DH Instruments PPC4, Operation And Maintenance Manual

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7. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 203 © 2009 DH Instruments, a Fluke Company
7.9.5 Vacuum Sensor
The vacuum sensor is a silicon solid state pressure sensor in the barometric range. The vacuum
sensor readings are used to determine whether a atmospheric pressure or a vacuum
pressure is applied to the PPC4
EXHAUST port (see Section 3.2.27.2).
7.9.6 Pressure Control Module
The pressure control module is an integrated assembly that includes two inlet (fast and slow);
two exhaust (fast and slow) control valves; vent valve and differential pressure regulators.
The differential pressure regulators use pressure feedback to maintain a constant differential
pressure across the control valves. The control valves are solenoid type, actuated by 12 V.
See Figure 31 for the pneumatic module schematic.
7.9.7 Display
Basic Interface (PPC4): 2 x 20 character vacuum fluorescent display.
Advanced Interface (PPC4-ui): 5.7” TFT QVGA LCD (320x240).
7.9.8 Driver Board
The driver board is controlled by the PowerPC board (see Section 7.9.2). It supports:
•
12 V drivers for internal and external solenoid valve actuation
•
Frequency counters (4) for Q-RPTs (see Section 7.9.3.1)
•
On-board barometer power and output (see Section 7.9.4)
•
Vacuum sensor power and output for ControlRef function (see Section 3.2.27.2)
•
Utility sensor power and output
•
Power to the system cooling fan
•
Keypad and display
•
USB, IEEE-488.2 and TCP/IP communications
•
Beeper