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5. MAINTENANCE, ADJUSTMENTS AND CALIBRATIONS
Page 117 © 2007 DH Instruments, a Fluke Company
5.4.4.2 POWER SUPPLY MODULE
+ 12 V DC (± 2 %) @ 2.1 Amps
5.4.4.3 DRIVER BOARD
The driver board is controlled by the mini micro board (see Section 5.4.4.1). It supports:
• Frequency counters (2) for reading Q-RPTs (see Section 5.4.4.5)
• On-board barometer power and output (see Section 5.4.4.4)
• Power to the system cooling fan
• Remote [ENT]
• Keypad and display
• Beeper
5.4.4.4 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 quartz reference pressure
transducer (see Section 3.2.2). The temperature sensor is used for temperature
compensation of the barometric sensor.
5.4.4.5 Q-RPT MODULE
The Q-RPT module is an integrated Quartz Reference Pressure Transducer (Q-
RPT) assembly. The module includes a Q-RPT, brackets to hold the transducer,
interconnecting tubing and a manifold with TEST(+)and ATM ports.
A Q-RPT provides very high precision, low uncertainty 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.
See Section 5.4.5, Figure 14 for a pneumatic schematic of the Q-RPT module
configuration.
HI Q-RPT MODULE
The RPM4 A70M/A20M-AF Hi Q-RPT is an A70M. The A70M has a pressure
range of atmosphere to 10 000 psi (70 MPa) absolute, 0 to 10 000 psi (70 MPa)
gauge.
LO Q-RPT MODULE
The RPM4 A70M/A20M-AF Lo Q-RPT is an A20M. The A20M has a pressure
range of atmosphere to 3 000 psi (20 MPa) absolute, 0 to 3 000 psi (20 MPa)
gauge.
5.4.4.6 DISPLAY
2 x 20 character vacuum fluorescent display.