DH Instruments PPC3 - Sounds; General Operating Principles; Automated Pressure Control

3. OPERATION
Page 19 © 2002-2007 DH Instruments, a Fluke Company
3.1.5 SOUNDS
PPC3 is equipped with a variable frequency tone device to provide audible feedback and
alarms. The beeper is used for the following indications.
Valid key press Brief beep. Choice between three frequencies
or NO sound is available (see Section 3.5.5.2).
Invalid key press Descending two tone “blurp”.
Leak check completed Three two second beeps (see Section 3.3.9).
Upper or lower limit exceeded Intermittent one second beeps (see Section 3.4.4)
External device not connected Eight second high frequency beep (see Section
2.3.7)
Pmax! (overpressure limit) exceeded Eight second high frequency beep (see Section
3.4.4.1).
AutoTest reading in tolerance/out of Ascending triad/descending triad (see Section
tolerance reading 3.3.10).
3.2 GENERAL OPERATING PRINCIPLES
3.2.1 AUTOMATED PRESSURE CONTROL
PPC3 automated pressure control provides automated adjustment and control of pressure to
a user designated target value. Pressing [ENT/SET P] from the MAIN RUN screen allows a
pressure control target value to be entered and executed. Pressing [ESC], a direct pressure
control key or a function key causes active pressure control to be interrupted. Sending a
remote command when in local mode also interrupts pressure control.
PPC3 supports two pressure control modes to meet different pressure setting and controlling
requirements: dynamic and static. Pressure control parameters for each control mode are
automatically set to optimal default values for the operating PPC3 range when the range is
selected or AutoRange is used (see Section 3.3.4). Control parameters can be customized
using the [SETUP], <6control> function (see Section 3.4.6).
Control parameters:
Target Value The pressure setpoint specified by the operator.
Hold Limit A symmetrical positive and negative limit around the target value within
which the controlled pressure is maintained.
Stability Limit A rate of change of pressure limit in units of pressure/second used as a
criterion for the Ready/Not Ready condition in static control or when
PPC3 is idle (control not active).
See this section, Dynamic Control and Static Control for a detailed explanation of each
control mode and its advantages, the default control parameters and the control
customization options.
Dynamic Control
Dynamic control mode is designed to set the pressure to the target value and control
continuously to keep pressure within the hold limit and as close to the target value as possible
(see Figure 6). The advantage of this control mode is that the final pressure achieved is the
same as the target value. The maximum value of the control error is equal to the hold limit. The
average value of the control error is generally much smaller than the hold limit.