> Turn the automated purging function ON and OFF (see Section
3.5.7.4).
<5lo vnt> Operate Q-RPT module Gxxx and BGxxx low VENT valve directly
(see Section
3.5.7.5).
3.5.7.1 <1CONFIG>
 PURPOSE
To run an automated routine that readjusts internal pressure control coefficients.
This function is considered part of PPC3 maintenance and is therefore covered
in the maintenance section of this manual (see Section 5.5).
 OPERATION
This function is considered part of PPC3 maintenance and is therefore covered
in the maintenance section of this manual (see Section 5.5).
3.5.7.2 <2CONTROL REF>
 PURPOSE
To specify whether PPC3 should automatically determine whether a vacuum
source or atmospheric pressure is connected to its EXHAUST port or to
manually set the EXHAUST port condition.
 PRINCIPLE
The PPC3 exhaust (down) control valves and the output of the exhaust pressure
regulator are connected to the PPC3 EXHAUST port (see Figure 12).
The response of the pressure control module, particularly when controlling
pressure near and under atmospheric pressure, changes depending on whether
the EXHAUST port is connected to a vacuum source or left open to atmosphere.
To use the proper pressure control algorithms, PPC3 must know the condition of
the EXHAUST port.
The ControlRef function allows the PPC3 to know whether its EXHAUST port is
at vacuum or atmospheric pressure. An independent exhaust pressure sensor
measures the pressure present at the port. Normally, the exhaust sensor output is
used automatically by PPC3 to determine the EXHAUST port condition.
If desired, this automatic determination can be overridden and the EXHAUST
port condition set manually.