DH Instruments PPC3 - 4 Purge; 5 Lo Vnt

3. OPERATION
Page 77 © 2002-2007 DH Instruments, a Fluke Company
 PRINCIPLE
PPC3’s that include an Axxx (absolute) and/or BGxxx (bi-directional gauge)
Q-RPT or a utility sensor (Auxxx)are equipped with a separate, on-board barometer.
The atmospheric pressure measurements made by the on-board barometer are
used for dynamic compensation of atmospheric pressure when using an Axxx
Q-RPT to make gauge pressure measurements (see Sections 3.3.3,  PRINCIPLE
and 3.2.3) and for static pressure compensation when using a BGxxx Q-RPT.
See Figure 13 for schematics showing the position of the on-board
barometer in PPC3’s measurement system.
The on-board barometer is a low accuracy sensor used only for measuring
small changes in atmospheric pressure over short periods of time
(see Section 3.2.3) and for line pressure compensation when using a BG15K Q-RPT.
PPC3 measurement uncertainty does not depend on the measurement
uncertainty of the on-board barometer.
 OPERATION
PPC3’s that have only Gxxx Q-RPTs (no Axxx or BGxxx) are NOT equipped with
an on-board barometer.
To view the current reading of the on-board barometer press [SPECIAL],
<7internal>, <3baro>. The display is in the active pressure unit of measure
(see Section 3.3.2).
3.5.7.4 <4PURGE>
 PURPOSE
To enable and disable the PURGE function and [PURGE] key which automate
use of the optional Self Purging Liquid Trap (SPLT) (see Section 3.3.8).
 OPERATION
To access the purge enable/disable function press [SPECIAL], <7internal>,
<4purge>. Select <1yes> to enable purge or <2no> to disable purge.
When the purge function is enabled, PPC3 makes background use of valve
driver channel #8 independently of user actions (see Sections 3.3.8, 3.4.7).
3.5.7.5 <5LO VNT>
 PURPOSE
To cause a PPC3 or external RPM4’s Gxxx or BGxxx Q-RPT TEST(-) vent valve
to stay open or closed rather than open and close automatically.
This feature is active only when the active Q-RPT is a Gxxx (gauge) or BGxxx
(bi-directional gauge) Q-RPT.