5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 139
© 2007 DH Instruments, a Fluke Company
5.9.2.2
HI Q-RPT OR UTILITY SENSOR
The higher range pressure transducer in a PPCH-G may be a Q-RPT (quartz
reference pressure transducer) or a utility sensor depending on the specified
PPCH-G configuration.
A Q-RPT is intended to provide very high precision, low uncertainty, traceable
pressure measurement. The basic sensing principle is the measurement of the
change in the natural oscillating frequency of a quartz tuning fork. Changes in
temperature and mechanical stress result from the change in pressure applied to
a connecting bellows or bourdon tube. Two independent quartz elements are used.
One quartz element is subjected to pressure related stress. The other quartz
element is used only to monitor temperature. See Section 1.2.2.1 for Q-RPT
specifications.
The utility sensor, present only if there is no Hi Q-RPT, is for pressure indication,
safety and housekeeping functions. It is a temperature compensated strain
gauge transducer.
5.9.2.3
TEST VENT VALVE
Open/close need valve. The valve is normally closed by the force of two
Belleville washers. It is opened by an opposing force applied by pneumatic
pressure on a bladder. The test vent valve fully opens the
TEST
port to
atmospheric pressure.
5.9.2.4
SUPPLY ISOLATION VAVLE
Open/close need valve. The valve is normally closed by the force of two
Belleville washers. It is opened by an opposing force applied by pneumatic
pressure on a bladder. The supply isolation valve shuts off the supply pressure
from the system. This is a safety feature to prevent unintentional increasing
pressure in the case of a power interruption.
5.9.2.5
LO Q-RPT, ISOLATION VALVE, VENT VALVE (OPTIONAL)
PPCH-G can be equipped with an optional Q-RPT of a lower range than the Hi
Q-RPT or utilitiy sensor. The Lo Q-RPT is of the same technology as the Hi Q-
RPT (see Section 5.9.2.2). The Lo Q-RPT isolation and vent valves are of the
same technology as the test vent valve (see Section 5.9.2.3).
5.9.2.6
SUPPLY ACCUMULATOR
High pressure aluminum volume of approximately 50 cc.
5.9.2.7
FRONT PANEL
Sheetmetal with inlaid overlay panel on which a membrane switch keypad and
electro-luminescent display are mounted.
5.9.2.8
ELECTRICAL CABLE TRACK
Articulated track to organize various cables connecting between the PPCH-G’s
lower mechanical unit and upper electrical unit. The track is articulated so that
the mechanical unit can slide out.
Содержание PPCH-G
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