DH Instruments PPC4, Руководство по эксплуатации и обслуживанию

Страница: 43 / 228

3. OPERATING PRINCIPLES
Page 31 © 2009 DH Instruments, a Fluke Company
most suitable for the typical user to operate within PPC4 pressure control and measurement
specifications. Each PPC4 default range has default control parameters and AutoRange
automatically sets control parameters appropriate for the AutoRange range.
Control mode parameters can be viewed and customized in the Control function
(see Section 5.7.8 in the Advanced Interface and Section 4.4.5 in the Basic Interface).
Customizing the hold and/or stability control parameters changes the conditions required for a
Ready condition to occur (see Section 3.2.3). This can be used to increase control speed
(reduce time to Ready ), usually by decreasing control precision, or to increase precision which
usually decreases control speed. For example, changing the dynamic pressure control hold limit
from its default value of ± 50 ppm of the active range to ± 100 ppm of the active range will
decrease the time required to set a pressure since the limit within which the pressure must be
set has increased. However, it will also increase the maximum possible control error when
Ready is indicated.
Table 6. Default Pressure Control Parameters
STATIC MODE DYNAMIC MODE
HOLD
LIMIT
± 1 % of range span ± 50 ppm of range span, 5 ppm of
Q-RPT span or 0.4 ppm of controller
span, whichever is greater
STABILITY
LIMIT
50 ppm of range span or 2 ppm of
Q-RPT span, per second, whichever
is greater 50 ppm of range span or 2 ppm of Q-RPT
span, per second, whichever is greater

OPERATION
For Basic Interface, see Section 4.4.5.
For Advanced Interface, see Section 5.7.8.
3.2.14 Vent

PURPOSE
The

control key activates a sequence to bring the test pressure to atmosphere.

PRINCIPLE
The Vent sequence controls the pressure to near atmospheric pressure then opens the
system vent valve (see Figure 32). In addition to bringing the PPC4 test pressure to
atmospheric pressure, the Vent sequence also opens the Q-RPT bypass valve for Gxxx and
BGxxx Q-RPTs and, after a delay, closes the control bypass valve to minimize consumption
of supply gas through the control circuit (See. Figure 31) During the Vent sequence the RED
Vent LED is blinking. Once the RED Vent LED is lighted and steady and the
Ready/Not
Ready indicator becomes GREEN then the system is fully vented.

OPERATION
For Basic Interface, see Section 4.2.2.
For Advanced Interface, see Section 5.5.3.
3.2.15 AutoTest

PURPOSE
To execute a programmed sequence of automated pressure control target values.
Note
AutoTest is available with the Advanced User Interface only.