PPC3™ OPERATION AND MAINTENANCE MANUAL
© 2002-2007 DH Instruments, a Fluke Company Page 136
5.8.3 Q-RPT MODULE
The Q-RPT module is an integrated assembly that mechanically manages the PPC3’s
pressure transducers. The module includes a Hi Q-RPT (quartz reference pressure
transducer) or utility sensor and may also have a Lo Q-RPT, brackets to hold the
transducer(s) interconnecting tubing, a manifold with the PPC3’s TEST(-), TEST(+) and
VENT ports and solenoid valves for AutoZeroing, measurement mode changes and switching
of the active transducer.
See Figure 13 for pneumatic schematics of different Q-RPT module configurations.
5.8.3.1 HI Q-RPT OR UTILITY SENSOR
The higher range pressure transducer in a PPC3 may be a Q-RPT (quartz reference
pressure transducer) or a utility sensor depending on the specified PPC3 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 in response to
changes in temperature and mechanical stress resulting 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 is for pressure indication, safety and housekeeping functions.
It is a temperature compensated micro-machined silicon sensor module.
5.8.3.2 LO Q-RPT
PPC3 may be equipped with a Lo Q-RPT. The Lo Q-RPT provides a lower
measurement range than the Hi Q-RPT or utility sensor. See Section 5.8.6.1 for
a description of Q-RPTs and section 1.2.2.1 for complete Q-RPT specifications.
5.8.4 ON-BOARD BAROMETER
The on-board barometer supports a board mounted, barometric range, micromachined
silicon sensor and an ambient temperature sensor. The barometer readings are used for
dynamic atmospheric pressure compensation when measuring gauge pressure with an
absolute reference transducer (see Section 3.2.3). The temperature sensor is used for
temperature compensation of the barometric sensor.
PPC3s that have only Gxxx Q-RPTs (no Axxx or BGxxx) are NOT equipped with an on-board
barometer.
5.8.5 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 PP3 EXHAUST port (see Section 3.5.7.2).
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