5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 133
© 2007 DH Instruments, a Fluke Company
Running the TPC Config routine may cause the set pressure to increase or decrease by up to 1.4 MPa
(200 psi).
The TPC CONFIG routine may be run at any pressure greater than 1 MPa (150 psi). Standard dynamic
pressure control mode must be active. The test system must be leak free (see Section 3.3.9 to leak
check). Wait at least five minutes after switching to dynamic control mode before running the TPC Config.
To access the CONFIG TPC function press
[SPECIAL]
,
<7internal>
,
<1config>
,
<1TPC>
,
<1run>
. The
display is:
Selecting
<1yes>
causes the volume determination routine to
run. While the routine is running,
<Running config…>
flashes
on the bottom line of the PPCH-G display.
Run TPC config?
1yes 2no
Completing the routine may take up to 2.5 minutes and cause the pressure to change by up to 1.4 MPa
(200 psi).
When the volume determination is complete the display is:
Vol estimate: 20 cc
Activate? 1yes 2no
Select
<1yes>
to activate the new volume determination. Select
<2no>
to retain the old volume
determination and return to the main run screen.
The volume configuration routine cannot be run under 1 MPa (150 psi). An error message is displayed if
the routine is initialized at a pressure under 1 MPa (150 psi).
5.6
VALVE OPENING POINT CONFIGURATION
PURPOSE
To run an automated routine that updates the opening point tables of PPCH-G’s servo-control valves.
Poor pressure control is usually caused by invalid control parameters, excessive leaks and restrictions in
the test system or other set up problems. These problems should be identified and eliminated before
resorting to use of the configuration function (see Section 6).
PRINCIPLE
PPCH-G uses servo-controlled needle valves to precisely admit and exhaust gas into and out of the test
volume. Knowledge of the opening points of these valves is critical to pressure control performance.
Systematically working into a large test volume (i.e. > 100 cc) and/or changes in the valves over time,
may make it desirable to update the valve opening point tables. The PPCH-G on-board valve opening
point configuration routine tests and updates the opening points.
The VALVE CONFIG function should be considered a maintenance function and used to attempt to
improve pressure control only when all other factors affecting pressure control have been examined and
eliminated (for example leaks, restrictions in test lines, unstable pressure supply, unstable vacuum
supply).
In addition, the VALVE CONFIG function allows valve opening point tables to be returned to original factory
values. This feature can be useful to return to known conditions after the on-board configuration function has
been run.
