DH Instruments PPC4, Operation And Maintenance Manual

Page: 209 / 228

7. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 197 © 2009 DH Instruments, a Fluke Company
7.4 Adjustment of Utility Sensor

PURPOSE
To adjust the output of the utility sensor, if present (see Section 1.2.2.2).

PRINCIPLE
PPC4s that do not have a Q-RPT in the Internal, Hi position, have a utility sensor.
The utility sensor output can be adjusted using PA and PM values in the same manner as for the Q-RPTs
(see Section 7.2.1.1).
Note
•
The utility sensor is not intended to serve as a pressure reference for low
uncertainty, traceable measurement. It is for indication, pressure control
and system maintenance functions only.
•
PPC4 measurement uncertainty when using Q-RPTs does not depend on
the measurement uncertainty of the utility sensor.

OPERATION
The procedure to adjust the output of the utility sensor is that same as for the calibration of an Internal, Hi (IH),
Standard Class, Q-RPT (see Section 7.2.4.1), but the calibration reference uncertainty can be between
0.01 and 0.05 % FS.
7.5 Pneumatic Control Module Configuration

PURPOSE
To run an automated routine that adjusts automated pressure control coefficients or to return automated
pressure control coefficients to factory default values.

PRINCIPLE
PPC4 uses factory configuration coefficients in the pressure control algorithms used for automated
pressure control. Changes in the pressure control elements over time or operation into an unusually large
test volume can cause pressure control performance to change. The PPC4 on-board configuration
routine automatically retunes the factory configuration coefficients to take these changes into account.
The Configuration function should be considered a maintenance function and only used to attempt to
improve pressure control 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). The configuration function may also be useful to speed up PPC4 pressure control when the
minimum test volume is in excess of 500 cc.
In addition, the Configuration function allows pressure control parameters to be returned to factory default
values. This feature can be useful to return to known conditions after the on-board configuration function has
been run.
Note
•
If the PPC4 Hi Q-RPT or utility sensor is an A350K or lower, the
configuration routine should be run twice, once with a vacuum source
attached to the EXHAUST port and once without. If the PPC4 Hi Q-RPT
or utility sensor is greater than A350K, the configuration routine can be
run with or without a vacuum pump connected to the EXHAUST port
(use the most common configuration).