DH Instruments PPCH-G, Руководство по эксплуатации и обслуживанию

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PPCH-G™ OPERATION AND MAINTENANCE MANUAL
© 2007 DH Instruments, a Fluke Company Page 132
 OPERATION
The procedure to adjust the output of the utility sensor is the same as for the calibration of an Internal, Hi (IH),
Q-RPT (see Section 5.2.1), but the calibration reference uncertainty can be between 0.01 and 0.05 % FS.
To view/edit the calibration information for a utility sensor, use
[SPECIAL]
,
<8cal>
,
<1Hi RPT>
. The
position designator of a PPCH-G utility sensor is always
<IuH>
.
5.5 THERMAL PRESSURE CONTROL UNIT (TPCU)
CONFIGURATION
 PURPOSE
To run an automated routine that determines the volume of the system into which PPCH-G is controlling
pressure to optimize the performance of thermal pressure control (TPC) used in standard dynamic control mode.

PRINCIPLE
PPCH-G uses thermal pressure control (TPC) for very fine pressure control around the target value in
standard dynamic control mode (see Section 3.2.2.2). For optimal TPC operation, PPCH-G must have a
valid estimation of the size of the volume connected to the PPCH-G
TEST
port. In standard dynamic
control mode operation, if PPCH-G’s estimation of the volume seems incorrect as evidenced by
unexpected control response, PPCH-G runs a 0.5 to 2.5 minute routine to determine the test volume.
The volume determination routine can also be initiated by the operator using
[SPECIAL]
,
<7Internal>
,
<1config>
,
<1TPC>
,
<1run>
.
The operator initiated volume determination routine can be useful after a test volume change to avoid the
increased control time and reduced control precision that may exist until PPCH-G automatically
determines the volume.
Thermal pressure control (TPC) is only used in standard dynamic control mode. Therefore, the volume
configuration routine only executes when standard dynamic control mode is active.
Due to the high compressibility of low pressure gas, the configuration routine does not produce reliable
results when run at a starting pressure under 1 MPa (150 psi). Therefore, the volume configuration routine
cannot be run under 1 MPa (150 psi).
The test volume that PPCH-G has determined can be viewed using [SPECIAL], <1config>, <1TPC>,
<2view>.
 OPERATION
Poor control is usually caused by invalid control parameters, excessive leaks and restrictions in the test
system or other set up problems. These problems should be identified and eliminated before resorting to use
of the configuration function (see Section 6).
PPCH-G uses self diagnostics to determine when to run the TPC configuration routine in standard
dynamic control mode. Therefore, it is not normally necessary to run the configuration routine separately.