DH Instruments PPC2 AF - 1000 M Ai N T E N an C E, Ad J U S T M E N T S an D C al I B R at I O; Maintenance; Pneumatic Control Module Configuration

5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 75 © 1998 DH Instruments, Inc.
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PPC2 AF was designed for maintenance free operation. No maintenance is required other than:
• Rezeroing of reference transducers as needed (see Section 5.2).
• Automated adjustment of pressure controlling parameters as needed (see Section 5.1.1).
• Adjustment of the on-board barometer as needed (see Section 5.3).
• Regular reference transducer calibration (see Section 5.4).
This section provides information on maintenance, adjustment and calibration procedures, certain repair
functions and recommended overhaul procedures.
PPC2 AF is a sophisticated pressure setting and measuring instrument with advanced on-board
features and functions. Before assuming that unexpected behavior is caused by system defect or
breakdown, the operator should use this manual and other training facilities to become thoroughly
familiar with PPC2 AF operation. For rapid assistance in specific situations, see Section 6.
PPC2 AF is covered by a limited 5 year warranty. Unauthorized service or repair during the warranty
period is undertaken at the owner's risk and may cause damage that is not covered under warranty
and/or may void the warranty (see Section 9.4).
5.1 MAINTENANCE
5.1.1 PNEUMATIC CONTROL MODULE CONFIGURATION
 PURPOSE
To run an automated routine that allows PPC2 AF to readjust automated pressure control
coefficients to take into account changes in the characteristics of its pressure control
hardware over time.
 PRINCIPLE
PPC2 AF uses hardware specific factory configuration coefficients in the pressure control algorithms
used for automated pressure control. Changes in the pressure control elements (valves, orifices
and pressure controllers) over time can cause pressure control performance to deteriorate as the
factory configuration values become less valid. The configuration routine automatically retunes the
factory configuration coefficients to take into account small changes in performance.
Use of the Cfg function should be considered a maintenance function used only when
PPC2 AF pressure control has deteriorated noticeably as evidenced by changes in the time
required to set a pressure, overshoot when setting a pressure and/or hunting around the
target value in dynamic control mode.
The Cfg function is only designed to compensate for the small changes in pressure control
hardware that may occur with normal wear over time. Major changes to the pressure control
hardware such as replacing a valve or pressure controller normally require a complete
recharacterization of the pneumatic module.